Annual Report (Form 10-K)

10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

☒	ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2021

OR

☐	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO

Commission File Number: 001-39662

SQZ BIOTECHNOLOGIES COMPANY

(Exact name of Registrant as specified in its Charter)

Delaware	46-2431115
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
200 Arsenal Yards Blvd, Suite 210 Watertown, MA	02472
(Address of principal executive offices)	(Zip Code)

Registrant's telephone number, including area code: (617) 758-8672

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.001 par value per share		SQZ		New York Stock Exchange

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐ No☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes☒ No ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer		☐		Accelerated filer		☐
Non-accelerated filer		☒		Smaller reporting company		☒
				Emerging growth company		☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐No ☒

The aggregate market value of common stock held by non-affiliates of the registrant computed by reference to the price of the registrant's common stock as of June 30, 2021, the last business day of the registrant's most recently completed second fiscal quarter, (based on the last reported sale price on the New York Stock Exchange as of such date) was approximately $348.8million.

The number of shares of Registrant's common stock outstanding as of March 11, 2022 was 28,147,555.

Table of Contents

		Page
PART I
Item 1.	Business	1
Item 1A.	Risk Factors	42
Item 1B.	Unresolved Staff Comments	94
Item 2.	Properties	94
Item 3.	Legal Proceedings	94
Item 4.	Mine Safety Disclosures	94
PART II
Item 5.	Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities	95
Item 6.	[Reserved]	95
Item 7.	Management's Discussion and Analysis of Financial Condition and Results of Operations	96
Item 7A.	Quantitative and Qualitative Disclosures About Market Risk	113
Item 8.	Financial Statements and Supplementary Data	113
Item 9.	Changes in and Disagreements With Accountants on Accounting and Financial Disclosure	113
Item 9A.	Controls and Procedures	113
Item 9B.	Other Information	113
Item 9C.	Disclosure Regarding Foreign Jurisdictions that Prevent Inspections	113
PART III
Item 10.	Directors, Executive Officers and Corporate Governance	114
Item 11.	Executive Compensation	116
Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters	117
Item 13.	Certain Relationships and Related Transactions, and Director Independence	117
Item 14.	Principal Accounting Fees and Services	117
PART IV
Item 15.	Exhibits, Financial Statement Schedules	118
Item 16	Form 10-K Summary	120

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements within the meaning of the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. In some cases, you can identify forward-looking statements by terms such as "may," "will," "should," "expect," "plan," "anticipate," "could," "intend," "target," "project," "contemplate," "believe," "estimate," "predict," "potential" or "continue" or the negative of these terms or other similar expressions, although not all forward-looking statements contain these words. All statements other than statements of historical fact contained in this Annual Report, including without limitation statements regarding our plans to develop, manufacture and commercialize our product candidates, the timing or outcome of our ongoing or planned clinical trials for SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and any of our other pipeline product candidates and any future product candidates, the clinical utility of our product candidates, the anticipated impact of the COVID-19 pandemic on our business and operations, including manufacturing, research and development, clinical trials and employees, our cash needs and availability, and the plans and objectives of management for future operations, are forward-looking statements.

The forward-looking statements in this Annual Report are only predictions and are based largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this Annual Report and are subject to a number of known and unknown risks, uncertainties and other important factors that could cause actual results to differ materially from those projected in the forward-looking statements, including, but not limited to, those described in the sections of this Annual Report entitled "Summary Risk Factors," "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations".

Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, you should not rely on these forward-looking statements as predictions of future events. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise.

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SUMMARY RISK FACTORS

We are subject to numerous risks and uncertainties, including those further described below in the section entitled "Risk Factors" in this Annual Report on Form 10-K, that represent challenges that we face in connection with the successful implementation of our strategy and the growth of our business. In particular, the following considerations, among others, may offset our competitive strengths or have a negative effect on our business strategy, which could materially adversely affect our business, financial conditions, results of operations, future growth prospects, or cause a decline in the price of our common stock:

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Except where the context otherwise requires or where otherwise indicated, the terms "SQZ Biotech", "SQZ Biotechnologies", "we", "us", "our", "our company", "the company", and "our business" refer to SQZ Biotechnologies Company and its consolidated subsidiaries.

PART I

Item 1. Business.

Overview

SQZ Biotechnologies is a clinical-stage biotechnology company focused on unlocking the full potential of cell therapies to benefit patients with cancer, autoimmune and infectious diseases, and other serious conditions. The company was founded on the therapeutic potential of Cell Squeeze®, our proprietary technology which allows for rapid delivery of a variety of cargo into different cell types. We aim to create multiple cell therapies that drive the immune system to combat diseases.

In oncology, we are developing cell therapy platforms that are based on directing tumor antigen-specific immune activation via engineered antigen presentation. We believe that by engineering physiological antigen presentation signals in subsets of peripheral blood cells that act on immune priming pathways, we have the potential to develop cell therapies that are designed to be potent drivers of tumor-specific immunity, well-tolerated, administered without lymphodepleting preconditioning or hospitalization, and produced in under 24 hours. We have three oncology candidates in clinical trials across our SQZ®Antigen Presenting Cell, or APC, SQZ®enhanced APC, or eAPC, and SQZ®Activating Antigen Carrier, or AAC, cell therapy platforms. In our autoimmune diseases portfolio, we are developing our SQZ®Tolerizing Antigen Carrier, or TAC, cell therapy platform with the aim to restore immune tolerance to self-antigens or other autoimmune disease-associated antigens that are central to disease pathogenesis.

In 2021, we executed on several key areas of our pipeline and advanced our APC platform objectives. As of December 31, 2021, we have dosed 20 patients in our Phase 1 trial for our lead APC candidate, SQZ-PBMC-HPV, in HPV16+ advanced solid tumors. We reported interim data from the first three monotherapy dose-escalation cohorts at the 2021 American Society of Clinical Oncology, or ASCO, Annual Meeting, and presented interim safety, biomarker, and clinical data from the highest dose SQZ-PBMC-HPV monotherapy cohort at the 2021 European Society for Medical Oncology Immuno-Oncology, or ESMO-IO, Congress. Key observations from the reported data include, as of a cutoff date of October 8, 2021 (n=18 patients):

We have advanced our trial to evaluate SQZ-PBMC-HPV in combination with checkpoint inhibitor therapies, and are continuing to enroll patients in the highest dose monotherapy cohort. We are targeting additional data in the second half of 2022.

We have continued to build upon the progress of our SQZ®APC platform through the development of the novel SQZ®eAPC platform. Our lead eAPC product candidate leverages the added capabilities and functionality of multiple antigen presentation and immunological signals achieved through multiplexed mRNA delivery to diverse immune cell types. In January 2022, we received allowance to proceed with clinical trials from the U.S. Food and Drug Administration, or FDA, under our Investigational New Drug, or IND, application for SQZ-eAPC-HPV, our lead eAPC candidate engineered with HPV16 antigens and costimulatory signals. We will initiate the SQZ-eAPC-HPV trial, the COMMANDER-001 Phase 1/2 study, in patients with HPV16+ advanced solid tumors in the first half

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of 2022. We anticipate initial interim data in the second half of 2022. In addition to our efforts in the oncology field, we are also continuing to advance the eAPC platform in the infectious diseases field.

In January 2021, we received allowance to proceed with clinical trials from the FDA under our IND for SQZ-AAC-HPV, our lead AAC product candidate derived from red blood cells engineered with tumor-specific antigens. We are currently enrolling monotherapy cohorts as part of the Phase 1 ENVOY-001 trial to assess safety and tolerability as well as secondary outcome measures of the investigational SQZ-AAC-HPV therapy in HPV16+ advanced solid tumors, with initial interim data targeted in the second half of 2022.

We are also advancing our SQZ®TAC platform focused on creating novel and proprietary cell therapies as it relates to modulating or restoring immune tolerance. We have selected Celiac disease as the first proposed autoimmune indication for SQZ® TAC platform development. We believe the evidence of a causal disease antigen and T-cell driven pathology, and the substantial unmet need for a tolerizing treatment option provide a compelling opportunity for us to pursue Celiac disease. We presented characterization of TAC-mediated mechanisms of antigen-specific tolerance in preclinical models at the 2021 Federation of Clinical Immunology Societies, or FOCIS, Meeting. We anticipate further development of our TAC-Celiac candidate through IND-enabling studies in 2022 to support an IND submission in the first half of 2023, and, in parallel, are planning to use our proprietary, point-of-care manufacturing system for the production of the clinical batches.

We believe that we can leverage our foundational Cell Squeeze®technology and our associated manufacturing systems, processes and capabilities, to enable our current and future therapeutic product candidates and to potentially improve the speed and reliability of cell therapy manufacturing beyond current practices. During our Phase 1 clinical trial, we have demonstrated the ability to manufacture our lead APC therapeutic candidate in under 24 hours, with a vein-to-vein time of approximately one week, and we have progressed a multi-functional cell therapy, through our eAPC platform, into clinical testing. Additionally, we continue to progress development of an automated, point-of-care manufacturing system that we believe has the potential to produce future therapeutic candidates with improved manufacturing efficiency and lower cost.

Oncology

We believe our oncology cell therapy approach, which utilizes our clinical-scale microfluidic Cell Squeeze® system for cytosolic delivery of diverse cell programming biomolecules, has the potential to confer several advantages, including:

Across our platforms, we believe our SQZ® cell therapy candidates have the potential for broad development spanning solid and hematological cancer types as a result of the different disease antigen cargo that can be squeezed into multiple cell types to drive targeted killing of tumor cells.

We are developing three oncology therapeutic candidates with unique product characteristics and mechanistic benefits based on the principles of antigen-specific immune stimulation:

SQZ® Antigen Presenting Cell Platform: The APC platform is focused on generating CD8+ T cell responses, which are known to be the driving force for adaptive immune responses, and when present in tumor tissue, are a powerful prognostic indicator for multiple tumor types. SQZ®APCs are created by ex vivo engineering of a patient's own peripheral blood mononuclear cells, or PBMCs, with specific tumor antigens to develop antigen presenting cells that, when administered to a patient, are designed to drive activation and proliferation of antigen-specific CD8+ T cells for antitumor activity. Through our Cell Squeeze®approach, which is designed to enable direct cytosolic delivery of peptide antigens, we believe that we can dramatically improve antigen presentation efficiency. We are currently enrolling patients in

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monotherapy and combination cohorts in the Phase 1 trial for SQZ-PBMC-HPV and announced interim clinical results in December 2021. Our findings demonstrated that SQZ-PBMC-HPV induced a radiographic response, led to symptomatic improvement, and showed CD8+ immune activity in a solid tumor patient, providing preliminary support for the potential cellular vaccine mechanism.

SQZ® Enhanced APC Platform: The eAPC platform has the potential to yield novel multi-engineered cell therapy candidates comprising antigenic, costimulatory and cytokine components. SQZ®eAPCs are designed to potentially augment the T cell activation signal and to elicit a polyclonal T cell response. In addition, eAPCs are engineered with mRNAs that encode full-length antigenic proteins, potentially eliminating existing HLA restrictions with the intent to substantially broaden the addressable patient population. Our first eAPC platform candidate, SQZ-eAPC-HPV, was developed by multiplexed engineering of PBMCs with five different mRNAs. We received allowance to initiate Phase 1/2 clinical testing from the FDA under our IND in January 2022.

SQZ® Activating Antigen Carrier Platform: SQZ®AACs are derived from engineering red blood cells, or RBCs, with the Cell Squeeze®technology to comprise tumor-specific antigens and adjuvant. AACs are designed to take advantage of the natural physiological process of aged RBC clearance to target resident, professional APCs in lymphoid organs that can subsequently prime endogenous T cells to drive antitumor activity. We are currently enrolling patients in the Phase 1 ENVOY-001 trial for the SQZ-AAC-HPV investigational therapy in HPV16+ advanced or metastatic tumors.

In addition to our ongoing clinical programs, in various preclinical studies, we demonstrated the potential of SQZ®APCs and AACs to elicit specific immune responses against a range of oncology targets, including non-viral antigens such as KRAS point mutants. We presented preclinical data for SQZ®APCs directed against KRAS G12D and G12V antigens, which are prevalent mutations in lung, colorectal and pancreatic cancers, at the American Association for Cancer Research, or AACR, 2021 Annual Meeting. We plan to continue IND-enabling activities in KRAS mutant tumors in 2022.

Autoimmune Diseases

We are developing our SQZ® Tolerizing Antigen Carrier platform with the aim to treat autoimmune diseases by inducing antigen-specific immune tolerance. Our TACs are derived from engineering RBCs to comprise disease-specific antigens and are designed to leverage the natural physiological process of aged RBC clearance. SQZ®TACs have demonstrated the potential to induce multiple mechanisms of immune tolerance, including the deletion of disease-driving T cells, in preclinical mouse models. We are targeting clinical development of our investigational TAC Celiac candidate manufactured with our point-of-care system. We plan to conduct IND-enabling activities in 2022 to support an IND submission in the first half of 2023.

Infectious Diseases

We believe our SQZ® APC, eAPC and AAC platforms have the potential to provide therapeutic benefit by driving antigen-specific immune responses in chronic and acute infectious disease settings. In preclinical studies, we have demonstrated the versatility of our APCs to elicit targeted CD8+ T cell activation for multiple well-known disease antigens, including in hepatitis B virus, or HBV, cytomegalovirus, or CMV, influenza A virus, or IAV, and simian immunodeficiency virus, or SIV. Chronic HBV represents a large patient population with significant unmet need, and clinical evidence suggests that the levels of virus-specific T cells are correlated with patient outcomes and disease control. As such, we believe it to be a promising indication to target with our SQZ®eAPCs. We plan to continue preclinical work of our eAPC program in chronic HBV in 2022.

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Our Product Pipeline

* Pursuant to a license and collaboration agreement in oncology, we and Roche alternate U.S. commercial rights for each APC oncology product developed. It has not yet been determined whether we or Roche will have U.S. commercial rights for SQZ-PBMC-HPV. We maintain commercial rights for APCs outside of oncology. For a detailed description of the collaboration agreement with Roche, see "-Collaboration, Research and License Agreements-Roche Collaboration."

** The JDRF T1D Fund has provided equity investments to help progress the T1D program.

Company History

Our founder and Chief Executive Officer, Dr. Armon Sharei, is the lead inventor of the Cell Squeeze®technology. This foundational technology is based on his prior team's work in the laboratories of Dr. Klavs Jensen and Dr. Robert Langer at the Massachusetts Institute of Technology. In a series of experiments with a complex, high-pressure, fluid-jet delivery system, the team discovered that rapid mechanical deformation of cells enables intracellular delivery of biomaterials, resulting in the first prototype of the SQZ®microfluidic chip. Through collaboration with leading scientists in the immunology and regenerative medicine fields, the team discovered the process' novel capabilities and potential for significant impact through engineering of cell biology and function. SQZ Biotechnologies was founded with the goal of realizing the broad potential of this technology and developing cellular medicines that are effective and well-tolerated, with improved therapeutic accessibility, for patients around the world.

Our Strategy

Our vision is to build a fully integrated cell therapy company leveraging the Cell Squeeze®technology to develop differentiated, engineered cellular therapies across a broad range of disease areas. We plan to develop, and if approved, commercialize, cellular therapeutics from our directed immunity platforms that can modulate targeted immune responses against cancer, autoimmune and infectious diseases. To enable a future with impactful SQZ®cell therapy products as compelling early-line treatment options for patients, we are executing a strategy with the following key elements:

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SQZ® Technology

We have developed the Cell Squeeze®technology to be a rapid and versatile method of biomolecule delivery to cells, and have demonstrated application of our clinical-scale Cell Squeeze®system to reliably yield patient dose production timelines of under 24 hours for our investigational SQZ-PBMC-HPV therapeutic candidate. As illustrated below, the Cell Squeeze®approach utilizes microfluidic mechanical deformation which facilitates squeezing cells at high speeds through constriction(s) to temporarily disrupt the cell membrane and allow the target cargo to enter directly into the cytosol. At the current clinical scale, our proprietary system processes over 10 billion patient cells per minute.

We believe there are several advantages of utilizing the Cell Squeeze®technology as the manufacturing foundation of our cell therapy product candidates:

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Our Differentiation

We believe our technologies, capabilities, and knowledge pertaining to the fields of cell engineering and immunology position us with the potential to create cell therapy candidates with differentiated and favorable product profiles for the treatment of cancer, autoimmune and infectious diseases. We believe our cell therapy platforms and product candidates have the potential to offer meaningful benefits to patients and have broad therapeutic scope based on the following advantages:

SQZ®Cell Therapy Platforms

Our cell therapy platforms are designed to modulate the immune system in a target-specific manner with applications in oncology, autoimmune and infectious diseases, and other serious conditions. We are developing platforms and product candidates based on two modalities: targeted immune activation (SQZ®APCs, eAPCs and

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AACs) and immune tolerization (SQZ®TACs). We believe our multi-platform strategy positions us to harness complementary mechanistic attributes and value creation pathways in the development of our product candidates, while building on established manufacturing competencies and platform technology advancements.

* Engineered cells derived from PBMCs, which are primarily composed of monocytes, T cells, B cells, and natural killer cells

** Engineered cells derived from RBCs

Our Manufacturing

Since our founding, we have invested in and advanced our Cell Squeeze®platform, which includes our proprietary Cell Squeeze® technology, methods, and systems, with the aim to enable a variety of cell engineering applications for the development of cell therapy product candidates. We believe that the ability to manufacture cell therapies rapidly and reliably is an important competitive advantage in the cell therapy field, and we continue to innovate our manufacturing systems, processes, and capabilities with the intent to decrease the time, cost and complexity associated with cell therapy production.

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With our current clinical-scale Cell Squeeze® system and associated manufacturing processes, we have demonstrated patient dose production times of under 24 hours and vein-to-vein times of approximately one week for our SQZ-PBMC-HPV therapeutic candidate. Our current manufacturing and release testing workflow is represented in the figure below.

We are also developing an automated, point-of-care system that could potentially streamline manufacturing and future product candidate development timelines, furthering our broader vision to improve the accessibility and patient impact potential of cell therapies. We are targeting initial clinical implementation of our point-of-care manufacturing system with our TAC platform in 2023 and are continuing to develop our latest generation system to potentially enable future implementation across our other cell therapy platforms.

Our Product Candidate Pipeline

Oncology

SQZ®Antigen Presenting Cell (APC) Platform

APC Platform Overview

The SQZ®APC platform is designed to generate tumor-specific CD8+ T cell activation to drive the antitumor immune response. CD8+ T cells are known to be important effectors of the adaptive immune system, and are foundational to the recent clinical success of immunotherapy in oncologic indications.

While there has been significant interest in therapeutic immunization approaches to prime CD8+ T cell responses in an antigen-specific manner, it has remained challenging to effectuate adequate responses for antitumor applications. We believe that our approach, utilizing Cell Squeeze® delivery, enables us to engineer antigen presentation in multiple peripheral blood cell types to create a cellular vaccine that has the potential to direct antigen-specific immunity.

To mount an immune response, CD8+ T cells require antigen presentation on major histocompatibility complex class I, or MHC-I, molecules by APCs. Antigenic peptides displayed on MHC-I are primarily sourced from the cytosol. Traditionally, antigen-targeted cell therapies and vaccine systems, which introduce antigens in the extracellular vicinity, have relied on a process called cross-presentation to route to the MHC-I pathway. Cross-presentation can generally be considered an ineffective mechanism of MHC-I presentation to CD8+ T cells, as typically only a fraction of introduced antigen material is present in the cytosol for MHC-I loading. In contrast, in

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preclinical studies, our microfluidic Cell Squeeze®technology demonstrated abilities to deliver a variety of antigens directly into the cytosol, enabling potent antigen presentation for CD8+ T cell priming. We presented in vitro potency data for our SQZ®APCs at the American Association for Cancer Research, or AACR, 2019 Annual Meeting, where we demonstrated Cell Squeeze®-mediated cytosolic delivery yielded 1000-fold more efficient CD8+ activation relative to cross-presentation in dendritic cells.

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Through accessing the MHC-I antigen presentation pathway in a physiological manner, we believe we can activate CD8-driven adaptive immunity against targeted diseases. Based on our preclinical research, we believe the SQZ®APC platform has the potential to achieve several coordinates of a T cell response:

In addition, we believe that our differentiated approach could potentially provide several therapeutic benefits, including rapid generation of targeted antigen-presenting cells through engineering of major PBMC cell types, improved tolerability due to the specific and directed nature of immune activation, and synergistic opportunities with other immune-oncology agents to remodel the tumor microenvironment and promote T cell tumor infiltration.

SQZ®APC Pipeline in Oncology

Our lead APC candidate, SQZ-PBMC-HPV, is an autologous, PBMC product engineered with HPV16 E6 and E7 synthetic long peptides for therapeutic applications in HPV16+ tumors. We are developing oncology product candidates from our APC platform in collaboration with Roche, whereby we and Roche will alternate U.S. commercial rights for each oncology product developed, and we maintain full commercial rights for our SQZ® APCs outside of oncology.

We believe that APCs can have broad therapeutic potential across a range of solid cancers, and that we can utilize current and future generations of our cell therapy platform to target a variety of tumor antigens with the aim to drive antitumor immunity. In preclinical studies, we have demonstrated the potential of APCs to generate functional T cell responses across multiple antigen target categories, including virally derived antigens, such as HPV, that are known to be highly immunogenic and point mutants, such as KRAS G12D and G12V, that are considered less immunogenic.

We intend to apply the insights gained from the development of our first product candidate to inform future clinical development pathways and to select future indications for pipeline expansion. In addition, we believe that the advancements that we have made on our cell engineering capabilities and our manufacturing platform could enable us to leverage common processes to potentially accelerate future product development opportunities, such as in KRAS mutant cancers.

Lead SQZ®APC Product Candidate: SQZ-PBMC-HPV

HPV+ Cancers Incidence and Unmet Need

Human papillomavirus, or HPV, infection causes some of the most common types of cancer, such as cervical and head and neck cancer, and there is significant need for new treatment options to address HPV+ tumors. According to the Centers for Disease Control , or CDC, in the United States, HPV+ tumors represent 3% of all cancers in women and 2% of all cancers in men, resulting in over 36,000 new cases of HPV+ tumors every year. HPV+ tumors represent 4.5% of all cancers worldwide, according to the International Journal of Cancer, resulting in 570,000 new cases for women and 60,000 new cases for men globally every year. According to the CDC, HPV infection plays a significant role in the formation of more than 90% of anal and cervical cancers, and most cases of vaginal (75%), oropharyngeal (70%), vulval (70%) and penile (60%) cancers. In addition, an increasing percentage of head and neck cancer is being attributed to HPV infection, particularly those arising from the oropharynx.

The standard first-line treatment for HPV+ cancers differs by tumor type but typically involves a combination of chemotherapy, radiation, surgery, and more recently, in certain HPV-associated tumor types, specific checkpoint inhibitors and molecular targeted therapies. However, in patients with recurrent, metastatic, or persistent disease, second-line treatment options are limited with deterioration in response rates and prognosis. For example, in recurrent or metastatic head and neck squamous cell carcinoma, or HNSCC, patients who have progressed during or after platinum-containing chemotherapy, the median overall survival is under 9 months.

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Preclinical Data for SQZ-PBMC-HPV in Solid Tumors

SQZ-PBMC-HPV demonstrated antitumor activity in murine models, and we believe these results suggest the potential for clinical benefit in patient populations with HPV+ cancers.

In November 2020, we presented the following key preclinical findings for SQZ-PBMC-HPV at the Society for Immunotherapy of Cancer, or SITC, Annual Meeting:

In a TC-1 murine tumor model, we observed pronounced tumor regression in the SQZ®APC-treated mice (n=15), while tumor growth persisted in the inactive control (n=30) and the E7 peptide vaccine (n=15) groups. We observed that the tumors of SQZ®APC-treated mice were made up of an average of 47% immune cells, as compared to only 20% in the peptide vaccine-treated mice, and 9% in the inactive control, as measured by CD45+ cells. Of those immune cells that are CD8+ T cells, an average of 87% of them were HPV-specific for the SQZ-treated mice, compared to only 33% in the peptide vaccine-treated mice and only 2% for the inactive control. In these experiments, the peptide vaccine contained ~15,000 times more antigen than the APCs, which we believe further supports the potential potency of the SQZ®APC platform.

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In the SQZ-PBMC-HPV alone group, 17% of TC-1 mice remained tumor free on Day 84. 100% of the mice that received the combination of SQZ-PBMC-HPV and PD1-IL2v were tumor free at Day 84. In contrast, all the mice in the untreated group and the PD1-IL2v groups had grown tumors and died by Day 45. Pharmacodynamic markers correlated with the efficacy we observed, as SQZ-PBMC-HPV immunization resulted in a 480-fold increase in tumor infiltration of E7-specific CD8+ T cells, and this increase was augmented by subsequent PD1-IL2v administration.

In December 2021, we presented additional preclinical data for SQZ-PBMC-HPV at our ESMO I-O company conference call and webcast:

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In a TC-1 murine tumor model, SQZ-PBMC-HPV plus cisplatin (5 mg/kg) resulted in enhanced tumor regression as compared to SQZ-PBMC-HPV and cisplatin alone regimens (n=10 per group).

Clinical Development of SQZ-PBMC-HPV in Solid Tumors

SQZ-PBMC-HPV is being evaluated in a Phase 1 clinical trial for the treatment of HPV16+ recurrent, locally advanced, or metastatic solid tumors. The trial is an open-label, multicenter, dose escalation and expansion study to determine the safety and tolerability, immunogenic effects, antitumor activity, and pharmacodynamics of SQZ-PBMC-HPV as monotherapy and in combination with immune checkpoint inhibitors, including atezolizumab, ipilimumab and nivolumab. The clinical trial has a flexible design to allow for additional potential combinations. We believe that positive data from this trial could support our development of a new differentiated treatment for patients with HPV16+ tumors.

The primary objectives of the trial are to measure and evaluate: 1) safety and tolerability, as assessed by the number of participants with treatment-related adverse events, 2) the recommended Phase 2 dose, or RP2D, of SQZ-PBMC-HPV monotherapy and in combination with checkpoint inhibitors as included in the study, and 3) antitumor activity of SQZ-PBMC-HPV monotherapy at the RP2D, based on tumor assessments using RECIST 1.1. The secondary objectives of the trial are to measure and evaluate: 1) antitumor activity in patients with recurrent, locally advanced, or metastatic solid tumors, and 2) manufacturing feasibility, as assessed by individual patient batch yields.

As of December 31, 2021, we have completed the monotherapy dose escalation portion of our Phase 1 trial for SQZ-PBMC-HPV and received the independent Data and Safety Monitoring Board, or DSMB, endorsement for advancement of our highest dose regimen into combination cohorts with immune checkpoint inhibitors. We are currently enrolling patients in combination cohorts and are continuing SQZ-PBMC-HPV monotherapy enrollment at the RP2D (5e6/kg double prime).

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Double prime regimen: Dosing at respective level on Day 0 and Day 1 followed by one dose every three weeks thereafter

In December 2021, we presented initial interim results from the monotherapy dose escalation portion of the SQZ-PBMC-HPV-101 trial in HPV16+ solid tumors at the ESMO I-O Congress. Our clinical data was reported for four monotherapy dose cohorts (n=18) in an advanced patient population with a median of four prior lines of therapy. The interim results demonstrated that SQZ-PBMC-HPV was well-tolerated and in the highest dose cohort, induced a radiographic response, and led to symptomatic improvement and CD8+ T cell infiltration in an advanced patient, which we believe is supportive of potential correlative benefit and of the proposed cellular vaccine mechanism. Additionally, all SQZ-PBMC-HPV patient batches were produced in under 24 hours with high viability. A summary of key findings, as of a cutoff date of October 8, 2021, are as follows:

One patient in Cohort 1 (0.5e6/kg) experienced grade 2 cytokine release syndrome, or CRS, which was classified as a treatment-related serious AE and resolved in under 24 hours. There was one Grade ≥3 related adverse event, Grade 3 anemia, observed in a Cohort 2 (2.5e6/kg) patient. AEs of special interest, as defined by those related to SQZ-PBMC-HPV mechanism of action, included one case of CRS and one case of infusion related reaction, or IRR, both of which were low grade events. We believe that these interim SQZ-PBMC-HPV safety and tolerability data, coupled with the potential removal of conventional lymphodepletion preconditioning, could support opportunities to transition to earlier-line patient populations for this and future APC product candidates.

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The patient, who was refractory to anti-PD-1 checkpoint inhibitor treatment, showed a complete response of the target lesion at the first two on-treatment radiographic assessments, and experienced an improvement in symptoms, including dysphagia. At the second on-treatment tumor assessment, despite continuing improvement of the target lesion and patient symptoms, a new dermal lesion was found in the previously irradiated region.

Several immune and histologic biomarkers that characterize the tumor immune phenotype support the potential mechanistic action of the APC product candidate. Among those observed included an 8-fold increase in tumor infiltrating CD8+ T cells (CD8+ TILs; CD8+ tumor-infiltrating lymphocytes), a substantial reduction in HPV16 E6 and E7-expressing tumor cells, and a 50-fold increase in PD-L1-positive tumor cells, which are indicative of induced tumor inflammation and HPV antigen-specific targeting.

Patient 17 matched tumor biopsies

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Survival follow-up: Patient 2 and 7 survival days at the time of data cut-off of October 8, 2021. Patient 17 survival days at the time of last dose.

We believe CD8+ TILs are a potentially relevant pharmacodynamic biomarker based on supportive evidence in the scientific literature, suggesting the potential for a strong correlation between increases in CD8+ TILs and clinical responses when patients are treated with immunotherapies and the prognostic role of CD8+ TILs for multiple tumor types.

Based on these interim data, we plan to continue enrollment for our highest dose SQZ-PBMC-HPV monotherapy cohort and combination cohorts with checkpoint inhibitor therapies. We anticipate additional data for SQZ-PBMC-HPV in the second half of 2022.

SQZ®Enhanced Antigen Presenting Cell (eAPC) Platform

eAPC Platform Overview

The SQZ®eAPC platform is designed to build on the biology of APCs by incorporating additional immune activation signals, such as costimulatory proteins (Signal 2) and cytokines (Signal 3), into the antigen presenting cells in an effort to create novel, multi-functional cell therapy product candidates for driving antitumor immunity.

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SQZ®eAPCs are generated through the engineering of patient B cells, T cells, Natural killer, or NK, cells, and monocytes with 5 mRNAs encoding antigen-specific and immunological functions in a single Cell Squeeze®step. We believe that our eAPC platform has the potential to provide several therapeutic benefits, including:

We believe that our approach to engineering PBMCs as eAPCs has the potential to represent an advancement over previous antigen-specific methods by augmenting the quantity, quality, and breadth of targeted T cell responses, and by integrating multiple immunological functions into a single therapeutic.

Preclinical Development of SQZ-eAPC-HPV in Solid Tumors

Our lead eAPC product candidate, SQZ-eAPC-HPV, is engineered with mRNA cargo encoding the full-length HPV16 E6 and E7 antigenic proteins, and is in development for the treatment of HPV16+ tumors. Additionally, SQZ-eAPC-HPV is designed to express CD86 as a costimulatory molecule for T cell activation, as well as proprietary, membrane-bound versions of IL-2 and IL-12 (mbIL-2 and mb-IL-12) in an effort to further potentiate T cell activation and expansion. Our IND for a Phase 1/2 clinical trial to study SQZ-eAPC-HPV was allowed to proceed by the FDA in January 2022.

In November 2021, we presented preclinical data for SQZ-eAPC-HPV at the SITC Annual Meeting, where we demonstrated the following:

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HPV16 E6 and E7 TCR-transduced CD8+ T cells were cultured for 6 days with autologous PBMCs that were squeezed in the presence of E6 and E7 mRNA and/or CD86, mbIL-2 and mbIL-12 mRNA. CD8+ T cells were restimulated with the E6 or E7 minimal epitopes, and intracellular cytokine staining for IFNγ was conducted to measure the expansion of HPV16-specific T cells.

Clinical Development of SQZ-eAPC-HPV in Solid Tumors

We plan to enroll adult patients in the Phase 1/2 COMMANDER-001 trial for SQZ-eAPC-HPV in recurrent, locally advanced, or metastatic HPV16+ solid tumors. The trial is an open-label, multicenter, dose escalation and expansion study to evaluate the safety and tolerability, immunogenic effects, antitumor activity, and pharmacodynamics of SQZ-eAPC-HPV as monotherapy and in combination with immune checkpoint inhibitors, including pembrolizumab. By not requiring any HLA inclusion criteria in the study, we expect to increase patient eligibility by approximately two- to three-fold. We anticipate initial interim data for SQZ-eAPC-HPV in the second half of 2022.

SQZ®Activating Antigen Carrier (AAC) Platform

AAC Platform Overview

The SQZ®AAC platform is designed to induce antigen presentation in vivo by deriving antigen carriers from engineering RBCs with tumor-specific antigens and adjuvant. Through replicating the physiological process of aged RBC clearance, engineered AACs are designed to act as a "Trojan horse" to deliver the tumor-specific antigen cargo and adjuvant components to endogenous antigen presenting cells in lymphoid compartments, to subsequently prime antitumor responses.

To stimulate the adaptive immune system against specific antigens to yield CD8+ T cells with antitumor activity, we believe sufficient delivery of target antigens to APCs in an activating context is needed to enable MHC loading and T cell priming in lymphoid organs. While one arm of our directed immunity approach is based on ex vivo generation

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of APCs, the AAC arm focuses on leveraging the natural process of aged RBC clearance to target resident, professional APC populations in vivo to drive antigen-specific activation. In preclinical studies, we have shown that AACs were rapidly taken up by professional APCs, such as macrophages and dendritic cells, or DCs, in the spleen and liver, and that AACs loaded with target antigens and adjuvant subsequently drove antigen-specific CD8+ T cell responses. At the 2020 SITC Annual Meeting, we presented murine data on the in vivo pharmacokinetics and functional activity of SQZ® AAC therapeutic immunization, which we believe support the potential of AACs as a differentiated, directed immunity platform.

We believe that current and future AAC product candidates could confer favorable attributes for a cellular therapy, including the potential for improved tolerability due to the physiological and targeted nature of immune activation, a more streamlined patient experience with whole blood collection without the need for leukapheresis and with administration via syringe push, and the potential for synergistic benefit with other immune-oncology and chemotherapeutic agents.

AAC Pipeline in Oncology

Our lead AAC candidate, SQZ-AAC-HPV, is an autologous, engineered RBC product candidate with HPV16 E6 and E7 synthetic long peptides for therapeutic applications in HPV16+ tumors. We are continuing to evaluate future opportunities to develop AAC candidates for defined tumor antigens, including KRAS point mutants.

We believe that AACs represent a complementary approach to our APC and eAPC platforms, and that we can strategically select and pursue disease antigens, within and outside of oncology, and clinical development pathways that could enable us to continue to build our portfolio value. We believe that AACs have the potential for broad therapeutic applications across disease types, and we are continuing to progress platform advancements that could enhance product potency, antigen breadth, and other characteristics, while leveraging our manufacturing platform to support product development timelines and costs.

Preclinical Data for SQZ-AAC-HPV in Solid Tumors

We presented the following key preclinical findings for SQZ-AAC-HPV at the SITC 2020 and 2021 Annual Meetings:

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Numbers in brackets indicate median survival

In a TC-1 murine tumor model, we observed meaningful tumor regression in the SQZ-AAC-HPV-E7 Prime + Boost group (n=10) as compared to the control group (n=10), and this effect corresponded with improved median survival of 51 days for the SQZ-AAC-HPV-E7 Prime + Boost regimen versus 36 days for the control. In addition, based on TIL analysis on Day 26 post-treatment, SQZ-AAC-HPV-E7 promoted an influx of CD8+ T cells in tumor tissue, of which over 70% were HPV antigen-specific, and generated an over 100-fold increase in the ratio of E7-specific CD8 + T cells to T regulatory cells as compared to the PBS control, which led to potent, antigen-specific antitumor responses.

In TC-1 tumor bearing mice treated with a low dose of cisplatin (5 mg/kg) before SQZ-AAC-HPV-E7 treatment, we observed dramatic tumor clearance in all mice (n=10).

We believe that these preclinical data for SQZ-AAC-HPV support the further study and development of SQZ® AACs as a potential immunotherapy platform for cancer treatment.

Clinical Development of SQZ-AAC-HPV in Solid Tumors

SQZ-AAC-HPV is being evaluated in a Phase 1 clinical trial, ENVOY-001, for the treatment of HPV16+ recurrent, locally advanced, or metastatic solid tumors. The trial is an open-label, multicenter study to determine the safety and

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tolerability, immunogenic effects, antitumor activity, and pharmacodynamics of SQZ-AAC-HPV as monotherapy and in combination with immune checkpoint inhibitors, including ipilimumab and nivolumab.

The primary objectives of the trial are to measure and evaluate: 1) safety and tolerability, as assessed by the number of patients with treatment-related adverse events, and 2) the RP2D for SQZ-AAC-HPV monotherapy and SQZ-AAC-HPV in combination with ipilimumab, nivolumab, and nivolumab plus ipilimumab. The secondary objectives of the trial are to measure and evaluate: 1) the antitumor activity of SQZ-AAC-HPV in patients with recurrent, locally advanced, or metastatic solid tumors, and 2) manufacturing feasibility in the monotherapy dose escalation phase of the trial, as measured by the number of potential doses from individual patient blood collection.

We received FDA allowance to proceed with clinical trials of SQZ-AAC-HPV in January 2021 and are targeting initial interim data in the second half of 2022. We intend to evaluate, and potentially implement, a global clinical development strategy for SQZ-AAC-HPV to enable clinical activities both inside and outside of the U.S.

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Autoimmune Diseases

SQZ®Tolerizing Antigen Carrier (TAC) Platform

TAC Platform Overview

Our SQZ®TAC platform is designed to induce antigen-specific immune tolerance in vivo by utilizing a similar approach to the AAC platform, whereby TACs are derived from engineering RBCs to modulate and suppress unwanted immune responses in a targeted manner.

As with our AAC platform, we utilize proprietary methods and processes for generating TACs, which induce changes associated with RBC senescence, to enable targeting to resident populations of professional APCs, such as macrophages, in lymphoid organs. SQZ®TACs are designed to take advantage of the naturally tolerogenic process of aged RBC clearance and are subsequently aimed to drive antigen-specific immune tolerance through multiple cellular mechanisms considered relevant to the pathology of complex autoimmune diseases. In preclinical studies with transgenic OT-I and OT-II murine models, we evaluated multi-modal mechanisms of tolerance induced by TAC treatment, including upregulation of markers of anergy associated with functional inactivation of CD8+ and CD4+ T cells, targeted deletion of antigen-specific T cells, and expansion of antigen-specific regulatory T cells, or Tregs. In January 2021, we presented key data and results from our TAC platform studies at the Antigen-Specific Immune Tolerance, or ASIT, Digital Summit:

We believe that the potential of TACs to regulate both autoreactive CD4+ T cells and CD8+ T cells through multiple pathways may enable the development of differentiated therapeutic candidates for the treatment of diverse autoimmune diseases.

TAC Pipeline for Autoimmune Diseases

In September 2021, we announced the selection of Celiac disease as our lead autoimmune indication for clinical translation. We believe the strong evidence of a causal disease antigen and T-cell driven pathology, and the substantial unmet need for a tolerizing treatment option provide a compelling opportunity for us to pursue Celiac disease. In addition, we believe that our advancement of a TAC product candidate is strengthened by our preclinical work demonstrating multi-mechanism, antigen-specific immune tolerance induction, our point-of-care manufacturing advantages, and our existing RBC product development capabilities.

We believe that our TAC approach has the potential to address some of the current limitations with standard of care treatments for patients with autoimmune diseases, which primarily entail broad immunosuppressive agents. Through

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non-specific dampening of immune responses, current immunosuppressive therapies can result in increased risk of opportunistic infection and cancerous malignancies, in addition to organ-specific complications associated with long-term usage.

Celiac Disease Prevalence and Unmet Need

Celiac disease is a chronic autoimmune disorder that occurs in genetically predisposed people. The disease is triggered by eating foods containing gluten, which is found in wheat, barley, and rye. Disease symptoms can include abdominal pain, diarrhea, nausea, vomiting, and other common signs. When gluten is ingested, the body mounts an immune response that attacks and damages the villi that line the small intestine, which can impact nutrient absorption. Many people who have Celiac disease have not been diagnosed; however, population-based studies indicate that the disease affects about 2 million people in the United States and approximately 1% of the population worldwide, with regional differences. There is currently no approved drug treatment and patients must therefore maintain a gluten-free diet, which involves strict, lifelong avoidance of exposure to gluten proteins. Long-term complications of Celiac disease may include malnutrition, accelerated osteoporosis, nervous system problems and issues related to reproduction. Rare complications can include cancer of the small intestine, cirrhosis, and non-Hodgkin lymphoma.

