 this post-effective amendment designates a new effective date for a previously filed post-effective amendment

The Securities and Exchange Commission has not approved or disapproved the fund’s shares or determined whether this prospectus is accurate or complete. Anyone who tells you otherwise is committing a crime.

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

Effective May 1, 2024, the Russell 3000^{^®} Index replaces the Russell 2000^{^®} Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000^{^®} Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.

You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, for minimum investment requirements and redemption procedures.

You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, to understand the tax treatment of your investment.

The fund, MFS, and/or its affiliates may make payments to insurance companies, other financial intermediaries, and all of their affiliates, for distribution and/or other services. These payments may create a conflict of interest for the insurance company or other financial intermediary to include the fund as an investment option in its product or to recommend the fund over another investment option. Ask your financial intermediary or insurance company, or visit your financial intermediary's or insurance company's website, for more information.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS seeks to achieve the fund's objective by actively identifying potential investments based on fundamental and quantitative analysis and then constructing a portfolio from these potential investments while managing various risk factors (e.g., issuer, industry, and sector weightings, market capitalization, and volatility) compared to the Russell 2000^{^®} Index, which represents the fund's investment universe.

MFS normally invests at least 80% of the fund’s net assets in equity securities of issuers with small market capitalizations. MFS generally defines small market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell 2000^{^®} Index over the last 13 months at the time of purchase. As of March 31, 2024, the range of the market capitalizations of the issuers in the Russell 2000^{^®} Index was between approximately $16.6 million and $59.1 billion. Issuers whose market capitalizations fall outside this definition after purchase continue to be considered to have a small market capitalization for purposes of the 80% policy.

In selecting investments for the fund, MFS is not constrained by any particular investment style. MFS may invest the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up approach to buying and selling investments for the fund. Investments are selected primarily based on blending fundamental and quantitative research. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition and market, economic, political, and regulatory conditions to determine a fundamental rating for an issuer. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. MFS uses quantitative analysis, including quantitative models that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, to determine a quantitative rating for an issuer. MFS combines the fundamental rating with the quantitative rating to create a blended rating for an issuer. (When the fundamental rating is not available, MFS treats the issuer as having a neutral fundamental rating. MFS' quantitative research generates ratings on a greater number of issuers than MFS' fundamental research.)

MFS constructs the portfolio using a portfolio optimization process that considers the blended rating, as well as issuer, industry, and sector weightings, market capitalization, volatility, and other factors. The portfolio managers have the discretion to adjust the inputs and parameters used in the optimization process and the fund's portfolio holdings based on factors such as the desired portfolio characteristics and the portfolio managers' qualitative assessment of the optimization results. MFS' goal is to construct an actively managed portfolio with a target predicted tracking error of approximately 3% compared to the Russell 2000^{^®} Index. Tracking error generally measures how the differences between the fund's returns and the Russell 2000^{^®} Index's returns have varied over a period of time. A lower tracking error means that there is generally less variation between the fund's returns compared to an index that represents the fund's investment universe. Third-party quantitative risk models are used in the portfolio construction process and to measure the predicted tracking error of the fund's portfolio.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

Equity Securities: Equity securities represent an ownership interest, or the right to acquire an ownership interest, in a company or other issuer. Different types of equity securities provide different voting and dividend rights and priorities in the event of bankruptcy of the issuer. Equity securities include common stocks, preferred stocks, securities convertible into stocks, equity interests in REITs, and depositary receipts for such securities.

REITs: REITs are pooled investment vehicles that invest primarily in income-producing real estate and/or real estate-related loans or interests. REITs include real estate investment trusts formed under U.S. law as well as similar entities formed under the laws of non-U.S. countries.

The share price of the fund will change daily based on changes in market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. 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 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 below carefully, because any one or more of these risks may result in losses to the fund.

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). In addition, MFS or the fund's other service providers may experience disruptions or operating errors that could negatively impact the fund.

Equity Market 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. Different parts of the market and different types of securities can react differently to these conditions. For example, the stocks of growth companies can react differently from the stocks of value companies, and the stocks of large cap companies can react differently from the stocks of small cap companies. Certain changes or events, such as political, social, or economic developments, including increasing or negative interest rates or the U.S. government's inability at times to agree on a long-term budget and deficit reduction plan (which has in the past resulted and may in the future result in a government shutdown); market closures and/or trading halts; government or regulatory actions, including sanctions, the imposition of tariffs or other protectionist actions and changes in fiscal, monetary, or tax policies; natural disasters; outbreaks of pandemic and epidemic diseases; terrorist attacks; war; and other geopolitical changes or 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.

Company Risk: Changes in the financial condition of a company or other issuer, changes in specific market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical, environmental, public health, and other conditions can adversely affect the prices of investments. The value of an investment held by the fund may decline due to factors directly related to the issuer, such as competitive pressures, cybersecurity incidents, financial leverage, historical and/or prospective earnings, management performance, labor and supply shortages, investor perceptions, and other factors. The prices of securities of smaller, less well-known issuers can be more volatile than the prices of securities of larger issuers or the market in general.

Small Cap Risk: The stocks of small cap companies can be more volatile than the stocks of larger companies due to limited product lines, financial and management resources, market and distribution channels. Small cap companies often have shorter operating histories and more limited publicly available information than larger, well-established companies. Their shares can be less liquid than those of larger companies, especially during market declines.

Investment Strategy Risk: There is no assurance that the fund's predicted tracking error will equal its target predicted tracking error at any point in time or consistently for any period of time, or that the fund's predicted tracking error and actual tracking error will be similar. The fund's strategy to target a predicted tracking error of approximately 3% compared to the Russell 2000^{^®} Index and to blend fundamental and quantitative research may not produce the intended results. In addition, MFS' fundamental research is not available for all issuers.

Foreign Risk: Investments in securities of foreign issuers, securities of companies with significant foreign exposure, and foreign currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. Political, social, diplomatic, and economic developments, U.S. and foreign government action, or the threat thereof, such as the imposition of currency or capital blockages, controls, or tariffs, economic and trade sanctions or embargoes, security trading suspensions, entering or exiting trade or other intergovernmental agreements, or the expropriation or nationalization of assets in a particular country, can cause dramatic declines in certain or all securities with exposure to that country and other countries. Sanctions, or the threat of sanctions, may cause volatility in regional and global markets and may negatively impact the performance of various sectors and industries, as well as companies in other countries, which could have a negative effect on the performance of the fund. In the event of nationalization, expropriation, confiscation or other government action, intervention, or restriction, the fund could lose its entire investment in a particular foreign issuer or country. Civil unrest, geopolitical tensions, wars, and acts of terrorism are other potential risks that could adversely affect an investment in a foreign security or in foreign markets or issuers generally. Economies and financial markets are interconnected, which increases the likelihood that conditions in one country or region can adversely impact issuers in different countries and regions. Less stringent regulatory, accounting, auditing, and disclosure requirements for issuers and markets are more common in certain foreign countries. Enforcing legal rights can be difficult, costly, and slow in certain foreign countries and with respect to certain types of investments, and can be particularly difficult against foreign governments. Changes in currency exchange rates can significantly impact the financial condition of a company or other issuer with exposure to multiple countries as well as affect the U.S. dollar value of foreign currency investments and investments denominated in foreign currencies. Additional risks of foreign investments include trading, settlement, custodial, and other operational risks, and withholding and other taxes. These factors can make foreign investments, especially those tied economically to emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to market, economic, industry, political, regulatory,

geopolitical, environmental, public health, and other conditions than the U.S. market.

REITs Risk: The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. REITs are affected by 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 REIT manager; and other factors. The real estate sector is particularly sensitive to economic downturns. Many real estate-related issuers, including REITs, utilize leverage (and some may be highly leveraged), which increases investment risk and could adversely affect the issuer’s operations and market value in periods of rising interest rates. 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. In addition, REITs may have limited diversification because they invest in a limited number of properties, a narrow geographic area, or a single type of property.

