X0306 4 2019-02-01 0 0001557746 Aclaris Therapeutics, Inc. ACRS 0001654301 Powala Christopher C/O ACLARIS THERAPEUTICS, INC. 640 LEE ROAD, SUITE 200 WAYNE PA 19087 0 1 0 0 Chief Reg & Develop Officer Common Stock 2019-02-01 4 M 0 3400 A 142843 D Common Stock 2019-02-01 4 F 0 1114 6.96 D 141729 D Common Stock 130434 I By Trust Restricted Stock Units 2019-02-01 4 M 0 3400 0.00 D Common Stock 3400 10200 D Restricted stock units convert into common stock on a one-for-one basis. 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 the restricted stock units being reported in this Form 4. These shares are held by the Christopher V. Powala Aclaris Irrevocable Trust, for which Mr. Powala serves as trustee. The shares underlying these restricted stock units vest in four equal annual installments beginning on February 1, 2019, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. /s/ Mark Ballantyne, Attorney-in-fact 2019-02-05