X0609 4 2026-10-20 0001818794 Dyne Therapeutics, Inc. DYN 0001814189 Kerr Douglas false C/O DYNE THERAPEUTICS, INC. 1560 TRAPELO ROAD WALTHAM MA 02451 false true false false Head of R&D and CMO false Common Stock 2026-10-20 4 A false 8000 0 A 170564 D Stock option (right to buy) 16.27 2026-10-20 4 A false 12000 0 A 2036-10-19 Common Stock 12000 12000 D Consists of shares of Common Stock issuable under 8,000 restricted stock units ("RSUs"). Each RSU represents the right to receive one share of Common Stock upon vesting. These RSUs are scheduled to vest in equal quarterly installments over four years with the first installment vesting on January 20, 2027. Includes 133,126 unvested RSUs. This option was granted on October 20, 2026. The shares underlying the option are scheduled to vest over four years in equal monthly installments through October 20, 2030. /s/ Ron Caponigro, Attorney-in-Fact 2026-10-22