Sec Form 3 Filing - Flynn James E @ Aclaris Therapeutics, Inc. - 2018-10-22

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Flynn James E 2. Issuer Name and Ticker or Trading Symbol Aclaris Therapeutics, Inc. [ ACRS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) X __ Other (specify below) Possible Member of 10% Group (Last) (First) (Middle) 780 THIRD AVENUE, 37TH FLOOR, 3. Date of Earliest Transaction (MM/DD/YY) 10/22/2018 (Street) NEW YORK, NY10017 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common stock 4,481,788 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Common stock 1,411,628 I Through Deerfield Special Situations Fund, L.P. ( 1 ) ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Cash-Settled Total Return Swap $ 14.55 ( 4 ) ( 3 ) 10/12/2021 Common Stock 411,822 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Cash-Settled Total Return Swap $ 13.1404 ( 4 ) ( 3 ) 10/12/2021 Common Stock 25,000 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Cash-Settled Total Return Swap $ 13.2302 ( 4 ) ( 3 ) 10/12/2021 Common Stock 17,343 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Cash-Settled Total Return Swap $ 13.25 ( 4 ) ( 3 ) 10/12/2021 Common Stock 13,340 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Cash-Settled Total Return Swap $ 13.25 ( 4 ) ( 3 ) 10/12/2021 Common Stock 1,565 I Through Deerfield Partners, L.P. ( 1 ) ( 2 ) Cash-Settled Total Return Swap $ 12.9893 ( 4 ) ( 3 ) 10/12/2021 Common Stock 187,752 I Through Deerfield Partners, L.P. ( 1 ) ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Flynn James E 780 THIRD AVENUE, 37TH FLOOR NEW YORK, NY10017 X Possible Member of 10% Group Deerfield Mgmt L.P. 780 THIRD AVENUE 37TH FLOOR NEW YORK, NY10017 X Possible Member of 10% Group DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) 780 THIRD AVENUE, 37TH FLOOR NEW YORK, NY10017 X Possible Member of 10% Group DEERFIELD PARTNERS, L.P. 780 THIRD AVENUE 37TH FLOOR NEW YORK, NY10017 X Possible Member of 10% Group Deerfield Special Situations Fund, L.P. 780 THIRD AVENUE, 37TH FLOOR NEW YORK, NY10017 X Possible Member of 10% Group Signatures /s/ Jonathan Isler, Attorney-in-Fact 10/23/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This Form 3 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P. ( 2 )In accordance with Instruction 5 (b)(iv) to Form 3, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise. ( 3 )Deerfield Partners has entered into a cash-settled total return swap agreement with an unaffiliated third party financial institution, which provides the Deerfield Partners with economic exposure to an aggregate of 656,822 notional shares. The swap agreement provides Deerfield Partners with economic results that are comparable to the economic results of ownership of, but do not provide Deerfield Partners with the power to vote or direct the voting of, or dispose of or direct the disposition of, the shares of common stock that are the subject of such swap agreement. ( 4 )Represents the reference price associated with the swap agreement.

Remarks: Jonathan Isler, Attorney-in-Fact: Power of Attorney, which is hereby incorporated by reference to Exhibit 24 to a Form 3 with regard to Proteon Therapeutics, Inc. filed with the Securities and Exchange Commission on August 4, 2017 by Deerfield Special Situations Fund, L.P., Deerfield Partners, L.P., Deerfield International Master Fund, L.P., Deerfield Private Design Fund III, L.P., Deerfield Private Design Fund IV, L.P., Deerfield Mgmt, L.P., Deerfield Mgmt III, L.P., Deerfield Mgmt IV, L.P., Deerfield Management Company, L.P., and James E. Flynn.

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 4(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).

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