Amendment: SEC Form SCHEDULE 13D/A filed by Design Therapeutics Inc.

One Letterman Drive, Building C, Suite C3-350, San Francisco, California 94129.

Logos Global is the investment adviser to several private funds, including Global Fund (collectively, the "Funds"). Logos Global GP is the general partner of Logos Global. Logos GP is the general partner of Global Fund. Dr. William is the control person of Logos Global, Logos Global GP and Logos GP and the portfolio manager of Global Fund.

During the last five years, none of the reporting persons has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

During the last five years, none of the reporting persons was a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

For citizenship of the reporting persons, see Item 6 of each reporting person's cover page.

Certain of the Funds acquired 1,217,627 shares of the Stock as a result of the automatic conversion of shares of Preferred Stock of the Issuer immediately prior to the completion of the Issuer's initial public offering on March 30, 2021. No additional consideration was paid for those shares of Stock. Dr. William was granted options to acquire 15,000 shares of the Stock for his services as a director. The shares of Stock held by Global Fund were acquired for a total purchase price of $5,503,042. The Funds used their working capital to make the foregoing purchases.

The reporting persons filed this Schedule 13D because Dr. William was on the Issuer's board of directors. Dr. William has resigned from the Issuer's board of directors on September 9, 2025. The reporting persons will routinely monitor the Issuer regarding a wide variety of factors that affect their investment considerations, including, current and anticipated future trading prices of the Stock and other securities, the Issuer's operations, assets, prospects, financial position, and business development, Issuer's management, Issuer-related competitive and strategic matters, general economic, financial market and industry conditions, and other investment considerations. Depending on their evaluation of various factors, the reporting persons may take such actions regarding their holdings of the Issuer's securities as they deem appropriate in light of circumstances existing from time to time. Such actions may include purchasing additional securities in the open market, through privately negotiated transactions with third parties or otherwise, and selling at any time, in the open market, through privately negotiated transactions with third parties or otherwise, all or part of the securities now owned or hereafter acquired by any of them. The reporting persons also may from time to time enter into or unwind hedging or other derivative transactions with respect to the Stock or pledge their interests in the Stock to obtain liquidity. In addition, from time to time the reporting persons and their representatives and advisers may communicate with other stockholders, industry participants and other interested parties about the Issuer. The reporting persons have no present plan or proposal that relates to or would result in any of the actions specified in clauses (a) through (j) of Item 4 of Schedule 13D of the Act. However, the reporting persons may recommend additional actions to the Issuer's management, board of directors and stockholders. Any such actions could involve one or more of the events referred to in clauses (a) through (j) of Item 4 of Schedule 13D, including, potentially, one or more mergers, consolidations, sales or acquisitions of assets, change in control, issuances, purchases, dispositions or pledges of securities or other changes in capitalization.

Aggregate number of shares beneficially owned by the reporting persons: Logos Global: 3,240,000 Logos Global GP: 3,240,000 Global Fund: 2,240,000 Logos GP: 2,240,000 Arsani William: 3,255,000 Aggregate percentage of the class of Stock beneficially owned by the reporting persons: Logos Global: 5.7% Logos Global GP: 5.7% Global Fund: 3.9% Logos GP: 3.9% Arsani William: 5.7%

Number of shares as to which the each reporting person has: (i) Sole power to vote or to direct the vote:? Logos Global: 0 Logos Global GP: 0 Global Fund: 0 Logos GP: 0 Arsani William: 15,000 (ii) Shared power to vote or to direct the vote:? Logos Global: 3,240,000 Logos Global GP: 3,240,000 Global Fund: 2,240,000 Logos GP: 2,240,000 Arsani William: 3,240,000 (iii) Sole power to dispose or to direct the disposition of: Logos Global: 0 Logos Global GP: 0 Global Fund: 0 Logos GP: 0 Arsani William: 15,000 (iv) Shared power to dispose or to direct the disposition of:? Logos Global: 3,240,000 Logos Global GP: 3,240,000 Global Fund: 2,240,000 Logos GP: 2,240,000 Arsani William: 3,240,000

The reporting persons engaged in the transactions set forth on Exhibit 99.2 in the Issuer's Common Stock in the 60 days preceding the date of this Schedule 13D. All transactions were effectuated in the open market through a broker.

Not applicable.

Not applicable.

Logos Global is the investment adviser to its clients pursuant to investment management agreements or limited partnership agreements providing to Logos Global the authority, among other things, to invest the funds of such clients in Stock, to vote and dispose of Stock and to file this statement on behalf of such clients. Pursuant to such limited partnership agreements, Logos Global and its affiliates are entitled to allocations based on assets under management and realized and unrealized gains. Pursuant to such investment management agreements, Logos Global is entitled to fees based on assets under management and realized and unrealized gains.

Exhibit 99.1 Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G. Exhibit 99.2 Transactions in the Past 60 Days