Preclinical Development of SQZ®TACs

In June 2021, we presented the following preclinical data for SQZ®TACs in Type 1 diabetes, or T1D, at the 2021 FOCIS Annual Meeting:

In the CD8+ transgenic NY8.3 induced diabetes murine model, TACs were loaded with the NY8.3 cognate epitope (TAC-NRPA7) for therapeutic treatment (n=10). TAC-NRPA7 treatment was able to durably protect mice from the development of T1D, as measured by blood glucose levels with a hyperglycemic threshold of over 250mg/dL. In addition, multiple immune markers corresponded with disease prevention outcomes, including the reduction of pathogenic CD8+ T cells in the pancreas by 60-fold and decreased secretion of proinflammatory cytokine interferon gamma by 375-fold.

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In a murine co-adoptive transfer model of T1D with BDC2.5 CD4+ and NY8.3 CD8+ T cells, treatment with TACs loaded with the BDC2.5 cognate epitope (TAC-p31) increased the frequency of BDC2.5 Tregs by 3.5-fold, which were subsequently able to exert bystander suppression of NY8.3 CD8+ T cells. Through bystander tolerogenic activity, TAC-p31 treatment led to a 10-fold reduction in the number of NY8.3 CD8+ T cells and a 9-fold reduction in interferon gamma secretion.

Infectious Diseases

Our Pipeline for Infectious Diseases

We believe that our cell therapy platforms aimed at antigen-specific immune activation have therapeutic potential across multiple infectious disease indications. Virus-specific CD8+ T cell activity has been shown to be associated with disease control and improved outcomes in certain diseases, such as chronic HBV, which could be a promising avenue for our directed immunity approach.

In preclinical studies, including those presented at the AACR 2021 Annual Meeting, we have demonstrated the potential of our APC platform to elicit CD8+ T cell responses against HBV (HBsAg), IAV (M1), and CMV (pp65) antigens. We expect that we will continue preclinical activities in chronic HBV with the eAPC platform in 2022, and that we will continue to build upon and apply key platform technologies and concepts, such as mRNA engineering of cells with immune activation signals, to advance our pipeline of infectious disease product candidates.

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Collaboration, Research and License Agreements

Roche Collaboration

In October 2018, we entered into a License and Collaboration Agreement, or the Roche Collaboration Agreement, under which we are collaborating with Hoffman-La Roche Inc. and F. Hoffman-La Roche Ltd., or together, Roche, in the development and commercialization of certain nucleated cell therapy product candidates that incorporate antigens for the treatment of oncologic indications in accordance with mutually agreed upon collaboration plans. The Roche Collaboration Agreement enhanced, replaced and terminated a 2015 collaboration agreement between us and Roche.

We agreed, under the Roche Collaboration Agreement, to collaborate with Roche in the development of a cell therapy for oncologic indications made from PBMCs. The initial mutually selected antigen target is HPV, which is the focus of our ongoing SQZ-PBMC-HPV Phase 1 clinical trial. We also agreed to use commercially reasonable efforts to mutually select additional antigens to develop collaboratively. For each mutually selected antigen (including HPV with respect to SQZ-PBMC-HPV), we are responsible for conducting all preclinical research, and all development activities occurring prior to achieving clinical proof of concept for a product candidate containing the antigen, generally through a Phase 1 clinical trial. With respect to each mutually selected antigen, we granted Roche an option, exercisable after we deliver to Roche a clinical proof-of-concept report for a product candidate containing the antigen, to obtain an exclusive license, under our intellectual property, to research, develop, make, use, import, sell, and otherwise exploit the product candidate worldwide for the treatment of oncologic indications using our SQZ platform and a microfluidic chip. We retain all rights with respect to any product for which Roche does not timely exercise its option, and we may elect to commercialize any such product independently. Following Roche's exercise of its option for a given product candidate, Roche is then responsible for the further clinical development of that product candidate, unless we exercise our option to exploit the product candidate in the United States, as further described below. Roche granted us an option, exercisable with respect to every alternating mutually selected antigen product for which Roche exercises its own option, beginning with the second, to retain the right under our intellectual property, and to obtain an exclusive license under Roche's intellectual property, to research, develop, make, use, import, sell and otherwise exploit the antigen product candidate in the United States. If we exercise our option, the parties will mutually determine how responsibility for clinical development will be allocated between them, but Roche has the final say as to which party will run each global clinical study. We own any invention relating solely to a product containing a mutually selected antigen that is developed prior to the exercise of Roche's option. If Roche exercises its option, Roche owns each subsequently developed invention relating solely to the antigen product candidate unless (a) it is solely related to the SQZ platform or microfluidic chips or is dominated by certain patents that belong to us and are necessary or useful for the practice of our SQZ platform or microfluidic chips, or (b) we exercise our option for the product candidate, in which case we will own such invention in the United States, and Roche will own such invention in all other jurisdictions. The budgeted development costs for these antigens are shared by the parties unless and until (i) Roche exercises its option with respect to a given antigen product candidate, and (ii) we do not exercise our option with respect to that antigen product candidate. In such case, Roche will be responsible for subsequent development costs.

Under the Roche Collaboration Agreement, if we propose an antigen that is not ultimately mutually selected for collaborative development, we may still pursue the development of product candidates containing that antigen. For each such antigen that we select, we may be responsible for conducting all preclinical research, and all development activities occurring prior to achieving a clinical proof of concept for an antigen product candidate containing the antigen. With respect to each such antigen product, Roche grants us an exclusive license under its intellectual property to research, develop, make, use, import, sell, and otherwise exploit the product in the United States. If we achieve a proof of concept for a product candidate containing such antigen, Roche will, for a limited period of time, have the option to obtain an exclusive license under our intellectual property to research, develop, make, use, import, sell, and otherwise exploit the product candidate worldwide (subject to our rights to exploit the product in the United States) for the treatment of oncologic indications using our SQZ platform and a microfluidic chip. We retain all rights with respect to any product candidate for which Roche does not timely exercise its option. Following Roche's exercise of its option, the parties will mutually determine how responsibility for clinical development will be allocated between them, but Roche has the final say as to which party will run each global clinical study. We own any invention relating solely to a product candidate containing an antigen we select that is developed prior to the exercise of Roche's option. If Roche exercises its option, we will own in the United States, and Roche will own in

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all other jurisdictions, each subsequently developed invention relating solely to the antigen product candidate, unless such invention is solely related to the SQZ platform or microfluidic chips or is dominated by certain patents that belong to us and are necessary or useful for the practice of our SQZ platform or microfluidic chips. We are responsible for all development costs for such antigen, unless and until Roche exercises its option, in which case the development costs subsequently incurred will be shared by the parties.

If Roche proposes an antigen and it is not ultimately mutually selected for collaborative development, Roche may elect to pursue the development of products containing that antigen. At Roche's cost, we are responsible for conducting all preclinical research, and all development activities occurring prior to achieving a clinical proof of concept for an antigen product candidate containing such antigen. Roche is responsible for all clinical development after a proof of concept is achieved. Roche owns any invention relating solely to antigen product candidates containing such antigen, unless the invention is solely related to the SQZ platform or microfluidic chips or is dominated by certain patents that belong to us and are necessary or useful for the practice of our SQZ platform or microfluidic chips. Roche is responsible for all of the development costs for product candidates containing such antigens.

Under the Roche Collaboration Agreement, preliminary collaboration plans with defined preclinical goals exist for eAPC development and for product candidates containing tumor cell lysate, or TCL. We are responsible for conducting preclinical research and development activities occurring prior to achieving a clinical proof of concept for each such product. With respect to each TCL product candidate, we granted Roche an option, exercisable after we deliver to Roche a clinical proof-of-concept report for such TCL product candidate, to obtain an exclusive license, under our intellectual property, to research, develop, make, use, import, sell, and otherwise exploit the product candidate worldwide for the treatment of oncologic indications using our SQZ platform and a microfluidic chip. We retain all rights with respect to any product candidate for which Roche does not timely exercise its option. Following Roche's exercise of its option, Roche is then responsible for the further clinical development of each such product candidate. We own any invention relating solely to a TCL product candidate that is developed prior to the exercise of Roche's option. If Roche exercises its option, each subsequently developed invention relating solely to a TCL product candidate will be owned by Roche, unless it is solely related to the SQZ platform or microfluidic chips or is dominated by certain patents that belong to us and are necessary or useful for the practice of our SQZ platform or microfluidic chips. Prior to the exercise of Roche's option for a given tumor lysate product candidate, we will share the budgeted Phase 1 clinical costs of developing that product candidate, with Roche responsible for a mid double-digit percentage of the costs and SQZ responsible for the remainder. After Roche exercises its option, we may in some cases elect to opt out of sharing development costs; in such cases, Roche is thereafter responsible for all development costs incurred after exercising its option with respect to a given tumor lysate product candidate. If we do not timely elect to opt out of sharing development costs incurred after Roche's option exercise, the costs will be shared, with Roche responsible for a mid double-digit percentage and SQZ responsible for the remainder. We will share certain profits and losses associated with the commercialization of TCL product candidates in the United States with Roche, unless we opt out of the cost sharing.

We own any invention developed under the Roche Collaboration Agreement that relates solely to the SQZ platform or microfluidic chips or is dominated by certain patents that belong to us and are necessary or useful for the practice of our SQZ platform or microfluidic chips. Any invention that does not relate solely to an antigen product candidate or TCL product candidate is owned by the party that invents it; if such invention is invented jointly, it is owned jointly by the parties. Each party may freely practice any jointly owned invention with no obligation to account to the other party.

Under the Roche Collaboration Agreement, Roche paid us an upfront payment of $45 million. We are eligible to receive aggregate milestone payments on a product-by-product basis of up to $1.6 billion upon the achievement of specified milestones, consisting of up to $217.0 million of development milestone payments, up to $240.0 million of regulatory milestone payments and up to $1.2 billion of sales milestone payments. Roche has agreed to pay us yearly tiered royalties based on net sales of antigen and TCL product candidates. For each antigen product candidate for which Roche commercializes outside of the United States, and we commercialize in the United States, Roche will pay us tiered royalties on net sales of the product candidate outside of the United States at rates ranging from a mid single-digit percentage to a mid-teens percentage, depending on net sales of the product candidate. For each such product, we will pay Roche tiered royalties on net sales of such product candidate in the United States at rates ranging from a mid single-digit percentage to a mid-teens percentage, depending on net sales of the product candidate in the United States. For antigen product candidates selected by Roche, rather than mutually, Roche will

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pay us tiered royalties on worldwide net sales of such product candidate at rates ranging from a mid single-digit percentage to a high single-digit percentage, depending on net sales of the product. For certain antigen product candidates with respect to which Roche commercializes worldwide, Roche will pay us tiered royalties at a rate ranging from a high single-digit percentage to a mid-teens percentage, depending on net sales of the product. No royalties will be due for SQZ antigens for which Roche does not exercise its option. For TCL product candidates, Roche will pay us tiered royalties on the aggregate net sales of all TCL products at rates ranging from either a mid single-digit percentage to a percentage in the low twenties, with the caveat that the rates for sales in the United States may instead range from a low teen percentage to a percentage in the mid twenties, depending on whether and when we opt out of sharing certain profits and costs of commercializing the TCL product candidate in the United States with Roche.

Either party may terminate the Roche Collaboration Agreement (a) in its entirety or on a product-by-product or country-by-country basis if the other party breaches materially and such breach remains uncured for 90 days, or (b) in its entirety for insolvency-related events involving the other party. We may terminate the Roche Collaboration Agreement in its entirety or on a product-by-product or country-by country basis, if Roche or its affiliates or sublicensees commences an action challenging certain patent rights licensed to us and sublicensed to Roche. Roche may terminate the Roche Collaboration Agreement without cause (a) in its entirety or on a product-by-product basis with 60 days' notice, if Roche is terminating prior to exercising an option under the agreement, (b) on a product-by-product basis with 90 days' notice, if Roche is terminating after exercising an option under the agreement, (c) on a product-by-product basis or country-by-country basis with 180 days' notice if Roche is terminating after exercising an option under the agreement, and such notice will become effective on or after the first commercial sale of the product. For any product candidate that is terminated, we may provide a continuation election notice to Roche, and, for consideration, obtain from Roche all reasonably requested rights to such terminated product candidate, including the transfer of ownership of all INDs and regulatory approvals, and copies of data and reports relating to the product candidate, among other things.

MIT License Agreement

We exclusively license certain foundational technology from the Massachusetts Institute of Technology, or MIT, pursuant to an Amended and Restated Exclusive Patent License Agreement dated as of December 2, 2015, or the MIT License Agreement. The MIT License Agreement replaced an earlier Exclusive Patent License Agreement dated as of May 10, 2013, which was entered into in connection with the organization of the company. Under the MIT License Agreement, MIT granted us a worldwide, royalty bearing license to develop, make, have made, use, sell, offer to sell, lease, and import products incorporating the patent rights and to develop use, sell, offer to sell and perform processes incorporating the patent rights for all research and therapeutic applications for the term of the MIT License Agreement. Our rights under the license are exclusive in our fields of use, except with respect to (a) MIT and Harvard University (which owns the patent rights jointly with MIT), each of which retain rights for research, teaching and educational purposes on their own behalf and on behalf of all other non-profit research institutions, (b) Howard Hughes Medical Institution, which has an irrevocable, non-exclusive, non-assignable, non-sublicensable, license to use the patent rights for its own research purposes and (c) the federal government, which retains a non-exclusive and non-transferrable license to practice any government-funded invention claimed in the patent rights, as provided by law. We also have the right to grant sublicenses to third parties, subject to written agreements containing similar protections of MIT and certain third-party beneficiaries as contained in the agreement.

We are required to use diligent efforts, or cause our affiliates or sublicensees to use diligent efforts, to develop licensed products, to introduce licensed products and processes into the commercial market and, thereafter, to make licensed products and processes reasonably available to the public. In addition, we are obligated to satisfy certain development and commercialization metrics and provide MIT with periodic progress reports. To date, we have met our diligence obligations under the agreement. For example, our collaboration with Roche and the commencement of our SQZ-PBMC-HPV trial meet clinical milestones under the agreement. After the fifth anniversary, and before the sixth anniversary, of the MIT License Agreement, the parties are obligated to discuss additional diligence obligations to continue the development and commercialization of licensed products and processes.

We are obligated to make certain payments to MIT including an up-front license issue fee, annual maintenance fees, clinical milestone payments, running royalties based on net sales (at a rate in the low single digits), reimbursement of patent costs, and sharing of sublicense income. In June of 2019, we agreed with MIT on a payment schedule for

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the sharing of certain amounts received by us from Roche. MIT prosecutes and maintains the patent rights in close consultation with us and our intellectual property counsel. We also provide certain indemnifications for liabilities arising from claims related to the exercise of our rights under the agreement.

Upon entering into the MIT License Agreement, we paid a nominal license issue fee. We agreed to pay MIT a nominal annual license maintenance fee for each calendar year. Each year's annual license maintenance fee may be credited to running royalties due in the same calendar year. We also agreed to pay MIT milestone payments in an aggregate amount of up to $1.8 million per licensed product or process that achieves certain clinical and regulatory milestones. Additionally, we agreed to pay royalties based on net sales of the licensed products or processes, at low single-digit rates that vary depending on whether sales are made in the therapeutic or research field. With respect to each sublicensee, we are obligated to pay MIT royalties equal to the lesser of (a) a low single-digit percentage of the sublicensee's net sales and (b) 50% of the running royalties owed to us by the sublicensee. We also agreed to pay MIT a percentage in the mid teens of our annual sublicense income (which does not include income from royalties).

The license will remain in effect until the expiration or abandonment of all issued patents and filed patent applications within the licensed patent rights. The agreement is terminable by us upon six months written notice, provided that we have paid all amounts due to MIT through such termination date, and by MIT for nonpayment of amounts due, our cessation of the business related to the agreement, our uncured material breach of the agreement or a challenge initiated by us of the validity, enforceability or non-infringement of the patents licensed to us under the agreement. In the event of any dispute relating to the agreement, either party may initiate mediation to facilitate a negotiated settlement prior to seeking other legal remedies.

Intellectual Property

We strive to protect and enhance the proprietary technology, inventions and improvements that we believe are commercially important to the development of our business, including by seeking, maintaining and defending patent rights, whether developed internally or licensed from third parties. We also rely on trade secrets, know-how, continuing technological innovation and in-licensing opportunities to develop, strengthen and maintain our proprietary position in our field.

Our future commercial success depends, in part, on our ability to: (i) obtain and maintain patent and other proprietary protection for commercially important technology, inventions and know-how related to our business; (ii) defend and enforce our intellectual property rights, in particular our patents rights; (iii) preserve the confidentiality of our trade secrets; and (iv) operate without infringing, misappropriating or violating the valid and enforceable patents and proprietary rights of third parties. Our ability to stop third parties from making, using, selling, offering to sell or importing our product candidates or any future products may depend on the extent to which we have rights under valid and enforceable patents or trade secrets that cover these activities.

Patents

The patent positions of biotechnology and pharmaceutical companies like ours are generally uncertain and can involve complex legal, scientific and factual issues. We cannot predict whether the patent applications we are currently pursuing will issue as patents in any particular jurisdiction or whether the claims of any issued patents will provide sufficient proprietary protection from competitors. We also cannot ensure that patents will issue with respect to any patent applications that we or our licensors may file in the future, nor can we ensure that any of our owned or licensed patents or future patents will be commercially useful in protecting our product candidates. In addition, the coverage claimed in a patent application may be significantly reduced before a patent is issued, and its scope can be reinterpreted and even challenged after issuance. As a result, we cannot guarantee that any of our products will be protected or remain protectable by enforceable patents. Moreover, any patents that we hold may be challenged, circumvented or invalidated by third parties. See "Risk factors-Risks related to our intellectual property" for a more comprehensive description of risks related to our intellectual property.

In the United States, the term of a patent covering an FDA-approved drug may, in certain cases, be eligible for a patent term extension under the Hatch-Waxman Act as compensation for the loss of patent term during the FDA regulatory review process. The period of extension may be up to 5 years but cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval. Only 1 patent among those eligible for an extension and only those claims covering the approved drug, a method for using it, or a method for manufacturing it

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may be extended. Similar provisions are available in Europe and in certain other jurisdictions to extend the term of a patent that covers an approved drug. It is possible that issued U.S. patents covering the use of products from our intellectual property may be entitled to patent term extensions. If our use of product candidates or the product candidate itself receives FDA approval, we intend to apply for patent term extensions, if available, to extend the term of patents that cover the approved use or product candidate. We also intend to seek patent term extensions in any jurisdictions where available, however, there is no guarantee that the applicable authorities, including the FDA, will agree with our assessment of whether such extensions should be granted, and even if granted, the length of such extensions. The duration of patents outside of the United States varies in accordance with provisions of applicable local law, but typically is also 20 years from the earliest effective filing date. However, the actual protection afforded by a patent varies on a product-by-product basis, from country-to-country, and depends upon many factors, including the type of patent, the scope of its coverage, the availability of regulatory-related extensions, the availability of legal remedies in a particular country and the validity and enforceability of the patent.

Our patent portfolio includes more than 35 patent families that we own or have licensed, that have been prosecuted and maintained to potentially secure exclusivity for various SQZ®candidates and platforms through to 2028-2043, without taking into account any patent term adjustments or extensions we may obtain. As of February 2, 2022, our portfolio is comprised of over 136 U.S. and foreign patents (including over 82 patents in various European countries) and over 305 U.S., Patent Cooperation Treaty (international), and foreign patent applications. These applications are designed to provide protection for various SQZ®product candidates and platforms including the Cell Squeeze®technology and current clinical candidates. In addition, these patents and applications contain a suite of claims directed to the SQZ®systems, devices, composition of matter and methods of use, including methods of inducing an immune response, tolerance, treating cancer, treating various autoimmune diseases, and various other diseases.

We diligently evaluate our intellectual property strategy as we develop new platform technologies and product candidates. We are positioned to file additional patent applications based on our patenting strategy, or where we seek to adapt to competition or seize business opportunities.

The Cell Squeeze®Platform

As of February 2, 2022, our Cell Squeeze®platform, which includes the Cell Squeeze®technology, methods and use, apparatus and components, and system, is comprised of 66 U.S. and foreign patents and 61 U.S., Patent Cooperation Treaty (international), and foreign patent applications. The patents and applications in this category are relevant or may be relevant to a variety of SQZ®technologies, platforms, and product candidates.

The Immune Activation Platform

As of February 2, 2022, our immune cell platform, which includes the current SQZ-PBMC-HPV and SQZ-eAPC-HPV clinical candidates as well as confidential candidates and technology, specialized Cell Squeeze®methods and use, as well as clinical formulations and protocols, is comprised of 4 US and foreign patents and 147 U.S., Patent Cooperation Treaty (international), and foreign patent applications.

As of February 2, 2022, our anucleate cell platform, which includes the current SQZ-AAC-HPV clinical candidate as well as confidential candidates and technology, specialized Cell Squeeze®methods and use, as well as clinical formulations and protocols, is comprised of 32 U.S. and foreign patents and 33 U.S., Patent Cooperation Treaty (international), and foreign patent applications.

The Immune Tolerance Platform

As of February 2, 2022, our autoimmune platform, which includes the current TAC technology as well as confidential candidates and technology, specialized Cell Squeeze®methods and use, is comprised of 26 U.S. and foreign patents and 31 U.S., Patent Cooperation Treaty (international), and foreign patent applications.

Exploratory Work

As of February 2, 2022, our earlier research and exploratory work, which includes confidential early-stage project candidates and specialized Cell Squeeze®methods and use, is comprised of 8 U.S. and foreign patents and 33 U.S., Patent Cooperation Treaty (international), and foreign patent applications.

Trademarks

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We currently own 35 allowed or registered trademarks in various jurisdictions worldwide, including four registered trademarks in the United States. We have 12 pending trademark applications worldwide, including 10 in the United States. Our trademark portfolio includes the following pending, allowed, or registered marks registered in the United States and certain other countries: Cell Squeeze, SQZ, SQZ Biotech, Empower Cells to Change Lives, SQZ Therapeutics, SQZ Activating Antigen Carriers, SQZ Antigen Carriers, SQZ Tolerizing Antigen Carriers, SQZ TX, SQZ-AC, SQZ-AAC, and SQZ-TAC.

Trade Secrets and Proprietary Information

We rely upon unpatented trade secrets, confidential know-how and continuing technological innovation to develop and maintain our competitive position. However, trade secrets and confidential know-how are difficult to protect. We seek to protect our proprietary information, in part, using confidentiality agreements with applicable collaborators, scientific advisors, employees and consultants. We also have agreements requiring assignment of inventions with our employees and selected consultants, scientific advisors and collaborators. These agreements may not provide meaningful protection. These agreements may also be breached, and we may not have an adequate remedy for any such breach. In addition, our trade secrets and/or confidential know-how may become known or be independently developed by a third party, or misused by any collaborator to whom we disclose such information. Despite any measures taken to protect our intellectual property, unauthorized parties may attempt to copy aspects of our products or obtain or use information that we regard as proprietary. Although we take steps to protect our proprietary information, third parties may independently develop the same or similar proprietary information or may otherwise gain access to our proprietary information. As a result, we may be unable to meaningfully protect our trade secrets and proprietary information.

Competition

As a clinical-stage biotechnology company, we face competition from a wide array of companies in the pharmaceutical and biotechnology industries. This competition includes both small companies and large companies with greater financial and technical resources and longer operating histories than our own. We also compete with the intellectual property, technology and product development efforts of academic, governmental and private research institutions.

Our competitors may have significantly greater financial resources, established presence in the market, expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement and marketing approved products than we do. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly if they establish collaborative arrangements with large companies.

The key competitive factors affecting the success of any products that we develop, if approved, are likely to be their efficacy, safety, convenience, price and the availability of reimbursement from government and other third-party payors. Our commercial opportunity for any of our product candidates could be reduced or eliminated if our competitors develop and commercialize products that are more effective, have fewer or less severe side effects, are more convenient, or are less expensive than any products that we may develop. Our competitors may also obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours and may commercialize products more quickly than we do.

We expect to compete with companies using other cell engineering approaches, such as electroporation and viral vectors. Companies that are engineering cells with some of these methods include Rubius Therapeutics, which is genetically engineering red blood cells, Fate Therapeutics, which is programing hematopoietic cells and other biotechnology companies working on single cell types.

We expect our lead product candidate, SQZ-PBMC-HPV, will compete with other product candidates for the treatment of HPV+ cancers. While there are currently no FDA-approved therapies that target HPV for HPV+ cancers, there are multiple competing clinical-stage product candidates in development targeting HPV+ cancers. These product candidates include genetically modified T cell therapies in clinical development by Kite, peptide vaccines in clinical development by ISA Pharma, biologics being developed by Cue Biopharma, therapeutics being

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developed by Rubius and nucleic acid vaccines in clinical development by BioNTech and clinical development by Inovio. Therapies that are not specific to HPV are also being explored and applied to HPV+ tumors, including tumor infiltrating lymphocytes developed by Iovance Biotherapeutics and immune checkpoint inhibitors that are approved for treatment in multiple solid tumors.

Government Regulation

The FDA and other regulatory authorities at federal, state, and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, post-approval monitoring, and post-approval reporting of biological product candidates such as those we are developing. We, along with third-party contractors, will be required to navigate the various preclinical, clinical and commercial approval requirements of the governing regulatory agencies of the countries in which we wish to conduct studies or seek approval or licensure of our product candidates. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

U.S. Biologics Regulation

The process required by the FDA before biologic product candidates may be marketed in the United States generally involves the following:

Prior to beginning the first clinical trial with a product candidate in the United States, we must submit an IND to the FDA. An IND is a request for authorization from the FDA to administer an investigational new drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes results of animal and in vitrostudies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the product; chemistry, manufacturing, and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises safety concerns or questions about the proposed clinical trial. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin. Submission of an IND therefore may or may not result in FDA authorization to begin a clinical trial.

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In addition to the submission of an IND to the FDA, supervision of certain human gene transfer trials may also require evaluation and assessment by an institutional biosafety committee, or IBC, a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to the public health or the environment, and such assessment may result in some delay before initiation of a clinical trial.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies performed since the last progress report, among other information, must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

Furthermore, an independent IRB for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site and must monitor the study until completed. Regulatory authorities, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk or that the trial is unlikely to meet its stated objectives. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board, which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. There are also requirements governing the reporting of ongoing clinical studies and clinical study results to public registries.

For purposes of BLA approval, human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved to gain more information about the product. These so-called Phase 4 studies may also be made a condition to approval of the BLA. Concurrent with clinical trials, companies may complete additional animal studies and develop additional information about the biological characteristics of the product candidate and must finalize a process for manufacturing the product in commercial quantities in accordance with cGMP. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, must develop methods for testing the identity, strength, quality and purity of the final product. Additionally, appropriate packaging must be selected and tested and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

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BLA Submission and Review by the FDA

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, nonclinical studies and clinical trials are submitted to the FDA as part of a BLA requesting approval to market the product for one or more indications. The BLA must include all relevant data available from preclinical and clinical studies, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product's chemistry, manufacturing, controls, and proposed labeling, among other things. Data can come from company-sponsored clinical studies intended to test the safety and effectiveness of a use of the product, or from a number of alternative sources, including studies initiated by investigators. The submission of a BLA requires payment of a substantial user fee to FDA, and the sponsor of an approved BLA is also subject to an annual program fee. A waiver of user fees may be obtained under certain limited circumstances. Additionally, no user fees are assessed on BLAs for products designated as orphan drugs, unless the product also includes a non-orphan indication.

Once a BLA has been submitted, within 60 days, the FDA first reviews the BLA to determine if it is substantially complete before the agency accepts it for filing. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the BLA must be resubmitted with the additional information. Once a BLA has been accepted for filing, the FDA's goal is to review standard applications within ten months after the filing date, or, if the application qualifies for priority review, six months after the filing date. Priority review designation will direct overall attention and resources to the evaluation of applications for products that, if approved, would be significant improvements in the safety or effectiveness of the treatment, diagnosis, or prevention of serious diseases or conditions. In both standard and priority reviews, the review process may be significantly extended by FDA requests for additional information or clarification. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facility in which it is manufactured, processed, packed, or held meets standards designed to assure the product's continued safety, purity and potency. The FDA may also convene an advisory committee to provide clinical insight on application review questions. The FDA is not bound by recommendations of an advisory committee, but it considers such recommendations when making decisions regarding approval.

Before approving a BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP. After the FDA evaluates a BLA and conducts inspections of manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A Complete Response Letter will describe all of the deficiencies that the FDA has identified in the BLA, except that where the FDA determines that the data supporting the application are inadequate to support approval, the FDA may issue the Complete Response Letter without first conducting required inspections, testing submitted product lots, and/or reviewing proposed labeling. In issuing the Complete Response Letter, the FDA may recommend actions that the applicant might take to place the BLA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor safety or efficacy of a product.

If regulatory approval or licensure of a product is granted, such approval will be granted for particular indications and may entail limitations on the indicated uses for which such product may be marketed. For example, the FDA may approve the BLA with a Risk Evaluation and Mitigation Strategy, or REMS, to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy to manage a known or potential serious risk associated with a medicine and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries, and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. The FDA may also require one or more Phase 4 post-market studies and surveillance to further assess and monitor the

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product's safety and effectiveness after commercialization, and may limit further marketing of the product based on the results of these post-marketing studies.

Expedited Development and Review Programs

A sponsor may seek approval of its product candidate under programs designed to accelerate FDA's review and approval of new drugs and biological products that meet certain criteria. Specifically, new drugs and biological products are eligible for fast track designation if they are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. For a fast track product candidate, the FDA may consider sections of the BLA for review on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the application, the FDA agrees to accept sections of the application and determines that the schedule is acceptable and the sponsor pays any required user fees upon submission of the first section of the application. A fast track-designated product candidate may also qualify for priority review, under which the FDA sets the target date for FDA action on the BLA at six months after the FDA accepts the application for filing. Priority review is granted when there is evidence that the proposed product would offer a significant improvement in the safety or effectiveness of the treatment, diagnosis or prevention of a serious disease or condition. If criteria are not met for priority review, the application is subject to the standard FDA review period of 10 months after FDA accepts the application for filing.

A product candidate intended to treat a serious or life-threatening disease or condition may also be eligible for breakthrough therapy designation to expedite its development and review. A product candidate can receive breakthrough therapy designation if preliminary clinical evidence indicates that the product candidate may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The designation includes all of the fast track program features, as well as more intensive FDA interaction and guidance beginning as early as Phase 1 and an organizational commitment to expedite the development and review of the product, including involvement of senior managers.

In addition, under the accelerated approval program, the FDA may approve a BLA for a product candidate intended to treat serious or life-threatening diseases or conditions upon a determination that the product candidate has an effect on either a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. Post-marketing studies or completion of ongoing studies after marketing approval are generally required to verify the biologic's clinical benefit in relationship to the surrogate endpoint or ultimate outcome in relationship to the clinical benefit. In addition, the FDA currently requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product. FDA may withdraw approval of a drug or indication approved under accelerated approval on an expedited basis if, for example, the confirmatory trial fails to verify the predicted clinical benefit of the product or if the sponsor fails to conduct such trials in a timely manner

Fast track designation, priority review, accelerated approval and breakthrough therapy designation do not change the standards for approval but may expedite the development or approval process. Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Orphan Drug Designation and Exclusivity

Under the Orphan Drug Act, the FDA may grant orphan designation to a drug or biologic intended to treat a rare disease or condition, defined as a disease or condition with a patient population of fewer than 200,000 individuals in the United States, or a patient population greater than 200,000 individuals in the United States and when there is no reasonable expectation that the cost of developing and making available the drug or biologic in the United States will be recovered from sales in the United States for that drug or biologic. Orphan drug designation must be requested before submitting a BLA. After the FDA grants orphan drug designation, the generic identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA.

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If a product that has orphan drug designation subsequently receives the first FDA approval for a particular active ingredient for the disease for which it has such designation, the product is entitled to orphan product exclusivity, which means that the FDA may not approve any other applications, including a full BLA, to market the same biologic for the same disease or condition for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity or if the FDA finds that the holder of the orphan drug exclusivity has not shown that it can assure the availability of sufficient quantities of the orphan drug to meet the needs of patients with the disease or condition for which the drug was designated. Orphan drug exclusivity does not prevent the FDA from approving a different drug or biologic for the same disease or condition, or the same drug or biologic for a different disease or condition. Among the other benefits of orphan drug designation are tax credits for certain research and a waiver of the BLA application user fee.

A designated orphan drug many not receive orphan drug exclusivity if it is approved for a use that is broader than the indication for which it received orphan designation. In addition, orphan drug exclusive marketing rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or, as noted above, if the second applicant demonstrates that its product is clinically superior to the approved product with orphan exclusivity or the manufacturer of the approved product is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

Post-Approval Requirements

Any products manufactured or distributed by us pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences, periodic reporting, product sampling and distribution, and advertising and promotion of the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing, annual program fees for any marketed products.

Biologic manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP, which impose certain procedural and documentation requirements upon us and our third-party manufacturers. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

The FDA may withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information; imposition of post-market studies or clinical studies to assess new safety risks; or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

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The FDA closely regulates the marketing, labeling, advertising and promotion of biologics. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available products for uses that are not described in the product's labeling and that differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict manufacturer's communications on the subject of off-label use of their products.

Biosimilars and Exclusivity

The Affordable Care Act, or ACA, signed into law in 2010, includes the Biologics Price Competition and Innovation Act, or the BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. The FDA has issued several guidance documents outlining an approach to review and approval of biosimilars. Biosimilarity, which requires that there be no clinically meaningful differences between the biological product and the reference product in terms of safety, purity, and potency, can be shown through analytical studies, animal studies, and a clinical study or studies. Interchangeability requires that a product is biosimilar to the reference product and the product must demonstrate that it can be expected to produce the same clinical results as the reference product in any given patient and, for products that are administered multiple times to an individual, the biologic and the reference biologic may be alternated or switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biologic.

Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first licensed by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a full BLA for the competing product containing that applicant's own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of its product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products. At this juncture, it is unclear whether products deemed "interchangeable" by the FDA will, in fact, be readily substituted by pharmacies, which are governed by state pharmacy law.

A biological product can also obtain pediatric market exclusivity in the United States. Pediatric exclusivity, if granted, adds six months to existing exclusivity periods and patent terms. This six-month exclusivity, which runs from the end of other exclusivity protection or patent term, may be granted based on the voluntary completion of a pediatric study in accordance with an FDA-issued "Written Request" for such a study.

FDA Regulation of Companion Diagnostics

Our product candidates may require use of an in vitrodiagnostic to identify appropriate patient populations. These diagnostics, often referred to as companion diagnostics, are regulated as medical devices. In the United States, the Federal Food, Drug, and Cosmetic Act, or FDCA, and its implementing regulations, and other federal and state statutes and regulations govern, among other things, medical device design and development, preclinical and clinical testing, premarket clearance or approval, registration and listing, manufacturing, labeling, storage, advertising and promotion, sales and distribution, export and import and post-market surveillance. Unless an exemption applies, companion diagnostic tests require marketing clearance or approval from the FDA prior to commercial distribution.

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The two primary types of FDA marketing authorization applicable to a medical device are premarket notification, also called 510(k) clearance, and premarket approval, or PMA.

If use of companion diagnostic is essential to safe and effective use of a drug or biologic product, then the FDA generally will require approval or clearance of the diagnostic contemporaneously with the approval of the therapeutic product. On August 6, 2014, the FDA issued a final guidance document addressing the development and approval process for "In VitroCompanion Diagnostic Devices." According to the guidance, for novel candidates such as our product candidates, a companion diagnostic device and its corresponding drug or biologic candidate should be approved or cleared contemporaneously by FDA for the use indicated in the therapeutic product labeling. The guidance also explains that a companion diagnostic device used to make treatment decisions in clinical trials of a drug generally will be considered an investigational device, unless it is employed for an intended use for which the device is already approved or cleared. If used to make critical treatment decisions, such as patient selection, the diagnostic device generally will be considered a significant risk device under the FDA's Investigational Device Exemption, or IDE, regulations. Thus, the sponsor of the diagnostic device will be required to comply with the IDE regulations. According to the guidance, if a diagnostic device and a drug are to be studied together to support their respective approvals, both products can be studied in the same investigational study, if the study meets both the requirements of the IDE regulations and the IND regulations. The guidance provides that depending on the details of the study plan and subjects, a sponsor may seek to submit an IND alone, or both an IND and an IDE. In July 2016, the FDA issued a draft guidance document intended to further assist sponsors of therapeutic products and sponsors of in vitrocompanion diagnostic devices on issues related to co-development of these products.

The FDA generally requires companion diagnostics intended to select the patients who will respond to cancer treatment to obtain approval of a PMA for that diagnostic contemporaneously with approval of the therapeutic. The review of these in vitrocompanion diagnostics in conjunction with the review of therapeutic candidates such as those we are developing involves coordination of review by the FDA's Center for Drug Evaluation and Research and by the FDA's Center for Devices and Radiological Health. The PMA process, including the gathering of clinical and pre-clinical data and the submission to and review by the FDA, can take several years or longer. It involves a rigorous premarket review during which the applicant must prepare and provide the FDA with reasonable assurance of the device's safety and effectiveness and information about the device and its components regarding, among other things, device design, manufacturing and labeling. PMA applications are also subject to an application fee. In addition, PMAs for certain devices must generally include the results from extensive pre-clinical and adequate and well-controlled clinical trials to establish the safety and effectiveness of the device for each indication for which FDA approval is sought. In particular, for a diagnostic, the applicant must demonstrate that the diagnostic produces reproducible results when the same sample is tested multiple times by multiple users at multiple laboratories. In addition, as part of the PMA review, the FDA will typically inspect the manufacturer's facilities for compliance with the Quality System Regulation, or QSR, which imposes elaborate testing, control, documentation and other quality assurance requirements.

If the FDA evaluations of both the PMA application and the manufacturing facilities are favorable, the FDA will either issue an approval letter or an approvable letter, which usually contains a number of conditions that must be met in order to secure the final approval of the PMA, such as changes in labeling, or specific additional information, such as submission of final labeling, in order to secure final approval of the PMA. If the FDA concludes that the applicable criteria have been met, the FDA will issue a PMA for the approved indications, which can be more limited than those originally sought by the applicant. The PMA can include post-approval conditions that the FDA believes necessary to ensure the safety and effectiveness of the device, including, among other things, restrictions on labeling, promotion, sale and distribution.

If the FDA's evaluation of the PMA or manufacturing facilities is not favorable, the FDA will issue an order denying approval of the PMA or issue a not approvable order. A not approvable letter will outline the deficiencies in the application and, where practical, will identify what is necessary to make the PMA approvable. The FDA may also determine that additional clinical trials are necessary, in which case the PMA approval may be delayed for several months or years while the trials are conducted and then the data submitted in an amendment to the PMA. Once granted, PMA approval may be withdrawn by the FDA if compliance with post approval requirements, conditions of approval or other regulatory standards is not maintained or problems are identified following initial marketing. PMA approval is not guaranteed, and the FDA may ultimately respond to a PMA submission with a not

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approvable determination based on deficiencies in the application and require additional clinical trial or other data that may be expensive and time-consuming to generate and that can substantially delay approval.

After a device is placed on the market, it remains subject to significant regulatory requirements. Medical devices may be marketed only for the uses and indications for which they are cleared or approved. Device manufacturers must also establish registration and device listings with the FDA. A medical device manufacturer's manufacturing processes and those of its suppliers are required to comply with the applicable portions of the QSR, which cover the methods and documentation of the design, testing, production, processes, controls, quality assurance, labeling, packaging and shipping of medical devices. Domestic facility records and manufacturing processes are subject to periodic unscheduled inspections by the FDA. The FDA also may inspect foreign facilities that export products to the United States.

Other Healthcare Laws

Pharmaceutical manufacturers are subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which they conduct their business. Such laws may include, without limitation, the U.S. federal anti-kickback , fraud and abuse, false claims, consumer fraud, pricing reporting,, and transparency laws and regulations as well as similar state and foreign laws in the jurisdictions outside the U.S. Violation of any such laws or any other governmental regulations that apply may result in penalties, including, without limitation, significant administrative, civil and criminal penalties, damages, fines, disgorgement, reputational harm, additional reporting obligations and oversight if we become subject to a corporate integrity agreement or other agreement to resolve allegations of non-compliance with these laws, the curtailment or restructuring of operations and exclusion from participation in governmental healthcare programs and imprisonment.

Coverage and Reimbursement

In the United States and markets in other countries, patients generally rely on third-party payors to reimburse all or part of the costs associated with their treatment. Sales of any pharmaceutical product depend, in part, on the extent to which such product will be covered by third-party payors, such as federal, state and foreign government healthcare programs, commercial insurance and managed healthcare organizations, and the level of reimbursement for such product by third-party payors.

