X0508 4 2025-12-31 0001557746 Aclaris Therapeutics, Inc. ACRS 0001957554 Balthaser Kevin C/O ACLARIS THERAPEUTICS, INC. 701 LEE ROAD, SUITE 103 WAYNE PA 19087 false true false false Chief Financial Officer 0 Common Stock 2025-12-31 4 M 0 73750 A 166358 D Common Stock 2025-12-31 4 F 0 19934 3.01 D 146424 D Common Stock 2026-01-01 4 M 0 7500 A 153924 D Common Stock 2026-01-01 4 F 0 2250 3.01 D 151674 D Common Stock 2026-01-02 4 M 0 13200 A 164874 D Common Stock 2026-01-02 4 F 0 4461 2.88 D 160413 D Restricted Stock Units 2025-12-31 4 M 0 73750 0 D Common Stock 73750 0 D Restricted Stock Units 2026-01-01 4 M 0 7500 0 D Common Stock 7500 7500 D Restricted Stock Units 2026-01-02 4 M 0 13200 0 D Common Stock 13200 13600 D Each restricted stock unit represents a contingent right to receive one share of common stock of the issuer. The transaction reported represents the withholding of shares by the issuer to satisfy the Reporting Person's tax withholding obligations in connection with the vesting and settlement of restricted stock units described in this Form 4. 50% of the shares underlying these restricted stock units vested on each of December 31, 2024 and December 31, 2025. The shares underlying these restricted stock units vest in four equal installments on the first, second, third and fourth anniversaries of January 1, 2023, subject to the Continuous Service of the Reporting Person (as defined in the Plan) as of each such date. The shares underlying these restricted stock units vest as to 33% on January 2, 2025, 33% on January 2, 2026, and 34% on January 2, 2027, subject to the Continuous Service (as defined in the Plan) of the Reporting Person as of each such date. /s/ Matthew Rothman, Attorney-in-Fact 2026-01-05