Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. The Fund’s Prospectus and Statement of Additional Information, both dated April 30, 2023, as may be subsequently amended, are incorporated by reference into this Summary Prospectus. You can find the Fund’s Prospectus, reports to shareholders and other information about the Fund online (https://www.driehaus.com/fund-resources). You can also get this information at no cost by calling 1-800-560-6111, by sending an email request to mutualfunds@driehaus.com, or by asking any financial advisor, bank, or broker-dealer who offers shares of the Fund.

Investment Objective

Driehaus Event Driven Fund seeks to provide positive returns over full-market cycles.

Fees and Expenses of the Fund

This 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.

Expense Example: This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. 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 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 81% of the average value of its portfolio.

Principal Investment Strategy

The Fund is actively managed by using techniques intended to provide positive returns over full-market cycles. In making investment decisions the Fund’s investment adviser, will employ event-driven strategies designed to exploit disparities or inefficiencies in U.S. and foreign (non-U.S.) equity and debt markets. The investment adviser will seek investment opportunities where a catalyst is expected to occur within the near to intermediate term, generally within 12 months, to unlock the value embedded in the investment opportunity. Investment opportunities will often center on corporate events such as bankruptcies, mergers, acquisitions, SPACs (“Special Purpose Acquisition Companies”), refinancings, corporate reactions to government and regulatory agency rulings, earnings surprises and other corporate events. The Fund will invest in a broad range of asset classes, including fixed-income and floating rate debt securities (across credit tiers), loans, equity securities across all market capitalizations, American Depositary Receipts and Global Depositary Receipts, options, futures and swaps. Securities held will be issued by, or be in reference to, U.S. and non-U.S. companies. The Fund may also invest in currencies.

The Fund seeks to target an annualized volatility, as measured by the standard deviation of returns, of less than that of the S&P 500^® Index over full-market cycles, which are typically periods of three to five years. Annualized volatility refers to the fluctuation of a security’s value on a yearly basis. The Fund’s volatility will be monitored daily and positions within the Fund will be adjusted as appropriate to attempt to achieve the stated volatility target. The Fund holds both long and short positions in debt securities (both sovereign and corporate), equity securities and currencies. The debt securities held in the Fund may be fixed income or floating rate securities, including fixed and floating rate loans. These securities may have a senior right to repayment (“Senior Loans”) and/or may be of either investment grade or non-investment grade (“junk”) credit quality. Debt securities may or may not have been rated by a rating agency and the investment adviser is not constrained by ratings when selecting debt securities for investment. The Fund may invest in debt securities of any maturity and does not attempt to maintain any pre-set average portfolio maturity or duration. The Fund also invests in common and preferred stocks across all market capitalizations and regions. The Fund may have significant exposure to foreign currencies and interest rates.

The Fund also holds derivative instruments, including swaps, options, futures and forwards that provide long and short exposures to debt securities, equity securities and currencies. The Fund may use derivatives to manage interest rate and currency risk, as part of a hedging strategy (attempting to reduce risk by offsetting one investment position with another) and/or to replicate outright long or short exposures. In addition to investing in outright long and short positions, as part of its investment strategy, the Fund will engage in a variety of arbitrage trading strategies that seek to take advantage of relative value opportunities between two or more securities. The Fund may hold a substantial position in cash and money market instruments. The cash holdings of the Fund will vary significantly based on the investment adviser’s use of equity and credit derivatives. Generally, the more derivatives held within the Fund, the higher its cash balance.

The securities and instruments that the Fund invests in may trade in markets in multiple countries. The Fund’s investments may be highly concentrated in a geographic region or country, including emerging market countries. The Fund may frequently and actively trade its portfolio.

Principal Risks

Event Risk. Event-driven opportunities may not occur as anticipated, resulting in potentially reduced returns or losses to the Fund as it unwinds trades where those opportunities do not materialize as anticipated.

Arbitrage Risk. Employing arbitrage strategies involves the risk that anticipated opportunities do not turn out as planned, resulting in potentially reduced returns or losses to the Fund.

Market Risk. The Fund is subject to market risk, which is the possibility that securities prices overall, including both debt and equity securities, will decline over short or long periods. Securities markets tend to move in cycles, with periods of rising prices and periods of falling prices. These fluctuations are expected to have a substantial influence on the value of the Fund’s shares. Due to the uncertainty caused by war, acts of terrorism, geopolitical conflict, public health issues, recessions, economic cycles, monetary and fiscal policy, company earnings, global pandemics and other risks, global markets may experience increased volatility which could adversely affect the performance of the Fund’s investments.