Significant uncertainty exists as to the coverage and reimbursement status of any newly approved product. Adequate coverage and reimbursement from governmental healthcare programs, such as Medicare and Medicaid, and commercial payors are critical to new product acceptance. The availability of coverage and extent of reimbursement by governmental and private payors are essential for most patients to be able to afford treatments. Decisions regarding the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. In the U.S., the Medicare program, which is administered by the Centers for Medicare & Medicaid Services, or CMS, an agency within the U.S. Department of Health and Human Services, or HHS, is increasingly used as a model for how commercial and other governmental payors develop their own coverage and reimbursement policies for new drugs and biologics. One third-party payor's decision to cover a particular product, however, does not ensure that other payors will also provide coverage for the product. As a result, the coverage determination process can require manufactures to provide scientific and clinical support for the use of a product to each payor separately and can be a time-consuming process, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. For products administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such drugs. Additionally, separate reimbursement for the product itself or the treatment or procedure in which the product is used may not be available, which may impact physician utilization. In addition, companion diagnostic tests require coverage and reimbursement separate and apart from the coverage and reimbursement for their companion pharmaceutical or biological products. Similar challenges to obtaining coverage and reimbursement, applicable to pharmaceutical or biological products, will apply to companion diagnostics.

In addition, third-party payors are increasingly reducing reimbursements for pharmaceutical products and services. The U.S. government and state legislatures have continued implementing cost-containment programs, including price controls, restrictions on coverage and reimbursement and requirements for substitution of generic products. Third-party payors are more frequently challenging the prices charged, examining the medical necessity and reviewing the cost-effectiveness of pharmaceutical products and biologics, in addition to questioning their safety and

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efficacy. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit sales of any product. Decreases in third-party reimbursement for any product or a decision by a third-party payor not to cover a product could reduce physician usage and patient demand for the product.

In international markets, reimbursement and healthcare payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies. For example, the European Union provides options for its member states to restrict the range of medicinal products for which their national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. A member state may approve a specific price for the medicinal product or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the medicinal product on the market. Pharmaceutical products may face competition from lower-priced products in foreign countries that have placed price controls on pharmaceutical products and may also compete with imported foreign products. Furthermore, there is no assurance that a product will be considered medically reasonable and necessary for a specific indication, will be considered cost-effective by third-party payors, that an adequate level of reimbursement will be established even if coverage is available or that the third-party payors' reimbursement policies will not adversely affect the ability for manufacturers to sell products profitably. Historically, products launched in the European Union do not follow price structures of the U.S. and generally prices tend to be significantly lower.

Healthcare Reform

In the United States and certain foreign jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes to the healthcare system. In March 2010, the ACA was signed into law, which substantially changed the way healthcare is financed by both governmental and private insurers in the United States. By way of example, the ACA increased the minimum level of Medicaid rebates payable by manufacturers of brand name drugs from 15.1% to 23.1%; required collection of rebates for drugs paid by Medicaid managed care organizations; imposed a non-deductible annual fee on pharmaceutical manufacturers or importers who sell certain "branded prescription drugs" to specified federal government programs, implemented a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted, or injected; expanded eligibility criteria for Medicaid programs; creates a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; and established a Center for Medicare Innovation at CMS to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drug spending.

Since its enactment, there have been judicial, executive and Congressional challenges to certain aspects of the ACA. On June 17, 2021, the United States Supreme Court dismissed the judicial challenge to the ACA without specifically ruling on the constitutionality of the ACA. Prior to the United States Supreme Court's decision, President Biden issued an executive order to initiate a special enrollment period from February 15, 2021 through August 15, 2021 for purposes of obtaining health insurance coverage through the ACA marketplace. The executive order also instructed certain governmental agencies to review and reconsider their existing policies and rules that limit access to healthcare, including among others, reexamining Medicaid demonstration projects and waiver programs that include work requirements, and policies that create unnecessary barriers to obtaining access to health insurance coverage through Medicaid or the ACA. Other legislative changes have been proposed and adopted since the ACA was enacted, including aggregate reductions of Medicare payments to providers of 2% per fiscal year and reduced payments to several types of Medicare providers, which will remain in effect through 2030, with the exception of a temporary suspension from May 1, 2020 through March 31, 2022 and a 1% reduction from April 1, 2022 through June 30, 2022, absent additional Congressional action.

There has also been increasing legislative and enforcement interest in the United States with respect to specialty drug pricing practices. Specifically, there have been several recent U.S. Congressional inquiries and proposed federal and state legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drugs. In addition, individual states in the United States have also become increasingly active in implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures and, in some cases, mechanisms to

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encourage importation from other countries and bulk purchasing. Furthermore, there has been increased interest by third party payors and governmental authorities in reference pricing systems and publication of discounts and list prices Further regulatory changes include passage of the Right to Try Act on May 30, 2018. The law, among other things, provides a federal framework for certain patients to access certain investigational new medical products that have completed a Phase 1 clinical trial and that are undergoing investigation for FDA approval. Under certain circumstances, eligible patients can seek treatment without enrolling in clinical trials and without obtaining FDA permission under the FDA expanded access program. There is no obligation for a pharmaceutical manufacturer to make its drug products available to eligible patients as a result of the Right to Try Act.

Data Privacy and Security Laws

Numerous state, federal and foreign laws, regulations and standards govern the collection, use, access to, confidentiality and security of health-related and other personal information, and could apply now or in the future to our operations or the operations of our partners. In the United States, numerous laws and regulations, including data breach notification laws, health information privacy and security laws and consumer protection laws and regulations govern the collection, use, disclosure, and protection of health-related and other personal information. In addition, certain foreign laws govern the privacy and security of personal data, including health-related data. Privacy and security laws, regulations, and other obligations are constantly evolving, may conflict with each other to complicate compliance efforts, and can result in investigations, proceedings, or actions that lead to significant civil and/or criminal penalties and restrictions on data processing.

Employees and Human Capital Resources

As of December 31, 2021, we had 116 total employees, of which 113 were full-time employees, including 33 employees with M.D. or Ph.D. degrees. Of our full-time employees, 81 employees are engaged in clinical, research and development, product development and quality assurance activities. None of our employees are represented by a labor union or covered by a collective bargaining agreement. We consider our relationship with our employees to be good. We believe our success depends on our ability to attract, retain, develop and motivate highly skilled personnel. In particular, we depend upon the personal efforts and abilities of the principal members of our senior management to partner effectively as a team, and who provide strategic direction, develop our business, manage our operations and maintain a cohesive and stable work environment. We also rely on highly qualified and skilled employees with technical expertise in operations, scientific knowledge, and quality management experience in order to operate our business successfully. Led by our experienced management team, we believe our strong culture and the disciplined execution of our employees will form the foundation of our success.

Available Information

We were incorporated in March 2013 under the laws of the State of Delaware. We file electronically with the SEC our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, proxy statements and other information. Our SEC filings are available to the public over the Internet at the SEC's website at http://www.sec.gov. We make available on our website at www.sqzbiotech.com, free of charge, copies of these reports and any amendments as soon as reasonably practicable after filing or furnishing them with the SEC.

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Item 1A. Risk Factors.

Investing in our common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described below, as well as the other information in this Annual Report on Form 10-K, including our consolidated financial statements and the related notes and "Management's Discussion and Analysis of Results of Operations and Financial Condition," before deciding whether to invest in our common stock. The occurrence of any of the events or developments described below could adversely affect our business, financial condition, results of operations and growth prospects. In such an event, the market price of our common stock could decline, and you may lose all or part of your investment. Additional risks and uncertainties not presently known to us or that we currently deem immaterial also may impair our business operations.

Risks Related to Our Financial Position and Need for Additional Capital

We have a limited operating history and no history of commercializing cell therapy products, which may make it difficult to evaluate the success of our business to date and to assess the prospects for our future viability.

We are a clinical-stage biotechnology company. Our operations to date have been limited to financing and staffing our company, developing our technology, and identifying and developing our product candidates. Our prospects must be considered in light of the uncertainties, risks, expenses, and difficulties frequently encountered by biotechnology companies in their early stages of operations. We have not yet demonstrated an ability to complete any clinical trials, obtain marketing approval, manufacture a commercial scale product, or conduct sales and marketing activities necessary for successful product commercialization, or arrange for third parties to do these activities on our behalf. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and obtaining marketing approval for and commercializing cell therapies.

In addition, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown obstacles. We will eventually need to transition from a company with a research and development focus to a company capable of supporting commercial activities. We may not be successful in this transition.

As we continue to build our business, we expect our financial condition and operating results may fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, you should not rely upon the results of any particular quarterly or annual period as indications of future operating performance.

We have incurred significant losses since inception and expect to incur significant additional losses for the foreseeable future. We have no products that have generated any commercial revenue and we may never achieve or maintain profitability.

We have incurred significant net losses since our inception, including net losses of $68.7 million and $50.5 million for the years ended December 31, 2021 and 2020, respectively. As of December 31, 2021, we had an accumulated deficit of $195.5 million. In addition, we have not commercialized any products and have never generated any revenue from product sales. We have devoted almost all of our financial resources to research and development, including our preclinical development activities and clinical trials of our product candidates.

We expect to continue to incur significant additional operating losses for the foreseeable future as we seek to advance product candidates through preclinical and clinical development, expand our research and development activities, develop new product candidates, complete preclinical studies and clinical trials, seek regulatory approval and, if we receive regulatory approval, commercialize our products. In order to obtain U.S. Food and Drug Administration, or FDA, approval to market any product candidate in the United States, we must submit to the FDA a biologics license application, or BLA, demonstrating that the product candidate is safe, pure and potent with respect to its intended use. This demonstration requires significant research and animal tests, which are referred to as nonclinical or preclinical studies, as well as human tests, which are referred to as clinical trials. Furthermore, the costs of advancing product candidates into each succeeding clinical phase tend to increase substantially over time. The total costs to advance any of our product candidates to marketing approval in even a single jurisdiction would be substantial and difficult to accurately predict. Because of the numerous risks and uncertainties associated with the development of cell therapies, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to begin generating revenue from the commercialization of products or achieve or maintain profitability. Our expenses will also increase substantially if and as we:

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Furthermore, our ability to successfully develop, commercialize and license our products and generate product revenue is subject to substantial additional risks and uncertainties. Each of our product candidates will require additional preclinical and/or clinical development, regulatory approval in multiple jurisdictions, the securing of manufacturing supply, capacity, distribution channels and expertise, the use of external vendors, the building of a commercial organization, substantial investment and significant marketing efforts before we generate any revenue from product sales. As a result, we expect to continue to incur operating losses and negative cash flows for the foreseeable future. These operating losses and negative cash flows have had, and will continue to have, an adverse effect on our stockholders' equity and working capital.

The amount of future losses and when, if ever, we will achieve profitability are uncertain. We have no products that have generated any commercial revenue, do not expect to generate revenues from the commercial sale of products in the foreseeable future, and might never generate revenues from the sale of products. Our ability to generate product revenue and achieve profitability will depend on, among other things, successful completion of the clinical development of our product candidates; obtaining necessary regulatory approvals from the FDA and international regulatory authorities; establishing manufacturing, sales, market acceptance of our products, if approved, and marketing infrastructure to commercialize our product candidates for which we obtain approval; and raising sufficient funds to finance our activities. We might not succeed at any of these undertakings. If we are unsuccessful at some or all of these undertakings, our business, prospects, and results of operations may be materially adversely affected.

We will require significant additional funding in order to complete development of and obtain regulatory approval for our product candidates and commercialize our products, if approved. If we are unable to raise capital when needed, we could be forced to delay, reduce or eliminate our product development programs or commercialization efforts.

We will require additional capital, which we may raise through equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements or other sources. Additional sources of financing might not be available on favorable terms, if at all. If we do not succeed in raising additional funds on acceptable terms, we might be unable to complete planned clinical trials or seek regulatory approvals of any of our product candidates from the FDA, or any foreign regulatory authorities, and could be forced to discontinue product development. In addition, attempting to secure additional financing may divert the time and attention of our management from day-to-day activities and harm our product candidate development efforts.

We will require substantial funds to further develop, seek regulatory approvals for, and if approved, commercialize our product candidates, including SQZ-PBMC-HPV, which is currently in Phase 1 clinical development, SQZ-AAC-HPV, which is currently in Phase 1 clinical development, and SQZ-eAPC-HPV for which an investigational new drug application, or IND, was allowed to proceed by the FDA in January 2022, and all of our other product candidates, which are in preclinical development.

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Based on our current operating plan, we believe that our existing cash and cash equivalents, will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2023. This estimate is based on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect. Changing circumstances could cause us to consume capital significantly faster than we currently anticipate, and we may need to spend more than currently expected because of circumstances beyond our control. Because the length of time and activities associated with successful development of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and our other product candidates is highly uncertain, we are unable to estimate the actual funds we will require for development, approval and any approved marketing and commercialization activities. Our future funding requirements, both near- and long-term, will depend on many factors, including but not limited to:

Depending on our business performance, the economic climate and market conditions, including market volatility resulting from the COVID-19 pandemic or other factors, we may be unable to raise additional funds through any sources. If we are unable to obtain adequate funding on a timely basis, we may be required to curtail or discontinue one or more of our development programs for SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or our other product candidates, or to reduce our operations. If we raise additional funds by issuing equity securities, our then-existing stockholders will experience dilution and the terms of any new equity securities may have preference over those of our existing common stock.

Raising additional capital may cause dilution to our stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

Until such time, if ever, as we can generate substantial revenue from product sales, we may finance our cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. In addition, we may seek additional capital due to favorable market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans.

To the extent that we raise additional capital through the sale of equity or convertible debt securities, our stockholders' ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect their rights as a common stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our operations, our ability to take specific actions, such as incurring additional debt, making capital expenditures, declaring dividends, redeeming our stock, making certain investments and engaging in certain merger, consolidation or asset sale transactions, among other restrictions. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may be required to relinquish valuable rights to our technologies, future

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revenue streams or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

The COVID-19 pandemic has impacted, and will likely continue to impact, our operations and clinical trial execution and may materially and adversely affect our business and financial results in the future.

The COVID-19 pandemic and government measures taken in response have had a significant impact, both direct and indirect, on businesses and commerce. For example, we have intermittently staggered activity at our principal executive offices and laboratory space located in Watertown, Massachusetts in response to government shelter-in-place orders and other restrictive measures. Many of these restrictions have since been eased or lifted in a phased-in approach over time. However, these government policies and directives are subject to change, including that additional, more restrictive orders, proclamations and/or directives may be issued in the future, as the effects and spread of the COVID-19 pandemic continue to evolve.

In response to these public health directives and to help reduce the risk to our employees, we took precautionary measures, including implementing work-from-home policies for our administrative employees and staggered work times for our lab employees. We plan to continue some or all of these measures and are assessing when and how to resume normal operations. The effects of the executive order and our work-from-home policies may negatively impact productivity, disrupt our business and delay our clinical programs and timelines and future clinical trials, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on our ability to conduct our business in the ordinary course. These and similar, and perhaps more severe, disruptions in our operations could negatively impact our business, results of operations and financial condition, including our ability to obtain financing.

Quarantines, shelter-in-place and similar government orders, or the perception that such orders, shutdowns or other restrictions on the conduct of business operations could occur, related to COVID-19 or other infectious diseases have impacted and may continue to impact personnel at third-party manufacturing facilities in the United States and other countries, or the availability or cost of materials, which would disrupt our supply chain. For example, we have experienced delays in receiving supplies of raw materials for our preclinical activities due to the impact of COVID-19 on our suppliers' ability to timely manufacture these materials. In addition, due to the decreased availability of commercial flights, we have had to arrange for private deliveries, including chartered planes, of some of our product candidates, which has resulted in an increase in cost.

In addition, our clinical trials may be affected by the COVID-19 pandemic, including:

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For example, we have experienced delays in opening clinical trial sites and sites that are open may also have challenges enrolling patients due to the COVID-19 pandemic. There has also been an industry-wide slowdown in enrollment in clinical trials due to the COVID-19 pandemic and we cannot predict when enrollment will return to pre-pandemic rates. In addition, some staff that are required to conduct certain testing, such as biopsies, at our clinical sites or at third-party vendors have been required to stay at home or have been reallocated to other activities, resulting in such tests not being performed or being delayed and specimens being of insufficient quantity and quality to be properly evaluated.

The global outbreak of the COVID-19 coronavirus continues to rapidly evolve. The extent to which the COVID-19 coronavirus may impact our business and clinical trials will depend on future developments, which are highly uncertain and cannot be predicted with confidence, such as the ultimate geographic spread of the disease, the duration of the outbreak, travel restrictions and social distancing in the United States and other countries, business closures or business disruptions, reopening plans, the resurgence of COVID-19, and the effectiveness of actions taken in the United States and other countries to contain and treat the disease.

Risks Related to Discovery, Development, Preclinical and Clinical Testing, Manufacturing and Regulatory Approval

Our business is highly dependent on the success of our product candidates, each of which will require significant additional preclinical and clinical testing before we can seek regulatory approval and potentially launch commercial sales. If our product candidates do not receive regulatory approval or are not successfully commercialized, or are significantly delayed in doing so, our business will be harmed.

A substantial portion of our business and future success depends on our ability to develop, obtain regulatory approval for and successfully commercialize our product candidates, including our most advanced product candidates, SQZ-PBMC-HPV, which is currently being evaluated in a Phase 1 clinical trial, as well as SQZ-AAC-HPV, which is currently being evaluated in a Phase 1 clinical trial, and SQZ-eAPC-HPV for which an IND was allowed to proceed by the FDA in January 2022. We currently have no products that are approved for commercial sale and have not completed the development of any product candidates, and we may never be able to develop marketable products. We expect that a substantial portion of our efforts and expenditures over the next few years will be devoted to SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and our other product candidates which will require additional preclinical and clinical development, management of clinical, medical affairs and manufacturing activities, obtaining regulatory approvals in multiple jurisdictions, securing of manufacturing supply, building of a commercial organization, substantial investment and significant marketing efforts before we can generate any revenues from any commercial sales from a product candidate, if approved. We cannot be certain that SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or our other product candidates will be successful in ongoing or future clinical trials, receive regulatory approval or be successfully commercialized even if we receive regulatory approval. Even if we receive approval to market SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and/or our other product candidates from the FDA or other regulatory bodies, we cannot be certain that such product candidates will be successfully commercialized, widely accepted in the marketplace or more effective than other commercially available alternatives. Nor can we be certain that, if and when approved, the safety and efficacy profile of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or our other product candidates will be consistent with the results observed in clinical trials.

If the required regulatory approvals for SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV are not obtained or are significantly delayed, or any approved products are not commercially successful, our business, financial condition and results of operations may be materially harmed.

SQZ-PBMC-HPV, SQZ-AAC-HPV and SQZ-eAPC-HPV are being developed under our SQZ APC, SQZ AAC and SQZ eAPC platforms, respectively, and the failure of any of these products to receive regulatory approval could adversely affect other product candidates being developed under those respective technology platforms. Moreover, if we experience similar regulatory or developmental issues with our other pipeline product candidates, our development plans and business could be significantly harmed. Further, our competitors may be developing products with similar mechanisms of action or treating similar indications and may experience problems with their products that could identify problems that would potentially harm our business.

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Preclinical and clinical development are lengthy and uncertain, and our preclinical programs or development candidates may be delayed or terminated, or may never advance to the clinic, any of which may affect our ability to obtain funding and may have a material adverse impact on our platforms or our business.

Much of our pipeline is in preclinical development, and these programs could be delayed or not advance into the clinic. Before we can initiate clinical trials for a product candidate, we must complete extensive preclinical studies, including in some cases good laboratory practice toxicology testing, that support our planned INDs in the United States, or similar applications in other jurisdictions. We must also complete extensive work on Chemistry, Manufacturing, and Controls, or CMC, activities, including product yield, product purity and product stability data, to be included in the IND submission. We cannot be certain of the timely completion or outcome of our preclinical testing and studies and cannot predict if the FDA or other regulatory authorities will accept the results of our preclinical testing or our proposed clinical programs or if the outcome of our preclinical testing, studies, and CMC activities will ultimately support the further development of our programs. As a result, we cannot be sure that we will be able to submit INDs or similar applications for our preclinical programs on the timelines we expect, if at all, and we cannot be sure that submission of INDs or similar applications will result in the FDA or other regulatory authorities allowing clinical trials to begin.

Further, we may perform preclinical and clinical development activities outside the United States. Conducting preclinical development and clinical trials in foreign countries, as we plan to do for certain of our product candidates, presents additional risks that may delay development of our product candidates or completion of our clinical trials. These risks include availability of and competition for skilled local personnel, the failure of enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, as well as political and economic risks relevant to these foreign countries.

We plan to conduct certain of our clinical trials for our product candidates in sites outside of the United States, including Europe and Asia. However, the FDA and other foreign equivalents may not accept data from foreign trials, in which case our development plans will be delayed, which could materially harm our business.

We may conduct certain of our clinical trials for our product candidates, other pipeline product candidates, or any of our future product candidates outside the United States, such as in Europe and Asia, including China and Taiwan. Although the FDA may accept data from clinical trials conducted outside the United States, acceptance of these data is subject to certain conditions imposed by the FDA. Where data from foreign clinical trials are intended to serve as the basis for marketing approval in the United States, the FDA may not approve the application on the basis of foreign data alone unless those data are applicable to the U.S. population and U.S. medical practice; the trials were performed by clinical investigators of recognized competence; and the data are considered valid without the need for an on-site inspection by the FDA or, if the FDA considers such an inspection to be necessary, the FDA is able to validate the data through an on-site inspection or other appropriate means.

For clinical trials that are conducted only at sites outside of the United States and not subject to an IND, the FDA requires the clinical trial to have been conducted in accordance with the good clinical practice requirements, or GCPs, and the FDA must be able to validate the data from the clinical trial through an on-site inspection if it deems such inspection necessary. There can be no assurance the FDA will accept data from clinical trials conducted outside of the United States. If the FDA does not accept data from our clinical trials of our product candidates, it would likely result in the need for additional clinical trials, which would be costly and time consuming and delay or permanently halt our development of our product candidates.

In addition, there are risks inherent in conducting clinical trials in multiple jurisdictions, inside and outside of the United States, such as:

The successful development of cellular therapeutics, such as the product candidates under our Cell Squeeze technology, is highly uncertain.

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We have no products approved for commercial sale and have not generated any revenue from product sales. Before we are able to generate any revenue from product sales, our current product candidates, and any future product candidates we develop, will require additional preclinical and clinical development, management of clinical, preclinical and manufacturing activities, marketing approval in the United States and other markets, demonstrating effectiveness to pricing and reimbursement authorities, obtaining sufficient manufacturing supply for both clinical development and commercial production, building of a commercial organization and substantial investment and significant marketing efforts. The success of our current and future product candidates will depend on several factors, including:

Because of the numerous risks and uncertainties associated with drug development, we are unable to predict the timing or amount of our expenses, or when we will be able to generate any meaningful revenue or achieve or maintain profitability, if ever. In addition, our expenses could increase beyond our current expectations if we are required by the FDA or foreign regulatory authorities to perform studies in addition to those that we currently anticipate, or if there are any delays in any of our or our future collaborators' clinical trials or the development of any of our product candidates. Even if one or more of our product candidates is approved for commercial sale, we anticipate incurring significant costs associated with commercializing any approved product candidate and ongoing compliance efforts.

Even if we are able to successfully commercialize a product candidate, we may not become profitable, and we will need to obtain additional funding through one or more equity or debt financings in order to continue operations. Revenue from the sale of any product candidate for which regulatory approval is obtained will be dependent, in part, upon the size of the markets in the territories for which we gain regulatory approval, the accepted price for the product, the ability to get reimbursement at any price and whether we own the commercial rights for that territory. If the number of addressable patients is not as significant as we anticipate, the indication approved by regulatory authorities is narrower than we expect, the reasonably accepted population for treatment is narrowed by competition, physician choice or treatment guidelines, or the price and available third-party reimbursement are lower than anticipated, we may not generate significant revenue from sales of such products, even if approved.

Our product candidates are based on a novel technology, which makes it difficult to predict the time and cost of development and of subsequently obtaining regulatory approval, if at all.

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Our Cell Squeeze technology is novel. As such, it is difficult to accurately predict the developmental challenges we may incur for our product candidates as they proceed through product discovery or identification, preclinical studies and clinical trials. In addition, because we are currently conducting a Phase 1 clinical trial of our initial product candidate, SQZ-PBMC-HPV, enrolling patients for a Phase 1 clinical trial for SQZ-AAC-HPV, and we have not commenced clinical trials of any of our other pipeline product candidates, we are continuing to assess the safety of our technology in humans and we have not yet been able to assess the efficacy of our technology in humans and there may be short-term or long-term effects from treatment with any product candidates that we develop that we cannot predict at this time. Also, animal models may not exist for some of the diseases we choose to pursue in our programs. Moreover, even if we obtain data from our clinical trials, because the Cell Squeeze technology applied in our programs is novel and has not been externally verified, our data may be difficult to replicate and/or subject to misinterpretation by us or others. As a result of these factors, it is difficult for us to predict the time and cost of product candidate development, and we cannot predict whether the application of our Cell Squeeze technology, or any similar or competitive cellular technologies, will result in the identification, development and regulatory approval of any products. There can be no assurance that any development challenges we experience in the future related to our Cell Squeeze technology or any of our research programs will not cause significant delays or unanticipated costs, or that such development problems can be solved. Any of these factors may prevent us from completing our preclinical studies or any clinical trials that we may initiate or commercializing any product candidates we may develop on a timely or profitable basis, if at all.

In addition, the clinical study requirements of the FDA and other regulatory authorities and the criteria these regulators use to determine the safety and efficacy of a product candidate vary substantially according to the type, complexity, novelty and intended use as well as market of the potential products. The regulatory approval process for novel product candidates such as ours can be more expensive and take longer than for other, better known or extensively studied therapeutic modalities and approaches. Further, as we are developing novel treatments, there is heightened risk that the FDA or comparable foreign regulatory bodies may not consider the clinical trial endpoints to provide clinically meaningful results, and the resulting clinical data and results may be more difficult to analyze. To date, few cell therapy products have been approved by the FDA or comparable foreign regulatory authorities, which makes it difficult to determine how long it will take or how much it will cost to obtain regulatory approvals for our product candidates in the United States, the European Union, or EU, or other jurisdictions. Further, approvals by one regulatory authority may not be indicative of what other regulatory authorities may require for approval.

Regulatory requirements governing cellular therapy products have evolved and may continue to change in the future. For example, the FDA established the Office of Tissues and Advanced Therapies within its Center for Biologics Evaluation and Research, or CBER, to consolidate the review of cellular therapy and related products, and the Cellular, Tissue and Gene Therapies Advisory Committee to advise CBER on its review. These and other regulatory review agencies, committees and advisory groups and the requirements and guidelines they promulgate may lengthen the regulatory review process, require us to perform additional preclinical studies or clinical trials, increase our development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of these treatment candidates or lead to significant post-approval limitations or restrictions.

We are subject to significant regulatory oversight by the FDA and foreign regulatory bodies in jurisdictions where we may seek to develop or commercialize our products. In addition to these government bodies, the applicable Institutional Biosafety Committee, or IBC, Institutional Review Board, or IRB, and similar cell therapy boards of each institution at which we or our collaborators conduct clinical trials of our product candidates, or a central IRB if appropriate, would need to review and approve the proposed clinical trial.

Changes in applicable regulatory guidelines may lengthen the regulatory review process, require us to perform additional studies or trials, increase our development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of our product candidates or lead to significant post-approval limitations or restrictions. As we advance our product candidates, we will be required to consult with regulatory authorities and comply with applicable guidelines. If we fail to do so, we may be required to delay or discontinue development of such product candidates. These additional processes may result in a review and approval process that is longer than we otherwise would have expected. Delays as a result of an increased or lengthier regulatory approval process or further restrictions on the development of our product candidates can be costly and could negatively impact our ability to complete clinical trials and commercialize our current and future product candidates in a timely manner, if at all.

Cellular therapies are a novel approach and negative perception of any product candidates that we or third parties develop could adversely affect our ability to conduct our business or obtain regulatory approvals for our product candidates.

The developmental and commercial success of our current product candidates, or any product candidates that we develop alone or with collaborators in the future, will depend in part on public acceptance of the use of cell therapy technology, including the candidates we are developing using our Cell Squeeze technology, for the prevention or treatment of human diseases. Adverse public perception of cell therapies may negatively impact our ability to raise capital or enter into strategic agreements for the development of product candidates.

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Cellular therapy remains a novel technology. The commercial success of our cellular therapy product candidates, if successfully developed and approved, may be adversely affected by claims that cellular therapy is unsafe, unethical or immoral. This may lead to unfavorable public perception and the inability of any of our product candidates to gain the acceptance of the public or the medical community. Unfavorable public perceptions may also adversely impact our or our collaborators' ability to enroll clinical trials for our product candidates.

Our success in commercializing any product candidates that receive regulatory approval will depend upon physicians who specialize in the treatment of diseases targeted by our product candidates prescribing treatments that involve the use of our product candidates in lieu of, or in addition to, existing treatments with which they are more familiar and for which greater clinical data may be available. Adverse events in clinical trials of our product candidates or in clinical trials of others developing similar products and the resulting publicity, as well as any other adverse events in the field of cellular therapies, could result in a decrease in demand for any product that we may develop. In addition, responses by the federal, state or foreign governments to negative public perception or ethical concerns may result in new legislation or regulations that could limit our ability to develop or commercialize any product candidates, obtain or maintain regulatory approval or otherwise achieve profitability. More restrictive statutory regimes, government regulations or negative public opinion would have an adverse effect on our business, financial condition, results of operations and prospects and may delay or impair the development and commercialization of our product candidates or demand for any products we may develop.

The regulatory approval processes of the FDA and comparable foreign regulatory authorities are lengthy, expensive, time-consuming, and inherently unpredictable. If we are ultimately unable to obtain regulatory approval for our product candidates, we will be unable to generate product revenue and our business will be seriously harmed.

We are not permitted to commercialize, market, promote or sell any product candidate in the United States without obtaining marketing approval from the FDA. Foreign regulatory authorities impose similar requirements. The time required to obtain approval by the FDA and comparable foreign regulatory authorities is unpredictable, typically takes many years following the commencement of clinical trials and depends upon numerous factors, including the type, complexity and novelty of the product candidates involved. In addition, approval policies, regulations or the type and amount of clinical data necessary to gain approval may change during the course of a product candidate's clinical development and may vary among jurisdictions, which may cause delays in the approval or the decision not to approve an application. Regulatory authorities have substantial discretion in the approval process and may refuse to accept any application or may decide that our data are insufficient for approval and require additional preclinical, clinical or other studies. We have not submitted for or obtained regulatory approval for any product candidate. We must complete additional preclinical or nonclinical studies and clinical trials to demonstrate the safety, purity and potency (or efficacy) of our product candidates in humans to the satisfaction of the regulatory authorities before we will be able to obtain these approvals, and it is possible that none of our existing product candidates or any product candidates we may seek to develop in the future will ever obtain regulatory approval. Applications for our product candidates could fail to receive regulatory approval for many reasons, including but not limited to the following:

This lengthy approval process, as well as the unpredictability of the results of clinical trials, may result in our failing to obtain regulatory approval to market any of our product candidates, which would seriously harm our business. In addition, even if we or our

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collaborators were to obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications than we request, may impose significant limitations in the form of narrow indications, warnings, or a Risk Evaluation and Mitigation Strategy, or REMS. Regulatory authorities may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. In addition, regulatory authorities in the EU may not approve the price we or our collaborators intend to charge for products we may develop. Any of the foregoing scenarios could seriously harm our business.

Our product candidates may be associated with serious adverse events, undesirable side effects or have other properties that could halt their clinical development, prevent their regulatory approval, limit their commercial potential or result in significant negative consequences.

Adverse events or other undesirable side effects caused by our product candidates could cause us or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities.

During the conduct of clinical trials, patients report changes in their health, including illnesses, injuries, and discomforts, to their study doctor. Often, it is not possible to determine whether or not the product candidate being studied caused these conditions. It is possible that as we test our product candidates in larger, longer and more extensive clinical trials, or as use of these product candidates becomes more widespread if they receive regulatory approval, illnesses, injuries, discomforts and other adverse events that were observed in previous trials, as well as conditions that did not occur or went undetected in previous trials, will be reported by patients. Many times, side effects are only detectable after investigational products are tested in large-scale clinical trials or, in some cases, after they are made available to patients on a commercial scale following approval.

If any serious adverse events occur, clinical trials or commercial distribution of any product candidates or products we develop could be suspended or terminated, and our business could be seriously harmed. Treatment-related side effects could also affect patient recruitment and the ability of enrolled patients to complete the trial or result in potential liability claims. Regulatory authorities could order us to cease further development of, deny approval of, or require us to conduct a stock recovery of, cease selling or recall any product candidates or products for any or all targeted indications. If we are required to delay, suspend or terminate any clinical trial or commercialization efforts, the commercial prospects of such product candidates or products may be harmed, and our ability to generate product revenues from them or other product candidates that we develop may be delayed or eliminated. Additionally, if one or more of our product candidates receives marketing approval and we or others later identify undesirable side effects or adverse events caused by such products, a number of potentially significant negative consequences could result, including but not limited to:

Any of these events could prevent us from achieving or maintaining market acceptance of the particular product candidate, if approved, and could seriously harm our business.

Clinical development is lengthy and uncertain. We may encounter substantial delays and costs in our clinical trials or may not be able to conduct or complete our clinical trials on the timelines we expect, if at all.

Clinical testing is expensive, time-consuming and subject to uncertainty. To date, we have not completed any clinical trials for any of our product candidates. We cannot guarantee that any clinical trials will be initiated or conducted as planned or completed on schedule, if at all. We also cannot be sure that submission of an IND or a clinical trial application, or CTA, will result in the FDA, Health Canada, or other regulatory authority, as applicable, allowing clinical trials to begin in a timely manner, if at all. For example,

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the FDA initially placed our IND for SQZ-PBMC-APC on clinical hold, pending receipt of additional data related to sterility testing, which was ultimately removed. Moreover, even if these trials begin, issues may arise that could cause regulatory authorities to suspend or terminate such clinical trials. A failure of one or more clinical trials can occur at any stage of testing, and our future clinical trials may not be successful. Events that may prevent successful or timely initiation or completion of clinical trials include:

In addition, disruptions caused by the COVID-19 pandemic may increase the likelihood that we encounter such difficulties or delays in initiating, enrolling, conducting or completing our planned and ongoing clinical trials. Any inability to successfully initiate or complete clinical trials, or any delay in an ongoing trial, could result in additional costs to us or impair our ability to generate revenue from product sales. For example, certain of the biopsy specimens taken as part of our ongoing clinical trial for SQZ-PBMC-HPV were of insufficient quantity and quality to be properly evaluated due to the impact of COVID-19 on transportation, logistics and staffing at

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our sites and vendors. In addition, if we make manufacturing or formulation changes to our product candidates, we may be required to or we may elect to conduct additional studies to bridge our modified product candidates to earlier versions. Clinical trial delays could also shorten any periods during which our products have patent protection and may allow our competitors to bring products to market before we do, which could impair our ability to successfully commercialize our product candidates and may seriously harm our business.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the data safety monitoring board for such trial or by the FDA or any other regulatory authority, or if the IRBs of the institutions in which such trials are being conducted suspend or terminate the participation of their clinical investigators and sites subject to their review. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial.

Delays in the completion of any clinical trial of our product candidates will increase our costs, slow down our product candidate development and approval process and delay or potentially jeopardize our ability to commence product sales and generate product revenue. In addition, many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates.

The limited number of patients who have the diseases for which some of our product candidates may be studied, or meet the eligibility criteria of our clinical trials, may make it more difficult for us to enroll or complete such clinical studies, or may result in findings in our clinical studies that do not reach levels of statistical significance sufficient for marketing approval.

There may be limited patient pools from which to draw for clinical studies. In addition to the rarity of these diseases, the eligibility criteria of our clinical studies will further limit some of the pool of available study participants as we will require that patients have specific characteristics that we can measure or to assure their disease is either severe enough or not too advanced to include them in a study. We may not be able to initiate or continue clinical trials on a timely basis or at all for any of our product candidates if we or our collaborators are unable to locate and enroll a sufficient number of eligible patients to participate in the trials as required by applicable regulations or as needed to provide appropriate statistical power for a given trial. Similarly, we plan to design and conduct clinical trials utilizing a limited number of patients in order to evaluate the safety and therapeutic activity of our product candidates. Conducting trials in smaller subject populations increases the risk that any safety or efficacy issues observed in only a few patients could prevent such studies from reaching statistical significance or otherwise meeting their specified endpoints, which could require us to conduct additional clinical studies, or delay or prevent our product candidates from receiving regulatory approval, which would seriously harm our business.

In addition, with respect to clinical trials for certain of our product candidates, such as for SQZ-PBMC-HPV, SQZ-AAC-HPV or SQZ-eAPC-HPV, there is substantial overlap between the populations of patients who are or would be eligible to be enrolled. If we conduct clinical trials for two or more of our product candidates simultaneously, either by choice or necessity, any patient enrollment in one of the clinical trials may be obtained at the expense of or to the detriment of patient enrollment in the other.

If we encounter difficulties enrolling patients in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

We may experience difficulties in patient enrollment in our clinical trials for a variety of reasons. The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the trial until its conclusion. The enrollment of patients depends on many factors, including:

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Additionally, disruptions caused by the COVID-19 pandemic may increase the likelihood that we encounter difficulties or delays in initiating or enrolling patients in our planned and ongoing clinical trials. For example, we have experienced delays in opening clinical trial sites and sites that are open may also have challenges enrolling patients due to the COVID-19 pandemic. There has also been an industry-wide slowdown in enrollment in clinical trials due to the COVID-19 pandemic and we cannot predict when enrollment will return to pre-pandemic rates.

In addition, our clinical trials will compete with other clinical trials for product candidates that are in the same therapeutic areas as our product candidates or similar areas, and this competition will reduce the number and types of patients available to us because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. Since the number of qualified clinical investigators is limited, we expect to conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which will reduce the number of patients who are available for our clinical trials at such clinical trial sites.

Delays in patient enrollment may result in increased costs or may affect the timing or outcome of our ongoing and planned clinical trials, which could prevent completion or commencement of these trials and adversely affect our ability to advance the development of our product candidates.

Interim, "topline" and preliminary data from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we may publish interim, "topline" or preliminary data from preclinical studies or clinical trials. Such data and related findings and conclusions are subject to change following more comprehensive reviews of the data related to the particular study or trial. We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. As a result, the results that we report may differ from future results of the same studies, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated. Preliminary or "topline" data also remain subject to audit and verification procedures that may result in the final data being materially different from the preliminary data we previously published. Interim data are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data, and as more patient data become available. As a result, interim, "topline" and preliminary data should be viewed with caution until the final data are available. Additionally, interim data from clinical trials that we may complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available. Adverse differences between preliminary, "topline" or interim data and final data could seriously harm our business.

Further, others, including regulatory authorities, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or weigh the importance of data differently, which could impact the value of the particular program, the approvability or commercialization of the particular product candidate or product and our company in general. In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is the material or otherwise appropriate information to include in our disclosure. Any information we determine not to disclose may ultimately be deemed significant by you or others with respect to future decisions, conclusions, views, activities or otherwise regarding a particular product candidate or our business. If the "topline," preliminary or interim data that we report differ from final results, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and commercialize, product candidates may be harmed, which could seriously harm our business.

We may not be successful in our efforts to identify and successfully develop additional product candidates.

Part of our strategy involves identifying novel product candidates. The process by which we identify product candidates may fail to yield product candidates for clinical development for a number of reasons, including those discussed in these risk factors and also:

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In addition, we may choose to focus our efforts and resources on a potential product candidate that ultimately proves to be unsuccessful, or to license or purchase a marketed product that does not meet our financial expectations. As a result, we may fail to capitalize on viable commercial products or profitable market opportunities, be required to forego or delay pursuit of opportunities with other product candidates or other diseases that may later prove to have greater commercial potential, or relinquish valuable rights to such product candidates through collaboration, licensing or other royalty arrangements in cases in which it would have been advantageous for us to retain sole development and commercialization rights. There may also be substantial overlap in the addressable market of patients which our product candidates, if approved, would be designed to treat. As a result, in order to reduce an overlap, we may seek to commercialize only certain of our product candidates and may forego commercializing other of our product candidates. If we are unable to identify and successfully commercialize additional suitable product candidates, this would adversely impact our business strategy and our financial position.

We may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

Because we have limited financial and managerial resources, we focus on research programs and product candidates that we identify for specific indications. As a result, we may forego or delay pursuit of opportunities with other product candidates or for other indications that later prove to have greater commercial potential. Our resource allocation decisions may cause us to fail to timely capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and product candidates for specific indications may not yield any commercially viable products. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to that product candidate through collaboration, licensing or other royalty arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to such product candidate.