REITs could be adversely affected by failure to qualify for the favorable tax treatment available to REITs under the Internal Revenue Code of 1986, as amended, or to maintain their exemption from registration under the Investment Company Act of 1940, as amended, and similar risks may also apply to securities of entities similar to REITs formed under the laws of non-U.S. countries.

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. These conditions include business environment changes; economic factors such as fiscal, monetary, and tax policies; inflation and unemployment rates; and government and regulatory changes. The fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed.

Liquidity Risk: Certain investments and types of investments are subject to restrictions on resale, may trade in the over-the-counter market, or may not have an active trading market due to adverse market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, including trading halts, sanctions, or wars. Investors trying to sell large quantities of a particular investment or type of investment, or lack of market makers or other buyers for a particular investment or type of investment may also adversely affect liquidity. At times, all or a significant portion of a market may not have an active trading market. Without an active trading market, it may be difficult to value, and it may not be possible to sell, these investments and the fund could miss other investment opportunities and hold investments it would prefer to sell, resulting in losses for the fund. In addition, 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, which could result in dilution of remaining investors' interests in the fund. The prices of illiquid securities may be more volatile than more liquid investments.

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. While it is impossible to predict the overall impact of these transactions over time, there could be adverse effects on the fund's performance to the extent that the fund may be required to sell securities or invest cash at times it would not otherwise do so. 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. In addition, a large redemption could result in the fund's current expenses being allocated over a smaller asset base, leading to an increase in the fund's expense ratio. 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.

Active and Frequent Trading: MFS may engage in active and frequent trading in pursuing the fund’s principal investment strategies. Frequent trading may increase transaction costs, which can reduce the fund’s return.

Operational and Cybersecurity Risk: The fund and its service providers, and your ability to transact with the fund, may be negatively impacted due to operational matters arising from, among other issues, human errors, systems and technology disruptions or failures, fraudulent activities, or cybersecurity incidents. Operational issues and cybersecurity incidents may cause the fund or its service providers, as well as securities trading venues and other market participants, to suffer data corruption and/or lose operational functionality, and could, among other things, interfere with the processing of shareholder transactions, impair the ability to calculate the fund's net asset value per share, impede trading of portfolio securities, and result in the theft, misuse, and/or improper release of confidential information relating to the fund or its shareholders. Such operational issues and cybersecurity incidents may result in losses to the fund and its shareholders. Because technology is frequently changing, new ways to carry out cyberattacks continue to develop. Therefore, there is a chance that certain risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the ability of the fund and its service providers to plan for or respond to a cyberattack. Furthermore, geopolitical tensions could increase the scale and sophistication of deliberate cybersecurity attacks, particularly those from nation-states or from entities with nation-state backing.

Temporary Defensive Strategy: In response to adverse market, economic, industry, political, or other conditions, MFS may depart from the fund’s principal investment strategies by temporarily investing for defensive purposes. When MFS invests defensively, different factors could affect the fund’s performance and the fund may not achieve its investment objective. In addition, the defensive strategy may not work as intended.

Further Information on Investment Strategies, Types, and Risks: Information about investment strategies and investment types not described in the prospectus and the risks associated with those investment strategies and investment types are described in the fund’s Statement of Additional Information (SAI).

MFS, located at 111 Huntington Avenue, Boston, Massachusetts 02199, serves as the investment adviser for the fund. Subject to the supervision of the fund’s Board of Trustees, MFS is responsible for managing the fund’s investments, executing transactions, and providing related administrative services and facilities under an Investment Advisory Agreement between the fund and MFS.

For the fiscal year ended December 31, 2023, the fund paid MFS an effective management fee equal to 0.39% of the fund’s average daily net assets.

The management fee set forth in the Investment Advisory Agreement is 0.40% of the fund's average daily net assets annually.

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. MFS has agreed in writing to waive at least 0.01% of its management fee as part of this agreement. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least April 30, 2025. For the fiscal year ended December 31, 2023, this management fee reduction amounted to 0.01% of the fund's average daily net assets.

MFS has agreed in writing to bear the fund’s expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that “Total Annual Fund Operating Expenses” do not exceed 0.60% of the class' average daily net assets annually for Initial Class shares and 0.85% of the class' average daily net assets annually for Service Class shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least April 30, 2025.

A discussion regarding the basis for the Board of Trustees’ approval of the Investment Advisory Agreement is available in the fund’s annual report for the one-year period ended December 31, 2023.

MFS is America’s oldest mutual fund organization. MFS and its predecessor organizations have a history of money management dating from 1924 and the founding of the first mutual fund, Massachusetts Investors Trust. Net assets under the management of the MFS organization were approximately $614 billion as of February 29, 2024.

Disclosure of Portfolio Holdings. The fund has established a policy with respect to the disclosure of fund portfolio holdings. A description of this policy is provided in the SAI.

The following information is available to you at mfs.com/vit3 by selecting the fund's name:

Holdings also include short positions, if any. Top 10 holdings exclude cash, cash equivalents, short-term investments, currency derivatives, and the cash portion of other derivatives. For purposes of full holdings, cash, cash equivalents, and short-term investments are aggregated and currency derivatives and the cash portion of other derivatives are aggregated.

Note that the fund or MFS may suspend the posting of this information or modify the elements of this Web posting policy without notice to shareholders. Once posted, the above information will generally remain available on mfs.com until at least the date on which the fund files a Form N-CSR or Form N-PORT for the period that includes the date as of which the mfs.com information is current.

Information regarding the portfolio manager(s) of the fund is set forth below. Further information regarding the portfolio manager(s), including other accounts managed, compensation, ownership of fund shares, and possible conflicts of interest, is available in the fund’s SAI.

MFS provides the fund with certain financial, legal, and other administrative services under a Master Administrative Services Agreement between the fund and MFS. Under the Agreement, MFS is paid an annual fee for providing these services.

MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, is the distributor of shares of the fund.

MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, provides dividend and distribution disbursing and transfer agent and recordkeeping functions in connection with the issuance, transfer, and redemption of each class of shares of the fund under a Shareholder Servicing Agent Agreement. MFSC receives a fee based on the costs it incurs in providing these services and a target profit margin. In addition, MFSC is reimbursed for out-of-pocket expenses.

The fund offers Initial Class and Service Class shares through this prospectus. All classes of the fund have the same investment objective and investments, but each class has its own expense structure.

The fund offers Initial Class and Service Class shares to separate accounts established by insurance companies to serve as investment vehicles for variable annuity and variable life insurance contracts and to any other investor permitted to hold shares of the fund without affecting the ability of insurance company separate accounts whose contracts are funded by the fund to satisfy the diversification requirements of Section 817(h) of the Internal Revenue Code (e.g., qualified pension and retirement plans and certain fund-of-funds).

The fund has adopted a plan in accordance with Rule 12b-1 under the Investment Company Act of 1940, as amended (the “Distribution Plan”). Under the Distribution Plan, Service Class shares pay distribution and/or service fees to MFD to support the sale and distribution of Service Class shares as well as shareholder servicing and account maintenance activities. These distribution and/or service fees equal on an annual basis up to 0.25% of average daily net assets of the class. These fees are paid out of fund assets of the Service Class shares. Because these fees are an ongoing expense

of the fund, they increase the cost of your investment over time and may cost you more than other types of sales charges.

The fund has not adopted a Rule 12b-1 plan with respect to its Initial Class shares.

Insurance companies that issue variable contracts and other eligible investors to whom shares of the fund are offered (collectively, together with their affiliates, "Financial Intermediaries") receive various forms of compensation in connection with the sale of shares of the fund and/or the servicing of accounts. Financial Intermediaries may receive such compensation (i) in the form of ongoing asset-based compensation paid by MFD based on Distribution Plan distribution and service payments received by MFD from the fund (as described under “Description of Share Classes-Distribution and Service Fees”), and (ii) in the form of payments paid by MFD and/or one or more of its affiliates (for purposes of this section only, collectively, "MFD") from MFD’s own additional resources.