Equity Securities Risk. In a company liquidation, the claims of secured and unsecured creditors and owners of bonds and preferred stocks take precedence over the claims of common stock shareholders.

Small- and Medium-Sized Company Risk. The Fund invests in companies that are smaller, less established, with limited operating histories and less liquid markets for their stock, and therefore may be riskier investments. While small- and medium-sized companies generally have the potential for rapid growth, the securities of these companies often involve greater risks than investments in larger, more established companies because small- and medium-sized companies may lack the management experience, financial resources, product diversification and competitive strengths of larger companies. In addition, in many instances the securities of small- and medium-sized companies are traded only over-the-counter or on a regional securities exchange, and the frequency and volume of their trading is substantially less than is typical of larger companies. The value of securities of smaller, less well-known issuers can be more volatile than that of larger issuers.

Micro-Cap Company Risk. The securities of micro-cap companies may be more volatile in price, have wider spreads between their bid and ask prices, and have significantly lower trading volumes than the securities of larger capitalization companies. As a result, the purchase or sale of more than a limited number of shares of the securities of a smaller company may affect its market price. The Fund may need a considerable amount of time to purchase or sell its positions in these securities. Some micro-cap companies are followed by few, if any, securities analysts, and there tends to be less publicly available information about such companies. Their securities generally have even more limited trading volumes and are subject to even more abrupt or erratic market price movements than are small-cap and mid-cap securities, and the Fund may be able to deal with only a few market-makers when purchasing and selling micro-cap securities. Such companies may also have limited markets, financial resources or product lines, may lack management depth, and may be more vulnerable to adverse business or market developments. These conditions, which create greater opportunities to find securities trading well below the Fund’s estimate of the company’s current worth, also involve increased risk.

Depositary Receipts Risk. Depositary receipts which include American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”). Investment in Depositary Receipts does not eliminate the risks inherent in investing in the securities of foreign issuers, which include market, political, tax, currency and regulatory risk. To the extent a Fund acquires Depositary Receipts through banks which do not have a contractual relationship with the foreign issuer of the security underlying the Depositary Receipts to issue and service such unsponsored Depositary Receipts, there may be an increased possibility that the Fund would not become aware of and be able to respond to corporate actions such as stock splits or rights offerings involving the foreign issuer in a timely manner. In addition, the lack of information may result in inefficiencies in the valuation of such instruments. In the case of an unsponsored Depositary Receipt, a Fund may bear higher expenses and encounter greater difficulty in receiving shareholder communications than it would have with a sponsored Depositary Receipt. The market value of Depositary Receipts is dependent upon the market value of the underlying securities and fluctuations in the relative value of the currencies in which the Depositary Receipts and the underlying securities are quoted.

Risks of Debt Securities. Debt securities may be subject to credit risk, interest rate risk, prepayment and extension risk as well as call risk. Credit risk is the failure of an issuer or borrower to make timely interest or principal payments, or a decline or perception of a decline in the credit quality of a bond or creditworthiness of a borrower, which can cause the security’s price to fall, potentially lowering the Fund’s share price. Credit spread risk is the risk that economic and market conditions or any actual or perceived credit deterioration may lead to an increase in the credit spreads (i.e., the difference in yield between two securities of similar maturity but different credit quality) and a decline in price of the issuer’s securities. Prices of bonds and Senior Loans tend to move inversely with changes in interest rates. Typically, a rise in rates will adversely affect bond and Senior Loan prices and, accordingly, the Fund’s share price. The longer a debt security’s effective maturity and duration, the more its price is likely to react to interest rates.

Interest rate changes normally have different effects on variable or floating rate securities than they do on securities with fixed interest rates. When interest rates fall, debt securities may be repaid more quickly than expected and the Fund may be required to reinvest the proceeds at a lower interest rate. This is referred to as “prepayment risk.” When interest rates rise, debt securities may be repaid more slowly than expected and the value of the Fund’s holdings may fall sharply. This is referred to as “extension risk.” If an issuer “calls” its bond before its maturity date during a time of declining interest rates, the Fund might have to reinvest the proceeds in an investment offering a lower yield.

