Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^*

RA CAPITAL MANAGEMENT, LLC

2. Date of Event Requiring Statement (MM/DD/YYYY) 10/7/2015

3. Issuer Name and Ticker or Trading Symbol

Aclaris Therapeutics, Inc. [ACRS]

(Last) (First) (Middle)

20 PARK PLAZA, SUITE 1200

4. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director ___ X ___ 10% Owner
_____ Officer (give title below) _____ Other (specify below)

(Street)

BOSTON, MA 02116

(City) (State) (Zip)

5. If Amendment, Date Original Filed (MM/DD/YYYY)

6. Individual or Joint/Group Filing (Check Applicable Line)

___ Form filed by One Reporting Person
_ X _ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock, $0.00001 par value	2237130 ⁽¹⁾	I	See Footnote ⁽²⁾ ⁽³⁾

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivate Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)

Explanation of Responses:
( 1)	These securities include 1,871,841 shares held by RA Capital Healthcare Fund, L.P. (the "Fund") and 365,289 shares held in an account owned by Blackwell Partners, LLC (the "Blackwell Account").
( 2)	RA Capital Management, LLC (the "Adviser") is the general partner of the Fund and the investment adviser of the Blackwell Account. Peter Kolchinsky is the sole manager of the Adviser. In their respective capacities, each of Mr. Kolchinsky and the Adviser may be deemed to beneficially own the reported securities for purposes of Section 13(d) of the Securities Exchange Act of 1934.
( 3)	The Adviser and Mr. Kolchinsky disclaim beneficial ownership of the reported securities for purposes of Rule 16a-1(a)(1) under the Exchange Act in reliance on Rule 16a-1(a)(1)(v) and (vii), respectively, and therefore disclaim any obligation to report ownership of the reported securities under Section 16a of the Exchange Act. The filing of this Form 3 shall not be construed as an admission that either the Adviser or Mr. Kolchinsky is or was, for purposes of Section 16 of the Exchange Act, the beneficial owner of any of the securities reported herein.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
RA CAPITAL MANAGEMENT, LLC 20 PARK PLAZA, SUITE 1200 BOSTON, MA 02116		X
Kolchinsky Peter 20 PARK PLAZA, SUITE 1200 BOSTON, MA 02116		X

Signatures
/s/ Peter Kolchinsky Manager of RA Capital Management, LLC		10/12/2015
^** Signature of Reporting Person		Date
/s/ Peter Kolchinsky, individually		10/12/2015
^** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.