Summary Prospectus      July 13, 2020
American Century Mid Cap Growth Impact ETF
Ticker: MID	Exchange: NYSE Arca, Inc.

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, reports to shareholders, and other information about the fund online at americancentury.com/etf-prospectus. You can also get this information at no cost by calling 833-ACI-ETFS or sending an email request to prospectus@americancentury.com. The fund’s prospectus and other information are also available from financial intermediaries through which shares of the fund may be purchased or sold.

This fund is different from traditional ETFs.

Traditional ETFs tell the public what assets they hold each day. This fund will not. This may create additional risks for your investment. For example:

●You may have to pay more money to trade the fund’s shares. This fund will provide less information to traders, who tend to charge more for trades when they have less information.

●The price you pay to buy fund shares on an exchange may not match the value of the fund’s portfolio. The same is true when you sell shares. These price differences may be greater for this fund compared to other ETFs because it provides less information to traders.

●These additional risks may be even greater in bad or uncertain market conditions.

●The ETF will publish on its website each day a “Proxy Portfolio” designed to help trading in shares of the ETF. While the Proxy Portfolio includes some of the ETF’s holdings, it is not the ETF’s actual portfolio.

The differences between this fund and other ETFs may also have advantages. By keeping certain information about the fund secret, this fund may face less risk that other traders can predict or copy its investment strategy. This may improve the fund’s performance. If other traders are able to copy or predict the fund’s investment strategy, however, this may hurt the fund’s performance.

For additional information regarding the unique attributes and risks of the fund, see Proxy Portfolio Risk, Premium/Discount Risk, Trading Issues Risk, and AP Concentration Risk in the Principal Risks section and The Proxy Portfolio section of the prospectus and the Statement of Additional Information.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the fund’s shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the fund or from your financial intermediary, such as a broker-dealer. Instead, the reports will be made available on a website, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from the fund or your financial intermediary electronically by calling or sending an email request.

You may elect to receive all future reports in paper free of charge. You can inform the fund or your financial intermediary that you wish to continue receiving paper copies of your shareholder reports by calling or sending an email request. Your election to receive reports in paper will apply to all funds held with the fund complex/your financial intermediary.

This summary prospectus incorporates by reference the fund’s prospectus and statement of additional information (SAI) each dated June 5, 2020 (as supplemented at the time you receive this summary prospectus). The fund's SAI and annual report may be obtained, free of charge, in the same manner as the prospectus.

Investment Objective

The fund seeks long-term capital growth.

Fees and Expenses

The following table describes the fees and expenses 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.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Management Fee	0.45%
Other Expenses1	0.00%
Total Annual Fund Operating Expenses	0.45%

¹  Other expenses are based on estimated amounts for the current fiscal year.

Example

The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other 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, that you earn 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:

1 year	3 years
$46	$145

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. Because the fund is new, the fund’s portfolio turnover rate is not available.

Principal Investment Strategies

The portfolio managers look for stocks of medium capitalization companies they believe will increase in value over time, using proprietary fundamental research. The initial research process begins by analyzing the United Nations Sustainable Development Goals (SDG) to identify companies that generate, or could generate, social and environmental impact alongside a financial return. SDGs are a collection of global goals set by the United Nations General Assembly—examples include: affordable and clean energy; decent work and economic growth; industry, innovation, and infrastructure; and responsible consumption and production. The portfolio managers make their investment decisions based primarily on their analysis of individual companies, rather than on broad economic forecasts. They generate an impact thesis to explain current or projected SDG alignment in combination with each security’s fundamental growth profile.

The portfolio managers may use commercial third party mapping tools, frameworks provided by sustainable investing platforms, or internal research, which may include engaging with a company’s leadership, to create each security’s SDG impact thesis. To decide whether a security aligns with an SDG, the portfolio managers place the most emphasis on the impact created by the product or service its issuing company produces. This helps the portfolio managers to avoid impact washing—investing in a company that is not truly advancing any of the SDGs, but is attempting to present itself as though it is (i.e. a company with a poor environmental track record touting that it will convert all of its delivery vehicles to clean burning natural gas, or a company with documented human rights abuses publicizing the diversity of its board of directors). While some securities in the fund’s portfolio may align with more than one SDG, to be eligible for selection by the portfolio managers, it is only necessary that a security aligns with one SDG. The fund does not prioritize any SDG over another, and so long as each security maps to at least one SDG, there is no minimum number of SDGs that must be represented in the portfolio. 

When evaluating a security’s potential for financial return, portfolio managers seek companies with attractive returns on invested capital that are demonstrating or expected to demonstrate long-term business improvement. Analytical indicators helping to identify or forecast signs of business improvement could include accelerating earnings or revenue growth rates, increasing cash flows, or other indications of the relative strength of a company’s business. This analysis supports the portfolio managers’ decisions to buy or hold the stocks of companies that meet their selection criteria and sell the stocks of companies whose characteristics no longer meet their criteria.