We may seek orphan drug designation for certain product candidates, but we may be unable to obtain such designation or to obtain or maintain the benefits associated with orphan drug designation, including market exclusivity, which may cause our product revenue, if any, to be reduced.

We may seek orphan product designation for some of our product candidates; however, we may never receive such designations. Under the Orphan Drug Act, the FDA may designate a drug or biologic product as an orphan drug if it is intended to treat a rare disease or condition, defined as a patient population of fewer than 200,000 in the United States, or a patient population greater than 200,000 in the United States where there is no reasonable expectation that the cost of developing the drug will be recovered from sales in the United States. Orphan drug designation must be requested before submitting a BLA.

In the United States, orphan drug designation entitles a party to financial incentives such as opportunities for grant funding towards clinical trial costs, tax advantages and application fee waivers. After the FDA grants orphan drug designation, the generic identity of the drug and its potential orphan use are disclosed publicly by the FDA.

In addition, if a product receives the first FDA approval for the indication for which it has orphan designation, the product is entitled to orphan drug exclusivity, which means the FDA may not approve any other application to market the same drug or biologic for the same indication for a period of seven years, except in limited circumstances, such as a showing of clinical superiority over the product with orphan exclusivity or where the manufacturer is unable to assure sufficient product quantity for the orphan patient population. Exclusive marketing rights in the United States may also be unavailable if we or our collaborators seek approval for an indication broader than the orphan designated indication and may be lost if the FDA later determines that the request for designation was materially defective.

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Even if we obtain orphan drug designation, we may not be the first to obtain marketing approval for any particular orphan indication due to the uncertainties associated with developing pharmaceutical products. Further, even if we obtain orphan drug exclusivity for a product candidate, that exclusivity may not effectively protect the product from competition because different drugs can be approved for the same diseases or conditions. Even after an orphan drug is approved, the FDA can subsequently approve the same drug for the same disease or condition if the FDA concludes that the later drug is clinically superior in that it is safer, more effective, or makes a major contribution to patient care. Orphan drug designation neither shortens the development time or regulatory review time of a drug or biologic nor gives the drug or biologic any advantage in the regulatory review or approval process.

Even if we complete the necessary preclinical studies and clinical trials, the marketing approval process is expensive, time-consuming and uncertain and may prevent us or any future collaboration partners from obtaining approvals for the commercialization of any product candidate we develop.

Any product candidate we may develop and the activities associated with their development and commercialization, including their design, testing, manufacture, safety, efficacy, recordkeeping, labeling, storage, approval, advertising, promotion, sale and distribution, are subject to comprehensive regulation by the FDA and other regulatory authorities in the United States and by comparable authorities in other countries. Any product candidates we develop may not be effective, may be only moderately effective, or may prove to have undesirable or unintended side effects, toxicities or other characteristics that may preclude our obtaining marketing approval or prevent or limit commercial use. Failure to obtain marketing approval for a product candidate will prevent us from commercializing the product candidate in a given jurisdiction. Our development programs are early-stage and we have not received approval to market any product candidates from regulatory authorities in any jurisdiction. It is possible that none of the product candidates we are developing or that we may seek to develop in the future will ever obtain regulatory approval. We have no experience in filing and supporting the applications necessary to gain marketing approvals and expect to rely on third-party CROs, suppliers, vendors or regulatory consultants to assist us in this process. Securing regulatory approval requires the submission of extensive preclinical and clinical data and supporting information to the various regulatory authorities for each therapeutic indication to establish the biologic product candidate's safety, purity, efficacy and potency. Securing regulatory approval also requires the submission of information about the product manufacturing process to, and inspection of manufacturing facilities by, the relevant regulatory authority.

Both in the United States and abroad, the process of obtaining marketing approvals, if approval is obtained at all, is expensive, may take many years, especially if additional clinical trials are required and can vary substantially based upon a variety of factors, including the type, complexity and novelty of the product candidates involved. Changes in marketing approval policies during the development period, changes in or the enactment of additional statutes or regulations, or changes in regulatory review for each submitted product application, may cause delays in the approval or rejection of an application. The FDA and comparable authorities in other countries have substantial discretion in the approval process and may refuse to accept any application or may decide that our data are insufficient for approval and require additional preclinical, clinical or other studies. In addition, varying interpretations of the data obtained from preclinical and clinical testing could delay, limit or prevent marketing approval of a product candidate. Any marketing approval we ultimately obtain may be limited or subject to restrictions or post-approval commitments that render the approved product not commercially viable.

If we experience delays in obtaining approval or if we fail to obtain approval of any product candidates we may develop, the commercial prospects for those product candidates may be harmed, and our ability to generate product revenue will be materially impaired.

Even if we obtain FDA approval of any of our product candidates, we may never obtain approval or commercialize such products outside of the United States, which would limit our ability to realize their full market potential.

In order to market any products outside of the United States, we must establish and comply with numerous and varying regulatory requirements of other countries regarding safety and efficacy. Clinical trials conducted in one country may not be accepted by regulatory authorities in other countries, and regulatory approval in one country does not mean that regulatory approval will be obtained in any other country. Approval procedures vary among countries and can involve additional product testing and validation and additional administrative review periods. Seeking foreign regulatory approvals could result in significant delays, difficulties and costs for us and may require additional preclinical studies or clinical trials which would be costly and time-consuming. Regulatory requirements can vary widely from country to country and could delay or prevent the introduction of our products in those countries. Satisfying these and other regulatory requirements is costly, time-consuming, uncertain and subject to unanticipated delays. In addition, our failure to obtain regulatory approval in any country may delay or have negative effects on the process for regulatory approval in other countries. We do not have any product candidates approved for sale in any jurisdiction, including international markets, and we do not have experience in obtaining regulatory approval in international markets. If we fail to comply with regulatory requirements in international markets or to obtain and maintain required approvals, our ability to realize the full market potential of our products will be harmed.

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Even if a current or future product candidate receives marketing approval, it may fail to achieve the degree of market acceptance by physicians, patients, third-party payors and others in the medical community necessary for commercial success.

If any current or future product candidate we develop receives marketing approval, whether as a single agent or in combination with other therapies, it may nonetheless fail to gain sufficient market acceptance by physicians, patients, third-party payors and others in the medical community. For example, current approved immunotherapies, and other cancer treatments like chemotherapy and radiation therapy, are well established in the medical community, and doctors may continue to rely on these therapies. If the product candidates we develop do not achieve an adequate level of acceptance, we may not generate significant product revenues and we may not become profitable. The degree of market acceptance of any product candidate, if approved for commercial sale, will depend on a number of factors, including:

We are developing a product candidate, and in the future may develop other product candidates, in combination with other therapies, which exposes us to additional risks.

SQZ-PBMC-HPV is being evaluated in a Phase 1 clinical trial, patients are being enrolled to evaluate SQZ-AAC-HPV in a Phase 1 clinical trial, and an IND was allowed to proceed by the FDA in January 2022 to evaluate SQZ-eAPC-HPV in clinical trials, and each of these candidates is designed to treat HPV16+ tumors as a monotherapy and in combination with other immune-oncology agents. In the future, we may develop product candidates to be used with one or more currently approved cancer therapies. Even if any product candidate we develop were to receive marketing approval or be commercialized for use in combination with other existing therapies, we would continue to be subject to the risks that the FDA or similar regulatory authorities outside of the United States could revoke approval of the therapy used in combination with our product candidate or that safety, efficacy, manufacturing or supply issues could arise with these existing therapies. Combination therapies are commonly used for the treatment of cancer, and we would be subject to similar risks if we develop any of our product candidates for use in combination with other drugs or for indications other than cancer. This could result in our own products being removed from the market or being less successful commercially.

We may also evaluate our product candidates in combination with one or more other cancer therapies that have not yet been approved for marketing by the FDA or similar regulatory authorities outside of the United States. We will not be able to market any product candidate we develop in combination with any such unapproved cancer therapies that do not ultimately obtain marketing approval.

If the FDA or similar regulatory authorities outside of the United States do not approve these other drugs or revoke their approval of, or if safety, efficacy, manufacturing or supply issues arise with, the drugs we choose to evaluate in combination with any product candidate we develop, we may be unable to obtain approval or subsequent commercial success.

The market opportunities for any current or future product candidate we develop, if and when approved, may be limited to those patients who are ineligible for established therapies or for whom prior therapies have failed, and may be small.

Cancer therapies are sometimes characterized as first-line, second-line or third-line, and the FDA often approves new therapies initially only for third-line use. When cancer is detected early enough, first-line therapy, usually chemotherapy, hormone therapy, surgery, radiation therapy or a combination of these, is sometimes adequate to cure the cancer or prolong life without a cure. Second- and third-line therapies are administered to patients when prior therapy is not effective. We expect to initially seek approval of our oncology product candidates as a therapy for patients who have received one or more prior treatments. Subsequently, for those products that prove to be sufficiently beneficial, if any, we would expect to seek approval potentially as a first-line therapy, but there is no guarantee that product candidates we develop, even if approved, would be approved for first-line therapy, and, prior to any such approvals, we may have to conduct additional clinical trials.

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The number of patients who have the cancers we are targeting may turn out to be lower than expected. Additionally, the potentially addressable patient population for our current programs or future product candidates may be limited, if and when approved. Even if we obtain significant market share for any product candidate, if and when approved, if the potential target populations are small, we may never achieve profitability without obtaining marketing approval for additional indications, including to be used as first- or second-line therapy.

Our investigational products, if approved, may face competition from biosimilars approved through an abbreviated regulatory pathway.

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, or collectively the ACA, includes a subtitle called the Biologics Price Competition and Innovation Act of 2009, or BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-approved reference biological product. Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first approved by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first approved. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a BLA for the competing product containing the sponsor's own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity, and potency of the other company's product.

We believe that any of our investigational products approved as a biological product under a BLA should qualify for the 12-year period of exclusivity. However, there is a risk that this exclusivity could be shortened due to Congressional action or otherwise, or that the FDA will not consider our investigational medicines to be reference products for competing products, potentially creating the opportunity for generic competition sooner than anticipated. Moreover, the extent to which a biosimilar, once approved, will be substituted for any one of our reference products in a way that is similar to traditional generic substitution for non-biological products is not yet clear, and will depend on a number of marketplace and regulatory factors that are still developing.

Disruptions at the FDA and other government agencies caused by funding shortages or global health concerns could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business.

The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, statutory, regulatory and policy changes, the FDA's ability to hire and retain key personnel and accept the payment of user fees, and other events that may otherwise affect the FDA's ability to perform routine functions. Average review times at the FDA have fluctuated in recent years as a result. In addition, funding of other government agencies that finance research and development activities is subject to the political process, which is inherently fluid and unpredictable. Disruptions at the FDA and other agencies may also slow the time necessary for new biologics or modifications to approved or licensed biologics to be reviewed and/or approved by necessary government agencies, which would adversely affect our business.

Separately, in response to the COVID-19 pandemic, in March 2020, the FDA announced its intention to postpone most inspections of foreign manufacturing facilities, and on March 18, 2020, the FDA temporarily postponed routine surveillance inspections of domestic manufacturing facilities. Subsequently, in July 2020, the FDA resumed certain on-site inspections of domestic manufacturing facilities subject to a risk-based prioritization system. The FDA utilized this risk-based assessment system to assist in determining when and where it was safest to conduct prioritized domestic inspections. Additionally, on April 15, 2021, the FDA issued a guidance document in which the FDA described its plans to conduct voluntary remote interactive evaluations of certain drug manufacturing facilities and clinical research sites, among other facilities. According to the guidance, the FDA may request such remote interactive evaluations where the FDA determines that remote evaluation would be appropriate based on mission needs and travel limitations. In May 2021, the FDA outlined a detailed plan to move toward a more consistent state of inspectional operations, and in July 2021, the FDA resumed standard inspectional operations of domestic facilities and was continuing to maintain this level of operation as of September 2021. More recently, the FDA has continued to monitor and implement changes to its inspectional activities to ensure the safety of its employees and those of the firms it regulates as it adapts to the evolving COVID-19 pandemic. Regulatory authorities outside the United States may adopt similar restrictions or other policy measures or reallocate resources in response to the COVID-19 pandemic. If a prolonged government shutdown occurs, or if global health concerns continue to prevent the FDA or other regulatory authorities from conducting their regular inspections, reviews or other regulatory activities, it could significantly impact the ability of the FDA or other regulatory authorities to timely review and process our regulatory submissions, which could have a material adverse effect on our business.

Our insurance policies are expensive and protect us only from some business risks, which leaves us exposed to significant uninsured liabilities.

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We do not carry insurance for all categories of risk that our business may encounter. Some of the policies we currently maintain include general liability, employment practices liability, property, auto, workers' compensation, umbrella, clinical trial, cyber and directors' and officers' insurance.

Any additional product liability insurance coverage we acquire in the future may not be sufficient to reimburse us for any expenses or losses we may suffer. Moreover, insurance coverage is becoming increasingly expensive and in the future we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against losses due to liability. If we obtain marketing approval for SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and/or any of our other product candidates, we intend to acquire insurance coverage to include the sale of commercial products; however, we may be unable to obtain product liability insurance on commercially reasonable terms or in adequate amounts. A successful product liability claim or series of claims brought against us could cause our stock price to decline and, if judgments exceed our insurance coverage, could adversely affect our results of operations and business, including preventing or limiting the development and commercialization of any product candidates we develop. We do not carry specific biological or hazardous waste insurance coverage, and our property, casualty and general liability insurance policies specifically exclude coverage for damages and fines arising from biological or hazardous waste exposure or contamination. Accordingly, in the event of contamination or injury, we could be held liable for damages or be penalized with fines in an amount exceeding our resources, and our clinical trials or regulatory approvals could be suspended.

Operating as a public company has and will continue to make it more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage. As a result, it may be more difficult for us to attract and retain qualified people to serve on our board of directors, our board committees or as executive officers. We do not know, however, if we will be able to maintain existing insurance with adequate levels of coverage. Any significant uninsured liability may require us to pay substantial amounts, which would adversely affect our cash position and results of operations.

Our business and operations may suffer in the event of information technology system failures, cyber-attacks or deficiencies in our cyber-security.

In the ordinary course of our business, we directly or indirectly collect and store sensitive data, including intellectual property, confidential information, preclinical and clinical trial data, proprietary business information and personal information, including health-related information, of our clinical trial subjects and employees, in our data centers and on our networks, or on those of third parties. The secure processing, maintenance and transmission of this information is critical to our operations. However, our information technology systems, as well as those of our CROs and other contractors and consultants, are vulnerable to attack and damage from computer viruses and malware (e.g. ransomware), malicious code, natural disasters (including hurricanes), terrorism, war and telecommunication and electrical failures, hacking, cyberattacks, phishing attacks and other social engineering schemes, employee theft or misuse, human error, fraud, denial or degradation of service attacks, sophisticated nation-state and nation-state-supported actors or unauthorized access or use by persons inside our organization, or persons with access to systems inside our organization. Attacks upon information technology systems are increasing in their frequency, levels of persistence, sophistication and intensity, and are being conducted by sophisticated and organized groups and individuals with a wide range of motives and expertise. As a result of the COVID-19 pandemic, we may also face increased cybersecurity risks due to our reliance on internet technology and the number of our employees who are working remotely, which may create additional opportunities for cybercriminals to exploit vulnerabilities. Furthermore, because the techniques used to obtain unauthorized access to, or to sabotage, systems change frequently and often are not recognized until launched against a target, we may be unable to anticipate these techniques or implement adequate preventative measures. We may also experience security breaches that may remain undetected for an extended period. Even if identified, we may be unable to adequately investigate or remediate incidents or breaches due to attackers increasingly using tools and techniques that are designed to circumvent controls, to avoid detection, and to remove or obfuscate forensic evidence.

We and certain of our service providers are from time to time subject to cyberattacks and security incidents. Although, to our knowledge, we have not experienced any significant system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations, our networks and the information stored there could be accessed, publicly disclosed, lost or stolen and it could result in a material disruption of our product candidate development programs. For example, the loss of preclinical studies or clinical trial data from completed, ongoing or planned studies or trials could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach were to result in a loss of or damage to our data or applications, or inappropriate disclosure of personal, confidential or proprietary information, we could incur liability and the further development of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any other product candidate could be delayed. Any such access, disclosure or other loss of information could also result in legal claims or proceedings, liability under laws that protect the privacy of personal information and significant regulatory penalties. Any such event could disrupt our operations, damage our reputation and cause a loss of confidence in us and our ability to conduct clinical trials, which could adversely affect our business, financial condition, results of operations.

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Risks Related to Healthcare Laws and Other Legal Compliance Matters

We are subject to extensive and costly government regulation.

Product candidates employing our technology are subject to extensive and rigorous domestic government regulation, including regulation by the FDA, the Centers for Medicare & Medicaid Services, or CMS, other divisions of the United States Department of Health and Human Services, the United States Department of Justice, state and local governments, and their respective equivalents outside of the United States. The FDA regulates the research, development, preclinical and clinical testing, manufacture, safety, effectiveness, record-keeping, reporting, labeling, packaging, storage, approval, advertising, promotion, sale, distribution, import and export of pharmaceutical products. If products employing our technologies are marketed abroad, they will also be subject to extensive regulation by foreign governments, whether or not they have obtained FDA approval for a given product and its uses. Such foreign regulation may be equally or more demanding than corresponding United States regulation.

Government regulation substantially increases the cost and risk of researching, developing, manufacturing and selling our products. The regulatory review and approval process, which includes preclinical testing and clinical trials of each product candidate, is lengthy, expensive and uncertain. We or our collaborators must obtain and maintain regulatory authorization to conduct preclinical studies and clinical trials. We or our collaborators must obtain regulatory approval for each product we intend to market, and the manufacturing facilities used for the products must be inspected and meet legal requirements. Securing regulatory approval requires the submission of extensive preclinical and clinical data and other supporting information for each proposed therapeutic indication in order to establish the product's safety and efficacy, potency and purity, for each intended use. The development and approval process takes many years, requires substantial resources, and may never lead to the approval of a product.

Even if we are able to obtain regulatory approval for a particular product, the approval may limit the indicated medical uses for the product, may otherwise limit our ability to promote, sell and distribute the product, may require that we conduct costly post-marketing surveillance, and/or may require that we conduct ongoing post-marketing studies. Material changes to an approved product, such as, for example, manufacturing changes or revised labeling, may require further regulatory review and approval. Once obtained, any approvals may be withdrawn, including, for example, if there is a later discovery of previously unknown problems with the product, such as a previously unknown safety issue.

If we, our collaborators, consultants, CMOs, CROs or other vendors, fail to comply with applicable regulatory requirements at any stage during the regulatory process, such noncompliance could result in, among other things, delays in the approval of applications or supplements to approved applications; refusal of a regulatory authority, including the FDA, to review pending market approval applications or supplements to approved applications; warning letters; fines; import and/or export restrictions; product recalls or seizures; injunctions; total or partial suspension of production; civil penalties; withdrawals of previously approved marketing applications or licenses; recommendations by the FDA or other regulatory authorities against governmental contracts; and/or criminal prosecutions.

Enacted and future healthcare legislation and policies may increase the difficulty and cost for us to obtain marketing approval of and commercialize our product candidates and could adversely affect our business.

In the United States, the EU, Asia and other jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes and proposed changes to the healthcare system that could prevent or delay marketing approval of our products in development, restrict or regulate post-approval activities involving any product candidates for which we obtain marketing approval, impact pricing and reimbursement and impact our ability to sell any such products profitably. In particular, there have been and continue to be a number of initiatives at the U.S. federal and state levels that seek to reduce healthcare costs and improve the quality of healthcare. In addition, new regulations and interpretations of existing healthcare statutes and regulations are frequently adopted.

In March 2010, the ACA was enacted, which substantially changed the way healthcare is financed by both governmental and private insurers. Among the provisions of the ACA, those of greatest importance to the pharmaceutical and biotechnology industries include the following:

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Since its enactment, there have been judicial, Congressional and executive challenges to certain aspects of the ACA. On June 17, 2021, the United States Supreme Court dismissed the judicial challenge to the ACA without specifically ruling on the constitutionality of the ACA. Prior to the United States Supreme Court's decision, President Biden issued an executive order to initiate a special enrollment period from February 15, 2021 through August 15, 2021 for purposes of obtaining health insurance coverage through the ACA marketplace. The executive order also instructed certain governmental agencies to review and reconsider their existing policies and rules that limit access to healthcare, including among others, reexamining Medicaid demonstration projects and waiver programs that include work requirements, and policies that create unnecessary barriers to obtaining access to health insurance coverage through Medicaid or the ACA. It is unclear how other healthcare reform measures under the Biden administration, if any, will impact our business.

In addition, other legislative changes have been proposed and adopted in the United States since the ACA was enacted. In August 2011, the Budget Control Act of 2011 resulted in aggregate reductions of Medicare payments to providers of 2% per fiscal year, which went into effect in April 2013 and, due to subsequent legislative amendments to the statute, will remain in effect through 2030, with the exception of a temporary suspension from May 1, 2020 through March 31, 2022 and a 1% reduction from April 1, 2022 through June 30, 2022, unless additional action is taken by Congress. In January 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, further reduced Medicare payments to several types of providers, including hospitals, imaging centers and cancer treatment centers, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. Additionally, the orphan drug tax credit was reduced as part of a broader tax reform. These new laws or any other similar laws introduced in the future may result in additional reductions in Medicare and other healthcare funding, which could negatively affect our customers and accordingly, our financial operations.

Moreover, payment methodologies may be subject to changes in healthcare legislation and regulatory initiatives. For example, CMS may develop new payment and delivery models, such as outcomes-based reimbursement. In addition, recently there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several U.S. Congressional inquiries and proposed and enacted federal legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, and review the relationship between pricing and manufacturer patient programs. We expect that additional U.S. federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the U.S. federal government will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures.

Individual states in the United States have also increasingly passed legislation and implemented regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Legally mandated price controls on payment amounts by third-party payors or other restrictions could harm our business, results of operations, financial condition and prospects. In addition, regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other healthcare programs. This could reduce the ultimate demand for our product candidates or put pressure on our product pricing.

In the EU, similar political, economic and regulatory developments may affect our ability to profitably commercialize our product candidates, if approved. In addition to continuing pressure on prices and cost containment measures, legislative developments at the EU or member state level may result in significant additional requirements or obstacles that may increase our operating costs. The delivery of healthcare in the EU, including the establishment and operation of health services and the pricing and reimbursement of

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medicines, is almost exclusively a matter for national, rather than EU, law and policy. National governments and health service providers have different priorities and approaches to the delivery of healthcare and the pricing and reimbursement of products in that context. In general, however, the healthcare budgetary constraints in most EU member states have resulted in restrictions on the pricing and reimbursement of medicines by relevant health service providers. Coupled with ever-increasing EU and national regulatory burdens on those wishing to develop and market products, this could prevent or delay marketing approval of our product candidates, restrict or regulate post-approval activities and affect our ability to commercialize our product candidates, if approved.

In Asia, comprehensive government regulation and supervision, encompassing the approval, registration, manufacturing, packaging, licensing and marketing of new drugs, could also affect our ability to receive marketing approval or commercialize our product candidates. For example, in order to conduct a clinical trial in China, sponsors must not only obtain the approval of the National Medical Product Administration of China, but also a separate approval from or filing with the Ministry of Science and Technology under the HGR Regulation for clinical trials involving HGR Materials or Information. Any failure to comply with these requirements could cause a clinical trial to be suspended by governing authorities and may result in fines. In recent years, the regulatory framework in Asia regarding the pharmaceutical industry has undergone significant changes, and we expect that it will continue to undergo significant changes, which may prevent or delay marketing approval of our product candidates, restrict or regulate post-approval activities and affect our ability to commercialize our product candidates, if approved.

In markets outside of the United States, the EU, and Asia, reimbursement and healthcare payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies.

In addition, legislative and regulatory proposals have been made to expand post-approval requirements and restrict sales and promotional activities for pharmaceutical products. We cannot be sure whether additional legislative changes will be enacted, or whether the FDA's regulations, guidance or interpretations will be changed, or what the impact of such changes on the marketing approvals of our product candidates, if any, may be. In addition, increased scrutiny by the U.S. Congress of the FDA's approval process may significantly delay or prevent marketing approval, as well as subject us to more stringent product labeling and post-marketing testing and other requirements.

We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action in the United States, the EU, Asia or any other jurisdiction. If we or any third parties we may engage are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we or such third parties are not able to maintain regulatory compliance, our product candidates may lose any regulatory approval that may have been obtained and we may not achieve or sustain profitability.

Even if we obtain regulatory approval for a product candidate, our products will remain subject to regulatory scrutiny and post-marketing requirements.

If one of our product candidates is approved, it will be subject to ongoing regulatory requirements for manufacturing, labeling, packaging, storage, advertising, promotion, sampling, record-keeping, conduct of post-marketing studies and submission of safety, efficacy, and other post- market information, including both federal and state requirements in the United States and requirements of comparable foreign regulatory authorities. Manufacturers and manufacturers' facilities are required to comply with extensive FDA and comparable foreign regulatory authority requirements, including ensuring that quality control and manufacturing procedures conform to current good manufacturing practice, or cGMP, regulations. As such, we and our contract manufacturers will be subject to continual review and inspections to assess compliance with cGMP and adherence to commitments made in any approved marketing application. Accordingly, we and others with whom we work must continue to expend time, money and effort in all areas of regulatory compliance, including manufacturing, production and quality control.

We will also have to comply with requirements concerning advertising and promotion for our products. Promotional communications with respect to prescription drugs and biologics are subject to a variety of legal and regulatory restrictions and must be consistent with the information in the product's approved label. As such, we may not promote our products "off-label" for indications or uses for which they do not have approval, though we may share truthful and not misleading information that is otherwise consistent with our product's FDA approved labeling. The holder of an approved application, such as a BLA, must submit new or supplemental applications and obtain approval for certain changes to the approved product, product labeling or manufacturing process. We could also be asked to conduct post-marketing clinical studies to verify the safety and efficacy of our products in general or in specific patient subsets. An unsuccessful post-marketing study or failure to complete such a study could result in the withdrawal of marketing approval or label restrictions.

If the FDA or another regulatory authority discovers previously unknown problems with a product, such as adverse events of unanticipated severity or frequency, or problems with the facility where the product is manufactured, or disagrees with the promotion, marketing or labeling of a product, such regulatory authorities may impose restrictions on that product or us, including requiring

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withdrawal of the product from the market. If we fail to comply with applicable regulatory requirements, a regulatory authority or enforcement authority may, among other things:

Any government investigation of alleged violations of law could require us to expend significant time and resources in response and could generate negative publicity. Any failure to comply with ongoing regulatory requirements may adversely affect our ability to commercialize and generate revenue from our products. If regulatory sanctions are applied or if regulatory approval is withdrawn, our business will be seriously harmed.

Moreover, the policies of the FDA and of other regulatory authorities may change, and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the United States or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained and we may not achieve or sustain profitability.

Our business operations and current and future relationships with investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers are and will be subject to applicable healthcare regulatory laws, which could expose us to penalties.

Our business operations and current and future arrangements with investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers, may expose us to broadly applicable fraud and abuse and other healthcare laws and regulations. These laws may constrain the business or financial arrangements and relationships through which we conduct our operations, including how we research, market, sell and distribute our product candidates, if approved. Such laws include:

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Ensuring that our internal operations and future business arrangements with third parties comply with applicable healthcare laws and regulations will involve substantial costs. It is possible that governmental authorities will conclude that our business practices, including our relationships with physicians and other healthcare providers, may not comply with current or future statutes, regulations, agency guidance or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of the laws described above or any other governmental laws and regulations that may apply to us, we may be subject to significant penalties, including civil, criminal and administrative penalties, damages, fines, exclusion from government-funded healthcare programs, such as Medicare and Medicaid or similar programs in other countries or jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, disgorgement, individual imprisonment, contractual damages, reputational harm, diminished profits and the curtailment or restructuring of our operations. If any of the physicians or other providers or entities with whom we expect to do business are found to not be in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs and imprisonment, which could affect our ability to operate our business. Further, defending against any such actions can be costly, time-consuming and may require significant personnel resources. Therefore, even if we are successful in defending against any such actions that may be brought against us, our business may be impaired.

We are subject to applicable data privacy, protection and security laws, regulations, standards and other requirements, and our actual or perceived failure to comply with such obligations could harm our business, results of operations and financial condition.

We are subject to diverse laws and regulations relating to data privacy and security, including in the United States, in the EU and the European Economic Area, or EEA, and in Asia. New privacy rules are being enacted in the United States and globally, and existing ones are being updated and strengthened. In the United States, HIPAA as amended by the Health Information Technology for

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Economic and Clinical Health Act of 2009, and regulations promulgated thereunder, or collectively, HIPAA, imposes, among other things, certain standards relating to the privacy, security, transmission and breach reporting of individually identifiable health information. Most healthcare providers, including research institutions from which we obtain patient health information, are subject to privacy and security regulations promulgated under HIPAA. While we do not believe we are currently classified as a covered entity or business associate under HIPAA and thus are not directly regulated under HIPAA, any person may be prosecuted under HIPAA's criminal provisions either directly or under aiding-and-abetting or conspiracy principles. Consequently, depending on the facts and circumstances, we could face substantial criminal penalties if we knowingly receive individually identifiable health information from a HIPAA-covered healthcare provider or research institution that has not satisfied HIPAA's requirements for disclosure of individually identifiable health information. In addition, we may maintain sensitive personally identifiable information, including health information, that we receive throughout the clinical trial process, in the course of our research collaborations, and directly from individuals (or their healthcare providers) who enroll in our patient assistance programs. As such, we may be subject to state laws requiring notification of affected individuals and state regulators in the event of a breach of personal information, which is a broader class of information than the health information protected by HIPAA. Moreover, patients about whom we or our collaborators obtain health-related information, as well as the providers who share this information with us, may have statutory or contractual rights that limit our ability to use and disclose the information. We may be required to expend significant capital and other resources to ensure ongoing compliance with applicable privacy and data security laws. Claims that we have violated individuals' privacy rights or breached our contractual obligations, even if we are not found liable, could be expensive and time-consuming to defend and could result in adverse publicity that could harm our business.

Certain states have also adopted comparable privacy and security laws and regulations, which govern the privacy, processing and protection of health-related and other personal information. Such laws and regulations will be subject to interpretation by various courts and other governmental authorities, thus creating potentially complex compliance issues for us and our future customers and strategic partners. For example, the California Consumer Privacy Act, or CCPA, took effect on January 1, 2020. The CCPA creates individual privacy rights for California consumers and increases the privacy and security obligations of entities handling certain personal information. The CCPA provides for civil penalties for violations, as well as a private right of action for data breaches that is expected to increase data breach litigation. Further, the California Privacy Rights Act, or CPRA, recently passed in California. The CPRA significantly amends the CCPA and will impose additional data protection obligations on covered businesses, including additional consumer rights processes, limitations on data uses, new audit requirements for higher risk data, and opt outs for certain uses of sensitive data. It will also create a new California data protection agency authorized to issue substantive regulations and could result in increased privacy and information security enforcement. The majority of the provisions will go into effect on January 1, 2023, and additional compliance investment and potential business process changes may be required. Similar laws have passed in Virginia and Colorado, and have been proposed in other states and at the federal level, reflecting a trend toward more stringent privacy legislation in the United States. The enactment of such laws could have potentially conflicting requirements that would make compliance challenging. In the event that we are subject to or affected by HIPAA, the CCPA, the CPRA or other domestic privacy and data protection laws, any liability from failure to comply with the requirements of these laws could adversely affect our financial condition.

Our activities outside the United States impose additional compliance requirements and generate additional risks of enforcement for noncompliance. Our clinical trial programs outside the United States may implicate international data protection laws, including the General Data Protection Regulation, or GDPR, and legislation of the EU member states implementing it. Certain health privacy laws, data breach notification laws, consumer protection laws and genetic testing laws may apply directly to our operations and/or those of our collaborators and may impose restrictions on our collection, use and dissemination of individuals' health information. In Europe, the GDPR went into effect in May 2018 and imposes strict requirements for processing the personal data of individuals within the EEA. If we do not comply with our obligations under the GDPR, we could be exposed to fines of up to the greater of €20 million or up to 4% of our total global annual revenue in the event of a significant breach or non-compliance. In addition, we may be the subject of litigation and/or adverse publicity, which could adversely affect our business, results of operations and financial condition. Among other requirements, the GDPR regulates transfers of personal data subject to the GDPR to third countries that have not been found to provide adequate protection to such personal data, including the United States; in July 2020, the Court of Justice of the EU, or CJEU, limited how organizations could lawfully transfer personal data from the EU/EEA to the United States by invalidating the Privacy Shield for purposes of international transfers and imposing further restrictions on the use of standard contractual clauses, or SCCs. The European Commission issued revised SCCs on June 4, 2021 to account for the decision of the CJEU and recommendations made by the European Data Protection Board. The revised SCCs must be used for relevant new data transfers from September 27, 2021; existing standard contractual clauses arrangements must be migrated to the revised clauses by December 27, 2022. The new SCCs apply only to the transfer of personal data outside of the EEA and not the United Kingdom, or the UK; the UK's Information Commissioner's Office launched a public consultation on its draft revised data transfers mechanisms in August 2021 and laid its proposal before Parliament, with the UK SCCs expected to come into force in March 2022, with a two-year grace period. There is some uncertainty around whether the revised clauses can be used for all types of data transfers, particularly whether they can be relied on for data transfers to non-EEA entities subject to the GDPR. As supervisory authorities issue further guidance on personal data export mechanisms, including circumstances where the SCCs cannot be used, and/or start taking enforcement action, we could suffer

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additional costs, complaints and/or regulatory investigations or fines, and/or if we are otherwise unable to transfer personal data between and among countries and regions in which we operate, it could affect the manner in which we provide our services, the geographical location or segregation of our relevant systems and operations, and could adversely affect our financial results.

Further, from January 1, 2021, we have had to comply with the GDPR and also the UK GDPR, which, together with the amended UK Data Protection Act 2018, retains the GDPR in UK national law. The UK GDPR mirrors the fines under the GDPR, i.e., fines up to the greater of €20 million (£17.5 million) or 4% of global turnover. The relationship between the UK and the EU in relation to certain aspects of data protection law remains unclear, and it is unclear how United Kingdom data protection laws and regulations will develop in the medium to longer term. The European Commission has adopted an adequacy decision in favor of the UK, enabling data transfers from EU member states to the UK without additional safeguards. However, the UK adequacy decision will automatically expire in June 2025 unless the European Commission re-assesses and renews or extends that decision.

Furthermore, in Asia, some countries are implementing or considering GDPR-like data protection laws. For example, in China, on June 10, 2021, the Standing Committee of the PRC National People's Congress published the Data Security Law of the People's Republic of China, or the Data Security Law, which took effect on September 1, 2021. The Data Security Law requires data processing (which includes the collection, storage, use, processing, transmission, provision and publication of data), to be conducted in a legitimate and proper manner. The Data Security Law imposes data security and privacy obligations on entities and individuals carrying out data processing activities and also introduces a data classification and hierarchical protection system based on the importance of data in economic and social development and the degree of harm it may cause to national security, public interests, or legitimate rights and interests of individuals or organizations if such data are tampered with, destroyed, leaked, illegally acquired or illegally used. The appropriate level of protection measures is required to be taken for each respective category of data.

Also in China, on August 20, 2021, the Standing Committee of the National People's Congress of the PRC promulgated the Personal Information Protection Law, which took effect on November 1, 2021. The Personal Information Protection Law raises the protection requirements for processing personal information, and many specific requirements of the Personal Information Protection Law remain to be clarified. We may be required to make further significant adjustments to our business practices to comply with the personal information protection laws and regulations in China, including the Personal Information Protection Law, or in other jurisdictions in Asia.

Although we work to comply with applicable laws, regulations and standards, our contractual obligations and other legal obligations, these requirements are evolving and may be modified, interpreted and applied in an inconsistent manner from one jurisdiction to another, and may conflict with one another or other legal obligations with which we must comply. Further, if we or third-party CMOs, CROs or other contractors or consultants fail to comply with applicable federal, state or local regulatory requirements, we could be subject to a range of regulatory actions that could affect our or our contractors' ability to develop and commercialize our product candidates and could harm or prevent sales of any affected products that we are able to commercialize, or could substantially increase the costs and expenses of developing, commercializing and marketing our products. Any failure or perceived failure by us or our employees, representatives, CMOs, CROs, contractors, consultants, collaborators, or other third parties to comply with data privacy and security requirements or adequately address privacy and security concerns, even if unfounded, could result in additional cost and liability to us, damage our reputation, and adversely affect our business and results of operations.

We are subject to environmental, health and safety laws and regulations, and we may become exposed to liability and substantial expenses in connection with environmental compliance or remediation activities.

Our operations, including our development, testing and manufacturing activities, are subject to numerous environmental, health and safety laws and regulations. These laws and regulations govern, among other things, the controlled use, handling, release and disposal of and the maintenance of a registry for, hazardous materials and biological materials, such as chemical solvents, human cells, carcinogenic compounds, mutagenic compounds and compounds that have a toxic effect on reproduction, laboratory procedures and exposure to blood-borne pathogens. If we fail to comply with such laws and regulations, we could be subject to fines or other sanctions.

As with other companies engaged in activities similar to ours, we face a risk of environmental liability inherent in our current and historical activities, including liability relating to releases of or exposure to hazardous or biological materials. Environmental, health and safety laws and regulations are becoming more stringent. We may be required to incur substantial expenses in connection with future environmental compliance or remediation activities, in which case, the production efforts of our third-party manufacturers or our development efforts may be interrupted or delayed.

We and our employees are increasingly utilizing social media tools as a means of communication both internally and externally.

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Despite our efforts to monitor evolving social media communication guidelines and comply with applicable rules, there is risk that the use of social media by us or our employees to communicate about our product candidates or business may cause us to be found in violation of applicable requirements. In addition, our employees may knowingly or inadvertently make use of social media in ways that may not comply with applicable laws and regulations, our policies and other legal or contractual requirements, which may give rise to regulatory enforcement action, liability, lead to the loss of trade secrets or other intellectual property or result in public exposure of personal information of our employees, clinical trial patients, customers and others. Furthermore, negative posts or comments about us or our product candidates in social media could seriously damage our reputation, brand image and goodwill. Any of these events could have a material adverse effect on our business, prospects, operating results and financial condition and could adversely affect the price of our common stock.

Changes in tax laws may impact our future financial position and results of operations.

New income, sales, use or other tax laws, statutes, rules, regulations or ordinances could be enacted at any time, or interpreted, changed, modified or applied adversely to us, any of which could adversely affect our business operations and financial performance. For example, the United States government may enact significant changes to the taxation of business entities including, among others, a permanent increase in the corporate income tax rate and the imposition of minimum taxes or surtaxes on certain types of income. In particular, in connection with the 2022 U.S. federal budget reconciliation, U.S. Congressional committees have proposed changes to tax law that could result in additional federal income taxes being imposed on us. Furthermore, for tax years beginning after December 31, 2021, the Tax Cuts and Jobs Act of 2017 eliminates the once available option to deduct research and development expenditures currently and requires taxpayers to amortize them over five years. The U.S. Congress is considering legislation that would defer the amortization requirement to future periods. We are currently unable to predict whether such changes will occur and, if so, the ultimate impact on us or our business. To the extent that such changes have a negative impact on us or our business, these changes may materially and adversely impact our financial condition, results of operations and cash flows.

Risks Related to Commercialization

Developments by competitors may render our products or technologies obsolete or non-competitive or may reduce the size of our markets.

Our industry has been characterized by extensive research and development efforts, rapid developments in technologies, intense competition and a strong emphasis on proprietary products. We face potential competition from many different sources, including pharmaceutical, biotechnology and specialty pharmaceutical companies either marketing or developing cell therapies or biologic or small molecule modalities for patients with cancer and other serious diseases. Academic research institutions, governmental agencies and public and private institutions are also potential sources of competitive products and technologies. Our competitors may have or may develop superior technologies or approaches, which may provide them with competitive advantages. Many of these competitors may also have compounds already approved or in development in the therapeutic categories that we are targeting with our current and future product candidates. In addition, many of these competitors, either alone or together with their collaborative partners, may operate larger research and development programs or have substantially greater financial resources than we do, as well as greater experience in:

If these competitors access the marketplace before we do with safer, more effective, or less expensive therapeutics, our product candidates, if approved for commercialization, may not be profitable to sell or worthwhile to continue to develop. Technology in the pharmaceutical industry has undergone rapid and significant change, and we expect that it will continue to do so. Any compounds, products or processes that we develop may become obsolete or uneconomical before we recover any expenses incurred in connection with their development. The success of our product candidates will depend upon factors such as product efficacy, safety, reliability, availability, timing, scope of regulatory approval, acceptance and price, among other things. Other important factors to our success include speed in developing product candidates, completing clinical development and laboratory testing, obtaining regulatory approvals and manufacturing and selling commercial quantities of potential products.