In addition, certain Financial Intermediaries receive payments from MFD from MFD’s own additional resources as incentives to market the MFS funds, to participate in MFD’s promotional efforts and/or in recognition of their marketing support, administrative services and/or transaction processing support. This compensation from MFD is not reflected in the "Fees and Expenses" table in the fund’s prospectus. MFD compensates Financial Intermediaries based on criteria established by MFD from time to time, including the distribution potential of the Financial Intermediary, the types of products and programs offered by the Financial Intermediary, eligibility for placement on the financial intermediary's preferred or recommended list, the financial and contractual terms with the financial intermediary, the level and/or type of marketing and administrative support provided by the Financial Intermediary, and the quality of the overall relationship with the Financial Intermediary. In particular, MFD normally considers the level of assets attributable to the Financial Intermediary, the level of redemptions by the Financial Intermediary, the level of access to the Financial Intermediary's representatives and management, the ability to educate the representatives of the Financial Intermediary, and the number of representatives of the Financial Intermediary potentially utilizing the MFS Funds with their clients.

The types of payments described above are not exclusive and such payments can be significant to the Financial Intermediary. In addition, the compensation that Financial Intermediaries receive may vary by class of shares sold and among Financial Intermediaries. Depending upon the arrangements in place at any particular time, Financial Intermediaries may have a financial incentive to recommend a particular investment vehicle that makes the fund available or recommend a particular fund or share class.

You can find further details in the SAI about the payments made by MFD and the services provided by Financial Intermediaries. Financial Intermediaries may charge you additional fees and/or commissions other than those disclosed in this prospectus. You should ask your Financial Intermediary for information about any payments it receives from MFD and any services it provides, as well as about any fees and/or commissions it charges you. Financial Intermediaries that market the funds may also act as, or be affiliated with, a broker/dealer in connection with a fund’s purchase or sale of portfolio securities. However, the fund and MFS do not consider Financial Intermediaries' purchases of shares of the fund as a factor when choosing brokers/dealers to effect portfolio transactions for the fund.

All purchases, redemptions, and exchanges of shares are made through insurance company separate accounts and other eligible investors that are the record owners of the shares. Contract holders and other eligible investors seeking to purchase, redeem, or exchange interests in the fund’s shares should consult with the insurance company or other eligible investor through which their investment in the fund is made. The fund may reject for any reason any purchase orders.

Insurance companies and other eligible investors are the designees of the fund for receipt of purchase, exchange, and redemption orders from contract holders and plan beneficiaries. An order submitted to the fund’s designee will receive the net asset value next calculated after the order is received by the fund's designee, provided that the fund receives notice of the order generally by 11:00 a.m., Eastern time, on the next day on which the New York Stock Exchange (the NYSE) is open for trading. The fund typically processes redemption proceeds to insurance company separate accounts or other eligible investors by the end of the next business day. However, the fund may delay processing your redemption request for up to seven days. Under unusual circumstances, such as when the NYSE is closed, trading on the NYSE is restricted, or as permitted by the Securities and Exchange Commission (the SEC), the fund may suspend redemptions or postpone payment for more than seven days.

The fund typically expects to meet redemption requests by holding cash and/or cash equivalents, selling investments, and using overdraft provisions or lines of credit. The fund may also meet redemption requests by redeeming shares in kind for large redemptions or during stressed market conditions. If MFS determines it to be feasible and appropriate, the fund may pay the redemption by a distribution in kind of portfolio securities (redemption in kind). In the event that the fund makes a redemption in kind, you should expect to incur brokerage and other transaction charges when converting the securities to cash, and the securities will likely increase or decrease in value before you sell them.

An exchange involves the redemption of shares of one fund and the purchase of shares of another fund. You can exchange your shares of the fund for shares of the same class of another fund at their respective net asset values if shares of that fund are available for purchase by the insurance company separate account or other eligible investor through which your investment in the fund is made. See the prospectus or other materials for the investment vehicle through which your investment in the fund is made for a further discussion of the exchange privilege. You should read the prospectus of the fund into which you are exchanging and consider the differences in investment objectives, policies, and risks, and in fees and expenses, before making an exchange.

Purchase and Exchange Limitation Policy. The MFS funds reserve the right to restrict or reject, without any prior notice, any purchase or exchange order, including transactions believed to represent frequent or other disruptive trading activity. In the event that MFSC rejects an exchange request, neither the redemption nor the purchase side of the exchange will be processed. Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC's judgment, in consultation with MFS, as appropriate, such delay would be in the fund’s best interest, in which case both the redemption and purchase side of the

exchange will receive the funds’ net asset values at the conclusion of the delay period.

Disruptive Trading Risks. To the extent that the MFS funds or their agents are unable to curtail disruptive trading practices in a fund (e.g., disruptive frequent trading) or to the extent there are large or frequent redemptions in a fund, these purchases and/or redemptions can interfere with the efficient management of the fund's portfolio, may result in increased transaction and administrative costs, and may adversely impact the fund’s performance.

In addition, to the extent that the fund invests in foreign securities, the interests of long-term shareholders may be diluted as a result of time-zone arbitrage, a short-term trading practice that seeks to exploit changes in the value of the fund’s investments that result from events occurring after the close of the foreign markets on which the investments trade, but prior to the time the fund determines its net asset value. The fund’s use of fair valuation can serve to reduce arbitrage opportunities available to short-term traders, but there is no assurance that the fund’s fair valuation policies and procedures will prevent dilution of the fund’s net asset value by short-term traders.

To the extent that the fund invests in securities that trade infrequently or are difficult to value, such as the securities of smaller companies, high yield debt instruments, and floating rate loans, the interests of long-term shareholders may be diluted as a result of price arbitrage, a short-term trading strategy that seeks to exploit perceived pricing inefficiencies in the fund’s investments. Such short-term trading strategies may interfere with efficient management of the fund's portfolio to a greater degree than funds that invest in more frequently traded or liquid securities, in part because the fund may have difficulty selling these portfolio securities at advantageous times or prices to satisfy large and/or frequent redemption requests. Any successful price arbitrage may also cause dilution in the value of fund shares held by other shareholders.

Insurance Contract or other Investment Vehicle Requirements and Limitations. The terms of a particular insurance contract or other eligible investment vehicle may also limit the ability of the insurance company or other eligible investor to prohibit transactions that MFSC might consider to be disruptive trading. Please refer to your insurance company variable contract or other material for the investment vehicle through which your investment in the fund is made regarding any restrictions on trading.

Frequent Trading. The fund is not intended to serve as a vehicle for frequent trading. The Board of Trustees of the fund has adopted the purchase and exchange limitation policy described above, which it believes is reasonably designed to discourage frequent fund share transactions. MFSC seeks to monitor and enforce this policy, subject to oversight by the Board of Trustees. The fund may alter its policies at any time without notice to shareholders.

Financial Intermediaries are required to reject any purchase or exchange orders in the fund if they believe the orders represent frequent trading activity unless they notify MFSC or an affiliate in writing that they do not monitor for frequent trading (“Waived Financial Intermediaries”). With respect to Waived Financial Intermediaries, MFSC will take action reasonably designed to discourage frequent trading that is not in the best interests of the fund by the customers of such Waived Financial Intermediary, including requesting underlying shareholder account data more frequently than from other Financial Intermediaries.

Certain Financial Intermediaries may use procedures to restrict frequent trading by their customers who invest in the fund while others may not employ any procedures to restrict frequent trading. Such procedures, if any, may be less restrictive than the fund’s purchase and exchange limitation policy, may permit transactions not permitted by the fund’s purchase and exchange limitation policy, and/or may prohibit transactions not subject to the fund’s purchase and exchange limitation policy.

