UBS Total Return Bond Fund

Summary Prospectus | October 26, 2018

Before you invest, you may want to review the Fund's prospectus and statement of additional information ("SAI"), which contain more information about the Fund and its risks. You can find the Fund's prospectus, SAI and other information about the Fund online at http://www.ubs.com/us/en/asset_management/individual_investors/mutual_fund.html. You can also get this information at no cost by calling 1-800-647 1568 or by sending an email request to ubs@fundinsite.com. The current prospectus and SAI, dated October 26, 2018, are incorporated by reference into this summary prospectus (i.e., they are legally a part of this summary prospectus).

Share Class: Ticker Symbol

Class A				Class P
UTBAX				UTBPX

Investment objective

The Fund seeks to maximize total return, consisting of capital appreciation and current income.

Fees and expenses

These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for a sales charge waiver or discount if you and your family invest, or agree to invest in the future, at least $100,000 in the Fund. More information about these and other discounts and waivers, as well as eligibility requirements for each share class, is available from your financial advisor and in "Managing your fund account" beginning on page 86 of the Fund's prospectus and in "Reduced sales charges, additional purchase, exchange and redemption information and other services" beginning on page 99 of the Fund's SAI. Different intermediaries and financial professionals may make available different sales charge waivers or discounts. These variations are described in Appendix A beginning on page A-1 of the prospectus.

Shareholder fees (fees paid directly from your investment)

	Class A			Class P
Maximum front-end sales charge (load) imposed on purchases (as a % of offering price)		3.75	%		None
Maximum contingent deferred sales charge (load) (CDSC) (as a % of purchase or sales price, whichever is less)		None¹			None

Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

	Class A			Class P
Management fees		0.50	%		0.50	%
Distribution and/or service (12b-1) fees		0.25			None
Other expenses		0.70			0.80
Acquired fund fees and expenses		0.01			0.01
Total annual fund operating expenses²		1.46			1.31
Less management fee waiver/expense reimbursements³		0.70			0.80
Total annual fund operating expenses after management fee waiver/expense reimbursements^2,3		0.76			0.51

¹ Purchases of $1 million or more that were not subject to a front-end sales charge are subject to a 1% CDSC if sold within one year of the purchase date.

² Since the "Acquired fund fees and expenses" are not directly borne by the Fund, they are not reflected in the Fund's financial statements, and therefore the amounts listed in "Total annual fund operating expenses" will differ from those presented in the Financial highlights.

³ The Trust, with respect to the Fund, and UBS Asset Management (Americas) Inc., the Fund's investment advisor and administrator ("UBS AM (Americas)" or the "Advisor"), have entered into a written agreement pursuant to which the Advisor has agreed to waive a portion of its management fees and/or to reimburse expenses (excluding expenses incurred through investment in other investment companies, interest, taxes, brokerage commissions and extraordinary expenses) to the extent necessary so that the Fund's ordinary operating expenses (excluding expenses incurred through investment in other investment companies, interest, taxes, brokerage commissions and extraordinary expenses), through the period ending October 29, 2019, do not exceed 0.75% for Class A shares and 0.50% for Class P shares. Pursuant to the written agreement, the Advisor is entitled to be reimbursed for any fees it waives and expenses it reimburses to the extent such reimbursement can be made during the three fiscal years following the date on which such fee waivers and expense reimbursements were made, provided that the reimbursement of the Advisor by the Fund will not cause the Fund to exceed the lesser of any applicable expense limit that is in place for the Fund (i) at the time of the waiver or reimbursement or (ii) at the time of the recoupment. The fee waiver/expense reimbursement agreement may be terminated by the Fund's Board of Trustees at any time and also will terminate automatically upon the expiration or termination of the Fund's advisory contract with the Advisor. Upon termination of the fee waiver/expense reimbursement agreement, however, UBS AM (Americas)'s three year recoupment rights will survive.

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods unless otherwise stated. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The costs described in the example reflect the expenses of the Fund that would result from the contractual fee waiver and expense reimbursement agreement with the Advisor for the first year only. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

	1 year		3 years		5 years		10 years
Class A	$	450	$	753	$	1,078	$	1,998
Class P		52		336		641		1,509

Portfolio turnover

The Fund pays transaction costs, such as mark-ups, 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 Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 236% of the average value of its portfolio.

Principal strategies

Principal investments

Under normal circumstances, the Fund invests at least 80% of its net assets (plus borrowings for investment purposes, if any) in bonds and/or instruments that provide exposure to bond markets.

