X0306 4 2021-12-10 0 0001818794 Dyne Therapeutics, Inc. DYN 0001824542 Beskrovnaya Oxana C/O DYNE THERAPEUTICS, INC. 1560 TRAPELO ROAD WALTHAM MA 02451 0 1 0 0 Chief Scientific Officer Common Stock 2021-12-10 4 A 0 36524 0.00 A 54369 D Stock Option (right to buy) 13.12 2021-12-10 4 A 0 54786 0.00 A 2031-12-09 Common Stock 54786 54786 D Consists of shares of Common Stock issuable under 36,524 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 March 10, 2022. Includes 50,991 unvested RSUs. Each unvested RSU represents the right to receive one share of Common Stock upon vesting. This option was granted on December 10, 2021. The shares underlying the option are scheduled to vest over four years in equal monthly installments through December 10, 2025. /s/ Richard Scalzo, Attorney-in-Fact 2021-12-14