Company: GANX
Filing Date: 2025-07-15
Form Type: 424B5
Source: 0001104659-25-068103
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Company: Gain Therapeutics, Inc.
Filing Date: 2025-07-15
Form: 424B5
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TABLE OF CONTENTS

**The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to these securities has been filed with the Securities and Exchange Commission and has become effective. This preliminary prospectus supplement is not an offer to sell these securities and is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.**

#### Filed Pursuant to Rule 424(b)(5)​

#### Registration No. 333-265061​

#### SUBJECT TO COMPLETION, DATED JULY 15, 2025

### PRELIMINARY PROSPECTUS SUPPLEMENT
**(To Prospectus Dated June 1, 2022)**

#### Shares of Common Stock
<div align='center'>**Pre-Funded Warrants to purchase up to Shares of Common Stock 
 Common Warrants to purchase up to Shares of Common Stock 
 Up to Shares of Common Stock Underlying the Pre-Funded Warrants 
 Up to Shares of Common Stock Underlying the Common Warrants**</div>

We are offering shares of our common stock, par value $0.0001 per share, and accompanying warrants (“Common Warrants”) to purchase up to shares of our common stock pursuant to this prospectus supplement and accompanying prospectus. The Common Warrants are being offered and sold at the rate of one Common Warrant to purchase one share of common stock for every two shares of common stock or Pre-Funded Warrants (as defined below) in lieu thereof. The public offering price for each set of two shares of common stock and accompanying Common Warrant to purchase one share of common stock is $ , yielding an effective price of $ per share and $ per Common Warrant. Each Common Warrant will have an exercise price of $ per share of common stock and will be immediately exercisable on the date of issuance. The Common Warrants will expire five years after the date of issuance. See “ Description of Securities We Are Offering ” in this prospectus supplement for additional information. The Common Warrants will be issued in book-entry form pursuant to a warrant agency agreement between us and Pacific Stock Transfer Company as warrant agent (the “Warrant Agent”).

We are also offering pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to an aggregate of shares of common stock in lieu of shares of common stock to those purchasers whose purchase of shares of common stock in this offering would result in the purchaser, together with its affiliates and certain related parties, beneficially