Summary Prospectus by Investment Company - Form 497K

Before you invest, you may want to review the Fund's Prospectus, which contains more information about the Fund and its risks. You can find the Fund's Prospectus, reports to shareholders, and other information about the Fund online at im.natixis.com/fund-documents. You can also get this information at no cost by calling 800-225-5478 or by sending an e-mail request to [email protected]. The Fund's Prospectus and Statement of Additional Information, each dated May 1, 2024, as may be revised or supplemented from time to time, are incorporated by reference into this Summary Prospectus.

Investment Goal

The Fund seeks total return with less risk than U.S. equity markets.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 61 of the Prospectus, in Appendix A to the Prospectus and on page 111 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees

Annual Fund Operating Expenses

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The

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Fund Summary

example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods.The example for Class C shares for the ten-year period reflects the conversion to Class A shares after eight years.The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio Turnover

The Fund 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 and may result in higher taxes for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 32% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

Under normal circumstances, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in equity securities. Equity securities purchased by the Fund may include the following U.S. exchange-listed securities: common stocks; American Depositary Receipts ("ADRs"), which are securities issued by a U.S. bank that represent interests in foreign equity securities; and interests in real estate investment trusts ("REITs"). The Fund ordinarily invests in a broadly diversified equity portfolio, while also writing (selling) index call options with an aggregate notional value approximately equal to the market value of the equity portfolio. Writing index call options is intended to reduce the Fund's volatility and provide steady cash flow. Cash flow from call option writing is intended to be an important source of the Fund's return, although the Fund's option writing activity reduces the Fund's ability to profit from increases in the value of its equity portfolio. The combination of a diversified stock portfolio and the steady cash flow from the sale of index call options is intended to moderate the volatility of returns relative to an all-equity portfolio. The Fund may invest in companies with small, medium or large market capitalizations.

The Fund's combination of a broadly diversified portfolio of common stocks and written index call options is similar to the components of the Cboe S&P 500 BuyWrite Index (the "BXM^SM"). The BXM^SM is a passive total return index based on (1) buying an S&P 500^® stock index portfolio, and (2) writing (selling) the near-term S&P 500^® Index "covered" call option. The Fund's more flexible, active option management approach creates the potential for it to achieve higher long-term returns than the BXM^SM while exhibiting a similar level of volatility, as defined by standard deviation of returns. The similarities between the BXM^SM and the Fund's equity investment strategy are expected to result in the Fund exhibiting a positive correlation to the broad U.S. equity markets similar to that exhibited by the BXM^SM.

With its core investment in equities, the Fund is intended to be significantly less vulnerable to fluctuations in value caused by interest rate volatility, a risk factor present in both fixed-income investments and "hybrid investments" (blends of equity and fixed-income securities). Through the use of index options, the Fund intends that its risk management strategy will reduce the volatility inherent in equity investments while also allowing for more participation in equity returns than hybrid investments. Thus, the Fund seeks to provide an efficient trade-off between risk and reward, where risk is characterized by volatility or fluctuations in value over time.

Purchasing Stocks

The Fund invests in a diversified stock portfolio, generally consisting of approximately 200 to 400 stocks (including ADRs and REITs), designed to support the Fund's index option-based risk management strategy as efficiently as possible while seeking to enhance the Fund's after-tax total return. The Adviser uses a multifactor quantitative model to construct the stock portfolio. The model evaluates U.S.-exchange-traded equities that meet the criteria and constraints established by the Adviser. Generally, the Adviser tries to minimize the difference between the performance of the Fund's stock portfolio and the performance of the index or indices underlying the Fund's option strategies while also considering other factors, such as predicted dividend yield. The Adviser monitors this difference and other factors, and rebalances and adjusts the stock portfolio from time to time, by purchasing and selling stocks. To the extent consistent with

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Fund Summary

the Fund's investment goal, the Adviser may also sell stocks to realize capital losses in an effort to minimize any required capital gain distributions. The Adviser expects the portfolio to generally represent the broad U.S. equity market.

Writing Index Call Options

The Fund continuously writes index call options, typically on broad-based securities market indices, with an aggregate notional value approximately equal to the market value of its broadly diversified stock portfolio. As the seller of the index call option, the Fund receives cash (the "premium") from the purchaser. The purchaser of an index call option has the right to any appreciation in the value of the index over a fixed price (the "exercise price") on a certain date in the future (the "expiration date"). If the purchaser does not exercise the option, the Fund retains the premium. If the purchaser exercises the option, the Fund pays the purchaser the difference between the value of the index and the exercise price of the option. The premium, the exercise price and the value of the index determine the gain or loss realized by the Fund as the seller of the index call option. The Fund can also repurchase the call option prior to the expiration date, ending its obligation. In such a case, the difference between the cost of repurchasing the option and the premium received will determine the gain or loss realized by the Fund.

Other Investments

The Fund may invest in foreign securities traded in U.S. markets (through ADRs or stocks traded in U.S. dollars). The Fund may enter into repurchase agreements and/or hold cash and cash equivalents.

Principal Investment Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund.

