13G Filing: James E. Flynn and Aclaris Therapeutics Inc (ACRS)

Aclaris Therapeutics, Inc.

101 Lindenwood Drive, Suite 400

Malvern, PA 19355

James E. Flynn, Deerfield Mgmt, L.P., Deerfield
Management Company, L.P., Deerfield Partners, L.P., Deerfield International Master Fund, L.P., Deerfield Special Situations Fund,
L.P.

James E. Flynn, Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Partners, L.P., Deerfield
International Master Fund, L.P., Deerfield Special Situations Fund, L.P., 780 Third Avenue, 37th Floor, New York, NY 10017

Deerfield Mgmt, L.P., Deerfield Management Company,
L.P., Deerfield Partners, L.P., Deerfield Special Situations Fund, L.P. – Delaware limited partnerships;

Deerfield International Master
Fund, L.P. – British Virgin Islands limited partnership;

James E. Flynn – United States citizen

Common Stock

00461U105

If This Statement is Filed Pursuant to
Rule 13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is a:

Broker or dealer registered under Section 15 of the
Exchange Act.

Insurance company as defined in Section 3(a)(19) of
the Exchange Act.

Investment company registered under Section 8 of the
Investment Company Act.

An employee benefit plan or endowment fund in accordance
with Rule 13d-1(b)(1)(ii)(F);

A parent holding company or control person in accordance
with Rule 13d-1(b)(1)(ii)(G);

(h)

A savings association as defined in Section 3(b) of
the Federal Deposit Insurance Act;

A church plan that is excluded from the definition
of an investment company under Section 3(c)(14) of the Investment Company Act;