Summary Prospectus by Investment Company (Form 497K)

WESTERN ASSET

MORTGAGE TOTAL RETURN

FUND

Before you invest, you may want to review the fund's Prospectus, which contains more information about the fund and its risks. You can find the fund's Prospectus and other information about the fund, including the fund's statement of additional information, shareholder reports and fund financial statements, online at https://www.franklintempleton.com/prospectus. You can also get this information at no cost by calling the fund at 877-6LM-FUND/656-3863 or by sending an e-mail request to [email protected], or from your financial intermediary. The fund's Prospectus and statement of additional information, each dated May 1, 2026 (as may be amended or supplemented from time to time), and the independent registered public accounting firm's report and financial statements for the fiscal year ended December 31, 2025, as filed on Form N-CSR, are incorporated by reference into this Summary Prospectus.

Investment objective

The fund seeks high current return.

Fees and expenses of the fund

The accompanying table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain funds distributed through Franklin Distributors, LLC ("Franklin Distributors" or the "Distributor"), the fund's distributor. More information about these and other discounts is available from your Service Agent, in the fund's Prospectus on page 27 under the heading "Additional information about each share class," in the appendix titled "Appendix: Waivers and Discounts Available from Certain Service Agents" on page A-1 of the fund's Prospectus and in the fund's Statement of Additional Information ("SAI") on page 96 under the heading "Sales Charge Waivers and Reductions for Class A Shares." "Service Agents" include banks, brokers, dealers, insurance companies, investment advisers, financial consultants or advisers, mutual fund supermarkets and other financial intermediaries that have entered into an agreement with the Distributor to sell shares of the fund.

If you purchase Class I shares or Class IS shares through a Service Agent acting solely as an agent on behalf of its customers, that Service Agent may charge you a commission. Such commissions, if any, are not charged by the fund and are not reflected in the fee table or expense example below.

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes:

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover. The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was

198% of the average value of its portfolio. If mortgage dollar roll transactions had been excluded, the fund's portfolio turnover rate for the most recent fiscal year would have been 79% of the average value of its portfolio.

Principal investment strategies

Under normal circumstances, the fund invests at least 80% of its assets in mortgage-backed securities. Mortgage-backed securities may be issued by private issuers, U.S. government-sponsored entities such as the Federal National Mortgage Association (Fannie Mae) or the Federal Home Loan Mortgage Corporation (Freddie Mac) and by agencies of the U.S. government, such as the Government National Mortgage Association (Ginnie Mae). Mortgage-backed securities represent direct or indirect participations in, or are collateralized by and payable from, mortgage loans secured by real property. These securities may or may not be backed by the full faith and credit of the U.S. government. Even when the U.S. government guarantees principal and interest payments on securities, this guarantee does not apply to losses resulting from declines in the market value of these securities. The fund may invest in government stripped mortgage-backed securities and other stripped securities. The fund may invest in securities of any maturity or duration, and the securities may have fixed, floating or variable rates. The fund may enter into dollar rolls (sometimes referred to as mortgage dollar rolls).

The fund will not invest more than 25% of its assets in mortgage-backed securities that are not issued or guaranteed by, or comprised of mortgage-backed securities issued or guaranteed by, a U.S. government agency or U.S. government-sponsored entity.

The fund focuses on securities rated investment grade (that is, securities rated in the Baa/BBB categories or above, or, if unrated, determined to be of comparable credit quality by the subadviser). The fund may invest up to 20% of its assets in securities rated below investment grade, or, if unrated, determined to be below investment grade by the subadviser.

Instead of, and/or in addition to, investing directly in particular securities, the fund may use instruments such as derivatives, including options, swaps, interest rate swaps, futures contracts, and other synthetic instruments that are intended to provide economic exposure to the securities or the issuer or to be used as a hedging technique. The fund may use one or more types of these instruments without limit, subject to applicable regulatory requirements. For additional information regarding derivatives, see "More on the fund's investment strategies, investments and risks-Derivatives" in the Prospectus. These instruments are taken into account when determining compliance with the fund's 80% policy.

The fund may also engage in a variety of transactions using derivatives in order to change the investment characteristics of its portfolio (such as shortening or lengthening duration) and for other purposes.

