144 0001498428 XXXXXXXX LIVE 0001818794 Dyne Therapeutics, Inc. 001-39509 1560 TRAPELO ROAD WALTHAM MA 02451 (781) 786-8230 Cox John Officer Common Stock Stifel Nicolaus & Company Inc

501 N Broadway St. Louis MO 63102

3311 60805.00 165313769 05/13/2026 Nasdaq Common Stock 05/12/2026 Restricted Stock Units Issuer N 11250 05/12/2026 Equity Compensation N John Cox

1560 Trapelo Rd Waltham MA 02451

Common Stock 03/05/2026 2732 40707.00 05/13/2026 /s/ James Weimer, as a duly authorized representative of STIFEL, as attorney-in-fact for John Cox