X0306 4 2021-05-03 0 0001557746 Aclaris Therapeutics, Inc. ACRS 0001654337 Ali-Jackson Kamil C/O ACLARIS THERAPEUTICS, INC. 640 LEE ROAD, SUITE 200 WAYNE PA 19087 0 1 0 0 Chief Legal Officer Common Stock 2021-05-03 4 M 0 15000 10.66 A 158618 D Common Stock 2021-05-03 4 S 0 10661 24.4578 D 147957 D Common Stock 2021-05-03 4 S 0 4339 24.9075 D 143618 D Common Stock 2021-05-04 4 M 0 15000 10.66 A 158618 D Common Stock 2021-05-04 4 S 0 13721 23.6055 D 144897 D Common Stock 2021-05-04 4 S 0 1279 24.4691 D 143618 D Common Stock 2021-05-05 4 M 0 15000 10.66 A 158618 D Common Stock 2021-05-05 4 S 0 14502 23.968 D 144116 D Common Stock 2021-05-05 4 S 0 498 24.3559 D 143618 D Employee Stock Option (Right to Buy) 10.66 2021-05-03 4 M 0 15000 0.00 D 2025-08-31 Common Stock 65416 50416 D Employee Stock Option (Right to Buy) 10.66 2021-05-04 4 M 0 15000 0.00 D 2025-08-31 Common Stock 50416 35416 D Employee Stock Option (Right to Buy) 10.66 2021-05-05 4 M 0 15000 0.00 D 2025-08-31 Common Stock 35416 20416 D These sales were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 10, 2021. The price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $23.82 to $24.81, 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 price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $24.82 to $24.99, 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 price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $23.17 to $24.13, 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 price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $24.19 to $24.71, 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 price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $23.32 to $24.30, 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 price reported is a weighted average sales price. The shares were sold in multiple transactions at prices ranging from $24.33 to $24.38, 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 option is fully vested. /s/ Mark Ballantyne, Attorney-in-Fact 2021-05-05