X0306 4 2021-03-02 0 0001818794 Dyne Therapeutics, Inc. DYN 0001847941 Farwell Wildon C/O DYNE THERAPEUTICS, INC. 830 WINTER STREET WALTHAM MA 02451 0 1 0 0 Chief Medical Officer Common Stock 2021-03-02 4 A 0 50000 0.00 A 50000 D Stock Option (right to buy) 17.77 2021-03-02 4 A 0 250000 0.00 A 2031-03-01 Common Stock 250000 250000 D Consists of shares of Common Stock issuable under 50,000 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 annual installments over four years with the first installment vesting on March 1, 2022. This option was granted on March 2, 2021. The shares underlying the option are scheduled to vest over four years, with 25% of the shares vesting on March 1, 2022 and the remaining shares vesting in equal quarterly installments thereafter. /s/ Richard Scalzo, Attorney-in-Fact 2021-03-04