Principal risks

Risk is inherent in all investing. The value of your investment in the fund, as well as the amount of return you receive on your investment, may fluctuate significantly. You may lose part or all of your investment in the fund or your investment may not perform as well as other similar investments. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or by any bank or government agency. The following is a summary

description of certain risks of investing in the fund. The relative significance of the risks of investing in the fund may change over time.

Market and interest rate risk. The market prices of securities held by the fund may go up or down, sometimes rapidly or unpredictably. If the market prices of the fund's securities fall, the value of your investment in the fund will decline. The market price of a security may fall due to general market conditions, such as real or perceived adverse economic or political conditions or trends, tariffs and trade disruptions, inflation, substantial economic downturn or recession, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment. Changes in market conditions will not typically have the same impact on all types of securities.

The value of your investment will generally go down when interest rates rise. A rise in rates tends to have a greater impact on the prices of longer term or duration securities. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the fund. Recently, there have been inflationary price movements. As a result, fixed income securities markets may experience heightened levels of interest rate volatility and liquidity risk. The U.S. government and the U.S. Federal Reserve, as well as certain foreign governments and central banks, have from time to time taken steps to support financial markets. The U.S. government and the U.S. Federal Reserve may, conversely, reduce market support activities. This and other government intervention may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. Changes in government activities in this regard, such as changes in interest rate policy, can negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund invests.

The maturity of a security may be significantly longer than its duration. A security's maturity and other features may be more relevant than its duration in determining the security's sensitivity to other factors affecting the issuer or markets generally such as changes in credit quality or in the yield premium that the market may establish for certain types of securities.

Market events risk. The market values of securities or other assets will fluctuate, sometimes sharply and unpredictably, due to factors such as economic events, governmental actions or intervention, actions taken by the U.S. Federal Reserve or foreign central banks, market disruptions caused by trade disputes, labor strikes or other factors, political developments, armed conflicts, economic sanctions and countermeasures in response to sanctions, major cybersecurity events, the global and domestic effects of widespread or local health, weather or climate events, and other factors that may or may not be related to the issuer of the security or other asset. Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, public health events, terrorism, wars, natural disasters and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the fund invests in securities of issuers located in or with significant exposure to the countries or markets directly affected, the value and liquidity of the fund's investments may be negatively affected. Ongoing or threatened armed conflicts throughout the world have caused and could continue to cause significant market disruptions and volatility. The hostilities and sanctions resulting from those hostilities have and could continue to have a significant impact on certain fund investments as well as fund performance and liquidity. Following Russia's invasion of

Ukraine in 2022, Russian stocks lost all, or nearly all, of their market value. Other securities or markets could be similarly affected by past or future geopolitical or other events or conditions. Furthermore, events involving limited liquidity, defaults, non-performance or other adverse developments that affect one industry, such as the financial services industry, or concerns or rumors about any events of these kinds, have in the past and may in the future lead to market-wide liquidity problems, may spread to other industries, and could negatively affect the value and liquidity of the fund's investments.

Raising the ceiling on U.S. government debt has become increasingly politicized. Any failure to increase the total amount that the U.S. government is authorized to borrow could lead to a default on U.S. government obligations, with unpredictable consequences for economies and markets in the U.S. and elsewhere. Recently, inflation and interest rates have been volatile and may increase in the future. These circumstances could adversely affect the value and liquidity of the fund's investments, impair the fund's ability to satisfy redemption requests, and negatively impact the fund's performance.

The United States and other countries are periodically involved in disputes over trade and other matters, which may result in tariffs, investment restrictions and adverse impacts on affected companies and securities or the broader U.S. or global economies. For example, the United States has imposed tariffs and other trade barriers on Chinese exports, has restricted sales of certain categories of goods to China, and has established barriers to investments in China. Trade disputes may adversely affect the economies of the United States and its trading partners, as well as companies directly or indirectly affected and financial markets generally. The United States government has prohibited U.S. persons from investing in Chinese companies designated as related to the Chinese military. These and possible future restrictions could limit the fund's opportunities for investment and require the sale of securities at a loss or make them illiquid. Moreover, the Chinese government is involved in a longstanding dispute with Taiwan that has included threats of invasion. If the political climate between the United States and China does not improve or continues to deteriorate, if China were to attempt unification of Taiwan by force, or if other geopolitical conflicts develop or get worse, economies, markets and individual securities may be severely affected both regionally and globally, and the value of the fund's assets may go down.