High Yield Risk. Low-rated and comparable unrated securities (“junk bonds”), involve greater risks than investment grade securities, including the possibility of default or bankruptcy. They are regarded as speculative with respect to the issuer’s capacity to pay interest and to repay principal. The market values of certain of these securities tend to be more sensitive to individual corporate development and changes in economic conditions than higher quality bonds. In addition, junk bonds tend to be less marketable than higher-quality debt securities because the market for them is not as broad or active. The lack of a liquid secondary market may have an adverse effect on market price and the Fund’s ability to sell particular securities.

Senior Loan Risk. Senior Loans are business loans made to borrowers that may be corporations, partnerships or other entities (each a “Borrower”). These Borrowers operate in a variety of industries and across geographic regions. Investing in Senior Loans involves investment risk and some Borrowers default on their Senior Loan repayments. Investments in Senior Loans typically are below investment grade and are considered speculative because of the credit risks of their Borrowers. Such Borrowers are more likely to default on their payments of interest and principal owed, and such defaults could reduce the Fund’s net asset value and income distributions. An economic downturn generally leads to a higher non-payment rate, and a Senior Loan may lose significant value before a default occurs. No active trading market may exist for certain Senior Loans, which may impair the ability of the Fund to realize full value upon its sale and which may make it difficult to value Senior Loans. Adverse market conditions may impair the liquidity of some actively traded Senior Loans. To the extent that a secondary market does exist for certain Senior Loans, the market may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods. Senior Loans are subject to the risk that when sold, such sale may not settle in a timely manner, resulting in a settlement date that may be much later than the trade date. Delayed settlement interferes with a Fund’s ability to realize the proceeds of Senior Loan sales in a timely way. There is no assurance that the liquidation of the collateral would satisfy the claims of the Borrower’s obligations in the event of the non-payment of scheduled interest or principal, or that the collateral could be readily liquidated. Senior Loans may not be deemed to be securities and, in such case, may not be afforded the anti-fraud protections of the Federal securities laws in the event of fraud or misrepresentation by a Borrower.

Liquidity Risk. When there is little or no active trading market for specific types of securities or an unusually high volume of redemptions or other similar conditions, it can become more difficult to sell the securities at or near their perceived value or the Fund may sell certain investments at a price or time that is not advantageous in order to meet redemption requests or other cash needs. In such a market, the value of such securities and the Fund’s share price may decrease and in extreme conditions the Fund could have difficulty meeting redemption requests. No active trading market may exist for some Senior Loans, derivatives, bonds or equities. Certain securities may be subject to restrictions on resale. The inability to dispose of (or convert to cash) Senior Loans, derivatives, bonds or equity securities in a timely fashion could result in losses to the Fund.

SPAC Risk. The Fund may invest in stock, warrants and other securities of special purpose acquisition companies (“SPACs”) or similar special purpose entities that pool funds to seek potential acquisition opportunities. A SPAC is a publicly listed acquisition vehicle formed to raise capital and acquire or merge with an existing, private operating company. Typically, SPACs have a predetermined time frame of two years to acquire or merge with a private operating company, and if no acquisition or merger occurs, the SPAC is liquidated. Unless and until the acquisition is completed, a SPAC generally invests its assets (less a portion retained to cover expenses) in U.S. Government securities, money market fund securities and cash; if an acquisition that meets the requirements for the SPAC is not completed within a pre-established period of time, the invested funds are returned to the entity’s shareholders. Because SPACs and similar entities are in essence blank check companies without an operating history or ongoing business other than seeking acquisitions, the value of their securities is particularly dependent on the ability of the entity’s management to identify and complete a profitable acquisition. Some SPACs may pursue acquisitions only within certain industries or regions which may increase the volatility of their prices. In addition, these securities may be considered illiquid and/or subject to restrictions on resale.

Manager Risk. How the investment adviser manages the Fund will impact the Fund’s performance. The Fund may lose money if the investment adviser’s investment strategy does not achieve the Fund’s objective or if the investment adviser does not implement the strategy successfully.

