Addex to Present Positive GABAB PAM Chronic Cough Data at the 10th American Cough Conference

Geneva, Switzerland, June 5, 2025-Addex Therapeutics(SIX/NASDAQ: ADXN), a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule allosteric modulators for neurological disorders, announced today that preclinical data from its gamma-aminobutyric acid sub-type B receptor (GABAB) positive allosteric modulator (PAM) cough program will be presented at the 10thAmerican Cough Conference (June 6-7) in Dulles, VA.

A presentation given by Mikhail Kalinichev, Head of Translational Science at Addex will describe the progress seen to date with the Addex GABAB PAM cough program, including antitussive data fromin vivomodels. Addex lead drug candidate is ready to start IND enabling studies.

Date:Saturday, June 7, 2025Time:11:20 am ESTTitle:Compound A, a novel positive allosteric modulator of the GABAB receptor, shows robust antitussive efficacy and signs of wide therapeutic margin in models of cough in guinea pigsLocation:Hyatt Regency Dulles, 2300 Dulles Corner Blvd., Herndon, VA, US, 20171

About GABAB activation and cough:The main inhibitory neurotransmitter GABA activates ionotropic (GABAA) and metabotropic (GABAB) types of receptors. GABAB receptors are widely expressed on airways and in the central and peripheral components of the cough neural circuit. Activating GABAB receptors to treat chronic cough has been clinically validated with baclofen, a selective GABAB agonist, that binds the receptor within the orthosteric GABA binding site. Baclofen is used off-label to treat chronic cough patients, but its wider use is limited due to serious side effects, short half-life and gradual loss of efficacy during chronic treatment. Targeting an allosteric site of the receptor is expected to provide many advantages, including higher selectivity, better tolerability and lack of tolerance compared to an orthosteric compound.

About Addex TherapeuticsAddex 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 also holds a 20% equity interest in a private spin out company, Neurosterix LLC, which is advancing a portfolio of allosteric modulator programs, including M4 PAM for schizophrenia, mGlu7 NAM for mood disorders and mGlu2 NAM for mild neurocognitive 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, visitwww.addextherapeutics.com

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.