There is no assurance that MFSC will be able to detect or prevent frequent trading. Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and MFSC is generally not able to identify trading by a particular underlying shareholder within an omnibus account, which makes it difficult or impossible to determine if a particular underlying shareholder is engaged in frequent trading. Omnibus accounts, in which shares are held in the name of a Financial Intermediary on behalf of multiple underlying shareholders, are a common form of holding shares among insurance companies offering insurance products.

MFSC reviews trading activity to detect trading activity that may be indicative of frequent trading based on its internal parameters for detecting frequent trading, including reviewing transactions that exceed a certain dollar amount, transactions involving similar dollar amounts, or transactions that occur close in time to other transactions in the same account or in multiple accounts that are under common ownership, control, or influence. Any or all of these parameters (including those not listed) may change at any time. If MFSC detects suspicious trading activity at the omnibus account level, it will contact the Financial Intermediary to request underlying shareholder level activity to determine whether there is underlying shareholder level frequent trading that is disruptive to a fund. However, the underlying shareholder data received may not reflect information about the ultimate underlying shareholders because there may be multiple layers of omnibus accounts. If disruptive frequent trading is identified, MFSC will take appropriate action, such as requesting the Financial Intermediary to prohibit purchases into the account by the underlying shareholder, requiring purchases by the underlying shareholder to be submitted only by mail, or prohibiting purchases from the Financial Intermediary. In reviewing trading activity, MFSC may determine that certain transactions entered into for legitimate purposes do not represent frequent trading activity that is disruptive to a fund.

MFSC’s ability to monitor and deter frequent trading in omnibus accounts depends on, among other factors, the frequency with which MFSC requests underlying shareholder account data from omnibus accounts. MFSC expects to request underlying shareholder data based on its assessment of the likelihood of frequent trading by underlying shareholders, among other factors. MFSC expects to request underlying shareholder data from Waived Financial Intermediaries more frequently than from other Financial Intermediaries. There is no assurance that MFSC will request data with sufficient frequency to detect or prevent frequent trading in omnibus accounts effectively.

notice (written or otherwise) of a dispute between registered or beneficial account owners or when MFSC believes a fraudulent transaction may occur or has occurred; and 3) change, impose, discontinue, or waive any fee it charges.

Anti-Money Laundering Restrictions. Federal law requires the fund to implement policies and procedures reasonably designed to prevent, detect and report money laundering and other illegal activity. The fund, consistent with applicable federal law, may redeem your shares and close your account; suspend, restrict or cancel purchase and redemption orders; process redemption requests and withhold your proceeds; and take other action if it is unable to verify your identity within a reasonable time or conduct required due diligence on your account or as otherwise permitted by its anti-money laundering policies and procedures.

Potential Conflicts. Shares of the fund are offered to the separate accounts of insurance companies that may be affiliated or unaffiliated with MFS and each other and may serve as the underlying investments for both variable annuity and variable life insurance contracts. Due to differences in tax treatment or other considerations, the interests of various contract owners might at some time be in conflict. The Board of Trustees which oversees the fund will monitor events in order to identify any material irreconcilable conflicts which may possibly arise and to determine what action, if any, should be taken in response. If such a conflict were to occur, one or more separate accounts of the insurance companies might be required to withdraw its investments in the fund. This might force the fund to sell securities at disadvantageous prices.

The price of each class of the fund’s shares is based on its net asset value. The net asset value of each class of shares is determined each day the NYSE is open for trading as of the close of regular trading on the NYSE (generally 4:00 p.m. Eastern time). However, net asset value may be calculated earlier in emergency situations or as otherwise permitted by the SEC. Current net asset values per share are provided each business day to insurance companies, plan sponsors and other shareholders. To receive current net asset values per share each business day, shareholders should call MFSC at 1-877-411-3325. Net asset value per share is computed by dividing the net assets allocated to each share class by the number of shares outstanding for that class. On days when the NYSE is closed (such as weekends and holidays), net asset value is not calculated, and the fund does not transact purchase and redemption orders. To the extent the fund's assets are traded in other markets on days when the fund does not price its shares, the value of the fund's assets will likely change when you will not be able to purchase or redeem shares of the fund.

To determine net asset value, the fund’s investments for which reliable market quotations are readily available are valued at market value, and funds in which the fund invests are generally valued at their net asset value per share. Certain short term debt instruments may be valued at amortized cost.

The Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund's investments to MFS pursuant to the fund's valuation policy and procedures approved by the Board of Trustees. The Board of Trustees has designated MFS as the "valuation designee" of the fund. As valuation designee, MFS will determine the fair value, in good faith, of securities and other instruments held by the fund for which market quotations are not readily available and, among other things, will assess and manage material risks associated with fair value determinations, select, apply, and test fair value methodologies, and oversee and evaluate pricing services used in valuing the fund's investments. If MFS determines that reliable market quotations are not readily available, investments are valued at fair value as determined in good faith by MFS in accordance with the fair valuation policy and procedures adopted by MFS.

In addition, investments may be valued at fair value if MFS determines that an investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as a foreign exchange or market) and prior to the determination of the fund's net asset value, or after the halting of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. Events that occur on a frequent basis after foreign markets close (such as developments in foreign markets and significant movements in the U.S. markets) and prior to the determination of the fund's net asset value may be deemed to have a material effect on the value of securities traded in foreign markets. Accordingly, foreign equity securities may often be valued at fair value. MFS generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost, and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment.

The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.

The fund intends to declare and pay any dividends to shareholders at least annually.

Dividends and capital gain distributions are automatically reinvested in additional shares of the fund.

The following discussion is very general. You are urged to consult your tax adviser regarding the effect that an investment in the fund may have on your particular tax situation, including possible foreign, state, and local taxes.

The fund is treated as a separate corporation for federal income tax purposes. As long as the fund qualifies for treatment as a regulated investment company (which the fund has done in the past and intends to do in the future), it pays no federal income or excise taxes on the net earnings and net realized gains it timely distributes to shareholders. In addition, the fund intends to continue to diversify its assets to satisfy the federal tax diversification rules applicable to separate accounts that fund variable insurance and annuity contracts.

Shares of the fund are offered to insurance company separate accounts and other eligible investors. You should consult with the insurance company that issued your variable contract or other eligible investor through which your investment in the fund is made to understand the tax treatment of your investment.

The summary prospectus, prospectus, and SAI for a fund provide information concerning the fund. The summary prospectus, prospectus, and SAI are updated at least annually and any information provided in a summary prospectus, prospectus, or SAI can be changed without a shareholder vote unless specifically stated otherwise. The summary prospectus, prospectus, and SAI are not contracts between the fund and its shareholders and do not give rise to any contractual rights or obligations or any shareholder rights other than any rights conferred explicitly by federal or state securities laws that may not be waived.

The annual fund operating expenses shown in “Fees and Expenses” are based on annualized expenses reported during the fund's most recently completed fiscal year expressed as a percentage of a class' average net assets during the period. Annual fund operating expenses have not been adjusted to reflect the fund's current asset size. In general, annual fund operating expenses, expressed as a percentage of a class' average net assets, increase as the fund’s assets decrease. Annual fund operating expenses will likely vary from year to year.

All performance information shown in the “Initial Class Bar Chart” and the “Performance Table” reflects any applicable fee reductions and waivers and expense reimbursements in effect during the periods shown; without these, the performance would have been lower.

From time to time, the fund may receive proceeds from litigation settlements, without which performance would be lower.

