GAIN THERAPEUTICS, INC. Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to be held on June 23, 2023 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. We encourage you to access and review all of the important information contained in the proxy materials before voting. The Notice, Proxy Statement and Annual Report on Form 10-K are available at: http://www.viewproxy.com/ganx/2023. If you want to receive a paper or e-mail copy of these documents, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed below on or before June 14, 2023 to facilitate timely delivery. Important information regarding the Internet availability of the Company’s proxy materials, instructions for accessing your proxy materials and voting online and instructions for requesting paper or e-mail copies of your proxy materials are provided on the reverse side of this Notice. STOCKHOLDERS ARE CORDIALLY INVITED TO ATTEND THE ANNUAL MEETING AND VOTE IN PERSON. To the Stockholders of Gain Therapeutics, Inc. Notice is hereby given that the 2023 Annual Meeting of Stockholders of Gain Therapeutics, Inc. will be held on June 23, 2023 at 8:30 a.m. EDT at the offices of Cooley LLP, 55 Hudson Yards, New York, New York 10001-2157. As a Registered Holder, you may vote your shares (1) in person at the Annual Meeting, or (2) in advance of the Annual Meeting by proxy through the internet, by telephone or by using a proxy card that you may request or that we may elect to deliver at a later time. For further instructions on how to attend and vote at the 2023 Annual Meeting of Stockholders, please see “How do I attend the Annual Meeting?” and “How do I vote?” in the Questions and Answers about these Proxy Materials and Voting section of the Proxy Statement. 1. Election of Directors 01 Matthias Alder 02 Khalid Islam, Ph.D. 03 Dov Goldstein, M.D 04 Hans Peter Hasler 05 Gwen Melincoff 06 Claude Nicaise, M.D. 07 Eric I. Richman 08 Jeffrey Riley 2. To ratify the selection by the Audit Committee of the Board of Directors of Ernst & Young AG as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2023. NOTE: Your proxy holder will also vote in their discretion on any other business as may properly come before the meeting or any adjournment or postponement thereof (including, without limitation, with discretionary authority under Proposal 1 to vote for a substitute nominee if any nominee is unable to serve or for good cause will not serve). The Board of Directors recommends you vote “FOR” the election of each named nominee for Director and “FOR” Proposal 2. INTERNET TELEPHONE E-MAIL The Securities and Exchange Commission rules permit us to make our proxy materials available to our stockholders via the Internet. Material for this Annual Meeting and future meetings may be requested by one of the following methods: To view your proxy materials online, go to http://www.viewproxy.com/ganx/2023. Have your 11 digit control number (located below) available when you access the website and follow the instructions. 877-777-2857 TOLL FREE requests@viewproxy.com * If requesting material by e-mail, please send a blank e-mail with the company name and your 11 digit control number (located below) in the subject line. No other requests, instructions or other inquiries should be included with your e-mail requesting material. You must use the 11 digit control number located in the box below. CONTROL NO.

GAIN THERAPEUTICS, INC. 4800 Montgomery Lane, Suite 220 Bethesda, MD, 20814 PROXY MATERIALS AVAILABLE TO VIEW OR RECEIVE The following proxy materials are available to you for review at: http://www.viewproxy.com/ganx/2023 Notice, Proxy Statement and Annual Report on Form 10-K ACCESSING YOUR PROXY MATERIALS ONLINE Have this notice available when you request a paper copy of the proxy materials or to vote your proxy electronically. You must reference your control number to vote by Internet or request a paper copy of the proxy materials. You May Vote Your Proxy When You View The Material On The Internet. You Will Be Asked To Follow The Prompts To Vote Your Shares. Your electronic vote authorizes the named proxies to vote your shares in the same manner as if you marked, signed, dated and returned the proxy card. REQUESTING A PAPER COPY OF THE PROXY MATERIALS By telephone please call 1-877-777-2857 or By logging onto http://www.viewproxy.com/ganx/2023 or By email at: requests@viewproxy.com Please include the company name and your control number in the e-mail subject line.

¨	Preliminary Proxy Statement
¨	Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
¨	Definitive Proxy Statement
x	Definitive Additional Materials
¨	Soliciting Material under § 240.14a-12

x	No fee required
¨	Fee paid previously with preliminary materials
¨	Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11