For purposes of the Fund's 80% policy above, the Fund's investments in bonds include a variety of fixed income securities, which may include, but are not limited to, securities of the US government, its agencies and government-sponsored enterprises, securities guaranteed by the US government, corporate debt securities of US and non-US issuers, including convertible securities, obligations of non-US governments or their subdivisions, agencies and government-sponsored enterprises, obligations of international agencies or supranational entities, mortgage-backed (including commercial and residential mortgage-backed securities) and asset-backed securities, and other securitized and structured securities.

Under normal circumstances, the Fund will invest at least 75% of its net assets in securities that, at the time of purchase, are rated investment grade by an independent rating agency (or, if unrated, are deemed to be of comparable quality by the Advisor), but may

invest up to 25% in securities rated below investment grade (also known as lower-rated or "junk bonds").

The Fund's investments in fixed income securities may have all types of interest rate payment and reset terms, including fixed rate, adjustable rate, zero coupon, pay-in-kind and auction rate features. In addition, the fixed income securities purchased by the Fund may be denominated in any currency, have coupons payable in any currency and may be of any maturity or duration.

The Fund invests in the United States and abroad, including emerging markets, and may purchase securities issued by domestic and foreign issuers. However, the Fund expects to limit foreign currency exposure to 25% of its net assets. Furthermore, no more than 25% of the Fund's net assets may be invested in emerging markets securities. Depending on its assessment of market conditions, the Advisor may choose to allocate the Fund's assets in any combination among these types of investments or may choose not to invest in these types of investments.

The Fund may, but is not required to, use exchange-traded or over-the-counter ("OTC") derivative instruments for risk management purposes or as part of the Fund's investment strategies. Generally, derivatives are financial contracts whose value depends upon, or is derived from, the value of an underlying asset, reference rate, index or other market factor and may relate to stocks, bonds, interest rates, credit, currencies or currency exchange rates, commodities and related indexes. The derivatives in which the Fund may invest include options (including, options on futures, forwards and swap agreements), futures, forward agreements, swap agreements (including, interest rate, total return, currency, credit default and inflation swaps), credit-linked securities and structured investments. All of these derivatives may be used for risk management purposes, such as hedging against a specific security or currency, or to manage or adjust the risk profile of the Fund. In addition, all of the derivative instruments listed above may be used for investment (non-hedging) purposes to earn income; to enhance returns; to replace more traditional direct investments; to obtain exposure to certain markets; or to establish net short positions for individual sectors, markets, currencies or securities. The Fund may use options, futures, swap agreements, credit-linked securities and structured investments to adjust the Fund's portfolio duration.

The Fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies.

Management process

The Advisor's investment strategy is based on identifying compelling and attractive opportunities where the Advisor believes that the return profile sufficiently

compensates for the risk of owning a position. The Advisor focuses on identifying relative value opportunities and discrepancies between observable market prices and the Advisor's own estimates of fundamental value across various maturities, sectors and issuers.

The investment process combines both a top-down and bottom-up dynamic approach to exploit diversified sources of alpha. The Advisor makes active decisions related to top-down factors, including duration, yield curve, and sector positioning. After defining these parameters, portfolio managers and credit research analysts work in close collaboration to develop investment themes for industry overweights and underweights as well as to determine the portions of the credit curve that are most attractive. The team then works to select securities to build optimal portfolios using bottom-up research and analysis.

Main risks

All investments carry a certain amount of risk, and the Fund cannot guarantee that it will achieve its investment objective. You may lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Below are some of the specific risks of investing in the Fund.

Credit risk: The risk that the Fund could lose money if the issuer or guarantor of a fixed income security, or the counterparty to or guarantor of a derivative contract, is unable or unwilling to meet its financial obligations. This risk is likely greater for lower quality investments than for investments that are higher quality.

Derivatives risk: The value of "derivatives"—so called because their value "derives" from the value of an underlying asset, reference rate or index—may rise or fall more rapidly than other investments. It is possible for the Fund to lose more than the amount it invested in the derivative. The risks of investing in derivative instruments also include market risk, management risk, counterparty risk (which is the risk that a counterparty to a derivative contract is unable or unwilling to meet its financial obligations) and the risk that changes in the value of a derivative may not correlate perfectly with the underlying asset, rate, index or overall market securities. Derivatives relating to fixed income markets are especially susceptible to interest rate risk and credit risk. In addition, many types of swaps and other non-exchange traded derivatives may be subject to liquidity risk, credit risk and mispricing or valuation complexity. These derivatives risks are different from, and may be greater than, the risks associated with investing directly in securities and other instruments.

