American Century^® Mid Cap Growth Impact - MID

Index performance does not represent the fund's performance. It is not possible to invest directly in an index.

Investment return and principal value of security investments will fluctuate. The value at the time of redemption may be more or less than the original cost. Past performance is no guarantee of future results.

The fund is an actively managed ETF that does not seek to replicate the performance of a specified index.

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.

A strategy or emphasis on environmental, social and governance factors ("ESG") may limit the investment opportunities available to a portfolio. Therefore, the portfolio may underperform or perform differently than other portfolios that do not have an ESG investment focus. A portfolio's ESG investment focus 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 underlying holdings that are not screened for ESG standards.

MID is classified as non-diversified. Because it is non-diversified, it may hold large positions in a small number of securities. To the extent it maintains such positions; a price change in any one of those securities may have a greater impact on the fund's share price than if it were diversified.

The gross expense ratio is the fund's total annual operating costs, expressed as a percentage of the fund's average net assets for a given time period. It is gross of any fee waivers or expense reimbursement. The net expense ratio is the expense ratio after the application of any waivers or reimbursement. This is the actual ratio that investors paid during the fund's most recent fiscal year. Please see the prospectus for more information.