144 0001789545 XXXXXXXX LIVE 0001818794 Dyne Therapeutics, Inc. 001-39509 1560 TRAPELO ROAD WALTHAM MA 02451 (781) 786-8230 Scalzo Richard William Officer Common Stock Stifel Nicolaus & Company Inc.

501 N Broadway St Louis MO 63102

1455 41220.00 101765958 12/11/2024 NASDAQ Common Stock 09/11/2024 Restricted Stock Units Issuer N 2981 12/11/2024 Compensation N Richard Scalzo

1560 TRAPELO ROAD WALTHAM MA 02451

Common Stock 09/11/2024 1468 46799.00 Richard Scalzo

1560 TRAPELO ROAD WALTHAM MA 02451

Common Stock 09/18/2024 1390 48024.00 Richard Scalzo

1560 TRAPELO ROAD WALTHAM MA 02451

Common Stock 09/11/2024 1468 46741.00 Richard Scalzo

1560 TRAPELO ROAD WALTHAM MA 02451

Common Stock 11/18/2024 2735 77099.00 12/11/2024 /s/ Dominick Iadicicco, as a duly authorized representative of STIFEL, as attorney-in-fact for Richard Scalzo