Addex Amends its at the Market Offering Agreement With H.C. Wainwright & Co.

Ad Hoc Announcement Pursuant to Art. 53 LR

Geneva, Switzerland, December 11, 2025 - Addex Therapeutics (SIX and Nasdaq: ADXN), a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule allosteric modulators for neurological disorders, today announced that it has amended its At The Market Offering Agreement (the “ATM Agreement”) with H.C. Wainwright & Co., LLC (“H.C. Wainwright & Co.”) initially entered into on January 30, 2024. The at-the-market offering program enables Addex to offer and sell, from time to time at its sole discretion, ADSs having an aggregate offering price of up to $3.3 million through H.C. Wainwright & Co., as its sales agent. The issuance and sale, if any, of the ADSs by the Company under the ATM Agreement will be made pursuant to the Company’s effective registration statement on Form F-3 (Registration Statement No. 333-291644).

H.C. Wainwright & Co. may sell the ADSs by any method permitted by law deemed to be an “at-the--market offering” as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended, including, without limitation, sales made through The Nasdaq Capital Market or on any other existing trading market for the ADSs. H.C. Wainwright & Co. will use commercially reasonable efforts to sell the ADSs from time to time, based upon instructions from the Company (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company will pay H.C. Wainwright & Co. a sales commission equal to three percent (3.0%) of the gross sales proceeds of any ADSs sold under the ATM Agreement. The Company also has provided H.C. Wainwright & Co. with customary indemnification and contribution rights.

Addex is not obligated to make any sales of ADSs under the ATM Agreement. The Company or H.C. Wainwright & Co. may suspend or terminate the offering of ADSs upon notice to the other party and subject to other conditions.

The foregoing description of the ATM Agreement is not complete and is qualified in its entirety by reference to the full text of the ATM Agreement.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. No sales of securities are being made under the ATM Agreement in Switzerland.

About Addex Therapeutics

Addex Therapeutics is a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule allosteric modulators for neurological disorders. Addex’s lead drug candidate, dipraglurant (mGlu5 negative allosteric modulator or NAM), is under evaluation for future development in brain injury recovery, including post-stroke and traumatic brain injury recovery. Addex’s partner, Indivior, has selected a GABAB PAM drug candidate for development in substance use disorders and has successfully completed IND enabling studies. Addex is advancing an independent GABAB PAM program for chronic cough. Addex holds a 20% equity interest in a private spin out company, Neurosterix US Holdings LLC, which is advancing a portfolio of allosteric modulator programs, including M4 PAM for schizophrenia, psychosis and mood-related disorders and mGlu7 NAM for mood disorders. In addition, Addex has invested in Stalicla, a private Swiss company pioneering a precision medicine approach for neurodevelopmental and neuropsychiatric disorders.

Addex shares are listed on the SIX Swiss Exchange and American Depositary Shares representing its shares are listed on the NASDAQ Capital Market, and trade under the ticker symbol “ADXN” on each exchange. For more information, visit

  

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Addex Forward Looking Statements:

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including statements about the intended use of proceeds of the offering. The words “may,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “project,” “potential,” “continue,” “target” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release, are based on management's current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, uncertainties related to market conditions. These and other risks and uncertainties are described in greater detail in the section entitled “Risk Factors” in Addex Therapeutics’ Annual Report on Form 20-F, prospectus and other filings that Addex Therapeutics may make with the SEC in the future. Any forward-looking statements contained in this press release represent Addex Therapeutics’ views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Addex Therapeutics explicitly disclaims any obligation to update any forward-looking statements.