144 0001528826 XXXXXXXX LIVE 0001818794 Dyne Therapeutics, Inc. 001-39509 1560 Trapelo Road Waltham MA 02451 781-786-8230 Joshua Brumm CEO and President Common Stock Stifel Financial Corporation

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

76582 1021580.00 58310703 06/09/2023 NASDAQ Common Stock 06/09/2023 Stock option exercise Issuer N 76582 06/09/2023 Cash N Joshua Brumm

1560 Trapelo Road Waltham MA 02451

Common Stock 03/14/2023 7318 97549.00 Joshua Brumm

1560 Trapelo Road Waltham MA 02451

Common Stock 06/08/2023 61000 806614.00 06/09/2023 /s/ Richard Scalzo, Attorney-in-Fact