The financial highlights are intended to help you understand the fund’s financial performance for the past five years. Certain information reflects financial results for a single fund share. The total returns in the financial highlights represent the rate by which an investor would have earned (or lost) on an investment in the fund (assuming reinvestment of all distributions) held for the entire period. The returns shown do not reflect fees and expenses imposed by the investment vehicle through which an investment in the fund is made. If these fees and expenses were included, they would reduce returns. This information has been audited by the fund’s independent registered public accounting firm, whose report, together with the fund’s financial statements, is included in the fund’s Annual Report to shareholders. The fund’s Annual Report is available upon request by contacting MFSC (please see back cover for address and telephone number). The fund’s independent registered public accounting firm is Deloitte & Touche LLP.

(g) The per share amount varies from the net realized and unrealized gain/loss for the period because of the timing of sales of fund shares and the per share amount of realized and unrealized gains and losses at such time.

(k) The total return does not reflect expenses that apply to separate accounts. Inclusion of these charges would reduce the total return figures for all periods shown.

(r) Certain expenses have been reduced without which performance would have been lower.

(s) From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(x) The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

Shareholder Communications with the Board of Trustees. Shareholders may mail written communications to the Board of Trustees to the attention of the Board of Trustees, [fund name], Massachusetts Financial Services Company, 111 Huntington Avenue, Boston, MA 02199, Attention: Fund Secretary. Shareholder communications must (i) be in writing and be signed by the shareholder, (ii) identify the MFS fund to which they relate and (iii) identify the class and number of shares held by the shareholder.

If you want more information about MFS Blended Research Small Cap Equity Portfolio, the following documents are available free upon request:

Annual/Semiannual Reports. These reports contain information about the fund’s actual investments. Annual reports discuss the effect of recent market conditions and investment strategies on the fund’s performance during its last fiscal year.

Statement of Additional Information (SAI). The SAI, dated April 29, 2024, as may be amended or supplemented from time to time, provides more detailed information about the fund and is incorporated into this prospectus by reference.

You can get free copies of the annual/semiannual reports, the SAI and other information about the fund, and make inquiries about the fund, by contacting:

Reports and other information about the fund are available on the EDGAR Database on the Commission’s Internet website at http://www.sec.gov, and copies of this information may be obtained, upon payment of a duplicating fee, by electronic request at the following e-mail address: publicinfo@sec.gov.

The investment objective of the fund is to seek a high level of total return consistent with a conservative level of risk relative to the other MFS Asset Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are MFS Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and MFS Growth Allocation Portfolio.)

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

The fund’s investment objective is to seek a high level of total return consistent with a conservative level of risk relative to the other MFS Asset Allocation Portfolios. The fund's objective may be changed without shareholder approval.

The fund is designed to provide diversification among different asset classes by investing its assets in other MFS mutual funds, 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 (“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”). The asset class allocations provide an initial layer of diversification for the fund.

As of April 1, 2024, 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 April 1, 2024, 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%.

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. This selection process provides a second layer of diversification within the asset class allocations.

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, 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.

Following is the list of underlying funds and their approximate strategic allocation weightings as of April 1, 2024:

All percentages are rounded to the nearest tenth of a percent. As a result, the sum of the underlying fund allocations in each asset class may not equal the asset class allocations for such asset class, and the asset class and underlying fund allocations presented in the table may not total 100%.

MFS may allocate the fund’s assets among any number of the underlying funds listed in Appendix A of this prospectus at any time. A description of the underlying funds is also set forth in Appendix A of this prospectus. The fund’s underlying fund allocations may vary significantly over time, and the fund may be invested in some but not all of the underlying funds in Appendix A at any time.

Although the underlying funds listed in Appendix A are categorized generally as Equity Funds (U.S. or International), Non-Traditional Funds, Bond Funds or Money Market Fund, many of the underlying funds can invest in a mix of securities (e.g., a U.S. Equity Fund can invest in international stocks, or a Non-Traditional Fund can invest in stocks and/or bonds).

The asset class allocations and the underlying funds and their weightings are not designed to take advantage of short-term market opportunities and have been selected for investment over longer time periods. The asset class allocations and the underlying funds and their weightings may be changed without shareholder approval or notice. The actual weightings can also deviate due to market movements and cash flows. MFS systematically rebalances the fund's investments in the underlying funds to reflect the fund’s current strategic allocations.

The principal investment types in which the underlying funds may invest include:

Debt Instruments: Debt instruments represent obligations of corporations, governments, and other entities to repay money borrowed, or other instruments believed to have debt-like characteristics. The issuer or borrower usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the instrument. Debt instruments generally trade in the over-the-counter market and can be less liquid than other types of investments, particularly during adverse market and economic conditions. During certain market conditions, debt instruments in some or many segments of the debt market can trade at a negative interest rate (i.e., the price to purchase the debt instrument is more than the present value of expected interest payments and principal due at the maturity of the instrument). Some debt instruments, such as zero coupon bonds or payment-in-kind bonds, do not pay current interest. Other debt instruments, such as certain mortgage-backed securities and other securitized instruments, make periodic payments of interest and/or principal. Some debt instruments are partially or fully secured by collateral supporting the payment of interest and principal.

Corporate Bonds: Corporate bonds are debt instruments issued by corporations or similar entities.

U.S. Government Securities: U.S. Government securities are securities issued or guaranteed as to the payment of principal and interest by the U.S. Treasury, by an agency or instrumentality of the U.S. Government, or by a U.S. Government-sponsored entity, including mortgage-backed securities and other types of securitized instruments issued or guaranteed by such entities. Certain U.S. Government securities are not supported as to the payment of principal and interest by the full faith and credit of the U.S. Treasury or the ability to borrow from the U.S. Treasury. Some U.S. Government securities are supported as to the payment of principal and interest only by the credit of the entity issuing or guaranteeing the security.

Foreign Government Securities: Foreign government securities are debt instruments issued, guaranteed, or supported, as to the payment of principal and interest, by foreign governments, foreign government agencies, foreign semi-governmental entities or supranational entities, or debt instruments issued by entities organized and operated for the purpose of restructuring outstanding foreign government securities. Foreign government securities may not be supported as to the payment of principal and interest by the full faith and credit of the foreign government.

Securitized Instruments: Securitized instruments are debt instruments that generally provide payments of principal and interest based on the terms of the instrument and cash flows generated by the underlying assets. Underlying assets include residential and commercial mortgages, debt instruments, loans, leases, and receivables. Securitized instruments are issued by trusts or other special purpose entities that hold the underlying assets. Certain securitized instruments offer multiple classes that differ in terms of their priority to receive principal and/or interest payments under the terms of the instrument. Securitized instruments include mortgage-backed securities, collateralized debt obligations, and other asset-backed securities. Certain mortgage-backed securities are issued on a delayed delivery or forward commitment basis where payment and delivery take place at a future date.

When-Issued, Delayed Delivery, and Forward Commitment Transactions: When-issued, delayed delivery, and forward commitment transactions, including securities purchased or sold in the to be announced (TBA) market, involve a commitment to purchase or sell a security at a predetermined price or yield at which payment and delivery take place after the customary settlement period for that type of security. Typically, no interest accrues to the purchaser until the security is delivered. When purchasing or selling securities pursuant to one of these transactions, payment for the securities is not required until the delivery date. In the TBA market, mortgage-backed securities are purchased and sold at predetermined prices on a delayed delivery or forward commitment basis with the underlying securities to be announced at a future date.

Inflation-Adjusted Debt Instruments: Inflation-adjusted debt instruments are debt instruments whose principal and/or interest are adjusted for inflation. Inflation-adjusted debt instruments issued by the U.S. Treasury pay a fixed rate of interest that is applied to an inflation-adjusted principal amount. The principal amount is adjusted based on changes in the Consumer Price Index. The principal due at maturity is typically equal to the inflation-adjusted principal amount, or to the instrument’s original par value, whichever is greater. Other types of inflation-adjusted debt instruments may use other methods of adjusting for inflation, and other measures of inflation. Other issuers of inflation-adjusted debt instruments include U.S. Government agencies, instrumentalities and sponsored entities, U.S. and foreign corporations, and foreign governments.