The fund will invest principally in exchange-traded common stocks. Under normal market conditions, the portfolio managers will invest at least 80% of the fund’s assets in securities of medium capitalization companies that the portfolio managers believe will create impact by aligning with at least one of the SDGs, as described above. The portfolio managers consider medium capitalization

companies to include those whose market capitalizations at the time of purchase are within the total capitalization range of the Russell Mid-Cap Growth Index. Though market capitalizations will change from time to time, as of April 30, 2020, the fund considers companies with market capitalizations between $562 million–$69 billion to be medium capitalization companies. The fund may purchase securities of small and large capitalization companies as well. The fund is nondiversified and normally invests in a relatively limited number of companies, generally 20–40 securities.

The fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies. This may cause higher transaction costs and may affect performance. It may also result in the realization and distribution of capital gains.

The fund is an actively managed, nontransparent exchange-traded fund (ETF) that does not seek to replicate the performance of a specified index. In lieu of publishing its portfolio contents (Actual Portfolio) daily, the fund publishes a proxy portfolio (Proxy Portfolio) each day and on its website. There is no minimum overlap required between the Actual Portfolio and the Proxy Portfolio.

Principal Risks

• Proxy Portfolio Risk - The goal of the Proxy Portfolio is, during all market conditions, to track closely the daily performance of the Actual Portfolio and minimize intra-day misalignment between the performance of the Proxy Portfolio and the performance of the Actual Portfolio. The Proxy Portfolio is designed to reflect the economic exposures and the risk characteristics of the Actual Portfolio on any given trading day.

◦ The Proxy Portfolio methodology is novel and not yet proven as an effective arbitrage mechanism. The effectiveness of the Proxy Portfolio as an arbitrage mechanism is contingent upon, among other things, the fund’s factor model analysis creating a proxy portfolio that performs in a manner substantially identical to the performance of the fund’s actual portfolio. While the Proxy Portfolio may include some of the fund’s holdings, it is not the fund’s Actual Portfolio. ETFs trading on the basis of a published Proxy Portfolio may exhibit wider premiums and discounts, bid/ask spreads, and tracking error than other ETFs using the same investment strategies that publish their portfolios on a daily basis, especially during periods of market disruption or volatility. Therefore, shares of the fund may cost investors more to trade than shares of a traditional ETF.

◦ Each day the fund calculates the overlap between the holdings of the prior Business Day’s Proxy Portfolio compared to the Actual Portfolio (Proxy Overlap) and the difference, in percentage terms, between the Proxy Portfolio per share NAV and that of the Actual Portfolio (Tracking Error). If the Tracking Error becomes large, there is a risk that the performance of the Proxy Portfolio may deviate from the performance of the Actual Portfolio.

◦ The fund’s Board of Trustees monitors its Tracking Error and bid/spread. If deviations become too large, the Board will consider the continuing viability of the fund, whether shareholders are being harmed, and what, if any, corrective measures would be appropriate. See the Statement of Additional Information for further discussion of the Board’s monitoring responsibilities.

◦ Although the fund seeks to benefit from keeping its portfolio information secret, market participants may attempt to use the Proxy Portfolio to identify a fund’s trading strategy, which if successful, could result in such market participants engaging in certain predatory trading practices that may have the potential to harm the fund and its shareholders.

• Premium/Discount Risk - Publication of the Proxy Portfolio is not the same level of transparency as the publication of the full portfolio by a fully transparent active ETF. Although the Proxy Portfolio is intended to provide investors with enough information to allow for an effective arbitrage mechanism that will keep the market price of the fund at or close to the underlying net asset value (NAV) per share of the fund, there is a risk (which may increase during periods of market disruption or volatility) that market prices will vary significantly from the underlying NAV of the fund. This means the price paid to buy shares on an exchange may not match the value of the fund’s portfolio. The same is true when shares are sold.

• Trading Issues Risk - If securities representing 10% or more of the fund’s Actual Portfolio do not have readily available market quotations, the fund will promptly request that the Exchange halt trading in the fund’s shares. Trading halts may have a greater impact on this fund compared to other ETFs due to the fund’s nontransparent structure. If the trading of a security held in the fund’s Actual Portfolio is halted, or otherwise does not have readily available market quotations, and the Advisor believes that the lack of any such readily available market quotations may affect the reliability of the Proxy Portfolio as an arbitrage vehicle, or otherwise determines it is in the best interest of the fund, the Advisor promptly will disclose on the fund’s website the identity and weighting of such security for so long as such security’s trading is halted or otherwise does not have readily available market quotations and remains in the Actual Portfolio. 

• Authorized Participant Concentration Risk - Only an authorized participant may engage in creation or redemption transactions directly with the fund. The fund may have a limited number of institutions that act as authorized participants. To the extent that these institutions exit the business or are unable to proceed with creation and/or redemption orders with respect to the fund and no other authorized participant is able to step forward to process creation and/or redemption orders, fund shares may trade at a discount to net asset value (NAV) and possibly face trading halts and/or delisting. This risk may be more pronounced in volatile markets, potentially where there are significant redemptions in ETFs generally. The fact that the fund is offering a novel and unique structure

may affect the number of entities willing to act as Authorized Participants. During times of market stress, Authorized Participants may be more likely to step away from this type of ETF than a traditional ETF.