Emerging market risk: There are additional risks inherent in investing in less developed countries that are

applicable to the Fund. Compared to the United States and other developed countries, investments in emerging market issuers may decline in value because of unfavorable foreign government actions, greater risks of political instability or the absence of accurate information about emerging market issuers. Further, emerging countries may have economies based on only a few industries and securities markets that trade only a small number of securities and employ settlement procedures different from those used in the United States. Prices on these exchanges tend to be volatile and, in the past, securities in these countries have offered greater potential for gain (as well as loss) than securities of companies located in developed countries. Further, investments by foreign investors are subject to a variety of restrictions in many emerging countries. Countries such as those in which the Fund may invest may experience high rates of inflation, high interest rates, exchange rate fluctuations or currency depreciation, large amounts of external debt, balance of payments and trade difficulties and extreme poverty and unemployment.

Foreign investing risk: The value of the Fund's investments in foreign securities may fall due to adverse political, social and economic developments abroad and due to decreases in foreign currency values relative to the US dollar. Investments in foreign government bonds involve special risks because the Fund may have limited legal recourse in the event of default. Also, foreign securities are sometimes less liquid and more difficult to sell and to value than securities of US issuers. These risks are greater for investments in emerging market issuers.

High yield bond risk: The risk that the issuer of bonds with ratings of Ba1 or lower by Moody's Investors Service, Inc. ("Moody's") or BB+ or lower by Standard & Poor's Financial Services LLC ("S&P") or Fitch Ratings, Inc. ("Fitch"), comparably rated by another nationally recognized statistical rating organization, or, if unrated, are determined to be of comparable quality by the Advisor, will default or otherwise be unable to honor a financial obligation (also known as lower-rated or "junk bonds"). These securities are considered to be predominately speculative with respect to an issuer's capacity to pay interest and repay principal in accordance with the terms of the obligations. Lower-rated bonds are more likely to be subject to an issuer's default or downgrade than investment grade (higher quality) bonds.

Interest rate risk: An increase in prevailing interest rates typically causes the value of fixed income securities to fall. Changes in interest rates will likely affect the value of longer-duration fixed income securities more than shorter-duration securities and higher quality securities more than lower quality securities. When interest rates are falling, some fixed income securities provide that the issuer may repay them earlier than the maturity date, and if this occurs the Fund may have to reinvest these repayments at lower interest rates. The risks associated

with rising interest rates may be more pronounced in the near future as interest rates rise from historically low rates.

Leverage risk associated with financial instruments: The use of financial instruments to increase potential returns, including derivatives used for investment (non-hedging) purposes, may cause the Fund to be more volatile than if it had not been leveraged. The use of leverage may also accelerate the velocity of losses and can result in losses to the Fund that exceed the amount originally invested.

Liquidity risk: The risk that investments cannot be readily sold at the desired time or price, and the Fund may have to accept a lower price or may not be able to sell the security at all. An inability to sell securities can adversely affect the Fund's value or prevent the Fund from taking advantage of other investment opportunities. Liquid portfolio investments may become illiquid or less liquid after purchase by the Fund due to low trading volume, adverse investor perceptions and/or other market developments. In recent years, the number and capacity of dealers that make markets in fixed income securities has decreased. Consequently, the decline in dealers engaging in market making trading activities may increase liquidity risk, which can be more pronounced in periods of market turmoil. Liquidity risk may be magnified in a rising interest rate environment or when investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. Liquidity risk includes the risk that the Fund will experience significant net redemptions at a time when it cannot find willing buyers for its portfolio securities or can only sell its portfolio securities at a material loss.

Management risk: The risk that the investment strategies, techniques and risk analyses employed by the Advisor may not produce the desired results.

Market risk: The risk that the market value of the Fund's investments may fluctuate, sometimes rapidly or unpredictably, as the stock and bond markets fluctuate. Market risk may affect a single issuer, industry, or sector of the economy, or it may affect the market as a whole.

