X0306 4 2022-06-14 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 2022-06-14 4 D 0 726 4.95 D 52950 D Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on December 10, 2021. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person. Includes 46,427 unvested RSUs. /s/ Richard Scalzo, Attorney-in-Fact 2022-06-15