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Our product candidates are intended to compete directly or indirectly with existing products and products currently in development. Even if approved and commercialized, our product candidates may fail to achieve market acceptance with hospitals, physicians or patients. Hospitals, physicians or patients may conclude that our potential products are less safe or effective or otherwise less attractive than these existing drugs. If our product candidates do not receive market acceptance for any reason, our revenue potential would be diminished, which would materially adversely affect our ability to become profitable.

Significant competition additionally exists in the treatment of cancer and other serious diseases for which we are developing our cell therapies. We will need to compete with all currently available or future therapies within the indications where our development is focused. SQZ-PBMC-HPV, SQZ-AAC-HPV and SQZ-eAPC-HPV, if approved and commercialized, will face significant competition with other product candidates for the treatment of HPV+ cancers. While there are currently no FDA-approved therapies that target HPV for HPV+ cancers, there are multiple competing clinical-stage product candidates in development targeting HPV+ cancers. These product candidates include genetically modified T cell therapies in clinical development, peptide vaccines in clinical development, and nucleic acid vaccines in clinical development. Therapies that are not specific to HPV are also being explored and applied to HPV+ tumors, including tumor infiltrating lymphocytes and immune checkpoint inhibitors that are approved for treatment in multiple solid tumors.

In addition, we generally expect to compete with companies using other cell engineering approaches, such as electroporation and viral vectors, including a biotechnology company that is genetically engineering red blood cells, a biotechnology company that is programing hematopoietic cells and other biotechnology companies working on single cell types. In addition, we also expect to compete more generally with companies developing biologic or small molecule modalities.

Many of our competitors have substantially greater capital resources, robust product candidate pipelines, established presence in the market and expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement and marketing approved products than we do. As a result, our competitors may achieve product commercialization or patent protection earlier than we can. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These competitors also compete with us in recruiting and retaining qualified clinical, regulatory, scientific, sales, marketing and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient, or are less expensive than any products that we may develop or that would render any products that we may develop obsolete or noncompetitive.

The successful commercialization of our product candidates will depend in part on the extent to which governmental authorities and health insurers establish coverage, adequate reimbursement levels and pricing policies. Failure to obtain or maintain coverage and adequate reimbursement for our product candidates, if approved, could limit our ability to market those products and decrease our ability to generate product revenue.

There is significant uncertainty related to the insurance coverage and reimbursement of newly approved products. In the United States, third-party payors, including private and governmental payors, such as the Medicare and Medicaid programs, play an important role in determining the extent to which new drugs and biologics will be covered. Our ability to successfully commercialize our product candidates will depend in part on the extent to which coverage and adequate reimbursement for these products and related treatments will be available from government health administration authorities, private health insurers and other organizations. Government authorities and other third-party payors, such as private health insurers and health maintenance organizations, decide which medications they will pay for and establish reimbursement levels. The availability of coverage and extent of reimbursement by governmental and private payors is essential for most patients to be able to afford treatments. The Medicare and Medicaid programs increasingly are used as models in the United States for how private payors and other governmental payors develop their coverage and reimbursement policies for drugs and biologics. Some third-party payors may require pre-approval of coverage for new or innovative drug therapies before they will reimburse healthcare providers who use such therapies. We cannot predict at this time what third-party payors will decide with respect to the coverage and reimbursement for our product candidates.

Third-party payors increasingly are challenging prices charged for pharmaceutical products and services, and many third-party payors may refuse to provide coverage and reimbursement for particular drugs and biologics when an equivalent generic drug, biosimilar or a less expensive therapy is available. It is possible that a third-party payor may consider our product candidates as substitutable and only offer to reimburse patients for the less expensive product.

For products administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such drugs. Even if we show improved efficacy or improved convenience of administration with our product candidates, pricing of existing third-party therapeutics may limit the amount we will be able to charge for our product candidates. These payors may deny or revoke the reimbursement status of a given product or establish prices

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for new or existing marketed products at levels that are too low to enable us to realize an appropriate return on our investment in our product candidates. If reimbursement is not available or is available only at limited levels, we may not be able to successfully commercialize our product candidates and may not be able to obtain a satisfactory financial return on our product candidates.

In the United States, third-party payors, including private and governmental payors, such as the Medicare and Medicaid programs, play an important role in determining the extent to which new drugs and biologics will be covered and reimbursed. The Medicare program is increasingly used as a model for how private and other governmental payors develop their coverage and reimbursement policies for new drugs. However, no uniform policy for coverage and reimbursement for products exists among third-party payors in the United States. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our product candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. Furthermore, rules and regulations regarding reimbursement change frequently, in some cases on short notice, and we believe that changes in these rules and regulations are likely.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in the EU and other jurisdictions have and will continue to put pressure on the pricing and usage of our product candidates. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medical products, but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the United States, the reimbursement for our product candidates may be reduced compared with the United States and may be insufficient to generate commercially reasonable revenue and profits.

Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. We expect to experience pricing pressures in connection with the sale of our product candidates due to the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative changes. The downward pressure on healthcare costs in general, particularly prescription drugs and biologics and surgical procedures and other treatments, has become intense. As a result, increasingly high barriers are being erected to the entry of new products.

If we are unable to establish sales, marketing and distribution capabilities either on our own or in collaboration with third parties, we may not be successful in commercializing our product candidates, if approved, and we may not be able to generate any product revenue.

We do not have any infrastructure for the sales, marketing or distribution of our products, and the cost of establishing and maintaining such an organization may exceed the cost-effectiveness of doing so.

We may build our own focused sales, distribution and marketing infrastructure to market SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV and our other product candidates, if approved, in the United States and other markets around the world. There are significant expenses and risks involved with establishing our own sales, marketing and distribution capabilities, including our ability to hire, retain and appropriately incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities could delay any product launch, which would adversely impact the commercialization of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates, if approved. Additionally, if the commercial launch of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

Factors that may inhibit our efforts to commercialize our product candidates on our own include:

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We may not have the resources in the foreseeable future to allocate to the sales and marketing of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV, any of our other pipeline product candidates or any future product candidates in the United States or in markets outside of the United States. Therefore, our future sales in these markets may largely depend on our ability to enter into and maintain collaborative relationships for such capabilities, the collaborator's strategic interest in the product and such collaborator's ability to successfully market and sell the product. For example, in October 2018, we entered into the Roche License and Collaboration Agreement, or the Roche Agreement, under which we are collaborating with Roche in the development and commercialization of certain antigen products, including SQZ-PBMC-HPV, and tumor cell lysate products in accordance with mutually agreed upon collaboration plans.

If we are unable to build our own sales force or access a collaborative relationship for the commercialization of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates, we may be forced to delay the potential commercialization of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates or reduce the scope of our sales or marketing activities for such product candidates. If we elect to increase our expenditures to fund commercialization activities ourselves, we will need to obtain additional capital, which may not be available to us on acceptable terms, or at all. We could enter into arrangements with collaborative partners at an earlier stage than otherwise would be ideal and we may be required to relinquish rights to any of our product candidates or otherwise agree to terms unfavorable to us, any of which may have an adverse effect on our business, operating results and prospects.

If we are unable to establish adequate sales, marketing and distribution capabilities, either on our own or in collaboration with third parties, we will not be successful in commercializing SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates and may not become profitable and may incur significant additional losses. We will be competing with many companies that currently have extensive and well-funded marketing and sales operations. Without an internal team or the support of a third party to perform marketing and sales functions, we may be unable to compete successfully against these more established companies.

In addition, even if we do establish adequate sales, marketing and distribution capabilities, the progress of general industry trends with respect to pricing models, supply chains and delivery mechanisms, among other things, could deviate from our expectations. If these or other industry trends change in a manner which we do not anticipate or for which we are not prepared, we may not be successful in commercializing our product candidates or become profitable.

Our future growth may depend, in part, on our ability to penetrate foreign markets, where we would be subject to additional regulatory burdens and other risks and uncertainties.

Our future profitability may depend, in part, on our ability to commercialize our product candidates in foreign markets for which we may rely on collaboration with third parties. We are evaluating the opportunities for the development and commercialization of our product candidates in foreign markets. We are not permitted to market or promote any of our product candidates before we receive regulatory approval from the applicable regulatory authority in that foreign market, and we may never receive such regulatory approval for any of our product candidates. To obtain separate regulatory approvals in other countries, we may be required to comply with numerous and varying regulatory requirements of such countries regarding the safety and efficacy of our product candidates and governing, among other things, clinical trials and commercial sales, pricing and distribution of our product candidates, and we cannot predict success in these jurisdictions. If we obtain approval of our product candidates and ultimately commercialize our product candidates in foreign markets, we would be subject to additional risks and uncertainties, including:

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Foreign sales of our product candidates could also be adversely affected by the imposition of governmental controls, political and economic instability, trade restrictions and changes in tariffs.

If SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other pipeline product candidates is approved for commercialization, we intend to selectively partner with third parties to market it in certain jurisdictions outside the United States. We expect that we will be subject to additional risks related to international pharmaceutical operations, including:

We have no prior experience in these areas. In addition, there are complex regulatory, tax, labor and other legal requirements imposed by the EU and many of the individual countries in Europe, as well as countries in Asia such as China and Taiwan, with which we will need to comply. Many U.S.-based biotechnology companies have found the process of marketing their own products internationally to be very challenging.

Certain legal and political risks are also inherent in foreign operations. There is a risk that foreign governments may nationalize private enterprises in certain countries where we may operate. In certain countries or regions, terrorist activities and the response to such activities may threaten our operations more than in the United States. Social and cultural norms in certain countries may not support compliance with our corporate policies, including those that require compliance with substantive laws and regulations. Also, changes in general economic and political conditions in countries where we may operate are a risk to our financial performance and future growth. Additionally, the need to identify financially and commercially strong partners for commercialization outside the United States who will comply with the high manufacturing and legal and regulatory compliance standards we require is a risk to our financial performance. As we operate our business globally, our success will depend, in part, on our ability to anticipate and effectively manage these and other related risks. There can be no assurance that the consequences of these and other factors relating to our international operations will not have an adverse effect on our business, financial condition or results of operations.

In some countries, particularly in Europe, the pricing of prescription pharmaceuticals is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a drug. To obtain reimbursement or pricing approval in some countries, we may be required to conduct clinical trials that compare the cost-effectiveness of our product candidates to other available therapies. If reimbursement of our products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, our business could be harmed, possibly materially.

Potential product liability lawsuits against us could cause us to incur substantial liabilities and limit commercialization of any products that we may develop.

The use of our product candidates, including SQZ-PBMC-HPV, SQZ-AAC-HPV and SQZ-eAPC-HPV, in clinical trials and the sale of any products for which we obtain marketing approval exposes us to the risk of product liability claims. Product liability claims might be brought against us by consumers, healthcare providers, pharmaceutical companies or others selling or otherwise coming into contact with our products. On occasion, large judgments have been awarded in class action lawsuits based on products that had

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unanticipated adverse effects. If we cannot successfully defend against product liability claims, we could incur substantial liability and costs, which may not be covered by insurance. In addition, regardless of merit or eventual outcome, product liability claims may result in:

Risks Related to Our Dependence on Third Parties

The Roche Agreement is important to our business. If we or Roche fail to adequately perform under the Roche Agreement, or if we or Roche terminate the Roche Agreement, the development and commercialization of certain of our product candidates could be materially delayed and our business would be adversely affected.

Under the Roche Agreement, Roche is jointly responsible for the clinical development, with Roche being primarily responsible for the late-stage clinical development, of certain of our product candidates, which includes our initial product candidate, SQZ-PBMC-HPV. We and Roche may be jointly responsible for conducting global clinical studies and coordinating commercial launch activities.

Termination of the Roche Agreement, in whole or in part, could cause significant delays in our development and commercialization efforts for our SQZ APC platform in oncology, including for SQZ-PBMC-HPV. If the Roche Agreement is terminated, we would need to expand our internal capabilities or enter into another agreement to compensate for the loss in funding and clinical development support from Roche. Any suitable alternative agreement would take considerable time to negotiate and could also be on less favorable terms to us. Whether or not we identify another suitable collaborator, we may need to seek additional financing to continue the development of our SQZ APC platform in oncology, including SQZ-PBMC-HPV, or we may be forced to discontinue development of our SQZ APC platform in oncology, including SQZ-PBMC-HPV, either of which could have a material adverse effect on our business.

In addition, under the Roche Agreement, we also agreed to use commercially reasonable efforts to mutually select and generate additional preclinical data on additional antigens other than the HPV targeted SQZ-PBMC-HPV to develop collaboratively. With respect to each mutually selected antigen, we granted Roche an option, exercisable after we supply Roche with a clinical proof of concept for a product containing the antigen, to obtain an exclusive license of our intellectual property to exploit the product worldwide for the treatment of oncologic indications using our SQZ platforms and a microfluidic chip. Roche granted us an option, exercisable with respect to every alternating mutually selected antigen product for which Roche exercises its own option, beginning with the second, to obtain an exclusive license of Roche's intellectual property to exploit the antigen product in the United States. If we exercise our option to obtain, or if this alternating option structure otherwise results in our obtaining, exclusive licenses with respect to antigen products that we are subsequently unable to exploit or otherwise unsuccessful in developing and commercializing, our business could be materially harmed.

Even if the Roche Agreement is adequately performed by us and Roche, any success of our product candidates subject to the agreement may be obtained at the expense of or to the detriment of our other wholly owned product candidates, which could limit our profitability.

There may be substantial overlap in the addressable market of patients which our product candidates, if approved, would be designed to treat. As a result, in order to reduce an overlap, we may seek to commercialize only certain of our product candidates and may forego commercializing other of our product candidates. Furthermore, such an overlap may exist between certain of our product candidates, including SQZ-PBMC-HPV, that are subject to the Roche Agreement, and other of our product candidates, such as SQZ-AAC-HPV, which are wholly owned. Therefore, even if the Roche Agreement is adequately performed by us and Roche and we are

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able to successfully commercialize a product candidate, such success may be obtained at the expense of or to the detriment of our other wholly owned product candidates, which could limit our profitability.

We rely on third parties for the manufacture of raw materials and product candidates for our research programs, preclinical studies and clinical trials and we do not have long-term contracts with many of these parties. This reliance on third parties increases the risk that we will not have sufficient quantities of such materials, product candidates, or any therapies that we may develop and commercialize, or that such supply will not be available to us at an acceptable cost, which could delay, prevent, or impair our development or commercialization efforts.

Although we currently conduct certain manufacturing operations internally for preclinical studies, we rely on third parties for the manufacture of raw materials for preclinical and clinical development, as well as for commercial manufacture if any of our product candidates receive marketing approval. We do not have a long-term agreement with many of the third-party manufacturers we currently use to provide preclinical and clinical raw materials, and we purchase any required materials on a purchase order basis. Certain of these manufacturers are critical to our production and the loss of these manufacturers to one of our competitors or otherwise, or an inability to obtain quantities at an acceptable cost or quality, could delay, prevent or impair our ability to timely conduct preclinical studies or clinical trials, and would materially and adversely affect our development and commercialization efforts.

The facilities used by third-party manufacturers to manufacture our product candidates must be approved by the FDA pursuant to inspections that will be conducted after we submit a BLA to the FDA. We do not control the manufacturing process of, and are dependent on, third-party manufacturers for compliance with cGMP requirements for manufacture of drug products and other laws and regulations. If these third-party manufacturers cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA or others, they will not be able to secure and/or maintain regulatory approval for their manufacturing facilities and may limit or restrict our clinical supply of product candidates and ability to supply any approved products to the market. Some of our contract manufacturers may not have produced a commercially approved product and therefore may not have previously obtained the requisite FDA approvals to do so. As such, regulatory authorities may identify compliance gaps or violations in the future, including if and when these contract manufacturers seek approval to manufacture and supply commercial product. In addition, we have limited control over the ability of third-party manufacturers to maintain adequate quality control, quality assurance and qualified personnel. If the FDA or a comparable foreign regulatory authority does not approve these facilities for the manufacture of our product candidates or if it withdraws any such approval in the future, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain regulatory approval for or market our product candidates, if approved.

Our failure, or the failure of our third-party manufacturers, to comply with applicable regulations could result in sanctions being imposed on us, including clinical holds, fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, seizures or recalls of product candidates or products, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect supplies of our products. In addition, we may be unable to establish any agreements with third-party manufacturers or to do so on acceptable terms.

Even if we are able to establish agreements with third-party manufacturers, reliance on third-party manufacturers entails additional risks, including:

Our product candidates and any products that we may develop may compete with other product candidates and products for access to manufacturing facilities. There are a limited number of manufacturers that operate under cGMP regulations and that might be capable of manufacturing for us. Any performance failure on the part of our existing or future manufacturers could delay clinical development or marketing approval, and any related remedial measures may be costly or time-consuming to implement. Moreover, as a result of the COVID-19 pandemic, third-party manufacturers may be affected, which could disrupt their activities and as a result we could face difficulty timely sourcing key components necessary for the manufacture of our product candidates and other materials, which may negatively affect our preclinical studies and clinical trials as well as other relationships and business plans. We do not currently have arrangements in place for redundant supply or a second source for all required raw materials used in the manufacture of our product candidates. If our current third-party manufacturers cannot perform as agreed, we may be required to replace such manufacturers and we may be unable to replace them on a timely basis or at all. Our current and anticipated future dependence upon others for the

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manufacture of our product candidates or products may adversely affect our future profit margins and our ability to commercialize any products that receive marketing approval on a timely and competitive basis.

We do not have multiple sources of supply for some of the components used in our product candidates, nor long-term supply contracts, and certain of our suppliers are critical to our production. If we were to lose a critical supplier, it could have a material adverse effect on our ability to complete the development of our product candidates. If we obtain regulatory approval for our product candidates, we would need to expand the supply of components in order to commercialize them.

We do not have multiple sources of supply for each of the components used in the manufacturing of our product candidates, including SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV. We also do not have long-term supply agreements with all of our component suppliers. We may not be able to establish additional sources of supply for our product candidates or may be unable to do so on acceptable terms. Manufacturing suppliers are subject to cGMP quality and regulatory requirements, covering manufacturing, testing, quality control and record keeping relating to our product candidates and subject to ongoing inspections by applicable regulatory authorities. Failure by any of our suppliers to comply with applicable regulations may result in long delays and interruptions in supply. Manufacturing suppliers are also subject to local, state and federal regulations and licensing requirements. Failure by any of our suppliers to comply with all applicable regulations and requirements may result in long delays and interruptions in supply.

The number of suppliers of the raw material components of our product candidates is limited. In the event it is necessary or desirable to acquire supplies from alternative suppliers, we might not be able to obtain them on commercially reasonable terms, if at all. It could also require significant time and expense to redesign our manufacturing processes to work with another company and redesign of processes can trigger the need for conducting additional studies such as comparability or bridging studies. Additionally, certain of our suppliers are critical to our production, and the loss of these suppliers to one of our competitors or otherwise would materially and adversely affect our development and commercialization efforts. Furthermore, suppliers have been experiencing and may continue to experience shortages, delayed shipments, surcharges and other supply chain issues caused by or related to the COVID-19 pandemic. COVID-19 restrictions have also led to a shortage of personnel to manufacture, package and ship supplies and consumables, further limiting the available supply. If our suppliers are not able to obtain materials needed for our product candidates in preclinical studies and clinical trials, there may be a material adverse impact on our business and financial condition.

As part of any marketing approval, regulatory authorities conduct inspections that must be successful prior to the approval of the product. Failure of manufacturing suppliers to successfully complete these regulatory inspections will result in delays. If supply from the approved supplier is interrupted, there could be a significant disruption in commercial supply. An alternative vendor would need to be qualified through a BLA amendment or supplement, which could result in further delay. The FDA or other regulatory authorities outside of the United States may also require additional studies if a new supplier is relied upon for commercial production. Switching vendors may involve substantial costs and is likely to result in a delay in our desired clinical and commercial timelines.

If we are unable to obtain the supplies we need at a reasonable price or on a timely basis, it could have a material adverse effect on our ability to complete the development of SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates or, if we obtain regulatory approval for SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV or any of our other product candidates, to commercialize them.

We rely on third parties to conduct our preclinical studies and clinical trials. Any failure by a third party to conduct the clinical trials according to GCPs and in a timely manner may delay or prevent our ability to seek or obtain regulatory approval for or commercialize our product candidates.

We are dependent on third parties to conduct critical aspects of our preclinical studies and clinical trials, including in our clinical trials for SQZ-PBMC-HPV, SQZ-AAC-HPV and SQZ-eAPC-HPV, and we expect to rely on third parties to conduct future clinical trials and preclinical studies for our other pipeline product candidates. Specifically, we have used and relied on, and intend to continue to use and rely on, medical institutions, clinical investigators, CROs and consultants to conduct our clinical trials in accordance with our clinical protocols and regulatory requirements. These CROs, investigators and other third parties play a significant role in the conduct and timing of these trials and subsequent collection and analysis of data. While we have agreements governing the activities of our third-party contractors, we have limited influence over their actual performance. Nevertheless, we are responsible for ensuring that each of our clinical trials is conducted in accordance with the applicable protocol and legal, regulatory and scientific standards, and our reliance on the CROs and other third parties does not relieve us of our regulatory responsibilities. We and our CROs are required to comply with GCP requirements, which are regulations and guidelines enforced by the FDA and comparable foreign regulatory authorities for all of our product candidates in clinical development. Regulatory authorities enforce these GCPs through periodic inspections of trial sponsors, principal investigators and trial sites. If we or any of our CROs or trial sites fail to comply with applicable GCPs, the clinical data generated in our clinical trials may be deemed unreliable, and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot assure you that upon inspection by a given regulatory authority, such regulatory authority will determine that any of our clinical trials

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complies with GCP regulations. In addition, our clinical trials must be conducted with product produced under cGMP regulations. Our failure to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process.

Any third parties conducting our clinical trials or preclinical studies are not and will not be our employees and, except for remedies available to us under our agreements with such third parties, we cannot guarantee that any such CROs, investigators or other third parties will devote adequate time and resources to such trials or perform as contractually required. If any of these third parties fail to meet expected deadlines, adhere to our clinical protocols or meet regulatory requirements, or otherwise performs in a substandard manner, our clinical trials may be extended, delayed or terminated. In addition, many of the third parties with whom we contract may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other drug development activities that could harm our competitive position. In addition, principal investigators for our clinical trials may serve as scientific advisors or consultants to us from time to time and may receive cash or equity compensation in connection with such services. If these relationships and any related compensation result in perceived or actual conflicts of interest, or the FDA concludes that the financial relationship may have affected the interpretation of the trial, the integrity of the data generated at the applicable clinical trial site may be questioned, and the utility of the clinical trial itself may be jeopardized, which could result in the delay or rejection of any BLA we submit to the FDA. Any such delay or rejection could prevent us from commercializing our product candidates.

If any of our relationships with these third parties terminate, we may not be able to enter into arrangements with alternative third parties or do so on commercially reasonable terms. Switching or adding additional CROs, investigators and other third parties involves additional cost and requires management time and focus. In addition, there is a natural transition period when a new CRO commences work. As a result, delays occur, which could materially impact our ability to meet our desired clinical development timelines. Though we carefully manage our relationships with our CROs, investigators and other third parties, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition and prospects.

We have collaborated and, in the future, may collaborate with third parties for the development and commercialization of our candidates. We may not succeed in establishing and maintaining collaborative relationships, which may significantly limit our ability to develop and commercialize our product candidates successfully, if at all.

We have collaborated and, in the future, may seek collaborative relationships for the development and commercialization of our product candidates. For example, we have entered into a collaborative relationship with Roche regarding the development of our initial product candidate, SQZ-PBMC-HPV. If we enter into any such arrangements with any third parties, we will likely have shared or limited control over the amount and timing of resources that our collaborators dedicate to the development or potential commercialization of any product candidates we may seek to develop with them. Our ability to generate product revenue from these arrangements with commercial entities will depend on our collaborators' abilities to successfully perform the functions assigned to them in these arrangements. We cannot predict the success of any collaboration that we enter into. Collaborations involving our product candidates pose the following risks to us:

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We may face significant competition in seeking appropriate collaborations. Recent business combinations among biotechnology and pharmaceutical companies have resulted in a reduced number of potential collaborators. In addition, the negotiation process is time-consuming and complex, and we may not be able to negotiate collaborations on a timely basis, on acceptable terms, or at all. If we are unable to do so, we may have to curtail the development of the product candidate for which we are seeking to collaborate or delay its potential commercialization or reduce the scope of any sales or marketing activities, or increase our expenditures and undertake development or commercialization activities at our own expense. If we elect to increase our expenditures to fund development or commercialization activities on our own, we may need to obtain additional capital, which may not be available to us on acceptable terms or at all. If we do not have sufficient funds, we may not be able to further develop product candidates or bring them to market and generate product revenue.

If we enter into collaborations to develop and potentially commercialize any product candidates, we may not be able to realize the benefit of such transactions if we or our collaborator elect not to exercise the rights granted under the agreement or if we or our collaborator are unable to successfully integrate a product candidate into existing operations and company culture. In addition, if our agreement with any of our collaborators terminates, our access to technology and intellectual property licensed to us by that collaborator may be restricted or terminate entirely, which may delay our continued development of our product candidates utilizing the collaborator's technology or intellectual property or require us to stop development of those product candidates completely. We may also find it more difficult to find a suitable replacement collaborator or attract new collaborators, and our development programs may be delayed or the perception of us in the business and financial communities could be adversely affected. Any collaborator may also be subject to many of the risks relating to product development, regulatory approval, and commercialization described in this "Risk Factors" section, and any negative impact on our collaborators may adversely affect us.

If we seek, but are not able to establish, collaborations, we may have to alter our development and commercialization plans.

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Our product development programs and the potential commercialization of our product candidates will require substantial additional capital. We may decide to collaborate with pharmaceutical and biotechnology companies for the development and potential commercialization of our product candidates. For example, we have entered into a collaborative relationship with Roche regarding the development of our initial product candidate, SQZ-PBMC-HPV.

We face significant competition in seeking appropriate collaborators. Whether we reach a definitive agreement for a collaboration will depend, among other things, upon our assessment of the collaborator's resources and expertise, the terms and conditions of the proposed collaboration and the proposed collaborator's evaluation of a number of factors. Those factors may include the design or results of clinical trials, the likelihood of approval by the FDA or comparable regulatory authorities outside the United States, the potential market for the subject product candidate, the costs and complexities of manufacturing and delivering such product candidate to patients, the potential of competing products, the existence of uncertainty with respect to our ownership of technology, which can exist if there is a challenge to such ownership without regard to the merits of the challenge and industry and market conditions generally. The collaborator may also consider alternative product candidates or technologies for similar indications that may be available to collaborate on and whether such a collaboration could be more attractive than the one with us for our product candidate. Collaborations are complex and time-consuming to negotiate and document. In addition, there have been a significant number of recent business combinations among large pharmaceutical companies that have resulted in a reduced number of potential future collaborators.

We may not be able to negotiate collaborations on a timely basis, on acceptable terms, or at all. If we are unable to do so, we may have to curtail the development of such product candidate, reduce or delay its development program or one or more of our other development programs, delay its potential commercialization or reduce the scope of any sales or marketing activities, or increase our expenditures and undertake development or commercialization activities at our own expense. If we elect to increase our expenditures to fund development or commercialization activities on our own, we may need to obtain additional capital, which may not be available to us on acceptable terms or at all. If we do not have sufficient funds, we may not be able to further develop our product candidates or bring them to market and generate product revenue.

We may enter into collaborations, in-licensing arrangements, joint ventures, strategic alliances or partnerships with third parties that may not result in the development of commercially viable products or the generation of significant future product revenues.

In the ordinary course of our business, we may enter into collaborations, in-licensing arrangements, joint ventures, strategic alliances, partnerships or other arrangements to develop new products and to pursue new markets. Proposing, negotiating and implementing collaborations, in-licensing arrangements, joint ventures, strategic alliances or partnerships may be a lengthy and complex process. Other companies, including those with substantially greater financial, marketing, sales, technology or other business resources, may compete with us for these opportunities or arrangements. We may not identify, secure, or complete any such transactions or arrangements in a timely manner, on a cost-effective basis, on acceptable terms or at all. We have limited institutional knowledge and experience with respect to these business development activities, and we may also not realize the anticipated benefits of any such transaction or arrangement. In particular, these collaborations may not result in the development of products that achieve commercial success or result in significant product revenues and could be terminated prior to developing any products.

Additionally, we may not be in a position to exercise sole decision making authority regarding the transaction or arrangement, which could create the potential risk of creating impasses on decisions, and our future collaborators may have economic or business interests or goals that are, or that may become, inconsistent with our business interests or goals. It is possible that conflicts may arise with our collaborators, such as conflicts concerning the achievement of performance milestones, or the interpretation of significant terms under any agreement, such as those related to financial obligations or the ownership or control of intellectual property developed during the collaboration. If any conflicts arise with any current or future collaborators, they may act in their self-interest, which may be adverse to our best interest, and they may breach their obligations to us. In addition, we may have limited control over the amount and timing of resources that any current or future collaborators devote to our or their future products. Disputes between us and our collaborators may result in litigation or arbitration, which would increase our expenses and divert the attention of our management. Further, these transactions and arrangements will be contractual in nature and will generally be terminable under the terms of the applicable agreements and, in such event, we may not continue to have rights to the products relating to such transaction or arrangement or may need to purchase such rights at a premium.

If we enter into in-bound intellectual property license agreements, we may not be able to fully protect the licensed intellectual property rights or maintain those licenses. Future licensors could retain the right to prosecute and defend the intellectual property rights licensed to us, in which case we would depend on the ability of our licensors to obtain, maintain and enforce such licensed intellectual property. These licensors may determine not to pursue litigation against other companies or may pursue such litigation less aggressively than we would. If our licensors do not adequately protect such licensed intellectual property, competitors may be able to use such intellectual property and erode or negate any competitive advantage we may have, which could materially harm our business, negatively affect our position in the marketplace, limit our ability to commercialize our products and product candidates and delay or

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render impossible our achievement of profitability. Further, entering into such license agreements could impose various diligence, commercialization, royalty or other obligations on us. Future licensors may allege that we have breached our license agreement with them, and accordingly seek to terminate our license, which could adversely affect our competitive business position and harm our business prospects.

Data provided by collaborators and others upon which we rely that have not been independently verified could turn out to be false, misleading or incomplete.

We rely on third-party vendors, such as CROs, scientists and collaborators to provide us with significant data and other information related to our projects, preclinical studies or clinical trials and our business. For example, in connection with the clinical development of SQZ-PBMC-HPV, we may rely on data provided by Roche with respect to atezolizumab. If such third parties provide inaccurate, misleading or incomplete data, our business, prospects and results of operations could be materially adversely affected.

Our employees and independent contractors, including principal investigators, CROs, consultants, vendors and any third parties we may engage in connection with research, development, regulatory, manufacturing, quality assurance and other pharmaceutical functions and commercialization may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements, which could have a material adverse effect on our business.

Misconduct by our employees and independent contractors, including principal investigators, CROs, consultants, vendors and any third parties we may engage in connection with research, development, regulatory, manufacturing, quality assurance and other pharmaceutical functions and commercialization, could include intentional, reckless or negligent conduct or unauthorized activities that violate: (i) the laws and regulations of the FDA, and other similar regulatory authorities, including those laws that require the reporting of true, complete and accurate information to such authorities; (ii) manufacturing standards; (iii) data privacy, security, fraud and abuse and other healthcare laws and regulations; or (iv) laws that require the reporting of true, complete and accurate financial information and data. Specifically, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Activities subject to these laws could also involve the improper use or misrepresentation of information obtained in the course of preclinical studies or clinical trials, creation of fraudulent data in preclinical studies or clinical trials or illegal misappropriation of drug product, which could result in regulatory sanctions and cause serious harm to our reputation. It is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with such laws or regulations. For example, we are currently evaluating certain exploratory preclinical experiments conducted by a former employee based on employee allegations of potential data integrity concerns. While these preclinical experiments do not relate to our product candidates in clinical trials or those for which we have submitted, or plan to submit, INDs, limited data from these experiments have been published or were incorporated in applications and interim reports for government grants that we have been awarded. We are following the review process required by the administrators of the grants and our internal policies to evaluate these data. While the amount we have received from these grants has not been significant, we are unable to predict the impact this evaluation may have on these grants, including the possibility that we may need to repay the funds we have received. We also have informed the journal in which a portion of the data was published about our investigation and the journal has issued an editorial expression of concern. We are unable to predict what further action, if any, the journal may take or the timing of such action, and we may decide or be asked to update, correct or retract the article in which the data appeared. Additionally, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, including in connection with the ongoing evaluation described above, and we are not successful in defending ourselves or asserting our rights, those actions could potentially have a significant impact on our business and results of operations, including the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, restitution, disgorgements, possible exclusion from participation in Medicare, Medicaid, other U.S. federal healthcare programs or healthcare programs in other jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, individual imprisonment, other sanctions, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations.

If our third-party manufacturers use hazardous and biological materials in a manner that causes injury or violates applicable law, we may be liable for damages.

Our research and development activities involve the controlled use of potentially hazardous substances, including chemical and biological materials, by our manufacturers. Our manufacturers are subject to federal, state and local laws and regulations in the United States governing the use, manufacture, storage, handling and disposal of medical and hazardous materials. Although we believe that our manufacturers' procedures for using, handling, storing and disposing of these materials comply with legally prescribed standards, we cannot completely eliminate the risk of contamination or injury resulting from medical or hazardous materials. As a result of any

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such contamination or injury, we may incur liability or local, city, state or federal authorities may curtail the use of these materials and interrupt our business operations. In the event of an accident, we could be held liable for damages or penalized with fines, and the liability could exceed our resources. Generally, we do not have any insurance for liabilities arising from medical or hazardous materials. Compliance with applicable environmental laws and regulations is expensive, and current or future environmental regulations may impair our research, development and production efforts, which could harm our business, prospects, financial condition or results of operations.

Risks Related to Our Intellectual Property

If we are unable to obtain, maintain, enforce and adequately protect our intellectual property rights with respect to our technology and product candidates, or if the scope of the patent protection obtained is not sufficiently broad, our competitors could develop and commercialize technology and products similar or identical to ours, and our ability to successfully develop and commercialize our technology and product candidates may be adversely affected.

We rely upon a combination of patents, trade secret protection and confidentiality agreements to protect our intellectual property and prevent others from duplicating SQZ-PBMC-HPV, SQZ-AAC-HPV, SQZ-eAPC-HPV, any of our other pipeline product candidates and any future product candidates.

The strength of patents in the biotechnology and pharmaceutical field involves complex legal, factual and scientific questions and can be uncertain. It is possible that we will fail to identify patentable aspects of our research and development output before it is too late to obtain patent protection. The patent applications that we own may fail to result in issued patents with claims that cover our product candidates in the United States or in other foreign countries. There is no assurance that all of the potentially relevant prior art relating to our patents and patent applications has been found, which can invalidate a patent or prevent a patent from issuing from a pending patent application. Even if patents do successfully issue and even if such patents cover our product candidates, third parties may challenge the inventorship, ownership, validity, enforceability or scope of such patents, which may result in such patents being narrowed or invalidated, or being held unenforceable.

Furthermore, even if they are unchallenged, our patents and patent applications may not adequately protect our intellectual property, provide exclusivity for our product candidates or prevent others from designing around our claims. In addition, no assurances can be given that third parties will not create new products or methods that achieve similar results without infringing upon our patents. Any of these outcomes could impair our ability to prevent competition from third parties, which may have an adverse impact on our business.

If the patent applications we hold with respect to our programs or product candidates fail to issue, if their breadth or strength of protection is threatened, or if they fail to provide meaningful exclusivity for our product candidates, it could dissuade companies from collaborating with us to develop product candidates and threaten our ability to commercialize future products. Several patent applications covering our product candidates have been filed recently. We cannot offer any assurances about which, if any, patents will issue, the breadth of any such patents or whether any issued patents will be found invalid or unenforceable or will be threatened by third parties. Any successful opposition to these patents or any other patents owned by us could deprive us of rights necessary for the successful commercialization of any product candidates that we may develop.

Further, if we encounter delays in regulatory approvals, the period of time during which we could market a product candidate under patent protection could be reduced. Since patent applications in the United States and most other countries are confidential for a period of time after filing, and some remain so until issued, we cannot be certain that we were the first to file any patent application related to a product candidate.

Furthermore, if third parties have filed such patent applications before enactment of the Leahy-Smith Act on March 16, 2013, an interference proceeding in the United States can be initiated by a third party to determine who was the first to invent any of the subject matter covered by the patent claims of our applications. In addition, patents have a limited lifespan. In the United States, the expiration of a patent is generally 20 years after it is filed. Various extensions may be available; however, the life of a patent, and the protection it affords, is limited. Even if patents covering our product candidates are obtained, once the patent life has expired for the patent covering a product, we may be open to competition from generic competing products.

The issuance of a patent is not conclusive as to its inventorship, ownership, scope, validity or enforceability, and our patents may be challenged in the courts or patent offices in the United States and abroad. In addition, the issuance of a patent does not give us the right to practice the patented invention. Third parties may have blocking patents that could prevent us from marketing our product candidate, if approved, or practicing our own patented technology. As a result, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain.

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In addition to the protection afforded by patents, we rely on trade secret protection and confidentiality agreements to protect proprietary know-how that is either not patentable or that we elect not to patent, processes for which patents are difficult to enforce and any other elements of our product candidate discovery and development processes that involve proprietary know-how, information or technology that is not covered by patents. However, trade secrets can be difficult to protect. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with our employees, consultants, scientific advisors and contractors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these individuals, organizations and systems, agreements or security measures may be breached, and we may not have adequate remedies for any breach. If any of our trade secrets are disclosed to a competitor or other third party, we are likely to lose trade secret protection.

Although we require all of our employees and consultants to assign their inventions to us, to the extent that employees or consultants use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions. Further, although we require that all of our employees, consultants, collaborators, advisors and any third parties who have access to our proprietary know-how, information or technology enter into confidentiality agreements, we cannot provide any assurances that our trade secrets and other confidential proprietary information will not be disclosed or that competitors will not otherwise gain access to our trade secrets or independently discover our trade secrets or develop substantially equivalent information and techniques. Any of these parties may breach these agreements and we may not have adequate remedies for any specific breach. Misappropriation or unauthorized disclosure of our trade secrets or other confidential proprietary information could impair our competitive position and may have a material adverse effect on our business. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret is difficult, expensive and time-consuming, and the outcome is unpredictable. Additionally, if the steps taken to maintain our trade secrets or other confidential proprietary information are deemed inadequate, we may have insufficient recourse against third parties for misappropriating the trade secret or other confidential proprietary information.

If we are unable to prevent material disclosure of the non-patented intellectual property related to our technologies to third parties, and there is no guarantee that we will have any such enforceable trade secret protection, we may not be able to establish or maintain a competitive advantage in our market, which could materially adversely affect our business, results of operations and financial condition.

Third-party claims of intellectual property infringement may prevent or delay our development and commercialization efforts.

Our commercial success depends in part on our avoiding infringement, or allegations of infringement, of the patents and other proprietary rights of third parties. There is a substantial amount of litigation, both within and outside the United States, involving patent and other intellectual property rights in the biotechnology and pharmaceutical industries, including patent infringement lawsuits, interferences, oppositions, reexamination, and inter partes review proceedings before the United States Patent and Trademark Office, or USPTO, and similar proceedings in foreign jurisdictions, such as oppositions before the European Patent Office. Numerous U.S. and foreign issued patents and pending patent applications, which are owned by third parties, exist in the fields in which we are pursuing development candidates. Many companies in intellectual property-dependent industries, including the biotechnology and pharmaceutical industries, have employed intellectual property litigation as a means to gain an advantage over their competitors. As the biotechnology and pharmaceutical industries expand and more patents are issued, and as we gain greater visibility and market exposure as a public company, the risk increases that our product candidates may be subject to claims of infringement of the patent rights of third parties. Some claimants may have substantially greater resources than we do and may be able to sustain the costs of complex intellectual property litigation to a greater degree and for longer periods of time than we could. In addition, patent holding companies that focus solely on extracting royalties and settlements by enforcing patent rights may target us.

Third parties may assert that we are employing their proprietary technology without authorization. There may be third-party patents or patent applications with claims to composition of matter, drug delivery, methods of manufacture or methods for treatment related to the use or manufacture of our product candidates. We cannot guarantee that our technologies, products, compositions and their uses do not or will not infringe third-party patent or other intellectual property rights. Because patent applications can take many years to issue, there may be currently pending patent applications which may later result in issued patents that our product candidates may infringe. In addition, third parties may obtain patents in the future and claim that use of our technologies infringes upon these patents. Pending patent applications that have been published can, subject to certain limitations, be later amended in a manner that could cover our product candidates or the use of our product candidates. After issuance, the scope of patent claims remains subject to construction as determined by an interpretation of the law, the written disclosure in a patent and the patent's prosecution history. Our interpretation of the relevance or the scope of a patent or a pending application may be incorrect, which may negatively impact our ability to market our product candidates. If any third-party patents were held by a court of competent jurisdiction to cover the composition of matter of any of our product candidates, the manufacturing process of any of our product candidates, the method of use for any of our product candidates, the holders of any such patents may be able to block our ability to commercialize such product candidate unless we

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obtained a license under the applicable patents, which may not be available or may not be available on commercially reasonable terms, or until such patents expire.

