Joint Filer Information

Names:	Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P.
Address:	780 Third Avenue, 37th Floor New York, NY 10017
Designated Filer:	James E. Flynn
Issuer and Ticker Symbol:	Aclaris Therapeutics, Inc. [ACRS]
Date of Earliest Transaction Required To be Reported:	June 27, 2019

The undersigned, Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. are jointly filing the attached Statement of Changes in Beneficial Ownership on Form 4 with James E. Flynn with respect to the beneficial ownership of securities of Aclaris Therapeutics, Inc.

Signatures:

DEERFIELD MGMT, L.P. By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD SPECIAL SITUATIONS FUND, L.P. By: Deerfield Mgmt, L.P., General Partner By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact
DEERFIELD MANAGEMENT COMPANY, L.P. By: Flynn Management LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD PARTNERS, L.P. By: Deerfield Mgmt, L.P., General Partner By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact