Summary Prospectus by Investment Company - Form 497K

Transamerica S&P 500 Index VP

Summary Prospectus May 1, 2024

Class

Initial & Service (No Ticker)

This summary prospectus is designed to provide shareholders with key portfolio information in a clear and concise format. Before you invest, you may want to review the portfolio's prospectus, which contains more information about the portfolio and its risks. You can find the portfolio's prospectus and other information about the portfolio, including the portfolio's statement of additional information and most recent reports to shareholders, online at www.transamericaseriestrust.com. You can also get this information at no cost by calling 866-414-6349 or by sending an e-mail request to [email protected], or from your financial professional. The portfolio's prospectus and statement of additional information, dated May 1, 2024, as supplemented from time to time, and the independent registered public accounting firm's report and financial statements in the portfolio's annual report to shareholders, dated December 31, 2023, are incorporated by reference into this summary prospectus.

Investment Objective:Seeks to provide investment results that, before expenses, correspond generally to the price and yield performance of the S&P 500® Index.

Fees and Expenses:This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the portfolio, but it does not reflect any charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, fees would be higher.

Shareholder Fees (fees paid directly from your investment)

Class:	Initial	Service
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	None	None
Maximum deferred sales charge (load) (as a percentage of purchase price or redemption proceeds, whichever is lower)	None	None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Class:	Initial	Service
Management fees	0.08%	0.08%
Distribution and service (12b-1) fees	None	0.25%
Other expenses	0.05%	0.06%
Recaptured expenses1	0.00%	0.01%
All other expenses	0.05%	0.05%
Total annual fund operating expenses	0.13%	0.39%

any of the 36 months from the date on which TAM waived fees and/or reimbursed expenses for the class if the class' total annual fund operating expenses have fallen to a level below the limits described above. In no case will TAM recapture any amount that would result, on any particular business day of the portfolio, in the class's total annual operating expenses exceeding the applicable limits described above or any other lower limit then in effect.

Example:This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio's operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 year	3 years	5 years	10 years
Initial Class	$13	$42	$73	$166
Service Class	$40	$125	$219	$493

Portfolio Turnover:The portfolio pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual portfolio operating expenses or in the Example, affect the portfolio's performance.

During the most recent fiscal year, the portfolio turnover rate for the portfolio was 8% of the average value of its portfolio.

Principal Investment Strategies:Under normal circumstances, the portfolio invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the S&P 500® Index (the "Index")1. Under normal circumstances, however, the portfolio intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes, including index futures contracts. The Index is a well-known stock market index that includes common stocks of approximately 500 companies from all major industries representing a significant portion of the market value of all common stocks publicly traded in the United States. Stocks in the Index are weighted according to their float adjusted capitalizations. The Index, which is constructed and maintained by S&P Dow Jones Indices LLC, is normally rebalanced each March, June, September and December,

1

Standard & Poor's does not sponsor the portfolio, nor is it affiliated in any way with the portfolio or the portfolio's advisers. "Standard & Poor's®," "S&P®," "S&P 500®," and "Standard & Poor's 500®" are trademarks of Standard & Poor's Financial Services LLC, a division of S&P Global. The portfolio is not sponsored, endorsed, sold or promoted by Standard & Poor's and Standard & Poor's makes no representation or warranty, express or implied, regarding the advisability of investing in the portfolio.

and is reconstituted on an as needed basis and on pre-determined dates as Index constituents change in size. The portfolio will concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The portfolio's sub-adviser, SSGA Funds Management, Inc. (the "sub-adviser"), does not sub-advise the portfolio according to traditional methods of "active" investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the sub-adviser utilizes a "passive" or "indexing" investment approach, seeking to provide investment results that, before expenses, correspond generally to the total return performance of the Index by employing a sampling strategy.

The sub-adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the portfolio may purchase a sample of stocks in the Index in proportions expected to replicate generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index when the Index is rebalanced and reconstituted. The portfolio may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The sub-adviser may at times, but is not required to, purchase or sell futures contracts in lieu of investment directly in the stocks included in the Index. The sub-adviser might do so, for example, in order to increase the portfolio's investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the sub-adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the portfolio but the sale has not yet been completed.

Principal Risks:Risk is inherent in all investing. Many factors and risks affect the portfolio's performance, including those described below. The value of your investment in the portfolio, as well as the amount of return you receive on your investment, may fluctuate significantly day to day and over time. You may lose part or all of your investment in the portfolio or your investment may not perform as well as other similar investments. The following is a summary description of principal risks (in alphabetical order after certain key risks) of investing in the portfolio. An investment in the portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.You may lose money if you invest in this portfolio.

Market - The market prices of the portfolio's securities or other assets may go up or down, sometimes rapidly or unpredictably, due to factors such as economic events, inflation, changes in interest rates, governmental actions or interventions, actions taken by the U.S. Federal Reserve or foreign central banks, market disruptions caused by tariffs, trade disputes or other factors, political developments, armed conflicts, economic sanctions, cybersecurity events, investor sentiment, the global and domestic effects of

widespread or local health, weather or climate events, and other factors that may or may not be related to the issuer of the security or other asset. If the market prices of the portfolio's securities and assets fall, the value of your investment in the portfolio could go down.

Economies and financial markets throughout the world are increasingly interconnected. Events or circumstances in one or more countries or regions could be highly disruptive to, and have profound impacts on, global economies or markets. As a result, whether or not the portfolio invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the portfolio's investments may go down.

Passive Strategy/Index - The portfolio is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the index or of the actual securities comprising the index. This differs from an actively-managed fund, which typically seeks to outperform a benchmark index. As a result, the portfolio's performance may be less favorable than that of a portfolio managed using an active investment strategy. The structure and composition of the index will affect the performance, volatility, and risk of the index and, consequently, the performance, volatility, and risk of the portfolio.

Index Fund - While the portfolio seeks to track the performance of the S&P 500® Index (i.e., achieve a high degree of correlation with the index), the portfolio's return may not match the return of the index. The portfolio incurs a number of operating expenses not applicable to the index, and incurs costs in buying and selling securities. In addition, the portfolio may not be fully invested at times, generally as a result of cash flows into or out of the portfolio or reserves of cash held by the portfolio to meet redemptions. The portfolio may attempt to replicate the index return by investing in fewer than all of the securities in the index, or in some securities not included in the index, potentially increasing the risk of divergence between the portfolio's return and that of the index.

Equity Securities - Equity securities generally have greater risk of loss than debt securities. Stock markets are volatile and the value of equity securities may go up or down, sometimes rapidly and unpredictably. The market price of an equity security may fluctuate based on overall market conditions, such as real or perceived adverse economic or political conditions or trends, tariffs and trade disruptions, inflation, substantial economic downturn or recession, changes in interest rates, or adverse investor sentiment. The market price of an equity security also may fluctuate based on real or perceived factors affecting a particular industry or industries or the company itself. If the market prices of the equity securities owned by the portfolio fall, the value of your investment in the portfolio will decline. The portfolio may lose its entire investment in the equity securities of an issuer. A change in financial condition or other event affecting a single issuer may adversely impact securities markets as a whole.

Large Capitalization Companies - The portfolio's investments in larger, more established companies may underperform other segments of the market because they may be less responsive to competitive challenges and opportunities and unable to attain high growth rates during periods of economic expansion.

Management - The value of your investment may go down if the investment manager's or sub-adviser's judgments and decisions are incorrect or otherwise do not produce the desired results, or if the investment strategy does not work as intended. You may also suffer losses if there are imperfections, errors or limitations in the quantitative, analytic or other tools, resources, information and data used, investment techniques applied, or the analyses employed or relied on, by the investment manageror sub-adviser, if such tools, resources, information or data are used incorrectly or otherwise do not work as intended, or if the investment manager's or sub-adviser's investment style is out of favor or otherwise fails to produce the desired results. Any of these things could cause the portfolio to lose value or its results to lag relevant benchmarks or other funds with similar objectives.

Counterparty - The portfolio could lose money if the counterparties to derivatives, repurchase agreements and/or other financial contracts entered into for the portfolio do not fulfill their contractual obligations. In addition, the portfolio may incur costs and may be hindered or delayed in enforcing its rights against a counterparty. These risks may be greater to the extent the portfolio has more contractual exposure to a counterparty.

Credit - If an issuer or other obligor (such as a party providing insurance or other credit enhancement) of a security held by the portfolio or a counterparty to a financial contract with the portfolio is unable or unwilling to meet its financial obligations, or is downgraded or perceived to be less creditworthy (whether by market participants, ratings agencies, pricing services or otherwise), or if the value of any underlying assets declines, the value of your investment will typically decline. A decline may be rapid and/or significant, particularly in certain market environments. In addition, the portfolio may incur costs and may be hindered or delayed in enforcing its rights against an issuer, obligor or counterparty.

Cybersecurity - Cybersecurity incidents, both intentional and unintentional, may allow an unauthorized party to gain access to portfolio assets, portfolio or shareholder data (including private shareholder information), or proprietary information, cause the portfolio or its service providers (including, but not limited to, the portfolio's investment manager, any sub-adviser(s), transfer agent, distributor, custodian, fund accounting agent and financial intermediaries) to suffer data breaches, data corruption or loss of operational functionality, or prevent portfolio investors from purchasing, redeeming or exchanging shares, receiving distributions or receiving timely information regarding the portfolio or their investment in the portfolio. Cybersecurity incidents may result in financial losses to the portfolio and its shareholders, and substantial costs may be incurred in order to prevent or mitigate any future cybersecurity incidents.

Derivatives - The use of derivatives involves a variety of risks, which may be different from, or greater than, the risks associated with investing in traditional securities, such as stocks and bonds. Risks of derivatives include leverage risk, liquidity risk, interest rate risk, valuation risk, market risk, counterparty risk and credit risk. Use of derivatives can increase portfolio losses, increase costs, reduce opportunities for gains, increase portfolio volatility, and not produce the result intended. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Even a small investment in derivatives can have a disproportionate impact on the portfolio. Derivatives may be difficult or impossible

to sell, unwind or value, and the counterparty (including, if applicable, the portfolio's clearing broker, the derivatives exchange or the clearinghouse) may default on its obligations to the portfolio. In certain cases, the portfolio may incur costs and may be hindered or delayed in enforcing its rights against or closing out derivatives instruments with a counterparty, which may result in additional losses. Derivatives are also generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative, including market risk, credit risk, liquidity risk, management risk and valuation risk. Also, suitable derivative transactions may not be available in all circumstances or at reasonable prices. The value of a derivative may fluctuate more or less than, or otherwise not correlate well with, the underlying assets, rates, indices or other indicators to which it relates. Using derivatives also subjects the portfolio to certain operational and legal risks. The portfolio may segregate cash or other liquid assets to cover the funding of its obligations under derivatives contracts or make margin payments when it takes positions in derivatives involving obligations to third parties. Rule 18f-4 under the 1940 Act provides a comprehensive regulatory framework for the use of derivatives by funds and imposes requirements and restrictions on portfolios using derivatives. Rule 18f-4 could have an adverse impact on the portfolio's performance and its ability to implement its investment strategies and may increase costs related to the portfolio's use of derivatives. The rule may affect the availability, liquidity or performance of derivatives, and may not effectively limit the risk of loss from derivatives.

Industry Concentration - The portfolio will concentrate its investments in issuers of one or more particular industries to the same extent that its underlying index is so concentrated and to the extent permitted by applicable regulatory guidance. Concentration in a particular industry heightens the risks associated with that industry. As a result, the portfolio may be subject to greater price volatility and risk of loss as a result of adverse economic, business or other developments affecting that industry than portfolios investing in a broader range of industries.

Large Shareholder - A significant portion of the portfolio's shares may be owned by one or more investment vehicles or institutional investors. Transactions by these large shareholders may be disruptive to the management of the portfolio. For example, the portfolio may experience large redemptions and could be required to sell securities at a time when it may not otherwise desire to do so. Such transactions may increase the portfolio's brokerage and/or other transaction costs. In addition, sizeable redemptions could cause the portfolio's total expenses to increase.

Leveraging - To the extent that the portfolio borrows or uses derivatives or other investments, such as ETFs, that have embedded leverage, your investment may be subject to heightened volatility, risk of loss and costs. Other risks also will be compounded because leverage generally magnifies the effect of a change in the value of an asset and creates a risk of loss of value on a larger pool of assets than the portfolio would otherwise have. Use of leverage may result in the loss of a substantial amount, and possibly all, of the portfolio's assets. The portfolio also may have to sell assets at inopportune times to satisfy its obligations.