Fund shares are not bank deposits and are not guaranteed, endorsed or insured by the Federal Deposit Insurance Corporation or any other government agency, and are subject to investment risks, including possible loss of the principal invested.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Call Options Risk: The value of the Fund's positions in index options will fluctuate in response to changes in the value of the underlying index. Writing index call options limits the opportunity to profit from an increase in the market value of stocks in exchange for up-front cash at the time of selling the call option. Unusual market conditions or the lack of a ready market for any particular option at a specific time may reduce the effectiveness of the Fund's option-based risk management strategy, and for these and other reasons the Fund's option strategy may not reduce the Fund's volatility to the extent desired.

Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds generally take precedence over the claims of those who own preferred stock or common stock. Securities of real estate-related companies and REITs in which the Fund may invest may be considered equity securities, thus subjecting the Fund to the risks of investing in equity securities generally. Small- and mid-capitalization and emerging growth companies may be subject to more abrupt price movements, limited markets and less liquidity than larger, more established companies, which could adversely affect the value of the Fund's equity portfolio.

Correlation Risk: The Fund's ability to manage the volatility of its equity portfolio by writing index options depends on the correlation between the returns of the equity portfolio and those of the index on which the Fund's index options are written. Accordingly, the effectiveness of the Fund's index option-based risk management strategy may be reduced to the extent the performance of the Fund's equity portfolio does not correlate to that of the indices underlying its option positions.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund's expenses.

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Fund Summary

REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) compare to those of a broad-based securities market index that reflects the performance of the overall market applicable to the Fund and an additional index that represents the market sectors in which the Fund primarily invests. Performance for Class C shares includes the automatic conversion to Class A shares after eight years, where applicable. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return. To the extent that a class of shares was subject to the waiver or reimbursement of certain expenses during a period, had such expenses not been waived or reimbursed during the period, total returns would have been lower.

Total Returns for Class Y Shares

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated to reflect the different sales load applicable to Class T shares.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who

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Fund Summary

hold their shares through tax-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund.After-tax returns for the other classes of the Fund will vary. Index performance reflects no deduction for fees, expenses or taxes.

Management

Investment Adviser

Gateway

Portfolio Managers

Daniel M. Ashcraft, CFA^®, Vice President and Portfolio Manager of the Adviser, has served as co-portfolio manager of the Fund since 2014.

Michael T. Buckius, CFA^®, President, Chief Executive Officer and Chief Investment Officer of the Adviser, has served as co-portfolio manager of the Fund since 2014.

Kenneth H. Toft, CFA^®, Senior Vice President and Portfolio Manager of the Adviser, has served as co-portfolio manager of the Fund since 2014.

Mitchell J. Trotta, CFA^®, Portfolio Manager of the Adviser, has served as co-portfolio manager of the Fund since 2021.

Purchase and Sale of Fund Shares

Class A and C Shares

The following chart shows the investment minimums for various types of accounts:

There is no subsequent investment minimum for these shares. There is no initial investment minimum for:

The minimum investment requirements for Class A shares may be waived or lowered for investments effected through certain financial intermediaries that have entered into special arrangements with Natixis Distribution, LLC (the "Distributor"). Consult your financial intermediary for additional information regarding the minimum investment requirement applicable to your investment.

Class N Shares

Class N shares of the Fund are subject to a $1,000,000 initial investment minimum. This minimum applies to Fee Based Programs and accounts (such as wrap accounts) where an advisory fee is paid to the broker-dealer or other financial intermediary. There is no subsequent investment minimum for these shares. There is no initial investment minimum for:

In its sole discretion, the Distributor may waive the investment minimum requirement for accounts as to which the Distributor reasonably believes will have enough assets to exceed the investment minimum requirement within a relatively short period of time following the establishment date of such accounts in Class N. The Distributor and the Fund, at any time, reserve the right to liquidate these accounts or any other account that does not meet the eligibility requirements of this class.

Class T Shares

Class T shares of the Fund are not currently available for purchase.

Class T shares of the Fund may only be purchased by investors who are investing through an authorized third party, such as a broker-dealer or other financial intermediary, that has entered into a selling agreement with the Distributor. Investors may not hold Class T shares directly with the Fund. Class T shares are

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Fund Summary

subject to a minimum initial investment of $2,500. There is no subsequent investment minimum for these shares. Not all financial intermediaries make Class T shares available to their clients.

Class Y Shares

Class Y shares of the Fund are generally subject to a minimum initial investment of $100,000. There is no subsequent investment minimum for these shares. There is no minimum initial investment for:

At the discretion of Natixis Advisors, clients of Natixis Advisors and its affiliates may purchase Class Y shares of the Fund below the stated minimums.

Due to operational limitations at your financial intermediary, certain fee based programs, retirement plans, individual retirement accounts and accounts of registered investment advisers may be subject to the investment minimums described above.

The Fund's shares are available for purchase and are redeemable on any business day through your investment dealer, directly from the Fund by writing to the Fund at Natixis Funds, P.O. Box 219579, Kansas City, MO 64121-9579, by exchange, by wire, by internet at im.natixis.com (certain restrictions may apply), through the Automated Clearing House system, or, in the case of redemptions, by telephone at 800-225-5478 or by the Systematic Withdrawal Plan.

Tax Information

Fund distributions are generally taxable to you as ordinary income or capital gains, except for distributions to retirement plans and other investors that qualify for tax-advantaged treatment under U.S. federal income tax law generally. Investments through such tax-advantaged plans will generally be taxed only upon withdrawal of monies from the tax-advantaged arrangement.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies may pay the intermediary for the sale of the Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

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