The legal threshold for initiating litigation or contested proceedings is low, so that even lawsuits or proceedings with a low probability of success might be initiated and require significant resources to defend. Litigation and contested proceedings can also be expensive and time-consuming, and our adversaries in these proceedings may have the ability to dedicate greater resources to prosecuting these legal actions than we can. The risks of being involved in such litigation and proceedings may increase if and as our product candidates near commercialization and as we gain the greater visibility associated with being a public company. Third parties may assert infringement claims against us based on existing patents or patents that may be granted in the future, regardless of the merit of such claims. We may not be aware of all intellectual property rights potentially relating to our technology and product candidates and their uses, or we may incorrectly conclude that third party intellectual property is invalid or that our activities and product candidates do not infringe such intellectual property. Thus, we do not know with certainty that our technology and product candidates, or our development and commercialization thereof, do not and will not infringe, misappropriate or otherwise violate any third party's intellectual property.

Parties making claims against us may obtain injunctive or other equitable relief, which could effectively block our ability to further develop and commercialize one or more of our product candidates and/or harm our reputation and financial results. Defense of these claims, regardless of their merit, could involve substantial litigation expense and could be a substantial diversion of management and employee resources from our business. In the event of a successful claim of infringement against us, we may have to pay substantial damages, including treble damages and attorneys' fees for willful infringement, pay royalties, redesign our infringing products, in the case of claims concerning registered trademarks, rename our product candidates, or obtain one or more licenses from third parties, which may require substantial time and monetary expenditure, and which might be impossible or technically infeasible. Furthermore, we may not be able to obtain any required license on commercially reasonable terms or at all. Even if we were able to obtain a license, it could be non-exclusive, thereby giving our competitors access to the same technologies licensed to us; alternatively or additionally it could include terms that impede or destroy our ability to compete successfully in the commercial marketplace.

If we are unable to obtain licenses from third parties on commercially reasonable terms or fail to comply with our obligations under such agreements, our business could be harmed.

It may be necessary for us to use the patented or proprietary technology of third parties to commercialize our products, in which case we would be required to obtain a license from these third parties. If we are unable to license such technology, or if we are forced to license such technology on unfavorable terms, our business could be materially harmed. If we are unable to obtain a necessary license, we may be unable to develop or commercialize the affected product candidates, which could materially harm our business and the third parties owning such intellectual property rights could seek either an injunction prohibiting our sales or an obligation on our part to pay royalties and/or other forms of compensation. Even if we are able to obtain a license, it may be non-exclusive, thereby giving our competitors access to the same technologies licensed to us.

If we are unable to obtain rights to required third-party intellectual property rights or maintain the existing intellectual property rights we have, we may be required to expend significant time and resources to redesign our technology, product candidates or the methods for manufacturing them or to develop or license replacement technology, all of which may not be feasible on a technical or commercial basis. If we are unable to do so, we may be unable to develop or commercialize the affected technology and product candidates, which could harm our business, financial condition, results of operations and prospects significantly.

Additionally, if we fail to comply with our obligations under license agreements, our counterparties may have the right to terminate these agreements or seek damages from us, in which event we might not be able to develop, manufacture or market, or may be forced to cease developing, manufacturing or marketing, any product that is covered by these agreements or may face other penalties under such agreements. Such an occurrence could materially adversely affect the value of the product candidate being developed under any such agreement. Termination of these agreements or reduction or elimination of our rights under these agreements, or restrictions on our ability to freely assign or sublicense our rights under such agreements when it is in the interest of our business to do so, may result in our having to negotiate new or reinstated agreements with less favorable terms, cause us to lose our rights under these agreements, including our rights to important intellectual property or technology, or impede, or delay or prohibit the further development or commercialization of one or more product candidates that rely on such agreements.

Although we or our licensors are not currently involved in any relevant litigation, we may become involved in lawsuits to protect or enforce our patents or other intellectual property, which could be expensive, time-consuming and unsuccessful.

Competitors and other third parties may infringe, misappropriate or otherwise violate our or our licensors' patents, trademarks, copyrights or other intellectual property. As a result, we or our licensors may need to file infringement, misappropriation or other intellectual property related claims against third parties. It may be difficult to detect infringers who do not advertise the components

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that are used in their products. Moreover, it may be difficult or impossible to obtain evidence of infringement in a competitor's or potential competitor's product. To counter infringement or unauthorized use, we may be required to file infringement claims on a country-by-country basis, which can be expensive and time-consuming and divert the time and attention of our management and scientific personnel. There can be no assurance that we will have sufficient financial or other resources to file and pursue such infringement claims, which typically last for years before they are concluded.

Any claims we assert against perceived infringers could also provoke these parties to assert counterclaims against us alleging that we infringe, misappropriate or otherwise violate their intellectual property. In addition, in a patent infringement proceeding, such parties could counterclaim that the patents we or our licensors have asserted are invalid or unenforceable, or both. In patent litigation in the United States, defendant counterclaims alleging invalidity or unenforceability are commonplace. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, including lack of novelty, obviousness or non-enablement. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the USPTO, or made a misleading statement, during prosecution. Third parties may institute such claims before administrative bodies in the United States or abroad, even outside the context of litigation. Such mechanisms include re-examination, post-grant review, inter partes review, interference proceedings, derivation proceedings and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). The outcome following legal assertions of invalidity and unenforceability is unpredictable.

In any such proceeding, a court may decide that a patent of ours, or a patent that we in-license, is not valid, is unenforceable and/or is not infringed, or may construe such patent's claims narrowly or refuse to stop the other party from using the technology at issue on the grounds that our patents do not cover the technology in question. An adverse result in any litigation or defense proceedings could put one or more of our patents at risk of being invalidated, interpreted narrowly or held unenforceable, could put our patent applications at risk of not issuing, and could limit our ability to assert those patents against those parties or other competitors and curtail or preclude our ability to exclude third parties from making and selling similar or competitive products. Similarly, if we assert trademark infringement claims, a court may determine that the marks we have asserted are invalid or unenforceable, or that the party against whom we have asserted trademark infringement has superior rights to the marks in question. In this case, we could ultimately be forced to cease use of such trademarks, which could materially harm our business and negatively affect our position in the marketplace.

Interference or derivation proceedings provoked by third parties or brought by us or declared by the USPTO may be necessary to determine the priority of inventions with respect to our patents or patent applications. An unfavorable outcome could require us to cease using the related technology or to attempt to license rights to it from the prevailing party. Our business could be harmed if the prevailing party does not offer us a license on commercially reasonable terms or at all, or if a non-exclusive license is offered and our competitors gain access to the same technology. Our defense of litigation or interference or derivation proceedings may fail and, even if successful, may result in substantial costs, and distract our management and other employees. In addition, the uncertainties associated with litigation could have a material adverse effect on our ability to raise the funds necessary to continue our research programs, license necessary technology from third parties, or enter into development partnerships that would help us bring our product candidates to market.

Even if we establish infringement, the court may decide not to grant an injunction against further infringing activity and instead award only monetary damages, which may or may not be an adequate remedy. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during this type of litigation. There could also be public announcements of the results of hearings, motions or other interim proceedings or developments. If securities analysts or investors perceive these results to be negative, it could have a material adverse effect on the price of our common stock.

Recent patent reform legislation has increased the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents, and may diminish the value of patents in general.

As is the case with other biopharmaceutical companies, our commercial success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biopharmaceutical industry involves both technological and legal complexity and is therefore costly, time-consuming and inherently uncertain. Recent wide-ranging patent reform legislation in the United States, including the Leahy-Smith America Invents Act, or the Leahy-Smith Act, could increase those uncertainties and costs.

The Leahy-Smith Act includes a number of significant changes to U.S. patent law, including provisions that affect the way patent applications are prosecuted and may also affect patent litigation. Under The Leahy-Smith Act, the United States transitioned from a "first-to-invent" to a "first-to-file" system for deciding which party should be granted a patent when two or more patent applications are filed by different parties claiming the same invention. This will require us to be cognizant going forward of the time from invention to filing of a patent application and be diligent in filing patent applications, but circumstances could prevent us from promptly filing patent applications on our inventions. The Leahy-Smith Act also enlarged the scope of disclosures that qualify as prior

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art, and it expanded the scope of procedures that a third party may use to challenge a U.S. patent, including post-grant review and inter partes review procedures. Because of a lower evidentiary standard in USPTO proceedings compared to the evidentiary standard in U.S. federal courts necessary to invalidate a patent claim, a third party could potentially provide evidence in a USPTO proceeding sufficient for the USPTO to hold a claim invalid even though the same evidence would be insufficient to invalidate the claim if first presented in a district court action. The Leahy-Smith Act and its implementation could increase the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents, all of which could have a material adverse effect on our business and financial condition.

In addition, recent court rulings in cases such as Association for Molecular Pathology v. Myriad Genetics, Inc., BRCA1- & BRCA2-Based Hereditary Cancer Test Patent Litigation, and Promega Corp. v. Life Technologies Corp.have narrowed the scope of patent protection available in certain circumstances and weakened the rights of patent owners in certain situations. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents once obtained. Depending on future actions by the U.S. Congress, the U.S. courts, the USPTO and the relevant law-making bodies in other countries, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future.

We may be subject to claims that our employees, consultants or independent contractors have wrongfully used or disclosed confidential information of third parties or that our employees have wrongfully used or disclosed alleged trade secrets of their former employers.

We may employ individuals who were previously employed at universities or other biotechnology or pharmaceutical companies, including our competitors or potential competitors. Although we try to ensure that our employees, consultants and independent contractors do not use the proprietary information or know-how of others in their work for us, we may be subject to claims that we or our employees, consultants or independent contractors have inadvertently or otherwise used or disclosed intellectual property, including trade secrets or other proprietary information, of any of our employee's former employers or other third parties. Litigation may be necessary to defend against these claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel, or our ability to hire personnel, which, in any case of the foregoing, could adversely impact our business. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to management and other employees.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The USPTO and European and other patent agencies require compliance with a number of procedural, documentary, fee payment and other similar provisions during the patent application process. Periodic maintenance fees, renewal fees, annuity fees and various other governmental fees on patents and/or applications will be due to be paid to the USPTO and various governmental patent agencies outside of the United States in several stages over the lifetime of the patents and/or applications. We have systems in place to remind us to pay these fees, and we employ an outside firm and rely on our outside counsel to pay these fees due to non-U.S. patent agencies. The USPTO and various non-U.S. governmental patent agencies require compliance with a number of procedural, documentary, fee payment and other similar provisions during the patent application process. We employ law firms and other professionals to help us comply, and in many cases, an inadvertent lapse can be cured by payment of a late fee or by other means in accordance with the applicable rules. However, there are situations in which non-compliance can result in abandonment or lapse of the patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. In such an event, our competitors might be able to enter the market, which could have a material adverse effect on our business.

Issued patents covering our product candidates could be found invalid or unenforceable if challenged in court.

If we initiated legal proceedings against a third party to enforce a patent covering one of our product candidates, the defendant could counterclaim that the patent covering our product candidate is invalid and/or unenforceable. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, including lack of novelty, obviousness or non-enablement. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the USPTO, or made a misleading statement, during prosecution. Third parties may also raise similar claims before administrative bodies in the United States or abroad, even outside the context of litigation.

Such mechanisms include re-examination, post-grant review and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). Such proceedings could result in revocation or amendment to our patents in such a way that they no longer cover our product candidates.

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The outcome following legal assertions of invalidity and unenforceability is unpredictable. With respect to the validity question, for example, we cannot be certain that there is no invalidating prior art, of which we and the patent examiner were unaware during prosecution. If a defendant were to prevail on a legal assertion of invalidity and/or unenforceability, we would lose at least part, and perhaps all, of the patent protection on one or more of our product candidates. Such a loss of patent protection could have a material adverse impact on our business. A defendant could also challenge our ownership of patents assigned to us. We cannot be certain that a third party would not challenge our rights to these patents and patent applications. Any legal proceeding or enforcement action can also be expensive and time-consuming.

Patent terms may be inadequate to protect our competitive position on our products for an adequate amount of time.

The term of any individual patent depends on applicable law in the country where the patent is granted. In the United States, provided all maintenance fees are timely paid, a patent generally has a term of 20 years from its application filing date or earliest claimed non-provisional filing date. Extensions may be available under certain circumstances, but the life of a patent and, correspondingly, the protection it affords is limited. Given the amount of time required for the development, testing and regulatory review of new product candidates, patents protecting such candidates might expire before or shortly after such candidates are commercialized. For patents that are eligible for extension of patent term, we expect to seek extensions of patent terms in the United States and, if available, in other countries. In the United States, the Drug Price Competition and Patent Term Restoration Act of 1984 permits a patent term extension of up to five years beyond the normal expiration of the patent, which is limited to the approved indication (or any additional indications approved during the period of extension). We might not be granted an extension because of, for example, failure to apply within applicable periods, failure to apply prior to the expiration of relevant patents or otherwise failure to satisfy any of the numerous applicable requirements. Moreover, the applicable authorities, including the FDA and the USPTO in the United States, and any equivalent regulatory authority in other countries, may not agree with our assessment of whether such extensions are available, and may refuse to grant extensions to our patents, or may grant more limited extensions than we request. If this occurs, our competitors may be able to obtain approval of competing products following our patent expiration by referencing our clinical and preclinical data and launch their product earlier than might otherwise be the case. If this were to occur, it could have a material adverse effect on our ability to generate product revenue.

We may not be able to protect our intellectual property rights throughout the world.

Filing, prosecuting and defending our intellectual property in all countries throughout the world could be prohibitively expensive, and our intellectual property rights in some countries outside the United States can be less extensive than those in the United States. Therefore, we may choose not to pursue or maintain protection for certain intellectual property in certain jurisdictions. In addition, the laws of some foreign countries do not protect intellectual property rights to the same extent as federal and state laws in the United States. Consequently, we may not be able to prevent third parties from practicing our inventions in all countries outside the United States, or from selling or importing products made using our inventions in and into the United States or other jurisdictions. Competitors may use our technologies in jurisdictions where we have not obtained patent protection to develop their own products and further, may export otherwise infringing products to territories where we have patent protection, but enforcement is not as strong as that in the United States. These products may compete with our products and our patents or other intellectual property rights may not be effective or sufficient to prevent such competitors from competing.

Many companies have encountered significant problems in protecting and defending intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets and other intellectual property protection, particularly those relating to biotechnology products, which could make it difficult for us to stop the infringement of our patents or marketing of competing products in violation of our proprietary rights generally. Proceedings to enforce our patent rights in foreign jurisdictions could result in substantial costs and divert our efforts and attention from other aspects of our business, could put our patents at risk of being invalidated or interpreted narrowly and our patent applications at risk of not issuing and could provoke third parties to assert claims against us. We may not prevail in any lawsuit that we initiate, and the damages or other remedies awarded, if any, may not be commercially meaningful. Accordingly, our efforts to enforce our intellectual property rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop or license. In addition, many countries have compulsory licensing laws under which a patent owner may be compelled to grant licenses to third parties (for example, the patent owner has failed to "work" the invention in that country, or the third party has patented improvements) or limit the enforceability of patents against government agencies or government contractors. In these countries, the patent owner may have limited remedies, which could materially diminish the value of the patent.

If our trademarks and trade names are not adequately protected, then we may not be able to build name recognition in our trademarks of interest and our business may be adversely affected.

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While we seek to protect the trademarks we use in the United States and in other countries, we may be unsuccessful in obtaining registrations and/or otherwise protecting these trademarks. If that were to happen, we may be prevented from using our names, brands and trademarks unless we enter into appropriate royalty, license or coexistence agreements, which may not be available or may not be available on commercially reasonable terms. Over the long term, if we are unable to establish name recognition based on our trademarks, trade names, service marks and domain names, then we may not be able to compete effectively, resulting in a material adverse effect on our business. Our registered or unregistered trademarks or trade names may be challenged, infringed, diluted or declared generic, or determined to be infringing on other marks. We rely on both registration and common law protection for our trademarks. We may not be able to protect our rights to these trademarks and trade names or may be forced to stop using these names, which we need to build name recognition among potential partners or customers in our markets of interest. At times, competitors may adopt trademarks and trade names similar to ours, thereby impeding our ability to build brand identity and possibly leading to market confusion. In addition, there could be potential trademark infringement claims brought by owners of other registered trademarks or trademarks that incorporate variations of our registered or unregistered trademarks. Over the long term, if we are unable to establish name recognition based on our trademarks, then we may not be able to compete effectively and our business may be adversely affected. During trademark registration proceedings, we may receive rejections. Although we would be given an opportunity to respond to those rejections, we may be unable to overcome such rejections. In addition, in the USPTO and in comparable agencies in many foreign jurisdictions, third parties are given an opportunity to oppose pending trademark applications and to seek to cancel registered trademarks. Opposition or cancellation proceedings may be filed against our trademarks, and our trademarks may not survive such proceedings. Effective trademark protection may not be available or may not be sought in every country in which our products are made available. Any name we propose to use for our products in the United States must be approved by the FDA, regardless of whether we have registered it, or applied to register it, as a trademark. The FDA typically conducts a review of proposed product names, including an evaluation of potential for confusion with other product names. If the FDA objects to any of our proposed product names, we may be required to expend significant additional resources in an effort to identify a usable substitute name that would qualify under applicable trademark laws, not infringe the existing rights of third parties and be acceptable to the FDA. If we are unable to establish name recognition based on our trademarks and trade names, we may not be able to compete effectively and our business may be adversely affected.

If we fail to comply with our obligations in our intellectual property licenses with third parties, or otherwise experience disruptions to our business relationships with our licensors, we could lose intellectual property rights that are important to our business.

We are party to license agreements that impose, and we may enter into additional licensing arrangements with third parties that may impose, diligence, development and commercialization timelines, milestone payment, royalty, insurance and other obligations on us. Under our existing licensing arrangements, we are obligated to pay royalties based on net sales of product candidates or related technologies to the extent they are covered by the agreements. We are also obligated to make certain milestone and license maintenance fee payments to licensors. If we fail to comply with such obligations under current or future licensing agreements, our counterparties may have the right to terminate these agreements or require us to grant them certain rights. Such an occurrence could materially adversely affect the value of any product candidate that is being developed under such agreement, or for which research, development or commercialization depends on rights licensed to us under such agreement. Termination of these agreements or reduction or elimination of our rights under these agreements may result in our having to negotiate new or reinstated agreements with less favorable terms, or cause us to lose our rights under these agreements, including our rights to important intellectual property or technology, which would have a material adverse effect on our business, financial condition, results of operations and prospects. Disputes which may arise regarding intellectual property subject to a licensing agreement include, but are not limited to:

In addition, the agreements under which we currently license intellectual property or technology from third parties are complex, and certain provisions in such agreements may be susceptible to multiple interpretations. The resolution of any contract interpretation disagreement that may arise could narrow what we believe to be the scope of our rights to the relevant intellectual property or technology, or increase what we believe to be our financial or other obligations under the relevant agreement, either of which could have a material adverse effect on our business, financial condition, results of operations and prospects. Moreover, if disputes over intellectual property that we have licensed prevent or impair our ability to maintain our current licensing arrangements on

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commercially acceptable terms, we may be unable to successfully develop and commercialize the affected technology and product candidates, which could have a material adverse effect on our business, financial conditions, results of operations and prospects.

Our current or future licensors may have relied on third-party consultants or collaborators or on funds from third parties such that our licensors are not the sole and exclusive owners of the patents and patent applications we in-license. If other third parties have ownership rights to patents and/or patent applications we in-license, they may be able to license such patents to our competitors, and our competitors could market competing products and technology. This could have a material adverse effect on our competitive position, business, financial conditions, results of operations and prospects.

In spite of our best efforts, our licensors might conclude that we have materially breached our license agreements and might therefore terminate the license agreements, thereby removing our ability to develop and commercialize product candidates and technology covered by these license agreements. If these in-licenses are terminated, or if the underlying intellectual property fails to provide the intended exclusivity, competitors would have the freedom to seek regulatory approval of, and to market, products and technologies identical to ours. This could have a material adverse effect on our competitive position, business, financial conditions, results of operations and prospects.

Our proprietary rights may not adequately protect our technologies and product candidates, and do not necessarily address all potential threats to our competitive advantage.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations, and may not adequately protect our business, or permit us to maintain our competitive advantage. The following examples are illustrative:

Risks Related to Employee Matters and Managing Growth

We will need to expand our organization, and we may experience difficulties in managing this growth, which could disrupt our operations.

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We expect to experience significant growth over time in the number of our employees and the scope of our operations, particularly in the areas of product candidate development, regulatory and clinical affairs and sales, marketing, manufacturing and distribution. To manage our growth activities, we must continue to implement and improve our managerial, operational and financial systems, expand our facilities and continue to recruit and train additional qualified personnel. Due to our limited financial resources and the limited experience of our management team in managing a company with such anticipated growth, we may not be able to effectively manage the expansion of our operations or recruit and train additional qualified personnel. Future growth would impose significant additional responsibilities on our management, including the need to identify, recruit, maintain, motivate and integrate additional employees, consultants and contractors. Also, our management may need to divert a disproportionate amount of its attention away from our day-to-day activities and devote a substantial amount of time to managing these growth activities. We may not be able to effectively manage the expansion of our operations, which may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. Our expected growth could require significant capital expenditures and may divert financial resources from other projects, such as the development of product candidates. If our management is unable to effectively manage our growth, our expenses may increase more than expected, our ability to generate and/or grow product revenues could be reduced, and we may not be able to implement our business strategy. Our future financial performance and our ability to commercialize our product candidates and compete effectively will depend, in part, on our ability to effectively manage any future growth.

Many of the biotechnology and pharmaceutical companies that we compete against for qualified personnel and consultants have greater financial and other resources, different risk profiles and a longer history in the industry than we do. If we are unable to continue to attract and retain high-quality personnel and consultants, the rate and success at which we can discover and develop product candidates and operate our business will be limited.

If we lose key management or scientific personnel, cannot recruit qualified employees, directors, officers or other significant personnel or experience increases in our compensation costs, our business may materially suffer.

We are highly dependent on our management and directors, including our Chief Executive Officer, Armon Sharei, Ph.D., among others. Due to the specialized knowledge each of our officers and key employees possesses with respect to our product candidates and our operations, the loss of service of key officers or directors could delay or prevent the successful enrollment and completion of our clinical trials. We carry limited key person life insurance on our Chief Executive Officer, but do not carry key person life insurance on our other officers or directors. In general, the employment arrangements that we have with our executive officers do not prevent them from terminating their employment with us at any time.

In addition, our future success and growth will depend in part on the continued service of our directors, employees and management personnel and our ability to identify, hire and retain additional personnel. If we lose one or more of our executive officers or key employees, our ability to implement our business strategy successfully could be seriously harmed. Furthermore, replacing executive officers and key employees, including the roles of Chief Financial Officer and Chief Medical Officer, may be difficult or costly and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to develop, gain regulatory approval of and commercialize product candidates successfully. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or effectively incentivize these additional key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. Additionally, competition for talent in the pharmaceutical and biotechnology industry has become increasingly intense, particularly in the last several months. In 2021, there was, and continues to be, a dramatic increase in workers leaving their positions throughout our industry and the U.S. economy that is being referred to as the "great resignation," and the market to build, retain and replace talent has become even more highly competitive. Furthermore, common stock and common stock option awards to employees may not serve as a valuable retention tool as a result of the volatility in the stock market and the market for smaller biotechnology companies in particular. Our future success depends on our ability to continue to attract and retain talented executive officers and other key employees.

Furthermore, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be engaged by entities other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high quality personnel, our ability to develop and commercialize product candidates will be limited.

Risks Related to Our Common Stock

Our executive officers, directors and principal stockholders, if they choose to act together, will continue to have the ability to control or significantly influence all matters submitted to stockholders for approval.

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Based on the number of shares of common stock outstanding as of March 11, 2022, our executive officers, directors and stockholders who owned more than 5% of our outstanding common stock and their respective affiliates, in the aggregate, hold shares representing approximately 50% of our outstanding voting stock. As a result, if these stockholders choose to act together, they would be able to control or significantly influence all matters submitted to our stockholders for approval, as well as our management and affairs. For example, these persons, if they choose to act together, would control or significantly influence the election of directors, the composition of our management and approval of any merger, consolidation or sale of all or substantially all of our assets.

A significant portion of our total outstanding shares are eligible to be sold into the market in the near future, which could cause the market price of our common stock to drop significantly, even if our business is doing well.

Sales of a substantial number of shares of our common stock in the public market, or the perception in the market that the holders of a large number of shares intend to sell shares, could reduce the market price of our common stock. As of March 11, 2022, we have 28,147,555 outstanding shares of common stock. Of these shares, holders of an aggregate of 2,869,294 shares of our common stock have rights, subject to specified conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or other stockholders, until such shares can otherwise be sold without restriction under Rule 144 or until the rights terminate pursuant to the terms of the stockholders' agreement between us and such holders. We have also registered shares of common stock that we may issue under our equity compensation plans. These shares can be freely sold in the public market upon issuance, subject to volume limitations applicable to affiliates and the lock-up agreements referred to above.

We are an "emerging growth company," and the reduced disclosure requirements applicable to emerging growth companies may make our common stock less attractive to investors.

We are an "emerging growth company," as defined in the JOBS Act, and may remain an emerging growth company until the last day of the fiscal year following the fifth anniversary of the closing of our initial public offering, or IPO. However, if certain events occur prior to the end of such five-year period, including if we become a "large accelerated filer," our annual gross revenues exceed $1.07 billion or we issue more than $1.0 billion of non-convertible debt in the previous three-year period, we will cease to be an emerging growth company prior to the end of such five-year period. For so long as we remain an emerging growth company, we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not emerging growth companies. These exemptions include:

We have taken advantage of reduced reporting burdens in this Annual Report on Form 10-K. In particular, in this Annual Report on Form 10-K, we have provided only two years of audited financial statements and have not included all of the executive compensation related information that would be required if we were not an emerging growth company. We cannot predict whether investors will find our common stock less attractive if we rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be reduced or more volatile. In addition, the JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. This allows an emerging growth company to delay the adoption of these accounting standards until they would otherwise apply to private companies.

We are a "smaller reporting company" and the reduced disclosure requirements applicable to smaller reporting companies may make our common stock less attractive to investors.

We are considered a "smaller reporting company." We are therefore entitled to rely on certain reduced disclosure requirements for as long as we remain a smaller reporting company, such as an exemption from providing selected financial data and certain executive compensation information and the option to present only two years of audited financial statements in our Annual Report on Form 10-K. In addition, for as long as we are a smaller reporting company with less than $100 million in annual revenue, we would be exempt from the requirement to obtain an external audit on the effectiveness of internal control over financial reporting provided in Section 404(b) of the Sarbanes-Oxley Act. These exemptions and reduced disclosures in our SEC filings due to our status as a smaller reporting company may make it harder for investors to analyze our results of operations and financial prospects. We cannot predict if

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investors will find our common stock less attractive because we may rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock prices may be more volatile.

Provisions in our restated certificate of incorporation and restated bylaws and under Delaware law could make an acquisition of our company, which may be beneficial to our stockholders, more difficult and may prevent attempts by our stockholders to replace or remove our current management.

Provisions in our restated certificate of incorporation and our restated bylaws may discourage, delay or prevent a merger, acquisition or other change in control of our company that stockholders may consider favorable, including transactions in which you might otherwise receive a premium for your shares. These provisions could also limit the price that investors might be willing to pay in the future for shares of our common stock, thereby depressing the market price of our common stock. In addition, because our board of directors is responsible for appointing the members of our management team, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors. Among other things, these provisions include those establishing:

Moreover, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the General Corporation Law of the State of Delaware, which prohibits a person who owns in excess of 15% of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired in excess of 15% of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner.

Our restated certificate of incorporation designates specific courts as the exclusive forum for certain litigation that may be initiated by our stockholders, which could limit our stockholders' ability to obtain a favorable judicial forum for disputes with us.

Our restated certificate of incorporation specifies that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for most legal actions involving claims brought against us

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by stockholders; provided that, the exclusive forum provision will not apply to suits brought to enforce any liability or duty created by the Securities Act, the Exchange Act, the rules and regulations thereunder or any other claim for which the federal courts have exclusive jurisdiction; and provided further that, if and only if the Court of Chancery of the State of Delaware dismisses any such action for lack of subject matter jurisdiction, such action may be brought in another state or federal court sitting in the State of Delaware. Our restated certificate of incorporation further provides that, unless we consent in writing to the selection of an alternative forum, the federal district courts of the United States of America shall, to the fullest extent permitted by law, be the sole and exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act. Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and to have consented to the provisions of our restated certificate of incorporation described above.

We believe these provisions benefit us by providing increased consistency in the application of Delaware law by chancellors particularly experienced in resolving corporate disputes and in the application of the Securities Act by federal judges, as applicable, efficient administration of cases on a more expedited schedule relative to other forums and protection against the burdens of multi-forum litigation. However, the provision may have the effect of discouraging lawsuits against our directors, officers, employees and agents as it may limit any stockholder's ability to bring a claim in a judicial forum that such stockholder finds favorable for disputes with us or our directors, officers, employees or agents. The enforceability of similar choice of forum provisions in other companies' certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection with any applicable action brought against us, a court could find the choice of forum provisions contained in our restated certificate of incorporation to be inapplicable or unenforceable in such action. If a court were to find the choice of forum provision contained in our restated certificate of incorporation to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could adversely affect our business, financial condition or results of operations.

Our ability to use our net operating losses and research and development credits to offset future taxable income may be subject to certain limitations.

As of December 31, 2021, we had U.S. federal net operating loss carryforwards, or NOLs, of $158.4 million, which may be available to offset future taxable income, if any, of which $11.3 million begin to expire in 2035 and of which $147.1 million do not expire but are generally limited in their usage to an annual deduction equal to 80% of annual taxable income. In addition, as of December 31, 2021, we had state NOLs of $152.0 million, which may be available to offset future taxable income, if any, and begin to expire in 2035. As of December 31, 2021, we also had federal and state research and development credit carryforwards of $8.1 million and $4.9 million, respectively, which will begin to expire in 2034 and 2030, respectively. In general, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, a corporation that undergoes an "ownership change," generally defined as a greater than 50% change by value in its equity ownership by certain shareholders or groups of shareholders over a three-year period, is subject to limitations on its ability to utilize its pre-change NOLs and its research and development credit carryforwards to offset future taxable income. Our existing NOLs and research and development credit carryforwards may be subject to limitations arising from previous ownership changes. In addition, future changes in our stock ownership, some of which might be beyond our control, could result in an ownership change under Section 382 and limitations on our ability to utilize NOLs and research and development credit carryforwards following any such ownership change. For these reasons, we may not be able to utilize a material portion of the NOLs or research and development credit carryforwards even if we attain profitability.

General Risk Factors

An active trading market for our common stock may not continue.

It is possible that an active trading market for our shares may not be sustained, which may make it difficult for our stockholders to sell their shares without depressing the market price for the shares, or at all. Further, an inactive market may also impair our ability to raise capital by selling shares of our common stock and may impair our ability to enter into strategic partnerships or acquire companies or products by using our shares of common stock as consideration.

The market price of our common stock may be volatile and fluctuate substantially, which could result in substantial losses for holders of our common stock.

Our stock price is likely to be volatile. The stock market in general and the market for smaller biotechnology and pharmaceutical companies in particular have experienced extreme volatility in recent months that has often been unrelated to the operating performance of particular companies. This volatility is likely to continue. As a result of this volatility, our stockholders may not be able to sell their common stock at or above the price they paid for it. The market price for our common stock may be influenced by many factors, including:

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If we fail to maintain effective internal control over financial reporting and effective disclosure controls and procedures, we may not be able to accurately report our financial results in a timely manner or prevent fraud, which may adversely affect investor confidence in our company.

We are a public company required to comply with the SEC's rules implementing Sections 302 and 404 of the Sarbanes-Oxley Act, which require management to certify financial and other information in our quarterly and annual reports and provide an annual management report on the effectiveness of controls over financial reporting. As an emerging growth company, our independent registered public accounting firm will not be required to attest to the effectiveness of our internal control over financial reporting pursuant to Section 404 until the date we are no longer an emerging growth company. At such time, our independent registered public accounting firm may issue a report that is adverse in the event material weaknesses have been identified in our internal control over financial reporting.

To achieve compliance with Section 404 within the prescribed period, we have been engaged in a process to document and evaluate our internal control over financial reporting, which has been, and will continue to be, both costly and challenging. In this regard, we will need to continue to dedicate internal resources, engage outside consultants, adopt a detailed work plan to assess and document the

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adequacy of internal control over financial reporting, continue steps to improve control processes as appropriate, validate through testing whether such controls are functioning as documented, and implement a continuous reporting and improvement process for internal control over financial reporting. Despite our efforts, there is a risk that we will not be able to conclude, within the prescribed timeframe or at all, that our internal control over financial reporting is effective as required by Section 404. We may discover significant deficiencies or material weaknesses in our internal control over financial reporting, which we may not successfully remediate on a timely basis or at all. Any failure to remediate any significant deficiencies or material weaknesses identified by us or to implement required new or improved controls, or difficulties encountered in their implementation, could cause us to fail to meet our reporting obligations or result in material misstatements in our financial statements. If we identify one or more material weaknesses, it could result in an adverse reaction in the financial markets due to a loss of confidence in the reliability of our financial statements.

Our disclosure controls and procedures may not prevent or detect all errors or acts of fraud.

We are subject to the periodic reporting requirements of the Exchange Act. We have refined our disclosure controls and procedures to provide reasonable assurance that information we must disclose in reports we file or submit under the Exchange Act is accumulated and communicated to management, and recorded, processed, summarized and reported within the time periods specified in the rules and forms of the SEC. We believe that any disclosure controls and procedures, no matter how well-conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

These inherent limitations include the realities that judgments in decision-making can be faulty, and that breakdowns can occur because of simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more people or by an unauthorized override of the controls. Accordingly, because of the inherent limitations in our control system, misstatements due to error or fraud may occur and not be detected.

Because we do not anticipate paying any cash dividends on our common shares in the foreseeable future, capital appreciation, if any, would be the sole source of gain for our stockholders.

We have never declared or paid any cash dividends on our common shares. We currently anticipate that we will retain all available funds and future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. As a result, capital appreciation, if any, of our common shares would be the sole source of gain on an investment in our common shares for the foreseeable future.

We could be subject to securities class action litigation.

In the past, securities class action litigation has often been brought against a company following a decline in the market price of its securities. This risk is especially relevant for us because biopharmaceutical companies have experienced significant stock price volatility in recent years. If we face such litigation, it could result in substantial costs and a diversion of management's attention and resources, which could harm our business.

We incur significant costs as a result of operating as a public company, and our management is required to devote substantial time to new compliance initiatives and corporate governance practices.

As a public company, we incur significant legal, accounting and other expenses that we did not incur as a private company, and these expenses will increase after we are no longer an emerging growth company. The Sarbanes-Oxley Act of 2002, the Dodd-Frank Wall Street Reform and Consumer Protection Act, the listing requirements of the NYSE and other applicable securities rules and regulations impose various requirements on public companies, including establishment and maintenance of effective disclosure and financial controls and corporate governance practices. Our management and other personnel devote a substantial amount of time to these compliance initiatives. Moreover, these rules and regulations have increased our legal and financial compliance costs and made some activities more time-consuming and costly. For example, operating as a public company has made and will continue to make it more expensive for us to obtain director and officer liability insurance, which in turn could make it more difficult for us to attract and retain qualified members of our board of directors.

These rules and regulations are often subject to varying interpretations, in many cases due to their lack of specificity, and, as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies. This could result in continuing uncertainty regarding compliance matters and higher costs necessitated by ongoing revisions to disclosure and governance practices.

If securities or industry analysts do not continue to publish research or reports about our business, or if they issue an adverse or misleading opinion regarding our stock, our stock price and trading volume could decline, even if our business is doing well.

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The trading market for our common stock is influenced by the research and reports that industry or securities analysts publish about us or our business. If no or few securities or industry analysts continue coverage of us, the trading price for our stock would be negatively impacted. If any of the analysts who cover us issue an adverse or misleading opinion regarding us, our business model, our intellectual property or our stock performance, or if our target preclinical studies or clinical trials and operating results fail to meet the expectations of analysts, our stock price would likely decline. If one or more of these analysts ceases coverage of us or fails to publish reports on us regularly, we could lose visibility in the financial markets, which in turn could cause our stock price or trading volume to decline.

The increasing focus on environmental sustainability and social initiatives could increase our costs, harm our reputation and adversely impact our financial results.

There has been increasing public focus by investors, environmental activists, the media and governmental and nongovernmental organizations on a variety of environmental, social and other sustainability matters. We may experience pressure to make commitments relating to sustainability matters that affect us, including the design and implementation of specific risk mitigation strategic initiatives relating to sustainability. If we are not effective in addressing environmental, social and other sustainability matters affecting our business, or setting and meeting relevant sustainability goals, our reputation may suffer. In addition, we may experience increased costs in order to execute upon our sustainability goals and measure achievement of those goals, which could have an adverse impact on our business and financial condition.

We or the third parties upon whom we depend may be adversely affected by natural disasters and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Natural disasters could severely disrupt our operations and have a material adverse effect on our business, results of operations, financial condition and prospects. If a natural disaster, power outage or other event occurred that prevented us from using all or a significant portion of our headquarters, that damaged critical infrastructure, such as the manufacturing facilities on which we rely, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible for us to continue our business for a substantial period of time. The disaster recovery and business continuity plans we have in place may prove inadequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our disaster recovery and business continuity plans, which could have a material adverse effect on our business. For example, following Hurricane Maria, shortages in production and delays in a number of medical supplies produced in Puerto Rico resulted, and any similar interruption due to a natural disaster affecting us or any of our third-party manufacturers could materially delay our operations.

Litigation against us could be costly and time-consuming to defend and could result in additional liabilities.

We may from time to time be subject to legal proceedings and claims that arise in the ordinary course of business or otherwise, such as claims brought by our customers in connection with commercial disputes and employment claims made by our current or former employees. Claims may also be asserted by or on behalf of a variety of other parties, including government agencies, patients or vendors of our customers, or stockholders.

Any litigation involving us may result in substantial costs, operationally restrict our business, and may divert management's attention and resources, which may seriously harm our business, overall financial condition and results of operations. Insurance may not cover existing or future claims, be sufficient to fully compensate us for one or more of such claims or continue to be available on terms acceptable to us. A claim brought against us that is uninsured or underinsured could result in unanticipated costs, thereby adversely impacting our results of operations and resulting in a reduction in the trading price of our stock.

We may engage in acquisitions or strategic partnerships that could disrupt our business, cause dilution to our stockholders, reduce our financial resources, cause or to incur debt or assume contingent liabilities, and subject us to other risks.

In the future, we may enter into transactions to acquire other businesses, products or technologies or enter into strategic partnerships, including licensing. If we do identify suitable acquisition or partnership candidates, we may not be able to make such acquisitions or partnerships on favorable terms, or at all. Any acquisitions or partnerships we make may not strengthen our competitive position, and these transactions may be viewed negatively by customers or investors. We may decide to incur debt in connection with an acquisition or issue our common stock or other equity securities to the stockholders of the acquired company, which would reduce the percentage ownership of our existing stockholders. We could incur losses resulting from undiscovered liabilities of the acquired business or partnership that are not covered by the indemnification we may obtain from the seller or our partner. In addition, we may not be able to successfully integrate any acquired personnel, technologies and operations into our existing business in an effective, timely and non-disruptive manner. Acquisitions or partnerships may also divert management attention from day-to-day responsibilities, lead to a loss of key personnel, increase our expenses and reduce our cash available for operations and other uses. We cannot predict the

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number, timing or size of future acquisitions or partnerships or the effect that any such transactions might have on our operating results.

Item 1B. Unresolved Staff Comments

None

Item 2. Properties.

Our principal office is located at 200 Arsenal Yards Blvd, Suite 210, Watertown, MA 02472, where we lease approximately 63,477 square feet of office and laboratory space. We lease this space under a lease agreement, as amended, that terminates on November 30, 2029. We believe that our facilities are sufficient to meet our current needs and that suitable additional space will be available as and when needed.

Item 3. Legal Proceedings.

We are not currently subject to any material legal proceedings.

Item 4. Mine Safety Disclosures.

Not applicable.

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PART II

Item 5. Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.

Market Information for Common Stock

Our common stock has been publicly traded on The New York Stock Exchange under the symbol "SQZ" since the initial public offering, or IPO, of our common stock on October 30, 2020. Prior to that time, there was no public market for our common stock. As of March 11, 2022, there were 65 holders of record of our common stock.