Inflation risk. Inflation risk is the risk that the value of assets or income from investments will be worth less in the future as prices go up and the purchasing power of money goes down. The market prices of debt securities generally fall as inflation increases because the purchasing power of the principal and income is expected to be less when paid. Inflation often is accompanied or followed by a recession, or period of decline in economic activity, which may include job loss and other hardships and may cause the value of securities to go down generally.

Credit risk. If an issuer or guarantor of a security held by the fund or a counterparty to a financial contract with the fund defaults or its credit is downgraded, or is perceived to be less creditworthy, or if the value of the assets underlying a security declines, the value of your investment will typically decline. Changes in actual or perceived creditworthiness may occur quickly. The fund could be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. Subordinated securities (meaning securities that rank below other securities with respect to claims on the issuer's assets) are more likely to suffer a credit loss

than non-subordinated securities of the same issuer and will be disproportionately affected by a default, downgrade or perceived decline in creditworthiness.

Mortgage-backed and asset-backed securities risk. When market interest rates increase, the market values of mortgage-backed securities decline. At the same time, mortgage refinancings and prepayments slow, which lengthens the effective duration of these securities. As a result, the negative effect of the interest rate increase on the market value of mortgage-backed securities is usually more pronounced than it is for other types of fixed income securities, potentially increasing the volatility of the fund. Conversely, when market interest rates decline, while the value of mortgage-backed securities may increase, the rate of prepayment of the underlying mortgages also tends to increase, which shortens the effective duration of these securities. Mortgage-backed securities are also subject to the risk that underlying borrowers will be unable to meet their obligations and the value of property that secures the mortgage may decline in value and be insufficient, upon foreclosure, to repay the associated loan. Investments in asset-backed securities are subject to similar risks. The ability of an issuer of asset-backed securities to enforce its security interest in the underlying assets may be limited, and therefore certain asset-backed securities present a heightened level of risk.

High yield ("junk") bonds risk. High yield bonds are generally subject to greater credit risks than higher-grade bonds, including the risk of default on the payment of interest or principal. High yield bonds are considered speculative, typically have lower liquidity and are more difficult to value than higher grade bonds. High yield bonds tend to be volatile and more susceptible to adverse events, credit downgrades and negative sentiments and may be difficult to sell at a desired price, or at all, during periods of uncertainty or market turmoil.

Derivatives risk. Using derivatives can increase fund losses and reduce opportunities for gains, such as when market prices, interest rates, currencies, or the derivatives themselves behave in a way not anticipated by the fund's subadviser. Using derivatives also can have a leveraging effect and increase fund volatility. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivatives may not be available at the time or price desired, may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. The value of a derivative may fluctuate more than the underlying assets, rates, indices or other indicators to which it relates. Use of derivatives may have different tax consequences for the fund than an investment in the underlying asset, and those differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and non-U.S. governments have adopted and implemented regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make derivatives more costly, limit their availability or utility, otherwise adversely affect their performance or disrupt markets.

Credit default swap contracts involve heightened risks and may result in losses to the fund. Credit default swaps may be illiquid and difficult to value. When the fund sells credit protection via a credit default swap, credit risk increases since the fund has exposure to both the issuer whose credit is the subject of the swap and the counterparty to the swap.

Forward roll transactions risk. Forward roll transactions (also referred to as mortgage dollar rolls) are transactions in which the fund sells mortgage-backed securities to a dealer and simultaneously agrees to repurchase similar securities in the future at a predetermined price. The fund's forward roll transactions could lose money if the price of the mortgage-backed securities sold falls below the agreed upon repurchase price, or if the counterparty is unable to honor the agreement. If the counterparty files for bankruptcy or becomes insolvent, the fund's right to repurchase securities may be limited. Forward roll transactions may have a leveraging effect on the fund, making the value of an investment in the fund more volatile, requiring the fund to liquidate portfolio securities when it may not be advantageous to do so and magnifying any change in the fund's net asset value.

