SUMMARY PROSPECTUS

September 28, 2023 (As Amended May 9, 2024)    

MFS^® Aggressive Growth Allocation Fund

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 and other information about the fund, including the fund’s reports to shareholders and statement of additional information, online at funds.mfs.com. You can also get this information at no cost by calling 1-800-225-2606 or by sending an e-mail request to orderliterature@mfs.com. The fund’s prospectus and statement of additional information, both dated September 28, 2023, as may be amended or supplemented from time to time, are incorporated by reference into this summary prospectus.

Summary of Key Information

Investment Objective

The fund's investment objective is to seek a high level of total return consistent with an aggressive level of risk relative to the other MFS Asset Allocation Funds. (The MFS Asset Allocation Funds currently are MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth Allocation Fund, and MFS Aggressive Growth Allocation Fund.)

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 15 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

# This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.

1 Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, such that "Other Expenses" do not exceed 0.13% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and 0.05% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2024.

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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 you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

1 Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.

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 when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 4% of the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification among different asset classes by investing its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund’s investment adviser), referred to as underlying funds.

MFS selects the asset class allocations based on a strategic asset allocation process that takes into account a variety of factors, including historical risk and performance, projected performance, and other factors. MFS’ analyses of projected performance are primarily based on quantitative models using various inputs such as valuation metrics, growth rates, profitability, yields, and inflation. MFS may also consider current market conditions, its qualitative assessment of the risk/return characteristics of asset classes, and other factors in determining these allocations.

MFS employs the strategic asset allocation process described above to determine the amount of the fund's assets invested in (1) underlying funds that invest primarily in equity securities (“Equity Funds”) and underlying funds that provide exposure to less traditional asset classes, such as real estate and commodities (“Non-Traditional Funds”) and (2) underlying funds that invest primarily in debt instruments (“Bond Funds”) and an underlying fund that invests in cash and/or cash equivalents (“Money Market Fund”).

MFS selects the underlying funds within each asset class based on underlying fund classifications, historical risk, historical and projected performance of the represented asset classes, as well as other factors.

Within the Equity Fund allocation, MFS seeks to diversify by geography (by including domestic and international underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds), and by style (by including both growth and value underlying funds). A portion of the fund’s assets is also allocated to Non-Traditional Funds (i.e., asset classes less correlated to the overall equity and debt markets), which MFS believes provides further diversification benefits.

Within the Bond Fund allocation, MFS includes underlying funds with varying degrees of geographic, interest rate, and credit exposure as potential investments for the fund, including exposure to below investment grade quality debt instruments. A portion of the fund’s assets may also be allocated to the Money Market Fund.

MFS normally invests the underlying funds’ assets across different industries, sectors, countries, and regions, but MFS may invest a significant percentage of the underlying funds' assets in issuers in a single industry, sector, country, or region.

As of September 1, 2023, the fund’s approximate long-term strategic allocation among asset classes was:

MFS may deviate from the long-term strategic allocations set forth above; however, any deviation from the long-term strategic allocation is not expected to be greater than plus or minus 10% under normal market conditions. Additionally, the fund’s allocation to Non-Traditional Funds will not typically exceed 20% of the fund’s assets.

As of September 1, 2023, the fund’s approximate strategic allocation among asset classes was:

All percentages are rounded to the nearest tenth of a percent. As a result, the sum of the asset class allocations presented in the table may not total 100%.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Allocation Risk: MFS' assessment of the risk/return potential of asset classes and underlying funds, and the resulting allocation

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among asset classes and underlying funds, may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes the fund to the risks of the underlying funds. Each underlying fund pursues its own investment objective and strategies and may not achieve its objective. In addition to the fees and expenses the fund bears directly, shareholders of the fund will indirectly bear the fees and expenses of the underlying funds.

Investment Selection Risk: MFS' investment analysis, its development and use of quantitative models, and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. The quantitative models used by MFS (both proprietary and third-party) may not produce the intended results for a variety of reasons, including the factors used in the models, the weight placed on each factor in the models, changes from the market factors' historical trends, changing sources of market return or market risk, and technical issues in the design, development, implementation, application, and maintenance of the models (e.g., incomplete, stale, or inaccurate data, human error, programming or other software issues, coding errors, and technology failures).

Equity Market Risk/Company Risk: Equity markets are volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general. Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market. The value of an investment held by the fund may decline due to factors directly related to the issuer.

Growth Company Risk: The stocks of growth companies can be more sensitive to the company’s earnings and more volatile than the market in general.

Value Company Risk: The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Intrinsic Value Strategy Risk: The stocks of companies that MFS believes are undervalued compared to their intrinsic value can continue to be undervalued for long periods of time, may not realize their expected value, and can be volatile.

Debt Market Risk: Debt markets can be volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single instrument, issuer, or borrower, a particular type of instrument, issuer, or borrower, a segment of the debt markets or the debt markets generally. Certain events can have a dramatic adverse effect on debt markets and may lead to periods of high volatility and reduced liquidity in a debt market or segment of a debt market.

Interest Rate Risk: In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities or durations, or that do not pay current interest.

Credit Risk: The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or other entity responsible for payment, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in, or perceptions of, the financial condition of the issuer, borrower, counterparty, or other entity, or underlying collateral or assets, or changes in, or perceptions of, specific or general market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.