• U.N. SDG Criteria Risk -Because the portfolio managers consider the U.N. SDG in stock selection, the fund may exclude the securities of certain issuers for extra-financial reasons, and the fund may forgo some market opportunities available to funds that do not consider SDG. The fund’s investment process may also result in the portfolio investing in securities or industry sectors that perform differently or maintain a different risk profile than the market generally or compared to funds that do not use the SDG. SDG considerations may be linked to long term rather than short term returns. Furthermore, when analyzing securities for SDG impact, the portfolio managers rely on the veracity of management’s claims about its business operations and governance, as well as information published by commercial and industry sources. Stocks selected by the portfolio managers may perform differently or not have the impact expected due to the portfolio managers’ judgments given available information, the weight placed on each SDG, and changes from historical trends. There is no guarantee that the investment process will result in effective investment decisions for the fund.

• Nondiversification Risk - The fund is classified as nondiversified. A nondiversified fund may invest a greater percentage of its assets in a smaller number of securities than a diversified fund. This gives the portfolio managers the flexibility to hold large positions in a smaller number of securities. If so, a price change in any one of those securities may have a greater impact on the fund’s share price than would be the case in a diversified fund and the fund may be more volatile than if it was diversified.

• Growth Stocks Risk - Investments in growth stocks may be more volatile than other stocks and the overall stock market. These stocks are typically priced higher than other stocks because of their growth potential, which may or may not be realized.

• Mid Cap Stocks Risk - The fund invests in medium-capitialization and smaller companies, which may be more volatile and subject to greater risk than larger companies. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs.

• Style Risk - If at any time the market is not favoring the fund’s growth investment style, the fund’s gains may not be as big as, or its losses may be bigger than, those of other equity funds using different investment styles.

• Market Trading Risk - The fund faces numerous market trading risks, including the potential lack of an active market for fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation and/or redemption process of the fund. Any of these factors, among others, may lead to the fund’s shares trading at a premium or discount to NAV. Thus, you may pay more (or less) than NAV when you buy shares of the fund in the secondary market, and you may receive less (or more) than NAV when you sell those shares in the secondary market. The portfolio managers cannot predict whether shares will trade above (premium), below (discount) or at NAV.

• Price Volatility Risk - The value of the fund’s shares may fluctuate significantly in the short term.

• Market Risk - The value of the fund’s shares will go up and down based on the performance of the companies whose securities it owns and other factors generally affecting the securities market. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.

• Large Shareholder Risk - Certain shareholders, including other funds advised by the advisor, may from time to time own a substantial amount of the shares of the fund. In addition, a third party investor, the advisor or an affiliate of the advisor, an authorized participant, a market maker, or another entity may invest in the fund and hold its investment for a limited period of time solely to facilitate commencement of the fund or to facilitate the fund’s achieving a specified size or scale. There can be no assurance that any large shareholder would not redeem its investment, that the size of the fund would be maintained at such levels or that the fund would continue to meet applicable listing requirements. Redemptions by large shareholders could have a significant negative impact on the fund. In addition, transactions by large shareholders may account for a large percentage of the trading volume on the NYSE Arca, Inc. and may, therefore, have a material upward or downward effect on the market price of the shares.

• Principal Loss Risk - At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.

An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.

Fund Performance

The fund’s performance history is not available as of the date of this prospectus. When the fund has investment results for a full calendar year, this section will feature charts that show annual total returns, highest and lowest quarterly returns and average annual total returns for the fund. This information indicates the volatility of the fund’s historical returns from year to year. For current performance information, please visit americancenturyetfs.com.

Performance information is designed to help you see how fund returns can vary. Keep in mind that past performance (before and after taxes) does not predict how the fund will perform in the future.

Portfolio Management

Investment Advisor

American Century Investment Management, Inc.

Portfolio Managers

Rob Brookby, Vice President and Senior Portfolio Manager, has been a member of the team that manages the fund since the fund’s inception.

Rene P. Casis, ETF Portfolio Manager, has been a member of the team that manages the fund since the fund’s inception.

Nalin Yogasundram, Portfolio Manager, has been a member of the team that manages the fund since the fund’s inception.

Purchase and Sale of Fund Shares

The fund is a nontransparent active ETF. Fund shares may only be purchased and sold on a national securities exchange through a broker-dealer. The price of fund shares is based on market price, and because ETF shares trade at market prices rather than NAV, shares may trade at a price greater than NAV (a premium) or less than NAV (a discount). The fund issues and redeems shares that have been aggregated into blocks of 5,000 shares or multiples thereof (Creation Units) to authorized participants who have entered into agreements with the fund’s distributor. The fund will generally issue and redeem Creation Units in return for a designated portfolio of securities (and an amount of cash) that the fund specifies each day.

Tax Information

Fund distributions are generally taxable as ordinary income or capital gains, unless you are investing through a tax-deferred account such as a 401(k) or individual retirement account (in which case you may be taxed upon withdrawal of your investment from such 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 advisor 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 salesperson to recommend the fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

©2020 American Century Proprietary Holdings, Inc. All rights reserved.

CL-SUM-96283   2007