Dividend Policy

We have never declared or paid any cash dividends on our common shares. We currently anticipate that we will retain all available funds and future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future.

Recent Sales of Unregistered Securities

None.

Use of Proceeds

On October 29, 2020, the SEC declared effective our registration statement on Form S-1 (File No. 333-249422), as amended, filed in connection with our IPO, or the Registration Statement. Pursuant to the Registration Statement, we registered the offer and sale of 5,073,529 shares of our common stock with a proposed maximum aggregate offering price of approximately $91.3 million. On November 3, 2020, we issued and sold 4,411,765 shares of our common stock at a price to the public of $16.00 per share. Upon completion of the IPO on November 3, 2020, we received net proceeds of approximately $65.6 million, after deducting underwriting discounts and commissions, but before deducting offering costs payable by us of $2.6 million. On November 12, 2020, in connection with the full exercise of the over-allotment option granted to the underwriters of our IPO, we issued and sold 661,764 additional shares of common stock at a price of $16.00 per share, generating additional net proceeds of $9.8 million after deducting underwriting discounts of $0.7 million. Net proceeds of approximately $72.5 million have been invested in money market funds. There has been no material change in the expected use of the net proceeds from our IPO as described in the final prospectus dated October 29, 2020 and filed with the SEC on October 30, 2020, pursuant to Rule 424(b)(4) (File No. 333-252666) of the Securities Act.

Issuer Purchases of Equity Securities

We did not repurchase any of our equity securities during the quarter ended December 31, 2021.

Item 6. [Reserved]

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Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations.

You should read the following discussion and analysis of our financial condition and results of operations together with our consolidated financial statements and related notes appearing at the end of this Annual Report on Form 10-K. Some of the information contained in this discussion and analysis or set forth elsewhere in this Annual Report on Form 10-K, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the "Risk Factors" section of this Annual Report on Form 10-K, our actual results could differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.

Overview

We are a clinical-stage biotechnology company focused on unlocking the full potential of cell therapies to benefit patients with cancer, autoimmune and infectious diseases, and other serious conditions. The company was founded on the therapeutic potential of Cell Squeeze®, our proprietary technology which allows for rapid delivery of a variety of cargo into different cell types. We aim to create multiple cell therapies that drive the immune system to combat diseases.

In oncology, we are developing cell therapy platforms that are based on directing tumor antigen-specific immune activation via engineered antigen presentation. We believe that by engineering physiological antigen presentation signals in subsets of peripheral blood cells that act on immune priming pathways, we have the potential to develop cell therapies that are designed to be potent drivers of tumor-specific immunity, well-tolerated, administered without lymphodepleting preconditioning or hospitalization, and produced in under 24 hours. We have three oncology candidates in clinical trials across our SQZ®Antigen Presenting Cell, or APC, SQZ®enhanced APC, or eAPC, and SQZ®Activating Antigen Carrier, or AAC, cell therapy platforms. In our autoimmune diseases portfolio, we are developing our SQZ®Tolerizing Antigen Carrier, or TAC, cell therapy platform with the aim to restore immune tolerance to self-antigens or other autoimmune disease-associated antigens that are central to disease pathogenesis.

In 2021, we executed on several key areas of our pipeline and advanced our APC platform objectives. As of December 31, 2021, we have dosed 20 patients in our Phase 1 trial for our lead APC candidate, SQZ-PBMC-HPV, in HPV16+ advanced solid tumors. We reported interim data from the first three monotherapy dose-escalation cohorts at the 2021 American Society of Clinical Oncology, or ASCO, Annual Meeting, and presented interim safety, biomarker, and clinical data from the highest dose SQZ-PBMC-HPV monotherapy cohort at the 2021 European Society for Medical Oncology Immuno-Oncology, or ESMO-IO, Congress. Key observations from the reported data include, as of a cutoff date of October 8, 2021 (n=18 patients):

We have advanced our trial to evaluate SQZ-PBMC-HPV in combination with checkpoint inhibitor therapies, and are continuing to enroll patients in the highest dose monotherapy cohort. We are targeting additional data in the second half of 2022.

We have continued to build upon the progress of our SQZ®APC platform through the development of the novel SQZ®eAPC platform. Our lead eAPC product candidate leverages the added capabilities and functionality of multiple antigen presentation and immunological signals achieved through multiplexed mRNA delivery to diverse immune cell types. In January 2022, we received allowance to proceed with clinical trials from the U.S. Food and Drug Administration, or FDA, under our Investigational New Drug, or IND, application for SQZ-eAPC-HPV, our lead eAPC candidate engineered with HPV16 antigens and costimulatory signals. We will initiate the SQZ-eAPC-HPV trial, the COMMANDER-001 Phase 1/2 study, in patients with HPV16+ advanced solid tumors in the first half of 2022. We anticipate initial interim data in the second half of 2022. In addition to our efforts in the oncology field, we are also continuing to advance the eAPC platform in the infectious diseases field.

In January 2021, we received allowance to proceed with clinical trials from the FDA under our IND for SQZ-AAC-HPV, our lead AAC product candidate derived from red blood cells engineered with tumor-specific antigens. We are currently enrolling monotherapy cohorts as part of the Phase 1 ENVOY-001 trial to assess safety and tolerability as well as secondary outcome measures of the investigational SQZ-AAC-HPV therapy in HPV16+ advanced solid tumors, with initial interim data targeted in the second half of 2022.

We are also advancing our SQZ® TAC platform focused on creating novel and proprietary cell therapies as it relates to modulating or restoring immune tolerance. We have selected Celiac disease as the first proposed autoimmune indication for SQZ® TAC platform development. We believe the evidence of a causal disease antigen and T-cell driven pathology, and the substantial unmet need for a

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tolerizing treatment option provide a compelling opportunity for us to pursue Celiac disease. We presented characterization of TAC-mediated mechanisms of antigen-specific tolerance in preclinical models at the 2021 Federation of Clinical Immunology Societies, or FOCIS, Meeting. We anticipate further development of our TAC-Celiac candidate through IND-enabling studies in 2022 to support an IND submission in the first half of 2023, and, in parallel, are planning to use our proprietary, point-of-care manufacturing system for the production of the clinical batches.

Since our inception, we have focused substantially all of our resources on building our Cell Squeeze technology, establishing and protecting our intellectual property portfolio, conducting research and development activities, developing our manufacturing process and manufacturing product candidate materials, preparing for and initiating clinical trials of our product candidates, organizing and staffing our company, business planning, raising capital and providing general and administrative support for these operations. We do not have any products approved for sale and have not generated any revenue from product sales. To date, we have funded our operations primarily with proceeds from sales of common and preferred stock, payments received under our collaboration agreements with Hoffman-La Roche Inc. and F. Hoffman La Roche Ltd., or together, Roche, and with proceeds from our initial public offering, or IPO, and follow-on offering of common stock, or the Follow-On Offering. In November 2020, we completed our IPO pursuant to which we issued and sold 5,073,529 shares of common stock, inclusive of 661,764 shares sold by us pursuant to the full exercise of the underwriters' option to purchase additional shares. We received aggregate net proceeds of approximately $75.5 million from the IPO, after deducting underwriting discounts and commissions, but before deducting offering costs payable by us, which were $2.6 million. In February 2021, we completed a public offering, or the Follow-On Offering, pursuant to which we issued and sold 3,000,000 shares of common stock. We received aggregate net proceeds of approximately $56.4 million, after deducting underwriting discounts and commissions, but before deducting offering costs payable by us, which were $0.8 million.

Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more of our product candidates. We reported a net loss of $68.7 million for the year ended December 31, 2021. As of December 31, 2021, we had an accumulated deficit of $195.5 million. We expect to continue to incur significant expenses and increasing operating losses for at least the next several years. We expect that our expenses and capital requirements will increase substantially in connection with our ongoing activities, particularly if and as we:

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for our product candidates. If we obtain regulatory approval for any of our product candidates, we expect to incur significant expenses related to developing our commercialization capability to support product sales, marketing and distribution.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed on favorable terms, or at all. If we fail to raise capital or enter into such agreements as, and when, needed, we would have to significantly delay, scale back or discontinue the development and commercialization of one or more of our product candidates.

Because of the numerous risks and uncertainties associated with cell therapy product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve or maintain profitability. Even if we are able to generate product sales, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a

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continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce or terminate our operations.

We believe that our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2023. See "-Liquidity and Capital Resources."

Impact of the COVID-19 Coronavirus

The COVID-19 pandemic and government measures taken in response have had a significant impact, both direct and indirect, on hospitals, businesses and commerce, as worker shortages have occurred, supply chains have been disrupted, and facilities and production have been suspended. The future progression of the pandemic and its effects on our business and operations are uncertain.

The COVID-19 pandemic has impacted and may continue to impact personnel at third-party manufacturing facilities or the availability or cost of materials, which would disrupt our supply chain. It also has affected and may continue to affect our ability to enroll patients in and timely complete our ongoing clinical trials of SQZ-PBMC-HPV, SQZ-AAC-HPV and SQZ-eAPC-HPV and delay the initiation of future clinical trials, disrupt regulatory activities or have other adverse effects on our business and operations. For example, we have experienced delays in receiving supplies of raw materials for our preclinical activities due to the impact of COVID-19 on our suppliers' ability to timely manufacture these materials, and we have experienced an increase in the transportation cost of our product candidates due to the decreased availability of commercial flights. In addition, we have experienced delays in opening clinical trial sites and sites that are open may also have challenges enrolling patients due to the COVID-19 pandemic. Further, staff shortages, including staff that are required to conduct certain testing, such as biopsies, at the Company's clinical sites or at third-party vendors have resulted in delays in site initiations and in some tests not being properly or timely performed or being delayed. In response to the public health directives and to help reduce the risk to our employees, we took precautionary measures, including implementing work-from-home policies for our administrative employees and staggered work times for our lab employees. We plan to continue to implement restrictive measures and are assessing when and how to resume normal operations. The effects of the public health directives and our work-from-home policies may negatively impact productivity, disrupt our business and delay our clinical programs and timelines and future clinical trials, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on our ability to conduct our business in the ordinary course. These and similar, and perhaps more severe, disruptions in our operations could negatively impact our business, results of operations and financial condition, including our ability to obtain financing.

The pandemic has already caused significant disruptions in the financial markets, and may continue to cause such disruptions, which could impact our ability to raise additional funds to support our operations. Moreover, the pandemic has significantly impacted inflation and economies worldwide and could result in adverse effects on our business and operations. We are monitoring the potential impact of the COVID-19 pandemic on our business and financial statements. To date, we have not incurred impairment losses in the carrying values of our assets as a result of the pandemic and we are not aware of any specific related event or circumstance that would require us to revise our estimates reflected in our consolidated financial statements. We cannot be certain what the overall impact of the COVID-19 pandemic will be on our business and people. The extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations, financial condition, and liquidity, including planned and future clinical trials and research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19, the actions taken to contain or treat it, and the duration and intensity of the related effects.

Components of Our Results of Operations

Revenue

To date, we have not generated any revenue from product sales and do not expect to do so for the next several years. All of our revenue to date has been derived from three collaboration agreements with Roche, which we entered into in 2015, 2017 and 2018, and, to a lesser extent, from government grants.

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If our development efforts for our product candidates are successful and result in regulatory approval or license or additional collaboration agreements with third parties, we may generate revenue in the future from product sales, payments from additional collaboration or license agreements that we may enter into with third parties, or any combination thereof. We expect that our revenue for the next several years will be derived primarily from our collaboration agreements with Roche as well as any additional collaborations that we may enter into in the future. We cannot provide assurance as to the timing of future milestone or royalty payments or that we will receive any of these payments at all.

Collaboration Revenue

2017 License and Collaboration Agreement with Roche

In April 2017, we entered into a second license and collaboration agreement with Roche, or the 2017 Roche Agreement, to allow Roche to use our Cell Squeeze technology to enable gene editing of immune cells to discover new targets in cancer immunotherapy. The 2017 Roche Agreement includes several licenses granted by Roche to us and by us to Roche in order to conduct a specified research program in accordance with a specified research plan.

Under the agreement, we received an upfront payment of $5.0 million as a technology access fee and are entitled to (i) payments of up to $1.0 million as reimbursement for our research costs; (ii) milestone payments of up to $7.0 million upon the achievement of specified development milestones; and (iii) annual maintenance fees ranging from $0.5 million to $0.9 million for each year following the fifth anniversary of the effective date, subject to specified prepayment discounts.

We assessed our accounting for the 2017 Roche Agreement under Accounting Standards Codification 606, Revenue from Contracts with Customers, or ASC 606 and identified the following promises under the agreement: (i) a non-exclusive license granted to Roche to perform research related to and use our Cell Squeeze technology for gene editing of immune cells; (ii) specified research and development services related to gene editing of immune cells through the research term; (iii) manufacturing activities to support the specified research plan; and (iv) participation on a joint research committee, or JRC. We concluded at the outset of the 2017 Roche Agreement that the first three promises should be combined into a single performance obligation and that the JRC participation had an immaterial impact on the accounting model.

We recognize revenue associated with the performance obligation as the research and development services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy the performance obligation. To date, the amounts received from Roche that had not yet been recognized as revenue have been deferred as a contract liability in our consolidated balance sheet and have been recognized over the remaining research and development period until the performance obligation is satisfied.

In early 2022, all active work streams under the 2017 Roche Agreement were concluded and the agreement was terminated. As of December 31, 2021, we determined that we expected to incur no additional costs to satisfy the remaining performance obligations under the 2017 Roche Agreement and we recognized revenue of $1.2 million under the 2017 Roche Agreement. There was no remaining deferred revenue under the 2017 Roche Agreement as of December 31, 2021.

2018 License and Collaboration Agreement with Roche

In October 2018, we entered into a third license and collaboration agreement with Roche, or the 2018 Roche Agreement, to jointly develop certain products based on mononuclear antigen presenting cells, or APCs, including human papilloma virus, or HPV, using our SQZ APC platform for the treatment of oncology indications. We granted Roche a non-exclusive license to our intellectual property, and Roche granted us a non-exclusive license to its and its affiliates' intellectual property for the purpose of performing research activities. In connection with this agreement, the parties terminated the original Roche Agreement entered into in 2015.

Under the 2018 Roche Agreement, Roche was granted option rights to obtain an exclusive license to develop APC products or products derived from the collaboration programs on a product-by-product basis in oncology and to develop a Tumor Cell Lysate, or TCL, product. For each of the APC products and TCL product, once Roche exercises its option and pays a specified incremental amount, Roche will receive worldwide, exclusive commercialization rights for the licensed products, subject to our alternating option to retain U.S. APC commercialization rights. Through December 31, 2021, Roche had not exercised any of its options under the 2018 Roche Agreement.

Under the 2018 Roche Agreement, we received an upfront payment of $45.0 million and are eligible to receive (i) reimbursement of a mid double-digit percentage of our development costs; (ii) aggregate milestone payments on a product-by-product basis of up to $1.6 billion upon the achievement of specified milestones, consisting of up to $217.0 million of development milestone payments, up to $240.0 million of regulatory milestone payments and up to $1.2 billion of sales milestone payments; and (iii) tiered royalties on annual net sales of APC and TCL products licensed under the agreement at specified rates ranging from a mid single-digit percentage to a percentage in the mid twenties. We received the upfront payment of $45.0 million in October 2018 upon execution of the agreement. In addition, during the second quarter of 2019, we received a payment of $10.0 million following the achievement of the first development milestone under the 2018 Roche Agreement related to submission by us of preclinical data to the FDA and during the first quarter of 2020, we received a payment of $20.0 million following the achievement of the second development milestone under

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the 2018 Roche Agreement related to first-patient dosing in a Phase 1 clinical trial. In the fourth quarter of 2021, we became entitled to receive a milestone payment of $3.0 million upon (i) the recommendation by an independent panel that we could advance our SQZ-PBMC-HPV clinical trial to combination therapy with checkpoint initiators and (ii) the initiation of that therapy. For additional information on the 2018 Roche Agreement, see "Business-Collaboration, Research and License Agreements-Roche Collaboration."

We assessed our accounting for the 2018 Roche Agreement in accordance with ASC 606 and identified the following promises under the agreement: (i) a non-exclusive license granted to Roche to use our intellectual property and collaboration compounds to conduct research activities related to the research plans under the 2018 Roche Agreement; (ii) specified research and development services related to HPV through Phase 1 clinical trials under a specified research plan; (iii) manufacturing of our SQZ APC platform and equipment in order to support the HPV research plan; (iv) specified research and development services on next-generation APCs under a research plan; (v) specified research and development services on TCL under a research plan; and (vi) participation on a joint steering committee, or JSC. We concluded at the outset of the 2018 Roche Agreement that there were three performance obligations under the agreement: (1) the license to our intellectual property, the research and development activities related to HPV through Phase 1 clinical trials under a specified research plan, and the manufacturing of our SQZ APC platform and equipment in order to support the HPV research plan, or the first performance obligation; (2) the license to our intellectual property and the research and development activities on next-generation APCs, or the second performance obligation; and (3) the license to our intellectual property and the research and development activities on TCL, or the third performance obligation. We also concluded that the JSC participation had an immaterial impact on the accounting model.

In addition, we determined that the upfront payment of $45.0 million as well as the reimbursable costs of $10.8 million estimated by us constituted the entirety of the consideration to be included in the transaction price. This transaction price of $55.8 million was initially allocated to the three performance obligations based on the relative standalone selling price of each obligation. The potential milestone payments that we may be eligible to receive were excluded from the transaction price at the outset of the arrangement. We reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, we will adjust our estimate of the transaction price.

In 2019, we evaluated our overall program priorities and determined that in 2020 we would continue to focus our resources on progressing the specified APC programs related to the 2018 Roche Agreement as well as our AAC and TAC platforms. As a result of our continuing focus on these specific programs, we reduced the level of priority of the TCL research activities under the 2018 Roche Agreement and expect to perform such TCL research activities over a longer time period than as originally expected under the research plan of the agreement.

We separately recognize revenue associated with each of the three performance obligations as the research, development and manufacturing services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy each performance obligation. The amounts received from Roche that have not yet been recognized as revenue are deferred as a contract liability in our consolidated balance sheet and will be recognized over the remaining research and development period until each performance obligation is satisfied.

During the year ended December 31, 2021, the total estimated costs expected to be incurred to satisfy the performance obligations under the 2018 Roche Agreement decreased by $7.3 million. During the year ended December 31, 2020, the total estimated costs expected to be incurred to satisfy the performance obligations increased by $7.3 million. We recognized revenue of $25.8 million and $20.5 million during the years ended December 31, 2021 and 2020, respectively, under the 2018 Roche Agreement. As of December 31, 2021 and 2020, we recorded as a contract liability deferred revenue related to the 2018 Roche Agreement of $21.2 million and $44.0 million, respectively, of which $12.0 million and $24.7 million, respectively, were current liabilities. As of December 31, 2021, the research and development services related to the first performance obligations was expected to be performed over a remaining period of one year. The expected remaining period of performance of our research and development services related to the third performance obligation is not currently determinable until TCL research activities resume, or the 2018 Roche Agreement is modified by us and Roche.

For additional information regarding our accounting for the three collaboration agreements with Roche, see "-Critical Accounting Policies and Significant Judgments and Estimates-Revenue Recognition for License and Collaboration Arrangements" and "Business-Collaboration, Research and License Agreements-Roche Collaboration."

Operating Expenses

Research and Development Expenses

Research and development expenses consist primarily of costs incurred for our research activities, including development of our product candidates and costs incurred under our collaboration arrangements with Roche, which include:

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We expense research and development costs as incurred. Nonrefundable advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed, or when it is no longer expected that the goods will be delivered or the services rendered. Upfront payments under license agreements are expensed upon receipt of the license, and annual maintenance fees under license agreements are expensed in the period in which they are incurred. Milestone payments under license agreements are accrued, with a corresponding expense being recognized, in the period in which the milestone is determined to be probable of achievement and the related amount is reasonably estimable.

Our direct research and development expenses are tracked on a program-by-program basis and consist of external costs and fees paid to consultants, contractors, CMOs and CROs in connection with our preclinical and clinical development and manufacturing activities. Such program costs also include the external costs of laboratory and consumable materials and costs of raw materials that are directly attributable to and incurred for any single program. We do not allocate employee costs, costs associated with our platform development and discovery efforts, payments made under third-party licensing agreements, costs of laboratory supplies and consumable materials that are not directly attributable to any single program, and facilities expenses, including rent, depreciation and other indirect costs, to specific product development programs because these costs are deployed across multiple programs and our platform technology and, as such, are not separately classified.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. We expect that our research and development expenses will increase substantially in connection with our planned preclinical and clinical development activities in the near term and in the future, particularly should Roche determine not to exercise its options and we decide to continue clinical development of a product candidate. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any of our product candidates. The successful development of our product candidates is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following:

A change in the outcome of any of these variables with respect to the development of any of our product candidates could significantly change the costs and timing associated with the development of that product candidate. In addition, we may never succeed in obtaining regulatory approval for any of our product candidates.

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General and Administrative Expenses

General and administrative expenses consist primarily of salaries and related costs, including stock-based compensation, for personnel in executive, finance and administrative functions. General and administrative expenses also include direct and allocated facility-related costs as well as professional fees for legal, patent, consulting, investor and public relations, accounting and audit services. We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued research activities and development of our product candidates. We also anticipate that we will incur increased accounting, audit, legal, regulatory, compliance and director and officer insurance costs as well as investor and public relations expenses associated with operating as a public company.

Other Income (Expense)

Interest Income

Interest income consists of interest earned on our cash equivalents and marketable securities balances.

Other Income (Expense), Net

Other income (expense), net consists of miscellaneous income and expense unrelated to our core operations.

Income Taxes

Since our inception, we have not recorded any income tax benefits for the net losses we have incurred in each year or for our earned research and development tax credits, as we believe, based upon the weight of available evidence, that it is more likely than not that all of our net operating loss, or NOL, carryforwards and tax credit carryforwards will not be realized. As of December 31, 2021, we had U.S. federal NOL carryforwards of $158.4 million, which may be available to offset future taxable income, of which $11.3 million begin to expire in 2034 and of which $147.1 million do not expire but are generally limited in their usage to an annual deduction equal to 80% of annual taxable income. In addition, as of December 31, 2021, we had state NOL carryforwards of $152.0 million, which may be available to offset future taxable income and begin to expire in 2035. As of December 31, 2021, we also had U.S. federal and state research and development tax credit carryforwards of $8.1 million and $4.9 million which will begin to expire in 2034 and 2030, respectively. We have recorded a full valuation allowance against our net deferred tax assets at each balance sheet date.

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Results of Operations

Comparison of the Years Ended December 31, 2021 and 2020

The following table summarizes our results of operations for the years ended December 31, 2021 and 2020:

		YEAR ENDED DECEMBER 31,
		2021			2020			CHANGE
		(in thousands)
Collaboration revenue		$	27,098			$	20,998			$	6,100
Operating expenses:
Research and development			70,148				51,545				18,603
General and administrative			25,719				20,511				5,208
Total operating expenses			95,867				72,056				23,811
Loss from operations			(68,769	)			(51,058	)			(17,711	)
Other income (expense):
Interest income			36				550				(514	)
Other income (expense), net			(8	)			(13	)			5
Total other income, net			28				537				(509	)
Net loss		$	(68,741	)		$	(50,521	)		$	(18,220	)

Revenue

Collaboration revenue was $27.1 million for the year ended December 31, 2021, compared to $21.0 million for the year ended December 31, 2020. We recognize revenue under our collaboration arrangements using an input measure, comparing our cumulative costs incurred to our total estimated costs of the research, development and manufacturing activities, as applicable, on each program. The increase in collaboration revenue of $6.1 million was due to the following:

During the years ended December 31, 2021 and 2020, we recognized total revenue of $25.8 million and $20.5 million, respectively, under the 2018 Roche Agreement. During the years ended December 31, 2021 and 2020, we recognized total revenue of $1.2 million and $0.5 million, respectively, under the 2017 Roche Agreement.

Research and Development Expenses

		YEAR ENDED DECEMBER 31,
		2021			2020			CHANGE
		(in thousands)
Direct research and development expenses by program:
SQZ-PBMC-HPV		$	15,751			$	14,973			$	778
SQZ-AAC-HPV			3,873				7,470				(3,597	)
SQZ-eAPC-HPV			15,071				1,581				13,490
Other programs			7,372				3,534				3,838
Unallocated research and development expenses:
Personnel related (including stock-based compensation)			18,408				14,694				3,714
Facility related			5,173				4,948				225
Laboratory and consumable materials			1,430				1,212				218
Platform-related external services and other			3,070				3,133				(63	)
Total research and development expenses		$	70,148			$	51,545			$	18,603

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Research and development expenses were $70.1 million for the year ended December 31, 2021, compared to $51.5 million for the year ended December 31, 2020. The net increase was primarily due to the following:

General and Administrative Expenses

		YEAR ENDED DECEMBER 31,
		2021			2020			CHANGE
		(in thousands)
Personnel related (including stock-based compensation)		$	12,685			$	8,971			$	3,714
Professional and consultant fees			4,144				5,022				(878	)
Patent related			1,910				2,424				(514	)
Facility related and other			6,980				4,094				2,886
Total general and administrative expenses		$	25,719			$	20,511			$	5,208

General and administrative expenses for the year ended December 31, 2021 were $25.7 million, compared to $20.5 million for the year ended December 31, 2020. The increase in general and administrative expenses was primarily due to the following:

Interest Income

Interest income for the years ended December 31, 2021 and 2020 was less than $0.1 million and $0.6 million, respectively. The decrease in interest income was due to a decrease in interest rates as well as lower average cash balances invested in marketable securities during 2021 as compared to 2020.

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Other Income (Expense), Net

Other income (expense) was not significant for both the years ended December 31, 2021 and 2020.

Liquidity and Capital Resources

Since our inception, we have incurred significant operating losses. We have not yet commercialized any of our product candidates and we do not expect to generate revenue from sales of any product candidates for the next several years, if at all. Through December 31, 2021, we have funded our operations from the sales of our common and preferred stock, upfront and milestone payments under our collaboration agreements with Roche, and with proceeds from our IPO and Follow-On Offering. In November 2020, we completed our IPO pursuant to which we issued and sold 5,073,529 shares of common stock, inclusive of 661,764 shares sold by us pursuant to the full exercise of the underwriters' option to purchase additional shares. We received aggregate net proceeds of approximately $75.5 million, after deducting underwriting discounts and commissions, but before deducting offering costs payable by us, which were $2.6 million. In February 2021, we completed the Follow-On Offering pursuant to which we issued and sold 3,000,000 shares of common stock. We received aggregate net proceeds of approximately $56.4 million, after deducting underwriting discounts and commissions, but before deducting offering costs payable by us, which were approximately $0.8 million. As of December 31, 2021, we had cash and cash equivalents of $143.5 million.

Cash Flows

The following table summarizes our sources and uses of cash for each of the periods presented:

		YEAR ENDED DECEMBER 31,
		2021			2020
		(in thousands)
Net cash used in operating activities		$	(82,137	)		$	(43,151	)
Net cash (used in) provided by investing activities			(613	)			57,823
Net cash provided by financing activities			55,906				116,416
Net increase (decrease) in cash, cash equivalents and restricted cash		$	(26,844	)		$	131,088

Operating Activities

During the year ended December 31, 2021, operating activities used $82.1 million of cash, primarily resulting from our net loss of $68.7 million and changes in our operating assets and liabilities of $32.9 million partially offset by net non-cash charges of $19.5 million. Net cash used by changes in our operating assets and liabilities for the year ended December 31, 2021 consisted of a $1.1 million increase in accounts receivable, a $0.5 million decrease in prepaid expenses and other current assets, a $1.0 million increase in accounts payable, a $23.8 million decrease in deferred revenue and a $8.7 million decrease in operating lease liabilities.

During the year ended December 31, 2020, operating activities used $43.2 million of cash, primarily resulting from our net loss of $50.5 million and changes in our operating assets and liabilities of $7.3 million partially offset by net non-cash charges of $14.6 million. Net cash used by changes in our operating assets and liabilities for the year ended December 31, 2020 consisted of a $2.9 million increase in prepaid expenses and other current assets, and a $9.0 million decrease in operating lease liabilities, partially offset by a $0.2 million increase in accrued expenses and a $4.7 million increase in deferred revenue.

In all periods presented, other changes in prepaid expenses and other current assets, accounts receivable, accounts payable, accrued expenses and other liabilities not described above were generally due to growth in our business, the advancement of our research programs and the timing of vendor invoicing and payments. In all periods presented, decreases in operating lease liabilities were primarily due to our recurring payments made under recorded operating lease liabilities, including those arising from embedded leases.

Investing Activities

During the year ended December 31, 2021, net cash used by investing activities was $0.6 million, consisting of purchases of property and equipment.

During the year ended December 31, 2020, net cash provided by investing activities was $57.8 million, consisting of maturities of marketable securities of $59.0 million, offset by purchases of property and equipment of $1.2 million.

The purchases of property and equipment in each period were primarily for equipment purchases and leasehold improvements related to the expansion of our research and development activities and the growth of our business.

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Financing Activities

During the year ended December 31, 2021, net cash provided by financing activities was $55.9 million, consisting primarily of net proceeds from our Follow-On Offering of $55.6 million and stock option exercises of $1.3 million, offset by the payment of issuance costs for prior period IPO common stock issuances of $1.1 million.

During the year ended December 31, 2020, net cash provided by financing activities was $116.4 million, consisting primarily of net proceeds from our IPO of $72.9 million, net proceeds from the issuance of Series D preferred stock of $42.0 million, and stock option exercises of $0.4 million.

Funding Requirements

We expect that our expenses will increase substantially in connection with our ongoing activities, particularly as we advance the preclinical activities and clinical trials for our product candidates in development. In addition, we expect to continue to incur additional costs associated with operating as a public company. The timing and amount of our operating and capital expenditures will depend largely on:

We believe that our existing cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2023. We have based this estimate on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, existing stockholders' interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect an investor's rights as a common stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making acquisitions or capital expenditures or declaring dividends. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates, or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we would be required to delay, scale back or discontinue our research, product development or future commercialization efforts, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

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Contractual Obligations and Commitments

Under license agreements with MIT and Erytech, we are obligated to pay annual license fees and to make contingent milestone and royalty payments. Under our license agreement with MIT, we are obligated to make aggregate milestone payments of up to $1.8 million upon the achievement of specified milestones, consisting of up to $0.8 million of development milestone payments and up to $1.0 million of regulatory milestone payments, as well as to pay royalties of low single-digit percentages of (i) our, and any of our affiliates' and sublicensees', net sales of licensed products in the research field and (ii) our, and any of our affiliates', net sales of licensed products in the therapeutic field. In addition, we are obligated to pay annual license maintenance fees of less than $0.1 million per year. For additional information on our license with MIT, see "Business-Collaboration, Research and License Agreements-MIT License Agreement."

Under our license agreement with Erytech, we are obligated to make aggregate milestone payments of up to $6.0 million upon the achievement of specified milestones, consisting of up to $1.0 million of development milestone payments and up to $5.0 million of regulatory milestone payments, for the first licensed product to achieve the specified milestones and payments of up to $50.0 million upon the achievement of specified sales milestones for all licensed products successfully developed under the agreement for each indication. In addition, we are obligated to pay tiered royalties ranging in the low single-digit percentages of annual net sales for each licensed product or licensed indication sold by us or our affiliates.

Under the 2018 Roche Agreement, if Roche exercises one of its options, then for each antigen product candidate for which Roche commercializes outside of the United States and we commercialize in the United States, we are obligated to pay Roche tiered royalties on net sales of such product candidate in the United States. The amount, timing and likelihood of such payments are not known. See "Business-Collaboration, Research and License Agreements-Roche Collaboration."

We enter into contracts in the normal course of business with CMOs, CROs and other third parties for preclinical research studies, manufacturing, clinical trials, services and testing. These contracts do not contain minimum purchase commitments and are cancelable by us upon prior written notice. Payments due upon cancellation consist only of payments for services provided or expenses incurred, including non-cancelable obligations of our service providers, up to the date of cancellation.

For additional information regarding our contractual commitments, see Notes 9 and 10 of our consolidated financial statements appearing at the end of this Annual Report on Form 10-K.

Critical Accounting Policies and Significant Judgments and Estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States, or GAAP. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenue, costs and expenses and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

While our significant accounting policies are described in more detail in Note 2 to our consolidated financial statements appearing at the end of this Annual Report on Form 10-K, we believe that the following accounting policies are those most critical to the judgments and estimates used in the preparation of our financial statements.

Revenue Recognition for License and Collaboration Arrangements

Under ASC 606, we recognize revenue when our customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that we determine are within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract, determine which goods or services are performance obligations and assess whether each promised good or service is distinct. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when, or as, that performance obligation is satisfied.

We enter into licensing arrangements that are within the scope of ASC 606, under which we may exclusively license to third parties rights to research, develop, manufacture and commercialize our product candidates. The terms of these arrangements typically include payment to us of one or more of the following: nonrefundable, upfront license fees; reimbursement of certain costs; customer option

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exercise fees; development, regulatory and sales milestone payments; and royalties on net sales of licensed products. The payment terms under our existing licensing arrangements are 60 days.

In determining the appropriate amount of revenue to be recognized as we fulfill our obligations under our arrangements, we perform the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the assessment of the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, we satisfy each performance obligation. As part of the accounting for these arrangements, we must use significant judgment to determine: (a) the performance obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; and (c) the standalone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above. We also use judgment to determine whether milestone payments or other variable consideration, except for royalties and sales-based milestones, should be included in the transaction price, as described below. The transaction price is allocated to each performance obligation based on the relative standalone selling prices of each performance obligation in the contract, and we recognize revenue based on those amounts when, or as, the performance obligations under the contract are satisfied.

The standalone selling price is the price at which an entity would sell a promised good or service separately to a customer. We estimate the standalone selling price of each of the identified performance obligations in our customer contracts, maximizing the use of observable inputs. Because we have not sold the same goods or services in our contracts separately to any customers on a standalone basis and there are no similar observable transactions in the marketplace, we estimate the standalone selling price of each performance obligation in our customer arrangements based on our estimate of costs to be incurred to fulfill our obligations associated with the performance, plus a reasonable margin.

We have determined that our only contract liability under ASC 606 is deferred revenue. Amounts received prior to revenue recognition are recorded as deferred revenue in the consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current portion of deferred revenue in the consolidated balance sheets. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion, in the consolidated balance sheets.

Exclusive Licenses

If the license to our intellectual property is determined to be distinct from the other promises or performance obligations identified in the arrangement, we recognize revenue from nonrefundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a promise or performance obligation is distinct from the other promises, we consider factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, we consider whether the collaboration partner can benefit from a promise for its intended purpose without the receipt of the remaining promises, whether the value of the promise is dependent on the unsatisfied promises, whether there are other vendors that could provide the remaining promises, and whether it is separately identifiable from the remaining promises. For licenses that are combined with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of progress and related revenue recognition. The measure of progress, and the resulting periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the research, development and licensing arrangement. Such a change could have a material impact on the amount of revenue we record in future periods. Under our existing license and collaboration agreements, we have concluded that the transfer of control to the customer occurs over the time period that the research and development services are to be provided by us, and this cost-to-cost method is, in management's judgment, the best measure of progress towards satisfying the performance obligation.

Research and Development Services

The promises under our license and collaboration arrangements often include research and development services to be performed by us on behalf of the partner. Payments or reimbursements resulting from our research and development efforts are estimated at the outset of the arrangement and considered part of the transaction price that is subsequently recognized as revenue because we are the principal in the arrangement for such efforts.

Customer Options

If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, we evaluate the customer options to determine if they are material rights at the outset of each arrangement. Options to acquire additional goods or services for free or at a discount are deemed to be material rights. If the goods and services underlying the customer options are not determined to be material rights, these customer options are not considered to be performance obligations in the arrangement because they are contingent upon exercise of the option. If the customer options are determined to be a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. We allocate the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the probability that the

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customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised.

Milestone Payments

At the inception of each arrangement that includes potential research, development or regulatory milestone payments, we evaluate whether the milestones are considered likely to be met and estimate the amount to be considered for inclusion in the transaction price using the most-likely-amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone payment value is included in the transaction price. For milestone payments due upon events that are not within the control of us or the licensee, such as regulatory approvals, we are not able to assert that it is likely that the regulatory approval will be granted and that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur until those approvals are received. In making this assessment, we evaluate factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period, we reevaluate the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price of the arrangement. Any such adjustments are recorded on a cumulative catch-up basis, which would affect the amounts of revenue and earnings in the period of adjustment.

Royalties

For arrangements that include sales-based royalties, including milestone payments due upon first commercial sales or based on a level of sales, that are the result of a customer-vendor relationship and for which the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) the occurrence of the related sales or (ii) the date upon which the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied. To date, we have not recognized any royalty revenue from any of our licensing arrangements.

Information regarding management's judgments and estimates applied in our accounting for our collaboration agreements with Roche in accordance with ASC 606 is summarized below. For additional information, see "-Components of Our Results of Operations-Revenue" and Note 11 to our consolidated financial statements appearing at the end of this Annual Report on Form 10-K.

2017 License and Collaboration Agreement with Roche

In April 2017, we entered into the 2017 Roche Agreement. Under the agreement, we received an upfront payment of $5.0 million as a technology access fee and are entitled to (i) payments of up to $1.0 million, in two tranches of $0.5 million, as reimbursement for our research costs; (ii) milestone payments of up to $7.0 million upon the achievement of specified development milestones; and (iii) annual maintenance fees ranging from $0.5 million to $0.9 million for each year following the fifth anniversary of the effective date, subject to specified prepayment discounts. Both we and Roche have specified obligations for performance during the term of the agreement.

We assessed our accounting for the 2017 Roche Agreement under ASC 606 as the transactions underlying the agreement were deemed to be transactions with a customer. We identified the following promises under the 2017 Roche Agreement: (i) a non-exclusive license granted to Roche to perform research related to and use our Cell Squeeze technology for gene editing of immune cells; (ii) specified research and development services related to gene editing of immune cells through the research term; (iii) manufacturing activities to support the specified research plan; and (iv) participation on a JRC. The annual maintenance fees described above were determined by us to be optional renewal payments. We concluded that each of the promises under the agreement was not distinct from the other promises in the arrangement. The research license was determined to not be distinct from the research and manufacturing activities primarily as a result of Roche being unable to benefit on its own or with other resources reasonably available in the marketplace because the license to our intellectual property requires significant specialized capabilities in order to be further developed, the research services necessary to develop the product are highly specialized, and our proprietary Cell Squeeze technology is a key capability of that development. The research and manufacturing services were determined not to be distinct because the promise under the agreement is to complete research and development, inclusive of the manufacturing. In addition, we determined that the impact of participation on the JRC was insignificant and had an immaterial impact on the accounting model. As such, we concluded that the first three promises should be combined into a single performance obligation. Based on these assessments, we identified one distinct performance obligation at the outset of the 2017 Roche Agreement.

As of entering into the 2017 Roche Agreement, we assessed whether the 2017 Roche Agreement was, for accounting purposes, a modification of the 2015 Roche Agreement or a separate contract and concluded that it was a separate contract because (i) the programs under the 2017 Roche Agreement were entirely new and distinct and are separate from programs under the 2015 Roche Agreement, (ii) the 2017 Roche Agreement and 2015 Roche Agreement were not negotiated together as a package with a single commercial objective and (iii) the amount of consideration paid under the 2017 Roche Agreement and 2015 Roche Agreement are not dependent on the price or performance under the other agreement. In addition, we determined that the upfront payment of $5.0 million as well as the expected reimbursable costs of $1.0 million constituted the entirety of the consideration to be included in the transaction price. The potential milestone payments that we may be eligible to receive were initially excluded from the transaction price of the arrangement as all development milestone payments did not meet the criteria for inclusion using the most-likely-amount method. We

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reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, we will adjust our estimate of the transaction price.

We recognize revenue associated with the performance obligation as the research, development and manufacturing services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy the performance obligation. The transfer of control to the customer occurs over the time period that the research and development services are to be provided by us, and this cost-to-cost method is, in management's judgment, the best measure of progress towards satisfying the performance obligation. The amounts received from Roche that were not yet recognized as revenue were deferred as a contract liability in our consolidated balance sheet and recognized over the remaining research and development period until the performance obligation is satisfied. There was no remaining deferred revenue under the 2017 Roche Agreement as of December 31, 2021.

