Sec Form 3 Filing - Monahan Joseph @ Aclaris Therapeutics, Inc. - 2021-05-05

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 Monahan Joseph 2. Issuer Name and Ticker or Trading Symbol Aclaris Therapeutics, Inc. [ ACRS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Scientific Officer (Last) (First) (Middle) C/O ACLARIS THERAPEUTICS, INC., 640 LEE ROAD, SUITE 200 3. Date of Earliest Transaction (MM/DD/YY) 05/05/2021 (Street) WAYNE, PA19087 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 57,132 D Common Stock 193 I By Spouse

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 Employee Stock Option (Right to Buy) $ 25.8 ( 1 ) 08/31/2027 Common Stock 56,000 D Employee Stock Option (Right to Buy) $ 22.09 ( 2 ) 01/31/2028 Common Stock 14,700 D Restricted Stock Units ( 4 ) ( 3 ) ( 3 ) Common Stock 2,333 D Restricted Stock Units ( 4 ) ( 5 ) ( 5 ) Common Stock 1,050 D Restricted Stock Units ( 4 ) ( 6 ) ( 6 ) Common Stock 27,500 D Restricted Stock Units ( 4 ) ( 7 ) ( 7 ) Common Stock 50,000 D Restricted Stock Units ( 4 ) ( 8 ) ( 8 ) Common Stock 37,500 D Restricted Stock Units ( 4 ) ( 9 ) ( 9 ) Common Stock 200,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Monahan Joseph C/O ACLARIS THERAPEUTICS, INC. 640 LEE ROAD, SUITE 200 WAYNE, PA19087 Chief Scientific Officer Signatures /s/ Mark Ballantyne, as Attorney-in-Fact 05/17/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The option vests over a period of four years. 75% of the shares are currently vested with the remaining 25% vesting on September 1, 2021, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. The expiration date of this option reported in the table is the day before the tenth anniversary of the grant date of the option. ( 2 )The option vests over a period of four years. 75% of the shares are currently vested with the remaining 25% vesting on February 1, 2022, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. The expiration date of this option reported in the table is the day before the tenth anniversary of the grant date of the option. ( 3 )The shares underlying these restricted stock units vest on September 1, 2021, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. ( 4 )Each restricted stock unit represents a contingent right to receive one share of common stock of the issuer. ( 5 )The shares underlying these restricted stock units vest on February 1, 2022, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. ( 6 )The shares underlying these restricted stock units vest over a period of two years, with 50% vesting on March 1, 2022 and 50% vesting on March 1, 2023, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. ( 7 )The shares underlying these restricted stock units vest on June 1, 2021, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. ( 8 )The shares underlying these restricted stock units vest over a period of three years, with one-third of the shares vesting on each of March 2, 2022, March 2, 2023 and March 2, 2024, subject to the reporting person's continuous service with the issuer as of the applicable vesting date. ( 9 )The shares underlying these restricted stock units vest over a period of four years, with 25% vesting on the first, second, third and fourth anniversaries of the date of grant, beginning on March 1, 2022, subject to the reporting person's continuous service with the issuer as of the applicable vesting date.

Remarks: Exhibit 24.1 - Power of Attorney

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* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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