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Preliminary Proxy Statement

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Confidential, For Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material Under §240.14a-12

Aclaris Therapeutics, Inc.

(Name of Registrant as Specified In Its Charter)

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Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on June 4, 2020. ACLARIS THERAPEUTICS, INC. ACLARIS THERAPEUTICS, INC. C/O BROADRIDGE P.O. BOX 1342 BRENTWOOD, NY 11717 You are receiving this communication because you hold shares in the company named above. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. proxy materials and voting instructions. D13105-P39190 See the reverse side of this notice to obtain Meeting Information Meeting Type: Annual Meeting For holders as of: April 6, 2020 Date: June 4, 2020 Time: 9:00 AM Eastern Time Location: Meeting live via the Internet-please visit www.virtualshareholdermeeting.com/ACRS2020. The company will be hosting the meeting live via the Internet this year. To attend the meeting via the Internet please visit www.virtualshareholdermeeting.com/ACRS2020 and be sure to have the information that is printed in the box marked by the arrow (located on the following page). XXXX XXXX XXXX XXXX

Before You Vote How to Access the Proxy Materials How To Vote Please Choose One of the Following Voting Methods D13106-P39190 Vote By Internet: Before The Meeting: Go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow (located on the following page) available and follow the instructions. During The Meeting: Go to www.virtualshareholdermeeting.com/ACRS2020. Have the information that is printed in the box marked by the arrow(located on the following page) available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENT2019 ANNUAL REPORT How to View Online: Have the information that is printed in the box marked by the arrow(located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET:www.proxyvote.com 2) BY TELEPHONE:1-800-579-1639 3) BY E-MAIL*:sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow(located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 21, 2020 to facilitate timely delivery. XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX

The Board of Directors recommends you vote FOR the following directors to hold office until the 2023 Annual Meeting: 1. Election of Directors Nominees: 01) Anand Mehra, M.D. 02) Andrew Powell, Esq. 03) Maxine Gowen, Ph.D. The Board of Directors recommends you vote FOR the following proposal: 2. To ratify the selection by the Audit Committee of the Board of Directors of PricewaterhouseCoopers LLP as the independent registered public accounting firm of Aclaris Therapeutics, Inc. for its fiscal year ending December 31, 2020. NOTE: Such other business as may properly come before the meeting or any adjournment thereof. D13107-P39190 Voting Items

D13108-P39190