2018 License and Collaboration Agreement with Roche

In October 2018, we entered into the 2018 Roche Agreement. Under the agreement, Roche was granted option rights to obtain an exclusive license to develop APC products or products derived from the collaboration programs on a product-by-product basis for oncologic indications. These option rights are exercisable upon the achievement of clinical Phase 1 proof of concept and expire, if unexercised, as of a date specified in the agreement. In addition, Roche was granted an option right to obtain an exclusive license to develop a TCL product. This option right is exercisable upon the achievement of clinical proof of concept and expires, if unexercised, as of a date specified in the agreement. For each of the APC products and TCL product, once Roche exercises its option and pays a specified incremental amount ranging from $15.0 million to $50.0 million for APC products and of $100.0 million for the TCL product, Roche will receive worldwide, exclusive commercialization rights for the licensed products, subject to our alternating option to retain U.S. APC commercialization rights. Through December 31, 2021, Roche had not exercised any of its options under the 2018 Roche Agreement.

Under the 2018 Roche Agreement, we received an upfront payment of $45.0 million and are eligible to receive (i) reimbursement of a mid double-digit percentage of our development costs; (ii) aggregate milestone payments on a product-by-product basis of up to $1.6 billion upon the achievement of specified milestones, consisting of up to $217.0 million of development milestone payments, up to $240.0 million of regulatory milestone payments and up to $1.2 billion of sales milestone payments; and (iii) tiered royalties on annual net sales of APC and TCL products licensed under the agreement at specified rates ranging from a mid single-digit percentage to percentage in the low twenties. We received the upfront payment of $45.0 million in October 2018 upon execution of the agreement. In addition, during the second quarter of 2019, we received a payment of $10.0 million following the achievement of the first development milestone under the 2018 Roche Agreement related to submission by us of preclinical data to the FDA, and during the first quarter of 2020, we received a payment of $20.0 million following the achievement of the second development milestone under the 2018 Roche Agreement related to first-patient dosing in a Phase 1 clinical trial.

We assessed our accounting for the 2018 Roche Agreement in accordance with ASC 606 and concluded that Roche is a customer prior to the exercise of any of its options under the agreement. We also identified the following promises under the 2018 Roche Agreement: (i) a non-exclusive license granted to Roche to use our intellectual property and collaboration compounds to conduct research activities related to the research plans under the 2018 Roche Agreement; (ii) specified research and development services related to HPV through Phase 1 clinical trials under a specified research plan; (iii) manufacturing of our SQZ APC platform and equipment in order to support the HPV research plan; (iv) specified research and development services on next-generation APCs under a research plan; (v) specified research and development services on TCL under a research plan; and (vi) participation on a JSC.

We concluded that, in the case of each performance obligation, the license to our intellectual property was not distinct as a result of Roche being unable to benefit from the license on its own or with other resources reasonably available in the marketplace because the license to our intellectual property requires significant specialized capabilities in order to be further developed. We concluded that the license to our intellectual property, research and development activities related to HPV, and manufacturing of our SQZ APC platform and equipment related to HPV were not distinct from each other because the research and manufacturing activities together customize and significantly modify the underlying technology. As such, we determined that each of these related promises under the agreement was not distinct from the others in this group and should be combined into a single performance obligation. We also concluded that the license to our intellectual property and the research and development activities on next-generation APCs were not distinct from each other because the research and development activities customize and significantly modify the underlying technology. As such, we determined that these related promises should be combined into a single performance obligation. Further, we concluded that the license to our intellectual property and the research and development activities on TCL were not distinct from each other because the research and development activities customize and significantly modify the underlying technology. As such, we determined that these related promises should be combined into a single performance obligation. We concluded that the three performance obligations were distinct from each other as they are separate programs and are unrelated. In addition, we determined that the impact of participation on the JSC was insignificant and had an immaterial impact on the accounting model.

Finally, we evaluated the option rights for licenses to develop, manufacture and commercialize the collaboration targets to determine whether these options provide Roche with any material rights for accounting purposes. We concluded that the option exercise prices

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were not below respective standalone selling prices, and, therefore, the options were marketing offers that do not provide material rights under ASC 606. Accordingly, the options were excluded as performance obligations at the outset of the 2018 Roche Agreement and will be accounted for as separate accounting contracts if and when each option exercise occurs.

Based on these assessments, we identified three performance obligations at the outset of the 2018 Roche Agreement: (1) the license to our intellectual property, the research and development activities related to HPV through Phase 1 clinical trials under a specified research plan, and the manufacturing of our SQZ APC platform and equipment in order to support the HPV research plan, or the first performance obligation; (2) the license to our intellectual property and the research and development activities on next-generation APCs, or the second performance obligation; and (3) the license to our intellectual property and the research and development activities on TCL, or the third performance obligation.

As of entering into the 2018 Roche Agreement, we assessed whether the 2018 Roche Agreement was, for accounting purposes, a modification of the two prior Roche agreements or a separate contract and concluded that it was a modification of the 2015 Roche Agreement. At the termination of the 2015 Roche Agreement, all deliverables were submitted to Roche for review, and as such, we completed all of our obligations under the 2015 Roche Agreement. Because the obligations under the 2015 Roche Agreement were completed at its termination and all arrangement consideration had been recognized as revenue, the accounting treatment as a modification determined by us would result in the same measurement and recognition patterns as would a separate contract. Further, we concluded that the 2018 Roche Agreement was a separate contract from the 2017 Roche Agreement because (i) we contracted to provide distinct goods and services associated with our gene editing platform to discover new targets in cancer immunotherapy, (ii) the 2018 Roche Agreement and 2017 Roche Agreement were not negotiated together as a package with a single commercial objective and (iii) the amount of consideration paid under the 2018 Roche Agreement and 2017 Roche Agreement are not dependent on the price or performance under the other agreement. In addition, we determined that the upfront payment of $45.0 million as well as the reimbursable costs of $10.8 million estimated by us constituted the entirety of the consideration to be included in the transaction price. This transaction price of $55.8 million was initially allocated to the three performance obligations based on the relative standalone selling price of each obligation. The potential milestone payments that we may be eligible to receive were excluded from the transaction price at the outset of the arrangement because (i) all development and regulatory milestone payments did not meet the criteria for inclusion using the most-likely-amount method and (ii) we recognize as revenue sales-based royalties and milestone payments at the later of the occurrence of the related sales or the date upon which the performance obligation has been satisfied because we believe that the license is the predominant item to which the royalties relate and have applied the sales-based royalty exception. We reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, we will adjust our estimate of the transaction price.

We determined the standalone selling price of each performance obligation under the 2018 Roche Agreement based on our estimate of our costs to be incurred to fulfil the research, development and manufacturing obligations associated with each of the three performance obligations, plus a reasonable margin.

During the fourth quarter of 2019, we evaluated our overall program priorities and determined that in 2020 we would continue to focus our resources on progressing the specified APC programs related to the 2018 Roche Agreement as well as our AAC and TAC platforms. As a result of our continuing focus on these specific programs, we reduced the level of priority of the TCL research activities under the 2018 Roche Agreement and expect to perform such TCL research activities over a longer time period than as originally expected under the research plan of the agreement. Consequently, in the fourth quarter of 2019, we reclassified $5.3 million of our current deferred revenue to non-current deferred revenue in our consolidated balance sheet, and such non-current deferred revenue will remain unrecognized as revenue until TCL research activities resume or the 2018 Roche Agreement is modified by us and Roche.

We separately recognize revenue associated with each of the three performance obligations as the research, development and manufacturing services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy each performance obligation. The transfer of control to the customer occurs over the time period that the research and development services are to be provided by us, and this cost-to-cost method is, in management's judgment, the best measure of progress towards satisfying each performance obligation. The amounts received that have not yet been recognized as revenue are deferred as a contract liability in our consolidated balance sheet and will be recognized over the remaining research and development period until each performance obligation is satisfied.

Accrued Research and Development Expenses

As part of the process of preparing our consolidated financial statements, we are required to estimate our accrued research and development expenses. This process involves estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the consolidated financial statements based on facts and circumstances known to us at that time. At each period end, we corroborate the accuracy of these estimates with the service

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providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include those related to fees paid to:

We record the expense and accrual related to contract research and manufacturing based on our estimates of the services received and efforts expended considering a number of factors, including our knowledge of the progress towards completion of the research, development and manufacturing activities; invoicing to date under the contracts; communication from the CMOs, CROs and other companies of any actual costs incurred during the period that have not yet been invoiced; and the costs included in the contracts and purchase orders. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or prepaid expense accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low in any particular period. To date, there have not been any material adjustments to our prior estimates of accrued research and development expenses.

Stock-Based Compensation

We measure stock-based awards granted to employees, non-employees and directors based on their fair value on the date of the grant using the Black-Scholes option-pricing model for options or the difference between the purchase price per share of the award, if any, and the fair value of our common stock for restricted common stock awards. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the award for employees and directors and the period during which services are performed for non-employees. We use the straight-line method to record the expense of awards with service-based vesting conditions.

The Black-Scholes option-pricing model uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our stock options, the risk-free interest rate for a period that approximates the expected term of our stock options, and our expected dividend yield.

Recently Issued Accounting Pronouncements

A description of recently issued accounting pronouncements that may potentially impact our financial position, results of operations or cash flows is disclosed in Note 2 to our consolidated financial statements appearing at the end of this Annual Report on Form 10-K.

Emerging Growth Company Status

The Jumpstart Our Business Startups Act of 2012 permits an "emerging growth company" such as us to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. We have elected not to "opt out" of such extended transition period, which means that when a standard is issued or revised and it has different application dates for public or private companies, we will adopt the new or revised standard at the time private companies adopt the new or revised standard and will do so until such time that we either (i) irrevocably elect to "opt out" of such extended transition period or (ii) no longer qualify as an emerging growth company. We may choose to early adopt any new or revised accounting standards whenever such early adoption is permitted for private companies.

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Item 7A. Quantitative and Qualitative Disclosures About Market Risk.

As of December 31, 2021, we had cash and cash equivalents of $143.5 million, which consisted of cash and money market funds. Interest income is sensitive to changes in the general level of interest rates; however, due to the nature of these balances, an immediate 10% change in interest rates would not have a material effect on the fair market value of our cash and cash equivalents.

We are not currently exposed to significant market risk related to changes in foreign currency exchange rates. Our operations may be subject to fluctuations in foreign currency exchange rates in the future.

We do not believe that inflation has had a material effect on our business, financial condition or results of operations. Our operations may be subject to inflation in the future as a result of the COVID-19 pandemic and its impact on pricing and the supply chain.

Item 8. Financial Statements and Supplementary Data.

The financial statements required to be filed pursuant to this Item 8 are appended to this Annual Report on Form 10-K. An index of those financial statements is found in Item 15, Exhibits and Financial Statement Schedules, of this Annual Report on Form 10-K.

Item 9. Changes in and Disagreements With Accountants on Accounting and Financial Disclosure.

None.

Item 9A. Controls and Procedures.

Limitations on effectiveness of controls and procedures

Management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures.

Evaluation of Disclosure Controls and Procedures

Our management, with the participation of our Chief Executive Officer (who is our principal executive officer and principal financial officer), evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2021. Based on this evaluation, our Chief Executive Officer concluded that, as of December 31, 2021, our disclosure controls and procedures were effective at the reasonable assurance level.

Management's Annual Report on Internal Controls Over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over our financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act). Our management conducted an assessment of the effectiveness of our internal control over financial reporting based on the criteria set forth in "Internal Control - Integrated Framework (2013)" issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this assessment, our management concluded that, as of December 31, 2021, our internal control over financial reporting was effective. As an "emerging growth company" as defined in the JOBS Act and a non-accelerated filer, we are not required to comply with the auditor attestation requirement of Section 404 of the Sarbanes-Oxley Act of 2002.

Changes in Internal Control Over Financial Reporting

No change in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the three months ended December 31, 2021 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

Item 9B. Other Information.

None.

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections

Not applicable.

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PART III

Item 10. Directors, Executive Officers and Corporate Governance.

Information About our Executive Officers and Directors

The following table provides information regarding our executive officers and members of our board of directors (ages as of the date of this Annual Report on Form 10-K):

Name	Age	Position
Armon Sharei, Ph.D.	34	President, Chief Executive Officer and Director
Lawrence Knopf	60	General Counsel
Howard Bernstein, M.D., Ph.D.	64	Chief Scientific Officer
David First	58	Chief People Officer
Micah Zajic	41	Chief Business Officer
Amy W. Schulman	61	Chair and Director
Paul Bolno, M.D.	48	Director
Bernard Coulie, M.D., Ph.D.	55	Director
Marc Elia	46	Director
Pushkal Garg, M.D.	54	Director
Klavs F. Jensen, Ph.D.	69	Director
Marc Schegerin, M.D.	46	Director
Sapna Srivastava, Ph.D.	51	Director
Patrick V.J.J. Vink, M.D.	58	Director

Executive Officers

Armon Sharei, Ph.D.has served as our Chief Executive Officer since January 2015, a member of our Board since March 2013 and was the lead inventor of our core technology and a founder of our company. Dr. Sharei holds a Ph.D. in Chemical Engineering from the Massachusetts Institute of Technology, as well as a B.S. with Honors and Distinction in Chemical Engineering from Stanford University. We believe that Dr. Sharei's experience in the industry and knowledge of our company qualify him to serve on our Board.

Lawrence Knopfhas served as our General Counsel since September 2019. Before joining us, from January 2017 to August 2019, Mr. Knopf served as an independent consultant and legal counsel to life science and other business enterprises, on a consulting, project and expert witness basis. Before that, from March 2011 to November 2016, Mr. Knopf served as Senior Vice President and General Counsel at HeartWare International, Inc., a publicly traded medical device company that was acquired by Medtronic in 2016. Mr. Knopf holds a J.D. from the University of Michigan Law School, and a B.S. in accounting and political science from the Wharton School of the University of Pennsylvania.

Howard Bernstein, M.D., Ph.D.has served as our Chief Scientific Officer since June 2015. Prior to joining us, from November 2008 to May 2015, Dr. Bernstein served as the Chief Scientific Officer of Seventh Sense Biosystems, a medical device company. Dr. Bernstein holds an M.D. from Harvard Medical School, a Ph.D. in Chemical Engineering from the Massachusetts Institute of Technology and a Bachelor of Engineering from McGill University. He is a member of the National Academy of Engineering and a Fellow of the American Institute of Medical and Biological Engineering.

David Firsthas served as our Chief People Officer since May 2020. Prior to joining us, from September 2018 to May 2020, Mr. First served as the Chief Human Resources Officer of Avedro Inc., a medical technology company that was acquired by Glaukos in 2019. Prior to joining Avedro Inc., Mr. First served as Vice President, Human Resources at Biogen Inc., a global healthcare company. Before that, from June 2015 to November 2017, Mr. First served as Global Head of Human Resources at HeartWare International, Inc., a publicly traded medical device company that was acquired by Medtronic in 2016. Mr. First holds an Master of Arts in Teaching from Union College, and a B.A. in economics from Union College.

Micah Zajichas served as our Chief Business Officer since September 2020. Prior to joining us, from April 2017 to September 2020, Mr. Zajic served as Vice President, Corporate Development at MeiraGTx Limited, a clinical stage gene therapy company. Prior to joining MeiraGTx, from 2014 to April 2017, Mr. Zajic served as Senior Director, Corporate Strategy at Alexion Pharmaceuticals Inc., a global biopharmaceutical company. Mr. Zajic started his career at Morgan Stanley, working in the Global Capital Markets and Investment Banking Division. Mr. Zajic holds a B.A. in Economics from Georgetown University.

Directors

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Amy W. Schulmanhas served as a member of our Board and as our Chair since June 2015. In July 2015, Ms. Schulman co-founded Lyndra Therapeutics, Inc., a pharmaceutical company, served as its Chief Executive Officer until February 2017 and as of September 2019 serves as Executive Chair. In addition, from August 2014 to November 2016, Ms. Schulman served as Chief Executive Officer of Arsia Therapeutics, Inc., a pharmaceutical company, until Arsia was acquired by Eagle Pharmaceuticals, Inc., a pharmaceutical company. Ms. Schulman joined Polaris Partners in August 2014 and became a Managing Partner in 2019. Since July 2014, Ms. Schulman has served as a senior lecturer at Harvard Business School. From January 2019 until January 2021, Ms. Schulman served as a director of Cyclerion Therapeutics, Inc. and currently serves as a director of Alnylam Pharmaceuticals, Inc. and on the Mount Sinai Hospital Board of Trustees. Ms. Schulman holds a J.D. from Yale Law School as well as B.A. degrees in Philosophy and English from Wesleyan University. We believe Ms. Schulman's extensive industry experience qualifies her to serve on our Board.

Paul B. Bolno, M.D. has served on our Board since June 2020. Since December 2013, Dr. Bolno has served as the President and Chief Executive Officer of Wave Life Sciences Ltd., a genetic medicines company, and has served as a director of Wave Life Sciences Ltd. since April 2014. Prior to joining Wave, Dr. Bolno served at GlaxoSmithKline, a pharmaceutical company, from 2009 to 2013 in various roles, including Vice President, Worldwide Business Development-Head of Asia BD and Investments, Head of Global Neuroscience BD, a director of Glaxo Welcome Manufacturing, Pte. Ltd. in Singapore and Vice President, Business Development for the Oncology Business Unit, where he helped establish GlaxoSmithKline's global oncology business and served as a member of the Oncology Executive Team, Oncology Commercial Board and Cancer Research Executive Team. Prior to GlaxoSmithKline, Dr. Bolno served as Director of Research at Two River LLC, a health care private equity firm, from 2004 to 2009. Dr. Bolno earned a medical degree from MCP-Hahnemann School of Medicine and an M.B.A. from Drexel University. He was a general surgery resident and cardiothoracic surgery postdoctoral research fellow at Drexel University College of Medicine. We believe that Dr. Bolno's experience in the biotechnology industry and leading a biopharmaceutical company qualify him to serve on our Board.

Bernard Coulie, M.D., Ph.D., has served as a member of our Board since July 2021. Dr. Coulie has served as Chief Executive Officer and as a Director for Pliant Therapeutics, Inc., a biopharmaceutical company, since February 2016. Prior to joining Pliant, Dr. Coulie cofounded ActoGeniX N.V., a biopharmaceutical company, and held roles of increasing responsibility there, including as Vice President R&D, Chief Medical Officer, and Chief Executive Officer, from September 2006 until February 2015, when it was acquired by Intrexon Corporation. Prior to cofounding ActoGeniX, Dr. Coulie held various positions with increasing responsibilities in drug discovery and clinical development at Johnson & Johnson Pharmaceutical Research and Development Europe. Dr. Coulie previously served as a director of ActoGeniX from April 2010 until February 2015, Biogazelle N.V. from July 2015 until November 2018, Myoscience from June 2016 until March 2019. Dr. Coulie is currently serving as a director and Chairman of Calypso BV. Dr. Coulie holds an M.D. and Ph.D. from the University of Leuven, Belgium and an MBA from the Vlerick Management School, Leuven, Belgium. We believe that Dr. Coulie's experience in the biotechnology industry and executive leadership at various biopharmaceutical companies qualify him to serve on our Board.

Marc Eliahas served as a member of our Board since May 2018. In September 2019, Mr. Elia founded M28 Capital, a healthcare sector investment fund. Prior to that, from January 2012 to September 2019, Mr. Elia served as a partner at Bridger Capital, an investment fund. Mr. Elia holds a B.A. in Economics from Carleton College. We believe that Mr. Elia's broad operational and transactional experience qualify him to serve on our Board.

Pushkal Garg, M.D. has served as a member of our Board since August 2018. Dr. Garg currently serves as Chief Medical Officer and Executive Vice President at Alnylam Pharmaceuticals, Inc., a biopharmaceutical company focused on the discovery, development, and commercialization of RNA interference therapeutics. Prior to joining Alnylam in October 2014, he held clinical development leadership roles at Bristol-Myers Squibb Corporation and Millennium Pharmaceuticals. Before joining the biopharmaceutical industry, he was on the faculty at Harvard Medical School and the Brigham and Women's Hospital in Boston. Dr. Garg holds an M.D. from the University of California, San Francisco, School of Medicine, where he also completed a residency in Internal Medicine, and an A.B. in Biochemistry from the University of California, Berkeley. We believe Dr. Garg's extensive medical and scientific knowledge and industry experience qualify him to serve on our Board.

Klavs F. Jensen, Ph.D.has served as a member of our Board since March 2013 and was a co-founder of our company. Since 1989, Dr. Jensen has served as Professor of Chemical Engineering and of Materials Science and Engineering at the Massachusetts Institute of Technology. From 2007 to 2015, Dr. Jensen served as Department Head for Chemical Engineering. Dr. Jensen was a member of the Board of Technical University of Denmark from 2009 to 2016. Dr. Jensen holds a Ph.D. in Chemical Engineering from the University of Wisconsin and an M.S. in Chemical Engineering from Technical University of Denmark. He is a member of the U.S. Academies of Engineering and Science. We believe Dr. Jensen's pioneering academic work, extensive medical and scientific knowledge and industry experience qualify him to serve on our Board.

Marc Schegerin, M.D. has served as a member of our Board since October 2020. Since April 2020, Dr. Schegerin has served as the Chief Financial Officer and Chief Operating Officer at Morphic Therapeutic, Inc., a biopharmaceutical company. From April 2018 to

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January 2020, Dr. Schegerin served as Chief Financial Officer, Treasurer and Head of Strategy & Communications at ArQule, an oncology-focused drug developer, until its acquisition by Merck & Co. in January 2020. Prior to this role, Dr. Schegerin served as a Director at Citigroup, from June 2016 to April 2018. Dr. Schegerin earned his M.D. from Dartmouth Medical School and M.B.A. from the Tuck School of Business at Dartmouth and undergraduate degrees in premedical studies from Harvard University and finance from Tulane University. We believe Dr. Schegerin's broad operational and transactional experience qualify him to serve on our Board.

Sapna Srivastava, Ph.D.has served as a member of our Board since October 2020. Dr. Srivastava served as the Interim Chief Financial Officer of eGenesis, Inc. from March 2021 to October 2021. From September 2017 to January 2019, Dr. Srivastava served as the Chief Financial and Strategy Officer at Abide Therapeutics, Inc., a biopharmaceutical company that was acquired by H. Lundbeck A/S in 2019. From April 2015 to December 2016, Dr. Srivastava served as the Chief Financial and Strategy Officer at Intellia Therapeutics, Inc., a genome editing company. Dr. Srivastava currently serves as a director of private company Asclepix Therapeutics, Inc. and multiple public companies, which are Talaris Therapeutics, Inc., Aura Biosciences, Nuvalent Inc, and Social Capital Suvretta Holdings Corp II . She also served as a director of VelosBio Inc. from October 2020 to December 2020. Dr. Srivastava holds a Ph.D. from N.Y.U. University School of Medicine and a B.S. from St. Xavier's College, University of Bombay. We believe Dr. Srivastava's broad financial, operational, and transactional experience qualify her to serve on our Board.

Patrick V.J.J. Vink, M.D.has served as a member of our Board since July 2021. He has significant experience as a senior executive, having worked in the pharmaceutical industry for more than 30 years. Since May 2020, Dr. Vink has served as Chairman at BiognoSys AG, a privately held proteomics company in Switzerland. Since June 2016, Dr. Vink has also served as Chairman of venture capital-backed NMD Pharma, a neurology biopharmaceutical company in Denmark and F2G Ltd, a rare fungal disease UK and Austria based company. In addition, Dr. Vink is a board member at Amryt Pharma PLC, Santhera AG and Spero Therapeutics, Inc. and in 2019 began working with Athyrium as a Senior Advisor. While serving in these capacities, Dr. Vink has been involved in initial public listings and geographic expansions and has contributed to the achievement of significant development and commercial milestones. Earlier in his career he held several leadership positions across the industry, including Head of Global Biopharmaceuticals for the Sandoz division of the Novartis Group, Vice President International Business for Biogen Inc., and Head of Worldwide Marketing, Cardiovascular and Thrombosis at Sanofi-Synthelabo Ltd. Dr. Vink also served as a member of the Executive Committee of the European Federation of Pharmaceutical Industries and Associations from 2013 to 2015. Dr. Vink graduated as a medical doctor from the University of Leiden, Netherlands in 1988 and obtained his Masters of Business Administration in 1992 at the University of Rochester. We believe Dr. Vink's broad experience and leadership positions in the industry qualify him to serve on our Board.

Code of Ethics

We have a written Code of Business Conduct and Ethics that applies to our directors, officers and employees, including our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions. We have posted a current copy of the Code of Business Conduct and Ethics on our website, www.sqzbiotech.com, in the "Investors and Media" section under "Governance." In addition, we intend to post on our website all disclosures that are required by law or the rules of the NYSE concerning any amendments to, or waivers from, any provision of the Code of Business Conduct and Ethics.

The remainder of the response to this Item 10 will be included in our definitive Proxy Statement to be filed with the SEC with respect to our 2022 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 11. Executive Compensation.

The information required by this Item 11 will be included in our Definitive Proxy Statement to be filed with the SEC with respect to our 2022 Annual Meeting of Stockholders and is incorporated herein by reference.

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Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

The table below sets forth the number of securities to be issued upon exercise of outstanding options, warrants and rights as of December 31, 2021.

Plan Category:		Number of Securities to be Issued Upon Exercise of Outstanding Options, Warrants and Rights					Weighted-Average Exercise Price of Outstanding Options, Warrants, and Rights				Number of Securities Available for Future Issuance under Equity Compensation Plans (excludes securities reflected in first column) (4)
Equity compensation plans approved by security holders (1)			4,339,523		(2)		$		9.75		(3)			3,195,622
Equity compensation plans not approved by security holders			-						-					-
Total			4,339,523				$		9.75					3,195,622

The remainder of the response to this Item 12 will be included in our definitive Proxy Statement to be filed with the SEC with respect to our 2022 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 13. Certain Relationships and RelatedTransactions, and Director Independence.

The information required by this Item 13 will be included in our Definitive Proxy Statement to be filed with the SEC with respect to our 2022 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 14. Principal Accounting Fees and Services.

The information required by this Item 14 will be included in our Definitive Proxy Statement to be filed with the SEC with respect to our 2022 Annual Meeting of Stockholders and is incorporated herein by reference.

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PART IV

Item 15. Exhibits, Financial Statement Schedules.

(a)(1) For a list of the financial statements included herein, see Index to the Consolidated Financial Statements on page F-1 of this Annual Report on Form 10-K, incorporated into this Item by reference.

(a)(2) All financial statement schedules have been omitted because they are either not required or not applicable or the information is included in the consolidated financial statements or the notes thereto.

(a)(3) Exhibits

The following is a list of exhibits filed as part of this Annual Report on Form 10-K:

Exhibit Number	Description	Form	File No.	Exhibit	Filing Date	Filed Herewith
3.1	Restated Certificate of Incorporation of SQZ Biotechnologies Company	8-K	001-39662	3.1	11/04/2020
3.2	Amended and Restated Bylaws of SQZ Biotechnologies Company	S-1/A	333-249422	3.4	10/26/2020
4.1	Amended and Restated Investors' Rights Agreement, dated as of December 19, 2019, as amended	S-1	333-252889	4.1	02/09/2021
4.2	Specimen Stock Certificate	S-1/A	333-249422	4.2	10/26/2020
4.3	Description of Securities	10-K	001-39662	4.3	03/18/2021
10.1#	2014 Stock Incentive Plan, as amended, and form of agreements thereunder	S-8	333-249774	99.1	10/30/2020
10.2#	2020 Incentive Award Plan and form of agreements thereunder	S-8	333-249774	99.2	10/30/2020
10.3#	Amended Non-Employee Director Compensation Program					*
10.4#	2020 Employee Stock Purchase Plan	S-8	333-249774	99.3	10/30/2020
10.5#	Form of Indemnification Agreement for Directors and Officers	S-1/A	333-249422	10.5	10/26/2020
10.6	Lease between the Registrant and Arsenal Yards Holding LLC, dated December 11, 2018	S-1/A	333-249422	10.6	10/26/2020
10.7†	License and Collaboration Agreement among Registrant, F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc., effective as of October 5, 2018	S-1	333-249422	10.7	10/09/2020
10.8†	Accord relating to License and Collaboration Agreement among Registrant, F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc., effective as of November 5, 2019	S-1	333-249422	10.8	10/09/2020
10.9†	Amended and Restated Exclusive Patent License Agreement, dated as of December 1, 2015, by and between the Registrant and Massachusetts Institute of Technology	S-1	333-249422	10.9	10/09/2020
10.10#	Employment Agreement between the Registrant and Howard Bernstein, dated October 29, 2020					*

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10.11#	Employment Agreement between the Registrant and David First, dated October 29, 2020					*
10.12#	Employment Agreement between the Registrant and Teri Loxam, dated October 23, 2020	S-1/A	333-249422	10.12	10/26/2020
10.13#	Employment Agreement between the Registrant and Oliver Rosen, M.D., dated October 23, 2020	S-1/A	333-249422	10.13	10/26/2020
10.14#	Employment Agreement between the Registrant and Armon Sharei, Ph.D., dated October 23, 2020	S-1/A	333-249422	10.14	10/26/2020
10.15#	Employment Agreement between the Registrant and Lawrence Knopf, dated October 29, 2020	S-1	333-252889	10.15	02/09/2021
10.16#	Employment Agreement between the Registrant and Micah Zajic, dated October 29, 2020	S-1	333-252889	10.16	02/09/2021
10.17#	Separation Agreement between the Registrant and Oliver Rosen, M.D., dated September 2, 2021	10-Q	001-39662	10.1	11/10/2021
10.18#	Separation Agreement between the Registrant and Teri Loxam, dated November 3, 2021					*
10.19#	Transition Consulting Agreement between the Registrant and Teri Loxam, dated November 11, 2021					*
21.1	Subsidiaries of the Registrant					*
23.1	Consent of PricewaterhouseCoopers LLP, Independent Registered Public Accounting Firm					*
31.1	Certification of Principal Executive Officer and Principal Financial Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.					*
32.1	Certification of Principal Executive Officer and Principal Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.					**
101.INS	Inline XBRL Instance Document					*
101.SCH	Inline XBRL Taxonomy Extension Schema Document					*
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document					*
101.DEF	Inline XBRL Taxonomy Extension Definition Linkbase Document					*
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document					*
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document					*
104	Cover Page Interactive Data File (embedded within the Inline XBRL)					*

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* Filed herewith.

** Furnished herewith.

# Indicates management contract or compensatory plan.

† Portions of this exhibit have been redacted in compliance with Regulation S-K Item 601(b)(10)(iv).

Item 16. Form 10-K Summary

None.

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this Report to be signed on its behalf by the undersigned, thereunto duly authorized.

		SQZ Biotechnologies Company
Date: March 16, 2022		By:	/s/ Armon Sharei, Ph.D.
			Armon Sharei, Ph.D.
			President and Chief Executive Officer

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, this Report has been signed below by the following persons on behalf of the Registrant in the capacities and on the dates indicated.

Name		Title		Date
/s/ Armon Sharei, Ph.D.		President, Chief Executive Officer and Director (principal executive officer and principal financial officer)		March 16, 2022
Armon Sharei, Ph.D.
/s/ Richard Capasso		Chief Accounting Officer (principal accounting officer)		March 16, 2022
Richard Capasso
/s/ Amy W. Schulman		Chair and Director		March 16, 2022
Amy W. Schulman
/s/ Paul Bolno, M.D.		Director		March 16, 2022
Paul Bolno, M.D.
/s/ Bernard Coulie, M.D., Ph.D.		Director		March 16, 2022
Bernard Coulie, M.D., Ph.D.
/s/ Marc Elia		Director		March 16, 2022
Marc Elia
/s/ Pushkal Garg, M.D.		Director		March 16, 2022
Pushkal Garg, M.D.
/s/ Klavs F. Jensen, Ph.D.		Director		March 16, 2022
Klavs F. Jensen, Ph.D.
/s/ Marc Schegerin, M.D.		Director		March 16, 2022
Marc Schegerin, M.D.
/s/ Sapna Srivastava, Ph.D.		Director		March 16, 2022
Sapna Srivastava, Ph.D.

/s/ Patrick V.J.J. Vink, M.D.		Director		March 16, 2022
Patrick V.J.J. Vink, M.D.

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Index to Consolidated Financial Statements

	Page
Report of Independent Registered Public Accounting Firm (PCAOB ID: 238)	F-2
Consolidated Balance Sheets	F-3
Consolidated Statements of Operations and Comprehensive Loss	F-4
Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit)	F-5
Consolidated Statements of Cash Flows	F-6
Notes to Consolidated Financial Statements	F-7

F-1

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Stockholders of SQZ Biotechnologies Company

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of SQZ Biotechnologies Company and its subsidiaries (the "Company") as of December 31, 2021 and 2020, and the related consolidated statements of operations and comprehensive loss, of convertible preferred stock and stockholders' equity (deficit) and of cash flows for the years then ended, including the related notes (collectively referred to as the "consolidated financial statements"). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2021 and 2020, and the results of its operations and its cash flows for the years then ended in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These consolidated financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's consolidated financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits of these consolidated financial statements in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. We believe that our audits provide a reasonable basis for our opinion.

/s/PricewaterhouseCoopers LLP

Boston, Massachusetts

March 16, 2022

We have served as the Company's auditor since 2019.

F-2

SQZ BIOTECHNOLOGIES COMPANY

Consolidated Balance Sheets

(In thousands, except share and per share amounts)

		DECEMBER 31,
		2021			2020
Assets
Current assets:
Cash and cash equivalents		$	143,513			$	170,357
Accounts receivable			3,000				1,892
Prepaid expenses and other current assets			4,122				4,582
Total current assets			150,635				176,831
Property and equipment, net			3,046				3,645
Restricted cash			2,305				2,305
Deferred offering costs			323				-
Operating lease right-of-use assets			69,843				48,360
Total assets		$	226,152			$	231,141
Liabilities and Stockholders' Equity
Current liabilities:
Accounts payable		$	3,971			$	3,708
Accrued expenses			6,810				7,358
Current portion of deferred revenue			12,507				25,917
Current portion of operating lease liabilities			9,936				8,210
Total current liabilities			33,224				45,193
Deferred revenue, net of current portion			9,196				19,659
Operating lease liabilities, net of current portion			59,756				38,885
Other liabilities			-				205
Total liabilities			102,176				103,942
Commitmentsand contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.001par value; 10,000,000shares authorized at December 31, 2021 and 2020, respectively; Noshares issued or outstanding.			-				-
Common stock, $0.001par value; 200,000,000shares authorized at December 31, 2021 and 2020, respectively; 28,133,368and 24,786,424shares issued and outstanding at December 31, 2021 and 2020, respectively.			28				25
Additional paid-in capital			319,458				253,943
Accumulated deficit			(195,510	)			(126,769	)
Total stockholders' equity			123,976				127,199
Total liabilities and stockholders' equity		$	226,152			$	231,141

The accompanying notes are an integral part of these consolidated financial statements.

F-3

SQZ BIOTECHNOLOGIES COMPANY

Consolidated Statements of Operations and Comprehensive Loss

(In thousands, except share and per share amounts)

		YEAR ENDED DECEMBER 31,
		2021			2020
Collaboration revenue		$	27,098			$	20,998
Operating expenses:
Research and development			70,148				51,545
General and administrative			25,719				20,511
Total operating expenses			95,867				72,056
Loss from operations			(68,769	)			(51,058	)
Other income (expense):
Interest income		36				550
Other income (expense), net			(8	)			(13	)
Total other income, net			28				537
Net loss			(68,741	)			(50,521	)
Net loss per share attributable to common stockholders, basic and diluted		$	(2.49	)		$	(9.35	)
Weighted-average common shares outstanding, basic and diluted			27,578,844				5,401,895
Comprehensive loss:
Net loss		$	(68,741	)		$	(50,521	)
Other comprehensive income (loss):
Reclassification adjustment for gains included in net loss, net of tax			-				(30	)
Comprehensive loss		$	(68,741	)		$	(50,551	)

The accompanying notes are an integral part of these consolidated financial statements.

F-4

SQZ BIOTECHNOLOGIES COMPANY

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit)

(In thousands, except share amounts)

		CONVERTIBLE PREFERRED STOCK				COMMON STOCK
		SHARES			AMOUNT				SHARES			AMOUNT			ADDITIONAL PAID-IN CAPITAL			ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)			ACCUMULATED DEFICIT			TOTAL STOCKHOLDERS' EQUITY (DEFICIT)
Balances at December 31, 2019			13,869,027				132,109					1,737,388				2				2,701				30				(76,248	)			(73,515	)
Issuance of Series D convertible preferred stock, net of issuance costs of $56			3,035,192				42,248					-				-				-				-				-				-
Conversion of convertible preferred stock into common stock			(16,904,219	)			(174,357	)				17,800,084				18				174,333				-				-				174,351
Issuance of common stock upon initial public offering, net of issuance costs of $2,621										5,073,529				5				72,873				-				-				72,878
Issuance of common stock upon exercise of stock options			-				-					164,945				-				434				-				-				434
Issuance of common stock										10,378				-				-				-				-				-
Stock-based compensation expense			-				-					-				-				3,602				-				-				3,602
Net loss			-				-					-				-				-				-				(50,521	)			(50,521	)
Other comprehensive income			-				-					-				-				-				(30	)			-				(30	)
Balances at December 31, 2020			-				-					24,786,324				25				253,943				-				(126,769	)			127,199
Issuance of common stock upon public offering, net of issuance costs of $798			-				-					3,000,000				3				55,599				-				-				55,602
Issuance of common stock upon exercise of stock options			-				-					333,417				-				1,307				-				-				1,307
Issuance of common stock under employee stock purchase plan			-				-					13,627				-				104										104
Stock-based compensation expense			-				-					-				-				8,505				-				-				8,505
Net loss			-				-					-				-				-				-				(68,741	)			(68,741	)
Balances at December 31, 2021			-			$	-					28,133,368			$	28			$	319,458			$	-			$	(195,510	)		$	123,976

The accompanying notes are an integral part of these consolidated financial statements.

F-5

SQZ BIOTECHNOLOGIES COMPANY

Consolidated Statements of Cash Flows

(In thousands)

		YEAR ENDED DECEMBER 31,
		2021			2020
Cash flows from operating activities:
Net loss		$	(68,741	)		$	(50,521	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense			1,208				1,342
Amortization of operating lease right-of-use assets			9,822				9,601
Stock-based compensation expense			8,505				3,602
Accretion of discounts on marketable securities			-				(5	)
Loss on disposal of property and equipment			7				-
Loss on termination of operating lease			-				108
Changes in operating assets and liabilities:
Accounts receivable			(1,108	)			(18	)
Prepaid expenses and other current assets			460				(2,920	)
Accounts payable			1,074				100
Accrued expenses			(283	)			246
Deferred revenue			(23,873	)			4,748
Deferred offering costs			(323	)			-
Operating lease liabilities			(8,710	)			(8,899	)
Other liabilities			(175	)			(535	)
Net cash used in operating activities			(82,137	)			(43,151	)
Cash flows from investing activities:
Purchases of property and equipment			(613	)			(1,177	)
Sales and maturities of marketable securities			-				59,000
Net cash (used in) provided by investing activities			(613	)			57,823
Cash flows from financing activities:
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts			-				75,494
Payment of initial public offering costs			(1,106	)			(1,515	)
Proceeds from issuance of convertible preferred stock, net of issuance costs paid in the period			-				42,248
Proceeds from follow-on public offering of common stock, net of commissions and underwriting discounts			56,400				-
Payment of follow-on public offering costs			(798	)			-
Payments of issuance costs of convertible preferred stock issued in prior period			-				(245	)
Proceeds from issuance of common stock under employee stock purchase plan			103				-
Proceeds from exercise of stock options			1,307				434
Net cash provided by financing activities			55,906				116,416
Net (decrease) increase in cash, cash equivalents and restricted cash			(26,844	)			131,088
Cash, cash equivalents and restricted cash at beginning of period			172,662				41,574
Cash, cash equivalents and restricted cash at end of period		$	145,818			$	172,662
Supplemental disclosure of non-cash investing and financing activities:
Conversion of convertible preferred stock into common stock		$	-			$	174,351
Lease assets obtained in exchange for operating lease liabilities		$	31,307			$	17,049
Initial public offering costs included in accounts payable and accrued expenses at end of period		$	-			$	1,106

The accompanying notes are an integral part of these consolidated financial statements.

F-6

SQZ BIOTECHNOLOGIES COMPANY

Notes to Consolidated Financial Statements

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, SQZ Biotechnologies Security Corporation and SQZ Biotech HK Limited. All intercompany accounts and transactions have been eliminated in consolidation.

Money market funds were valued by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. There were nochanges to the valuation methods during the years ended December 31, 2021 and 2020. The Company evaluates transfers between levels at the end of each reporting period. There were notransfers between Level 1 or Level 2 during the years ended December 31, 2021 and 2020.

F-15

In February 2020, as a result of the termination of the 2016 Lease (see Note 10), the Company removed from the consolidated balance sheet leasehold improvements with a cost of $2.7million and accumulated depreciation related to those leasehold improvements of $1.3million. The resulting $1.4million loss was recognized as a component of the $0.1million net loss recognized by the Company upon termination of the 2016 Lease (see Note 10).

F-19

F-27