Real Estate-Related Investments: Real estate-related investments include REITs, issuers similar to REITs formed under the laws of non-U.S. countries, and other U.S. and foreign issuers that earn at least 50% of their gross revenues or net profits from real estate activities or from products or services related to the real estate sector. Real estate activities include owning, developing, managing, or acting as a broker for real estate. Examples of real estate products or services include building supplies and mortgage servicing. REITs are pooled investment vehicles that invest primarily in income-producing real estate or real estate-related loans or interests. Equity REITs invest most of their assets directly in U.S. or foreign real property, receive most of their income from rents and may also realize gains by selling appreciated property. Mortgage REITs invest most of their assets in real estate mortgages and receive most of their income from interest payments. Hybrid REITs combine the characteristics of both equity REITs and mortgage REITs.

Derivatives: Derivatives are financial contracts whose value is based on the value of one or more underlying indicators or the difference between underlying indicators. Underlying indicators may include a security or other financial instrument, asset, currency, interest rate, credit rating, commodity, volatility measure, or index. Derivatives often involve a counterparty to the transaction. Derivatives include futures, forward contracts, options, swaps, and certain complex structured securities.

The share price of the fund will change daily based on the performance of the underlying funds. Underlying fund performance will change daily based on changes in interest rates and market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. 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 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 below carefully, because any one or more of these risks may result in losses to the fund.

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

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 debt markets generally. Certain changes or events, such as political, social, or economic developments, including increasing and negative interest rates or the U.S. government's inability at times to agree on a long-term budget and deficit reduction plan (which has in the past resulted and may in the future result in a government shutdown); market closures and/or trading halts; government or regulatory actions, including sanctions, the imposition of tariffs or other protectionist actions and changes in fiscal, monetary, or tax policies; natural disasters; outbreaks of pandemic and epidemic diseases; terrorist attacks; war; and other geopolitical changes or 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 a segment of a debt market.

long-term interest rates, and interest rates in different countries, do not necessarily move in the same direction or by the same amount. An instrument’s reaction to interest rate changes depends on the timing of its interest and principal payments and the current interest rate for each of those time periods. The price of an instrument trading at a negative interest rate responds to interest rate changes like other debt instruments; however, an instrument purchased at a negative interest rate is expected to produce a negative return if held to maturity. Fluctuations in the market price of fixed-rate instruments held by the fund may not affect interest income derived from those instruments, but may nonetheless affect the fund's share price, especially if an instrument has a longer maturity or duration and is therefore more sensitive to changes in interest rates.

Inflation-adjusted debt instruments tend to react to changes in “real” interest rates. “Real” interest rates represent nominal interest rates reduced by the inflation rate.

Credit Risk: The price of a debt instrument depends, in part, on the issuer's or borrower's credit quality or ability to pay principal and interest when due. The price of a debt instrument is likely to fall if an issuer or borrower defaults on its obligation to pay principal or interest, if the instrument's credit rating is downgraded by a credit rating agency, or based on other changes in, or perceptions of, the financial condition of the issuer or borrower. For certain types of instruments, including derivatives, the price of the instrument depends in part on the credit quality of the counterparty to the transaction. For other types of debt instruments, including securitized instruments, the price of the debt instrument also depends on the credit quality and adequacy of the underlying assets or collateral as well as whether there is a security interest in the underlying assets or collateral. Enforcing rights, if any, against the underlying assets or collateral may be difficult.

Below investment grade quality debt instruments can involve a substantially greater risk of default or can already be in default, and their values can decline significantly over short periods of time. Below investment grade quality debt instruments are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and principal. 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. The market for below investment grade quality debt instruments can be less liquid, especially during periods of recession or general market decline.

Prepayment/Extension Risk: Many types of debt instruments, including mortgage-backed securities, securitized instruments, certain corporate bonds, and municipal housing bonds, and certain derivatives, are subject to the risk of prepayment and/or extension. Prepayment occurs when unscheduled payments of principal are made or the instrument is called or redeemed prior to an instrument’s maturity. When interest rates decline, the instrument is called, or for other reasons, these debt instruments may be repaid more quickly than expected. As a result, the holder of the debt instrument may not be able to reinvest the proceeds at the same interest rate or on the same terms, reducing the potential for gain. When interest rates increase or for other reasons, these debt instruments may be repaid more slowly than expected, increasing the potential for loss. In addition, prepayment rates are difficult to predict and the potential impact of prepayment on the price of a debt instrument depends on the terms of the instrument.

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 both can decline. In addition, the measure of inflation used may not correspond to the actual rate of inflation experienced by a particular individual.

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.

government action, or the threat thereof, such as the imposition of currency or capital blockages, controls, or tariffs, economic and trade sanctions or embargoes, security trading suspensions, entering or exiting trade or other intergovernmental agreements, or the expropriation or nationalization of assets in a particular country, can cause dramatic declines in certain or all securities with exposure to that country and other countries. Sanctions, or the threat of sanctions, may cause volatility in regional and global markets and may negatively impact the performance of various sectors and industries, as well as companies in other countries, which could have a negative effect on the performance of the fund. In the event of nationalization, expropriation, confiscation or other government action, intervention, or restriction, the fund could lose its entire investment in a particular foreign issuer or country. Civil unrest, geopolitical tensions, wars, and acts of terrorism are other potential risks that could adversely affect an investment in a foreign security or in foreign markets or issuers generally. Economies and financial markets are interconnected, which increases the likelihood that conditions in one country or region can adversely impact issuers in different countries and regions. Less stringent regulatory, accounting, auditing, and disclosure requirements for issuers and markets are more common in certain foreign countries. Enforcing legal rights can be difficult, costly, and slow in certain foreign countries and with respect to certain types of investments, and can be particularly difficult against foreign governments. Changes in currency exchange rates can significantly impact the financial condition of a company or other issuer with exposure to multiple countries as well as affect the U.S. dollar value of foreign currency investments and investments denominated in foreign currencies. Additional risks of foreign investments include trading, settlement, custodial, and other operational risks, and withholding and other taxes. These factors can make foreign investments, especially those tied economically to emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions than the U.S. market.

Emerging Markets Risk: Investments tied economically to emerging markets, especially frontier markets (emerging markets that are early in their development), can involve additional and greater risks than the risks associated with investments in developed markets. Emerging markets typically have less developed economies and markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, less trading volume, less stringent investor protection and disclosure standards, less reliable settlement practices, greater government involvement in the economy, and greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments than developed countries. Financial and other disclosures by emerging market issuers may be considerably less reliable than disclosures made by issuers in developed markets. In addition, the Public Company Accounting Oversight Board, which regulates auditors of U.S. public companies, may not be able to inspect audit work papers in certain emerging market countries. Emerging markets can also be subject to greater political, social, geopolitical, and economic instability and more susceptible to environmental problems. In addition, many emerging market countries with less established health care systems have experienced outbreaks of pandemics or contagious diseases from time to time. These factors can make emerging market investments more volatile and less liquid than investments in developed markets.

Currency Risk: Changes in currency exchange rates can significantly impact the financial condition of a company or other issuer with exposure to multiple countries. In addition, a decline in the value of a foreign currency relative to the U.S. dollar reduces the value of the foreign currency and investments denominated in that currency. In addition, the use of foreign exchange contracts to reduce foreign currency exposure can eliminate some or all of the benefit of an increase in the value of a foreign currency versus the U.S. dollar. The value of foreign currencies relative to the U.S. dollar fluctuates in response to, among other factors, interest rate changes, intervention (or failure to intervene) by the U.S. or foreign governments, central banks, or supranational entities such as the International Monetary Fund, the imposition of currency controls, and other political or regulatory conditions in the United States or abroad. Foreign currency values can decrease significantly both in the short term and over the long term in response to these and other conditions.

