X0306 4 2016-10-26 0 0001557746 Aclaris Therapeutics, Inc. ACRS 0001654337 Ali-Jackson Kamil C/O ACLARIS THERAPEUTICS, INC. 101 LINDENWOOD DRIVE, SUITE 400 MALVERN PA 19355 0 1 0 0 Chief Legal Officer Common Stock 2016-10-26 4 M 0 3912 1.52 A 79869 D Common Stock 2016-10-26 4 S 0 3912 21.83 D 75957 D Employee StockOption (right to buy) 1.52 2016-10-26 4 M 0 3912 0.00 D 2024-12-07 Common Stock 3912 6522 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 14, 2016. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $21.36 to $22.20, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. 25% of the shares underlying this option, representing a right to purchase a total of 10,434 shares, vested on December 8, 2015 and the remaining shares vest in 36 equal monthly installments thereafter, subject to the reporting person's continued service with the issuer as of the applicable vesting date. /s/ Brian F. Leaf, Attorney-in-fact 2016-10-28