144 0001824542 XXXXXXXX LIVE 0001818794 Dyne Therapeutics, Inc. 001-39509 1560 Trapelo Road Waltham MA 02451 (781)-786-8230 Oxana Beskrovnaya Officer Common Stock Stifel Financial Corporation

3 Bryant Park, 4th Floor 1095 Avenue of the Americas New York NY 10036

45326 860378 61375598 01/03/2024 NASDAQ Common Stock 01/03/2024 Stock option exercise Issuer N 45326 01/03/2024 Cash N Oxana Beskrovnaya

1560 Trapelo Road Waltham MA 02451

Common Stock 12/11/2023 1467 15726 The sales reported in this Form 144 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 30, 2023. Securities sold on December 11, 2023 represent shares sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on December 10, 2021 and December 9, 2022. 01/03/2024 06/30/2023 /s/ Richard Scalzo, Attorney-in-Fact