Mortgage- and asset-backed securities risk: The Fund may invest in mortgage- and asset-backed securities that are subject to prepayment or call risk, which is the risk that the borrower's payments may be received earlier or later than expected due to changes in prepayment rates on underlying loans. Faster prepayments often happen when interest rates are falling. As a result, the Fund may reinvest these early payments at lower interest rates, thereby reducing the Fund's income. Conversely, when interest rates rise, prepayments may happen more slowly, causing the security to lengthen in duration. Longer duration securities tend to be more

volatile. Securities may be prepaid at a price less than the original purchase value. An unexpectedly high rate of defaults on the mortgages held by a mortgage pool may adversely affect the value of mortgage-backed securities and could result in losses to the Fund.

Portfolio turnover risk: High portfolio turnover from frequent trading will increase the Fund's transaction costs and may increase the portion of the Fund's capital gains that are realized for tax purposes in any given year. The Fund does not restrict the frequency of trading in order to limit expenses or the tax effect that its distributions may have on shareholders.

US Government securities risk: There are different types of US government securities with different levels of credit risk, including the risk of default, depending on the nature of the particular government support for that security. For example, a US government-sponsored entity, although chartered or sponsored by an Act of Congress, may issue securities that are neither insured nor guaranteed by the US Treasury and are therefore riskier than those that are.

Performance

Risk/return bar chart and table

The Fund's Class P shares acquired the assets and liabilities of Fort Dearborn Income Securities, Inc., a closed-end fund (the "Predecessor Fund"), prior to the opening of business on May 23, 2016 (the "Reorganization"). The Predecessor Fund was also managed by the Advisor, and the day-to-day management of, and investment decisions for, the Fund and the Predecessor Fund are made by the same portfolio management team. The Funds have generally similar investment objectives and strategies. Therefore, the information shown below for Class P shares reflects the historical performance of the Predecessor Fund for periods prior to the Reorganization.

The performance information that follows shows the Fund's performance information in a bar chart and an average annual total returns table. The bar chart and average annual return table show the performance of the Predecessor Fund's performance adopted by the Class P shares of the Fund for periods prior to the Reorganization. The information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual total returns compare with those of a broad measure of market performance. The performance information shown for periods prior to the Reorganization is for the Predecessor Fund and may not be representative of performance of the Fund. An index reflects no deduction for fees, expenses or taxes. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Updated

performance for the Fund is available at https://www.ubs.com/us-mutualfundperformance.

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

Total return (Class P)

Total return January 1 - September 30, 2018: (2.12)%
Best quarter during calendar years shown—3Q 2009: 10.32%
Worst quarter during calendar years shown—3Q 2008: (8.01)%

Average annual total returns
(for the periods ended December 31, 2017)

Class (inception date)	1 year			5 years			10 years			Life of class
Class A (09/29/16) Return before taxes		0.71	%		—	%		—	%		(1.90	)%
Class P (12/19/72) Return before taxes		4.80			1.33			5.44			7.69
Return after taxes on distributions		3.71			(0.27	)		3.34			4.02
Return after taxes on distributions and sale of fund shares		2.71			0.33			3.47			4.04
Bloomberg Barclays US Aggregate Bond Index		3.54			2.10			4.01			*

* Average annual total returns for the Bloomberg Barclays US Aggregate Bond Index for the life of each class were as follows: Class A—0.18; Class P—N/A.

Investment advisor

UBS Asset Management (Americas) Inc. serves as the investment advisor to the Fund.

Portfolio managers

• Scott E. Dolan, portfolio manager of the Predecessor Fund since 2012 and of the Fund since its inception.

• Craig G. Ellinger, portfolio manager of the Predecessor Fund since 2012 and of the Fund since its inception.

• Jeffrey Haleen, portfolio manager of the Fund since April 2018.

• Branimir Petranovic, portfolio manager of the Fund since April 2018.

Purchase & sale of Fund shares

You may purchase, redeem or exchange shares of the Fund on any business day, which is any day the New York Stock Exchange ("NYSE") is open for business. You may purchase, redeem or exchange Class A or P shares of the Fund either through a financial advisor or directly from the Fund. In general, the minimum initial investment for Class A shares is $1,000, and the minimum subsequent investment is $100; and the minimum investment for Class P shares is $5 million ($1,000 for investors who are clients of wrap fee advisory programs (with a minimum subsequent investment of $100)).

Tax information

The dividends and distributions you receive from the Fund are taxable and generally will be taxed as ordinary income, capital gains, or some combination of both, unless you are investing through a tax-advantaged arrangement, such as a 401(k) plan or an individual retirement account, in which case your distributions may be taxed as ordinary income when withdrawn from the tax-advantaged account.

Payments to broker-dealers and other financial intermediaries

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

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