X0306 4 2023-03-01 0 0001557746 Aclaris Therapeutics, Inc. ACRS 0001861790 Monahan Joseph C/O ACLARIS THERAPEUTICS, INC. 640 LEE ROAD, SUITE 200 WAYNE PA 19087 0 1 0 0 Chief Scientific Officer Common Stock 2023-03-01 4 M 0 13750 A 105136 D Common Stock 2023-03-01 4 M 0 50000 A 155136 D Common Stock 2023-03-01 4 M 0 10925 A 166061 D Common Stock 2023-03-02 4 S 0 14800 12.3665 D 151261 D Common Stock 2023-03-02 4 M 0 12500 A 163761 D Common Stock 2023-03-03 4 S 0 16037 12.6342 D 147724 D Common Stock 193 I By Spouse Restricted Stock Units 2023-03-01 4 M 0 13750 0.00 D Common Stock 13750 0 D Restricted Stock Units 2023-03-01 4 M 0 50000 0.00 D Common Stock 50000 100000 D Restricted Stock Units 2023-03-01 4 M 0 10925 0.00 D Common Stock 10925 32775 D Restricted Stock Units 2023-03-02 4 M 0 12500 0.00 D Common Stock 12500 12500 D Each restricted stock unit represents a contingent right to receive one share of common stock of the issuer. Shares sold to satisfy withholding tax obligations upon the delivery of shares of common stock for restricted stock units that vested on March 1, 2023 pursuant to preexisting sell-to-cover elections. The price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $11.90 to $12.68, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. Shares sold to satisfy withholding tax obligations upon the delivery of shares of common stock for restricted stock units that vested on March 1, 2023 and March 2, 2023 pursuant to preexisting sell-to-cover elections. The price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $12.43 to $12.93, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares underlying these restricted stock units vest in four equal annual installments beginning on March 1, 2020, subject to the Reporting Person's continuous service with the issuer as of the applicable vesting date. The shares underlying these restricted stock units vest in four equal annual installments beginning on March 1, 2022, subject to the Reporting Person's continuous service with the issuer as of the applicable vesting date. The shares underlying these restricted stock units vest in four equal annual installments beginning on March 1, 2023, subject to the Reporting Person's continuous service as an officer with the issuer as of the applicable vesting date. The shares underlying these restricted stock units vest in four equal annual installments beginning on March 2, 2021, subject to the Reporting Person's continuous service with the issuer as of the applicable vesting date. /s/ Mark Ballantyne, Attorney-in-fact 2023-03-03