Real Estate-Related Investment Risk: The risks of investing in real estate-related investments include certain risks associated with the direct ownership of real estate and the real estate industry in general. Real estate-related investments are affected by general, regional and local economic conditions; difficulties in valuing and disposing of real estate; and 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 REIT manager; and other factors. The real estate sector is particularly sensitive to economic downturns. Equity REITs may be affected by changes in the value of the underlying property owned by the trusts. Mortgage REITs may be affected by default or payment problems relating to underlying mortgages, the quality of credit extended and prepayments of the underlying mortgages. Equity and mortgage REITs could be adversely affected by failure to qualify for the favorable tax treatment available to REITs under the Internal Revenue Code of 1986, as amended, or to maintain their exemption from registration under the Investment Company Act of 1940, as amended. The securities of small 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. In addition, REITs may have limited diversification because they invest in a limited number of properties, a narrow geographic area, or a single type of property.

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, and the seller loses the opportunity to benefit if the price of the security rises. When-issued, delayed delivery, and forward commitment transactions can involve leverage.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to, and potentially greater than, the risks of the underlying indicator(s). Gains or losses from derivatives can be substantially greater than the derivatives’ original cost and can sometimes be unlimited. Derivatives can involve leverage. Derivatives can be complex instruments and can involve analysis and processing that differs from that required for other investment types used by the fund. If the value of a derivative does not change as expected relative to the value of the market or other indicator to which the derivative is intended to provide exposure, the derivative may not have the effect intended. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments.

Leveraging Risk: Certain transactions and investment strategies can result in leverage. Leverage involves investment exposure in an amount exceeding the initial investment. In transactions involving leverage, a relatively small change in an underlying indicator can lead to significantly larger losses to the fund. Leverage can cause increased volatility by magnifying gains or losses.

Counterparty and Third Party Risk: Transactions involving a counterparty other than the issuer of the instrument, including clearing organizations, or a third party responsible for servicing the instrument or effecting the transaction, 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. If a counterparty or third party fails to meet its contractual obligations, goes bankrupt, or otherwise experiences a business interruption, the fund could miss investment opportunities, lose value on its investments, or otherwise hold investments it would prefer to sell, resulting in losses for the fund.

The fund pays no management fee to MFS; however, the underlying funds pay management fees to MFS which are reflected under “Summary of Key Information-Fees and Expenses” above.

MFS 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 0.20% of the class' average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least April 30, 2025.

A discussion regarding the basis for the Board of Trustees’ approval of the Investment Advisory Agreement is available in the fund’s annual report for the one-year period ended December 31, 2023.

Disclosure of Portfolio Holdings. The fund has established a policy with respect to the disclosure of fund portfolio holdings. A description of this policy is provided in the SAI.

The following information is available to you at mfs.com/vit3 by selecting the fund's name:

Top 10 holdings, top 10 equity holdings, and top 10 fixed income holdings are aggregated holdings of the underlying MFS funds. Top 10 holdings exclude cash, cash equivalents, short-term investments, currency derivatives, and the cash portion of other derivatives.

Full holdings of the underlying MFS funds in which the fund invests are available 19 days after month end or 24 days after month end (depending on the underlying fund). The most recently disclosed full holdings of the underlying MFS funds are available by selecting an underlying fund’s name under “MFS Fund Holdings (%)” on the fund’s Website at mfs.com. For purposes of full holdings, cash, cash equivalents, and short-term investments are aggregated and currency derivatives and the cash portion of other derivatives are aggregated.

MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, is the distributor of shares of the fund.

The fund has not adopted a Rule 12b-1 plan with respect to its Initial Class shares.

purposes of this section only, collectively, "MFD") from MFD’s own additional resources.

through which your investment in the fund is made regarding any restrictions on trading.

Reservation of Other Rights. In addition to the rights expressly stated elsewhere in this prospectus, subject to applicable rules, laws and regulations, MFSC reserves the right to: 1) alter, add, or discontinue any conditions of purchase, redemption, service, or privilege at any time without notice; 2) freeze any account or suspend account services when MFSC has received reasonable notice (written or otherwise) of a dispute between registered or beneficial account owners or when MFSC believes a fraudulent transaction may occur or has occurred; and 3) change, impose, discontinue, or waive any fee it charges.

the net assets allocated to each share class by the number of shares outstanding for that class. On days when the NYSE is closed (such as weekends and holidays), net asset value is not calculated, and the fund does not transact purchase and redemption orders. To the extent the fund's assets are traded in other markets on days when the fund does not price its shares, the value of the fund's assets will likely change when you will not be able to purchase or redeem shares of the fund.

Under the fund's valuation policy and procedures, market quotations are not considered to be readily available for debt instruments and many types of derivatives. These investments are generally valued at fair value as determined by MFS based on information from third-party pricing services or otherwise determined by MFS in accordance with its fair valuation policy and procedures. These valuations can be based on both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, spreads, and other market data.

The fund intends to declare and pay any dividends to shareholders at least annually.

Dividends and capital gain distributions are automatically reinvested in additional shares of the fund.

The annual fund operating expenses shown in “Fees and Expenses” are based on annualized expenses reported during the fund’s most recently completed fiscal year, and a weighted average of the total annual fund operating expenses and the fee charged (if any) by the fund(s) in which the fund invested during the fund’s most recently completed fiscal year, expressed as a percentage of a class' average net assets during the period. The fund invests in Initial Class shares of the underlying funds. Annual fund operating expenses have not been adjusted to reflect the fund’s current asset size. In general, annual fund operating expenses, expressed as a percentage of a class' average net assets, increase as the fund’s assets decrease. Annual fund operating expenses will likely vary from year to year.

All performance information shown in the “Initial Class Bar Chart” and the “Performance Table” reflects any applicable fee reductions

and waivers and expense reimbursements in effect during the periods shown; without these, the performance would have been lower.

From time to time, the fund may receive proceeds from litigation settlements, without which performance would be lower.

The following is a list of the underlying funds in which the fund may invest at any time.

The following is a description of the underlying funds in which the fund may invest. Further information about each underlying fund (other than MFS Institutional Money Market Portfolio, which is only offered to certain investment companies advised by MFS), including a copy of an underlying fund's most recent Prospectus, SAI, and Annual and Semi-Annual Reports, may be obtained on the fund’s Website at insurancefunds.mfs.com, or by contacting MFSC.

The fund’s investment objective is to seek total return with an emphasis on current income, but also considering capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests at least 80% of the fund’s net assets in U.S. and foreign government securities.

MFS normally invests the fund’s assets primarily in debt instruments of the U.S. Government and of foreign governments in developed countries.

MFS normally invests the fund's assets across different countries and regions, but MFS may invest more than 25% of the fund’s assets in one country or a limited number of countries. MFS generally invests the fund's assets in at least three different countries and invests a percentage of the fund's net assets in securities of foreign issuers equal to at least the lesser of 40% or the percentage of foreign issuers in the JPMorgan Global Government Bond Index (Unhedged) less 15%.

MFS primarily invests the fund’s assets in investment grade quality debt instruments, but may also invest in below investment grade quality debt instruments.

The fund is a non-diversified fund. This means that MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments.

MFS allocates the fund's assets across countries primarily based on fundamental economic and financial analysis of the creditworthiness of each country and the relative values of countries' external debt, currencies, and local market debt. In selecting investments, MFS may consider economic and financial fundamentals, liquidity, duration, yield curve positioning, relative value, and other factors. Quantitative tools that systematically evaluate these and other factors may also be considered. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer or instrument.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

MFS normally invests at least 80% of the fund’s net assets in U.S. Government securities. MFS may also invest the fund's assets in other debt instruments.

MFS generally invests substantially all of the fund’s assets in investment grade quality debt instruments.