Leverage risk. The value of your investment may be more volatile if the fund borrows or uses instruments, such as derivatives, that have a leveraging effect on the fund's portfolio. Other risks described in the Prospectus also will be compounded because leverage generally magnifies the effect of a change in the value of an asset and creates a risk of loss of value on a larger pool of assets than the fund would otherwise have had. The fund may also have to sell assets at inopportune times to satisfy its obligations created by the use of leverage or derivatives. The use of leverage is considered to be a speculative investment practice and may result in the loss of a substantial amount, and possibly all, of the fund's assets. In addition, the fund's portfolio will be leveraged if it exercises its right to delay payment on a redemption, and losses will result if the value of the fund's assets declines between the time a redemption request is deemed to be received by the fund and the time the fund liquidates assets to meet redemption requests.

Illiquidity risk. Some assets held by the fund may be or become impossible or difficult to sell and some assets that the fund wants to invest in may be impossible or difficult to purchase, particularly during times of market turmoil or due to adverse changes in the conditions of a particular issuer. These illiquid assets may also be volatile and difficult to value. Markets may become illiquid quickly. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. As a general matter, dealers have been less willing to make markets in recent years. Federal banking regulations may also cause certain dealers to reduce their inventories of certain securities, which may further decrease the fund's ability to buy or sell such securities. During times of market turmoil, there have been, and may be, no buyers or sellers for securities in entire asset classes. If the fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, or to try to limit losses, the fund may be forced to sell at a substantial loss or may not be able to sell at all. The fund may not receive its proceeds from the sale of certain securities for an extended period (for example, several weeks or even longer). The liquidity of certain assets, particularly of privately-issued and non-investment grade mortgage-backed securities, asset-backed securities and collateralized debt obligations, may be difficult to ascertain and may change over time.

Valuation risk. The sales price the fund could receive for any particular portfolio investment may differ from the fund's valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair value methodology. These differences may increase significantly and affect fund investments more broadly during periods of market volatility. Investors who purchase or redeem fund shares on days when the fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than

they would have received if the fund had not fair-valued securities or had used a different valuation methodology. The fund's ability to value its investments may be impacted by technological issues and/or errors by pricing services or other third party service providers. The valuation of the fund's investments involves subjective judgment, which may prove to be incorrect.

Prepayment or call risk. Many issuers have a right to prepay their fixed income securities. Issuers may be more likely to prepay their securities if interest rates fall. If this happens, the fund may not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on prepaid securities. The fund may also lose any premium it paid to purchase the securities.

Transactions by affiliated funds and by other significant investors. The fund may be an investment option for mutual funds and exchange-traded funds ("ETFs") that are managed by Franklin Templeton Fund Adviser, LLC and its affiliates, unaffiliated mutual funds and ETFs and other investors with substantial investments in the fund. As a result, from time to time, the fund may experience relatively large redemptions. In addition, a large number of shareholders collectively may purchase or redeem fund shares in large amounts rapidly or unexpectedly. In the event of such redemptions, the fund could be required to liquidate its assets at inopportune times or at a loss or depressed value, which could cause the value of your investment to decline. Large redemptions of fund shares may indirectly result in required distributions to non-redeeming shareholders, and those distributions would generally be taxable to shareholders who do not hold their fund shares in an IRA, 401(k) plan or other tax-advantaged plan. Redemptions may result in the recognition of short-term capital gains by the fund, and distributions of short-term capital gains will generally be taxed at ordinary income tax rates for shareholders who hold fund shares in a taxable account. These transactions may also increase transaction costs. Similarly, large fund share purchases may adversely affect the fund's performance to the extent that the fund is delayed in investing new cash or otherwise maintains a larger cash position than it ordinarily would.

Extension risk. When interest rates rise, repayments of fixed income securities, particularly asset- and mortgage-backed securities, may occur more slowly than anticipated, extending the effective duration of these fixed income securities at below market interest rates and causing their market prices to decline more than they would have declined due to the rise in interest rates alone. This may cause the fund's share price to be more volatile.

Risk of investing in fewer issuers. To the extent the fund invests its assets in a small number of issuers, or in issuers in related businesses or that are subject to related operating risks, the fund will be more susceptible to negative events affecting those issuers.

Portfolio management risk. The value of your investment may decrease if the subadviser's judgment about the quality, relative yield, value or market trends affecting a particular security, industry, sector or region, or about interest rates or other market factors, is incorrect or does not produce the desired results, or if there are imperfections, errors or limitations in the models, tools and data used by the subadviser. In addition, the fund's investment strategies or policies may change from time to time. Those changes may not lead to the results intended by the subadviser and could have an adverse effect on the value or performance of the fund.