Liquidity - The portfolio may make investments that are illiquid or that become illiquid after purchase. Illiquid investments can be difficult to value, may trade at a discount from comparable, more liquid investments, and may be subject to wide fluctuations

in value. Liquidity risk may be magnified in rising interest rate or volatile environments. If the portfolio is forced to sell an illiquid investment to meet redemption requests or other cash needs, the portfolio may be forced to sell at a substantial loss or may not be able to sell at all. Liquidity of particular investments, or even entire asset classes, including U.S. Treasury securities, can deteriorate rapidly, particularly during times of market turmoil, and those investments may be difficult or impossible for the portfolio to sell. This may prevent the portfolio from limiting losses.

Tracking Error - Imperfect correlation between the underlying portfolio securities held by the portfolio and those in the index that the portfolio tracks, portfolio fees and expenses, maintenance of cash balances to meet redemption requests, rounding of prices, changes to an index and regulatory and tax requirements may cause tracking error, which is the divergence of a portfolio's performance from that of the portfolio's benchmark index.

Performance:The bar chart and the table below provide some indication of the risks of investing in the portfolio. The bar chart shows how the portfolio's performance has varied from year to year. The table shows how the portfolio's average annual total returns for different periods compare to the returns of a broad measure of market performance.

The performance calculations do not reflect any charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, performance would be lower.

Index returns are since inception of the oldest share class.

As with all mutual funds, past performance is not a prediction of future results. Updated performance information is available on our website at www.transamerica.com/annuities-performance-center or by calling 1-800-851-9777.

Annual Total Returns (calendar years ended December 31) - Service Class

	Quarter Ended	Return
Best Quarter:	6/30/2020	20.50%
Worst Quarter:	3/31/2020	-19.68%

Average Annual Total Returns (periods ended December 31, 2023)

	1 Year	5 Years	Since Inception	Inception Date
Initial Class	26.09%	15.49%	11.12%	1/12/2018
Service Class	25.73%	15.20%	12.41%	5/1/2017
S&P 500® Index (reflects no deduction for fees, expenses or taxes)	26.29%	15.69%	12.94%	5/1/2017

Management:

Investment Manager: Transamerica Asset Management, Inc. Sub-Adviser: SSGA Funds Management, Inc. Portfolio Managers:
Keith Richardson	Portfolio Manager	since January 2019
Karl Schneider	Portfolio Manager	since May 2017

Purchase and Sale of Portfolio Shares: Shares of the portfolio may only be purchased or redeemed through variable life insurance policies and variable annuity contracts offered by the separate accounts of participating life insurance companies. Please refer to the corresponding prospectus of the policy or annuity contract that you have chosen for more information about the terms of the offering. Shares of the portfolio may also be sold to the asset allocation portfolios and to other funds of funds.

The portfolio does not have any initial or subsequent investment minimums. However, your insurance company may impose investment minimums.

The portfolio will not be charged and does not intend to pay any 12b-1 fees on Initial Class shares through May 1, 2025. The maximum 12b-1 fee on Initial Class shares is 0.15%. The portfolio reserves the right to pay such fees after that date.

Tax Information: Distributions made by the portfolio to an insurance company separate account, and exchanges and redemptions of portfolio shares made by the separate account, ordinarily do not cause the owners of insurance policies and annuity contracts invested in the separate account to recognize income or gain for federal income tax purposes. Please refer to the corresponding prospectus of the policy or annuity contract that you have chosen for more information regarding the tax consequences of your investment.

Payments to Broker-Dealers and Other Financial Intermediaries: The portfolio is generally only available as an underlying investment option for separate accounts of Transamerica life insurance companies to fund benefits under variable life insurance policies and variable annuity contracts. The portfolio and/or its affiliates may make payments to a Transamerica insurance company (or its affiliates) and to broker-dealers and other financial intermediaries for the sale of variable contracts (and thus, indirectly, the portfolio's shares) and related services. These payments may create a conflict of interest by influencing the Transamerica insurance company or other intermediary to recommend the variable contracts that invest in the portfolio. Ask your salesperson or visit your financial intermediary's website for more information.

In an effort to reduce paper mailings and conserve natural resources, we encourage you to visit our website, www.transamerica.com, to set up an account and enroll in eDelivery.

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