X0508 4 2025-12-17 0 0001599901 Avidity Biosciences, Inc. RNA 0001715283 Mosbrooker Eric C/O AVIDITY BIOSCIENCES, INC. 3020 CALLAN RD. SAN DIEGO CA 92121 0 1 0 0 Chief Commercial Officer 0 Common Stock 2025-12-17 4 A 0 72000 0 A 127000 D Common Stock 2025-12-17 4 F 0 36564 71.87 D 90436 D Common Stock 2025-12-17 4 F 0 11426 71.87 D 79010 D Represents shares acquired upon the vesting of performance-based restricted stock units (PSUs). Each PSU represented a contingent right to receive one share of the Issuer's common stock. The PSUs were originally granted to the Reporting Person on October 30, 2024. The PSUs were accelerated and settled on December 17, 2025 for tax planning purposes and such shares remain subject to recoupment by the Issuer if the Reporting Person's employment is terminated by the Issuer for cause or by the Reporting Person without good reason. Represents the number of shares withheld by the Issuer to cover tax withholding in connection with the settlement of PSUs on December 17, 2025. Represents the number of shares withheld by the Issuer to cover tax withholding in connection with the settlement of restricted stock units on December 17, 2025. /s/ John B. Moriarty, Jr., J.D., Attorney-in-Fact 2025-12-19