Redemption risk. The fund may experience heavy redemptions that could cause the fund to liquidate its assets at inopportune times or unfavorable prices or increase or accelerate taxable gains or transaction costs and may negatively affect the fund's net asset value, performance, or ability to satisfy redemptions in a timely manner, which could cause the value of your investment to decline.

Cybersecurity risk. Like other funds and business enterprises, the fund, the manager, the subadviser and their service providers are subject to the risk of cyber incidents occurring from time to time. Cybersecurity incidents, whether intentionally caused by third parties or otherwise, may allow an unauthorized party to gain access to fund assets, fund or customer data (including private shareholder information) or proprietary information, cause the fund, the manager, the subadviser and/or their service providers (including, but not limited to, fund accountants, custodians, sub-custodians, transfer agents and financial intermediaries) to suffer data breaches, data corruption or loss of operational functionality, or prevent fund investors from purchasing, redeeming or exchanging shares, receiving distributions or receiving timely information regarding the fund or their investment in the fund. The fund, the manager, and the subadviser have limited ability to prevent or mitigate cybersecurity incidents affecting third party service providers, and such third party service providers may have limited indemnification obligations to the fund, the manager, and/or the subadviser. Cybersecurity incidents may result in financial losses to the fund and its shareholders, and substantial costs may be incurred in order to prevent or mitigate any future cybersecurity incidents. Issuers of securities in which the fund invests are also subject to cybersecurity risks, and the value of these securities could decline if the issuers experience cybersecurity incidents.

New ways to carry out cyber attacks continue to develop. There is a chance that some risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the fund's ability to plan for or respond to a cyber attack.

These and other risks are discussed in more detail in the Prospectus or in the Statement of Additional Information.

Performance

The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund's performance from year to year for Class A shares. The table shows the average annual total returns of each class of the fund that has been in operation for at least one full calendar year and also compares the fund's performance with the average annual total returns of a broad measure of market performance and an additional index with characteristics relevant to the fund. Performance for classes other than those shown may vary from the performance shown to the extent the expenses for those classes differ. The fund makes updated performance information, including its current net asset value, available at www.franklintempleton.com/prospectus (select fund and share class), or by calling the fund at 877-6LM-FUND/656-3863.

The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.

Sales charges are not reflected in the accompanying bar chart, and if those charges were included, returns would be less than those shown.

Best Quarter (12/31/2023): 6.96 Worst Quarter (09/30/2022): (6.00)

No one index is representative of the fund's portfolio.

The after-tax returns are shown only for Class A shares, are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns for classes other than Class A will vary from returns shown for Class A.

Important data provider notices and terms are available at www.franklintempletondatasources.com. Such information is subject to change.

Management

Investment manager: Franklin Templeton Fund Adviser, LLC ("FTFA")

Subadviser: Western Asset Management Company, LLC ("Western Asset")

Investment professionals: Primary responsibility for the day-to-day management of the fund lies with the following investment professionals. These investment professionals, all of whom are employed by Western Asset, work together with a broader investment management team.

Purchase and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund's net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund's initial and subsequent investment minimums generally are set forth in the accompanying table:

Your Service Agent may impose higher or lower investment minimums, or may impose no minimum investment requirement.

For more information about how to purchase, redeem or exchange shares, and to learn which classes of shares are available to you, you should contact your Service Agent, or, if you hold your shares or plan to purchase shares through the fund, you should contact the fund by phone at 877-6LM-FUND/656-3863, by regular mail at Legg Mason Funds, P.O. Box 33030, St. Petersburg, FL 33733-8030 or by express, certified or registered mail at Legg Mason Funds, 100 Fountain Parkway, St. Petersburg, FL 33716-1205.

Tax information

The fund's distributions are generally taxable as ordinary income or capital gains.

Payments to broker/dealers and other financial intermediaries

The fund's related companies pay Service Agents for the sale of fund shares, shareholder services and other purposes. These payments create a conflict of interest by influencing your Service Agent or its employees or associated persons to recommend the fund over another investment. Ask your financial adviser or salesperson or visit your Service Agent's or salesperson's website for more information.