MFS may purchase or sell securities for the fund on a when-issued, delayed delivery, or forward commitment basis where payment and delivery take place at a future settlement date, including mortgage-backed securities purchased or sold in the to be announced (TBA) market. When MFS sells securities for the fund on a when-issued, delayed delivery, or forward commitment basis, the fund typically owns or has the right to acquire securities equivalent in kind and amount to the deliverable securities.

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

MFS may engage in active and frequent trading in pursuing the fund’s principal investment strategies.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers in light of the issuers’ financial condition and market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality and terms, any underlying assets and their credit quality, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer or instrument. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek total return with an emphasis on high current income, but also considering capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests directly and/or indirectly through investment in mutual funds advised by MFS at least 80% of the fund’s net assets in high income debt instruments.

MFS may invest up to 100% of the fund’s assets in below investment grade quality debt instruments.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers in light of the issuers’ financial condition and market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality and terms, any underlying assets and their credit quality, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer or instrument. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek total return that exceeds the rate of inflation over the long-term, with an emphasis on current income, but also considering capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests at least 80% of the fund’s net assets in inflation-adjusted debt instruments and other instruments with similar economic characteristics.

MFS generally focuses the fund’s investments in inflation-adjusted debt instruments issued by U.S. and foreign governments. MFS may also invest the fund’s assets in inflation-adjusted debt instruments of other issuers, other instruments with similar economic characteristics to these instruments, including derivatives, and non-inflation-adjusted debt instruments.

MFS primarily invests the fund’s assets in investment grade quality debt instruments, but may also invest in below investment grade quality debt instruments.

MFS normally invests the fund's assets across different countries and regions, but MFS may invest a significant percentage of the fund's assets in issuers in a single country or region.

The fund is a non-diversified fund. This means that MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

MFS allocates the fund’s assets across countries, maturities, and types of debt instruments based on its evaluation of U.S. and foreign macroeconomic factors, including interest rates, inflation rates, and monetary and fiscal policies.

resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek total return with an emphasis on current income, but also considering capital preservation. The fund's objective may be changed without shareholder approval.

The fund’s dollar-weighted average effective maturity will normally not exceed five years. In determining an instrument’s effective maturity, MFS uses the instrument’s stated maturity or, if applicable, an earlier date on which MFS believes it is probable that a maturity-shortening device (such as a call, put, pre-refunding, prepayment or redemption provision, or an adjustable coupon) will cause the instrument to be repaid. Such an earlier date can be substantially shorter than the instrument’s stated maturity.

MFS generally invests substantially all of the fund’s assets in investment grade quality debt instruments.

MFS invests the fund’s assets in U.S. securities and U.S. dollar-denominated foreign securities.

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

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers in light of the issuers’ financial condition and market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality and terms, any underlying assets and their credit quality, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer or instrument. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

MFS normally invests at least 80% of the fund’s net assets in debt instruments.

MFS primarily invests the fund’s assets in investment grade quality debt instruments, but may also invest in below investment grade quality debt instruments.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers in light of the issuers’ financial condition and market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality and terms, any underlying assets and their credit quality, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer or instrument. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek current income consistent with preservation of capital and liquidity. The fund's objective may be changed without shareholder approval.

MFS normally invests the fund’s assets in U.S. dollar-denominated money market instruments and repurchase agreements.

The fund does not seek to maintain a stable share price. In buying and selling investments for the fund, MFS follows U.S. Securities and Exchange Commission rules for money market funds regarding credit quality, diversification, liquidity, and maturity.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests at least 80% of the fund’s net assets in equity securities of issuers that are tied economically to emerging market countries.

Emerging market countries include countries determined to have emerging market economies, taking into account a number of factors, including whether a particular country has a low- to middle-income economy according to the International Bank for Reconstruction and Development (the World Bank), the country’s designation by the International Monetary Fund as an emerging market, the country's inclusion in an emerging market or frontier emerging market index, and other factors that demonstrate that the country's financial and capital markets are in the development phase. Emerging market countries include countries located in Latin America, Asia, Africa, the Middle East, and developing countries of Europe, primarily Eastern Europe.

MFS generally considers the issuer of a security or other investment to be tied economically to emerging market countries if: (i) the security or other investment is issued or guaranteed by the government of an emerging market country or any of its agencies, authorities or instrumentalities; (ii) the issuer is organized under the laws of, and maintains a principal office in, an emerging market country; (iii) the issuer has its principal securities trading market in an emerging market country; (iv) a third party has identified an emerging market country as the issuer’s “country of risk”; (v) the issuer is included in an index which is representative of emerging market countries; (vi) the issuer derives 50% or more of its total revenues from goods sold or services performed in emerging market countries; or (vii) the issuer has 50% or more of its assets in emerging market countries.

MFS may also invest in equity securities of issuers that are not tied economically to emerging market countries.

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests the fund’s assets primarily in foreign equity securities, including emerging market equity securities.

MFS focuses on investing the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies). Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests the fund’s assets primarily in foreign equity securities, including emerging market equity securities.

MFS focuses on investing the fund's assets in the stocks of companies that it believes are undervalued compared to their intrinsic value. MFS evaluates the intrinsic value of a company by considering the full context of how the company's cash flows are generated. MFS focuses on companies it believes have intrinsic value greater than the perceived value by the marketplace and seeks to invest in companies that exhibit characteristics such as cash flow in excess of capital expenditures, conservative balance sheets, sustainable competitive advantages, high returns on capital, and/or the ability to weather economic downturns. These companies may have stock prices that are higher relative to their earnings, dividends, assets, or other financial measures than companies generally considered value companies under a traditional value investment strategy.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease currency exposure.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests the fund’s assets primarily in foreign equity securities, including emerging market equity securities.

In conjunction with a team of investment research analysts, sector leaders select investments for the fund. MFS generally manages the fund to be sector neutral to the MSCI EAFE (Europe, Australasia, Far East) Index using MFS' custom industry and sector categories to classify the fund and the MSCI EAFE (Europe, Australasia, Far East) Index's holdings.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

While MFS may invest the fund’s assets in securities of companies of any size, MFS primarily invests in securities of companies with large capitalizations.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests at least 80% of the fund’s net assets in issuers with medium market capitalizations. MFS generally defines medium market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell Midcap^{^®} Growth Index over the last 13 months at the time of purchase. As of March 31, 2024, the range of the market capitalizations of the issuers in the Russell Midcap^{^®} Growth Index was between approximately $799.90 million and $89.01 billion. Issuers whose market capitalizations fall outside this definition after purchase continue to be considered to have a medium market capitalization for purposes of the 80% policy.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

MFS normally invests at least 80% of the fund’s net assets in issuers with medium market capitalizations. MFS generally defines medium market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell Midcap^{^®} Value Index over the last 13 months at the time of purchase. As of March 31, 2024, the range of the market capitalizations of the issuers in the Russell Midcap^{^®} Value Index was between approximately $351.89 million and $89.0 billion. Issuers whose market capitalizations fall outside this definition after purchase continue to be considered to have a medium market capitalization for purposes of the 80% policy.

MFS focuses on investing the fund's assets in the stocks of companies that it believes are undervalued compared to their perceived worth (value companies). Value companies tend to have stock prices that are low relative to their earnings, dividends, assets, or other financial measures.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis where MFS believes such factors could materially impact the economic value of an issuer. ESG factors considered may include, but are not limited to, climate change, resource depletion, an issuer's governance structure and practices, data protection and privacy issues, and diversity and labor practices. Quantitative screening tools that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors, may also be considered.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

The fund’s investment objective is to seek capital appreciation. The fund's objective may be changed without shareholder approval.

While MFS may invest the fund’s assets in securities of companies of any size, MFS primarily invests in securities of companies with small capitalizations.