144 0001824673 XXXXXXXX LIVE 0001818794 Dyne Therapeutics, Inc. 001-39509 1560 Trapelo Road Waltham MA 02451 (781)-786-8230 Jonathan McNeill Officer Common Stock Stifel Financial Corporation

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

2009 36246 61375598 01/04/2024 NASDAQ Common Stock 01/04/2024 Stock option exercise Issuer N 2009 01/04/2024 Cash N Jonathan McNeill

1560 Trapelo Road Waltham MA 02451

Common Stock 12/11/2023 1245 13346 Jonathan McNeill

1560 Trapelo Road Waltham MA 02451

Common Stock 01/02/2024 11900 155890 Jonathan McNeill

1560 Trapelo Road Waltham MA 02451

Common Stock 01/03/2024 17991 337048 The sales reported in this Form 144 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023. 01/04/2024 06/29/2023 /s/ Richard Scalzo, Attorney-in-Fact