Below investment grade quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Below investment grade quality debt instruments are regarded as having predominantly speculative characteristics. Below investment grade quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Prepayment/Extension Risk: Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

Municipal Risk: The price of a municipal instrument can be volatile and significantly affected by adverse tax changes or court rulings, legislative or political changes, changes in specific or general market and economic conditions and developments, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in certain industries can significantly affect the fund and the overall municipal market. Municipal instruments may be more susceptible to downgrades or defaults during economic downturns or similar periods of economic stress, which in turn could affect the market values and marketability of many or all municipal obligations of issuers in a state, U.S. territory, or possession.

Focus Risk: Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed.

Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging markets or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

Emerging Markets Risk: Investments tied economically to emerging markets, especially frontier markets, can involve additional and greater risks than the risks associated with investments in developed markets. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, greater government involvement in the economy, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater political, social, geopolitical, and economic instability than developed markets.

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Currency Risk: The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, and changes in currency exchange rates impact the financial condition of companies or other issuers and may change the value in U.S. dollars of investments denominated in foreign currencies.

Real Estate-Related Investment Risk: The risks of investing in real estate-related securities include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; difficulties in valuing and disposing of real estate; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; the management skill and creditworthiness of the real estate investment trust (REIT) manager; and other factors. The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

Commodity-Related Investments Risk: The value of commodity-related investments may be more volatile than the value of equity securities or debt instruments and may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, currency fluctuations, geopolitical events, or factors affecting a particular industry or commodity. The price of a commodity-related investment may be affected by demand/supply imbalances in the market for the commodity.

When-Issued, Delayed Delivery, and Forward Commitment Transaction Risk: The purchaser in a when-issued, delayed delivery or forward commitment transaction assumes the rights and risks of ownership, including the risks of price and yield fluctuations and the risk that the security will not be issued or delivered as anticipated. When-issued, delayed delivery, and forward commitment transactions can involve leverage.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost. Derivatives can involve leverage.

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability or willingness to perform in accordance with the terms of the transaction.

Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares. These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance and one or more other measures of performance for markets in which the fund may invest.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Class A Bar Chart. The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.

The total return for the six-month period ended June 30, 2023, was 9.48%. During the period(s) shown in the bar chart, the highest quarterly return was 18.98% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (20.56)% (for the calendar quarter ended March 31, 2020).

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Performance Table.

As of December 31, 2022, the MFS Aggressive Growth Allocation Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 60% Standard & Poor's 500 Stock Index; 30% MSCI EAFE (Europe, Australasia, Far East) Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index. The components and weightings of the Blended Index may have differed during the periods and may differ in the future.

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. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Investment Adviser

MFS serves as the investment adviser for the fund.

Portfolio Manager(s)

Joseph Flaherty, Jr., has announced his intention to retire effective June 1, 2025, and he will no longer be a portfolio manager of the fund as of that date.

Purchase and Sale of Fund Shares

You may purchase and redeem shares of the fund each day the New York Stock Exchange (the NYSE) is open for trading. You may purchase or redeem shares either by having your financial intermediary process your purchase or redemption, or through MFS Service Center, Inc. (MFSC) by overnight mail (MFSC, Suite 219341, 430 W 7^th Street, Kansas City, MO 64105-1407), by mail ([Fund Name], P.O. Box 219341, Kansas City, MO 64121-9341), by telephone (1-800-225-2606), or via the Internet at mfs.com (MFS Access).

The fund’s initial and subsequent investment minimums generally are as follows:

Purchases of Class B shares are closed to new and existing investors except through reinvestment of dividends and capital gain distributions. Existing investors may continue to exchange their Class B shares for the same share class of another MFS fund.

Effective after the close of business on September 29, 2023, purchases of Class R1 and Class R2 shares are closed to new eligible investors. After the close of business on September 29, 2023, existing eligible investors can make additional purchases and reinvest distributions in Class R1 and Class R2 shares in any account open as of the close of business on September 29, 2023. Existing eligible investors, after the close of business on September 29, 2023, may also exchange their Class R1 and Class R2 shares for the same share class of another MFS fund, open new Class R1 and Class R2 share accounts in other MFS funds, and transfer some or all of the shares in their account to another account and such account will be treated as having been open as of the close of business on September 29, 2023. Subject to the approval of the fund’s Board of Trustees, the fund may in the future (i) close purchases of Class R1 and/or Class R2 shares to existing eligible investors; (ii) terminate and liquidate Class R1 and/or Class R2 shares; or (iii) convert Class R1 and/or Class R2 shares to another share class of the fund. Such actions may be undertaken without

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shareholder approval, but the fund expects to provide shareholders with at least 60 days’ notice before taking any such action.

Taxes

If your shares are held in a taxable account, the fund’s distributions will be taxed to you as ordinary income and/or capital gains. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

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, MFS, and/or MFS’ affiliates may pay the financial intermediary for the sale of shares of the fund and/or the servicing of shareholder accounts. These payments may create a conflict of interest by influencing your broker/dealer or other financial intermediary and your salesperson to recommend the fund over another investment. Ask your financial intermediary or visit your financial intermediary’s website for more information.

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