Risks of Derivatives. Derivative instruments (such as swaps, options, futures and forwards) often have risks similar to their underlying currency, security or index, in addition to other risks. The use of derivatives also involves risks different from, and possibly greater than, the risks associated with investing directly in the underlying assets. Derivatives can be highly volatile, illiquid and difficult to value, and there is a risk of imperfect correlation between the value of the derivative and the underlying instrument. Derivative instruments may give rise to leverage and losses on derivatives may substantially exceed the initial investment. When used for hedging, the change in value of the derivative may also not correlate specifically with the currency, security or other risk being hedged. Further, since the Fund may invest in derivatives for speculative purposes, losses from speculative positions in a derivative may be much greater than the derivative’s original cost and may be substantial. With over-the-counter derivatives, there is the risk that the other party to the transaction could default. Derivatives may be subject to pricing or “basis” risk, which exists when a particular derivative becomes extraordinarily expensive relative to historical prices or the prices of its corresponding instrument.

Risks of Holding Cash or Similar Instruments. During periods when the Fund holds a substantial position in cash and money market instruments, the Fund will earn less income than it would if it invested in higher yielding securities. Holding a large cash position for an extended period of time may result in the Fund not achieving its investment objective. To the extent that

the Fund invests in money market mutual funds for its cash position, the Fund will indirectly bear its pro rata portion of such funds’ management fees and operational expenses. These expenses are in addition to the expenses the Fund bears directly in connection with its own operations.

Short Sale Risk. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as “covering” the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. The amount the Fund could lose on a short sale is theoretically unlimited (as compared to a long position, where the maximum loss is the amount invested). The use of short sales also may cause the Fund to have higher expenses than those of other funds due to the payment of dividends and interest, if any, in connection with the short positions as well as the cost to borrow the security.

Allocation Risk. The Fund’s overall risk level will depend on the companies, countries, regions, markets, market sectors, industries and asset classes in which the Fund is invested. Because the Fund may have significant weightings in a particular company, country, region, asset class, industry, market or market sector, the value of the Fund’s shares may be affected by events that adversely affect that company, country, region, market, industry, asset class, or market sector and may fluctuate more than that of a less focused fund.

Growth Stock Risk. Growth stocks are typically priced higher than other stocks, in relation to earnings and other measures, because investors believe they have more growth potential. This potential may or may not be realized and, if it is not realized, may result in a loss to the Fund. Growth stock prices also tend to be more volatile than the overall market.

Shareholder Concentration Risk. The Fund may be an investment option for unaffiliated mutual funds and other investors with substantial investments in the Fund. As a result, the Fund may have large inflows and outflows of cash from time to time. This could have adverse effects on the Fund’s performance if the Fund were required to sell securities or invest cash at times when it otherwise would not do so. This activity could also accelerate the realization of capital gains and increase the Fund’s transaction costs.

Performance

The bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows the volatility—or variability—of the Fund’s Investor Shares annual total returns over time and shows that Fund performance can change from year to year. The table shows the Fund’s average annual total returns for certain time periods compared to the returns of a broad-based securities index. Of course, the Fund’s past performance (before and after taxes) is not necessarily an indication of its future performance. Updated performance information is available by visiting www.driehaus.com/performance or by calling 1-800-560-6111.

Annual Returns for the years ended December 31

During the period shown in the bar chart, the highest return for a quarter was 14.79% (quarter ended 6/30/20) and the lowest return for a quarter was –9.26% (quarter ended 3/31/20).

The table shows returns on a before-tax and after-tax basis. After-tax returns are shown only for Investor Shares and after-tax returns for Institutional Shares will vary from Investor Shares. After-tax returns are calculated using the highest historic marginal individual federal 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 the table. After-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).

Portfolio Management

Investment Adviser

Driehaus Capital Management LLC (“DCM”)

Portfolio Managers

Purchase and Sale of Fund Shares

In general, you can buy or sell shares of the Fund by regular mail addressed to Driehaus Mutual Funds, P.O. Box 4766, Chicago, IL 60680-4766, or by overnight delivery addressed to Driehaus Mutual Funds, c/o Northern Trust, 333 South Wabash Avenue, W-38, Chicago, IL 60604, or by phone at 1-800-560-6111 on any business day. You may also buy and sell shares through a financial professional.

Tax Information

The Fund’s distributions may be taxable as ordinary income or capital gains, unless you are investing through a tax-advantaged arrangement, such as a 401(k) or an IRA. If you are investing through a tax-advantaged arrangement, assets held through such arrangement may be taxable upon withdrawal.

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/or its related companies may pay the intermediary for the sale of Fund shares and/or related services, including recordkeeping, administrative and other sub-transfer agency services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

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