Ad Hoc Announcement Pursuant to Art. 53 LR  Geneva, Switzerland, April 21, 2026 - Addex Therapeutics (NASDAQ:ADXN), a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule

ADXN

Addex GABAB PAM Candidate Demonstrates Robust Anti-Tussive Activity in Non-Human Primate Chronic Cough Model

Addex Reveals Promising New Treatment for Chronic Cough in Preclinical Study

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  <section data-block="information">
    <h3>Information</h3>
    <p>Ad Hoc Announcement Pursuant to Art. 53 LR  Geneva, Switzerland, April 21, 2026 - Addex Therapeutics (NASDAQ:ADXN), a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule</p>
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  <section data-block="ai-summary-paragraph">
    <h3>AI Summary</h3>
    <p>Addex Therapeutics announced robust anti-cough activity of its new GABAB PAM drug in non-human primates, suggesting potential as a chronic cough treatment. This breakthrough could positively impact investor sentiment and elevate ADXN&#039;s market position owing to the drug&#039;s favorable side-effect profile compared to existing therapies.</p>
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  <section data-block="ai-summary-bullets">
    <h3>Key Points</h3>
    <ul><li>Addex reports significant anti-cough effects of GABAB PAM in preclinical models.</li><li>CEO claims drug has potential for chronic cough treatment without major side effects.</li><li>Efficacy in non-human primates matches baclofen; superior to existing treatments.</li><li>Data suggest improved tolerability and a wider therapeutic margin for GABAB PAM.</li><li>Addex has advancing pipeline including other neuro-related drug candidates.</li></ul>
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  <section data-block="companies-mentioned">
    <h3>Companies Mentioned</h3>
    <ul><li><strong>Indivior (INDV)</strong>: Indivior is partnering with Addex on substance use disorder therapies.</li><li><strong>Neurosterix LLC (N/A)</strong>: Neurosterix focuses on advanced allosteric modulator programs related to ADXN&#039;s research.</li><li><strong>Stalicla (N/A)</strong>: Stalicla is pursuing a precision medicine approach relevant to ADXN&#039;s therapeutic goals.</li></ul>
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  <section data-block="category">
    <h3>Research Analysis</h3>
    <p>This news fits in the &#039;Research Analysis&#039; category due to the disclosure of significant preclinical data relating to a novel treatment. Such advancements are key indicators for potential drug development success.</p>
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  <section data-block="market-moving">
    <h3>Market-Moving</h3>
    <ul><li>Positive preclinical results may drive ADXN shares higher in the near term.</li><li>Improved therapeutic profile over current treatments could attract investor interest.</li><li>Increased demand for chronic cough treatments may enhance ADXN&#039;s market valuation.</li><li>Pending further clinical validation could lead to significant stock price movements.</li></ul>
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  <section data-block="key-facts">
    <h3>Key Facts</h3>
    <ul><li>Date of announcement: April 21, 2026.</li><li>GABAB PAM drug candidate shows efficacy in non-human primate model.</li><li>Antitussive efficacy compared favorably to baclofen and other treatments.</li><li>Wide therapeutic margin enhances potential market acceptance.</li><li>Addex is also advancing a pipeline for neurological disorders.</li></ul>
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  <section data-block="trading-thesis">
    <h3>Trading Thesis</h3>
    <p>Invest in ADXN for potential near-term upside from positive clinical developments.</p>
  </section>
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<link type="text/css" rel="stylesheet" href="https://www.globenewswire.com/styles/gnw_nitf.css"></link><p><b>Ad Hoc Announcement Pursuant to Art. 53 LR</b></p>  <p align="justify"><b>Geneva, Switzerland, April 21, 2026</b> <b>-</b> <a href="https://www.globenewswire.com/Tracker?data=1O9Ugb07lLu1EXydV_jV3EeLb4SlAtREr3mqnAZMdi4BMPNHDThIt1ddy8Wz4fB-ekBjsYjIByy85_pt9MVN1GIJdEqv9mHs9AoOl8acEpcKSMMG5WZNNneE2g8pj3FG" rel="nofollow" target="_blank"><u>Addex Therapeutics</u></a> (NASDAQ:<a class="ticker" href="https://www.benzinga.com/quote/ADXN">ADXN</a>), a clinical-stage biopharmaceutical company focused on developing a portfolio of novel small molecule allosteric modulators for neurological disorders, announced today robust anti-tussive activity of its novel gamma-aminobutyric acid sub-type B receptor (GABAB) positive allosteric modulator (PAM) in a non-human primate (NHP) chronic cough model. </p>  <p align="justify">"These important data in non-human primates together with previously reported guinea pig data demonstrates the therapeutic potential of our highly selective, orally available GABAB PAM," said Tim Dyer, CEO of Addex. "Chronic cough is a difficult to treat disease in need of novel therapeutics with the efficacy of baclofen, which is used off-label in these patients, but without the dose limiting side effects. Based on the data generated to date, we believe our GABAB PAM drug candidate has this therapeutic profile and the potential to be a once daily treatment for patients suffering from chronic cough." </p>  <p align="justify">In the NHP model of chronic cough, the GABAB PAM drug candidate significantly reduced citric acid-induced cough frequency. In the same model, the antitussive efficacy of the GABAB PAM drug candidate was similar to that observed with baclofen. </p>  <p align="justify">As previously reported, in the citric acid induced guinea pig model of chronic cough, the GABAB PAM drug candidate significantly reduced cough frequency, increased cough latency and showed no signs of tolerance after sub-chronic treatment. In the same model, the antitussive efficacy of the GABAB PAM drug candidate appears to be superior to that observed with nalbuphine, baclofen, codeine or a P2X3 inhibitor. In addition, the GABAB PAM candidate demonstrated better tolerability and a wider therapeutic margin than that observed with nalbuphine, baclofen, or codeine, while being similar to that of a P2X3 inhibitor, based on the compound's activity on respiratory rate.</p>  <p align="justify"><b>About GABAB activation and chronic cough</b> <br></br>The main inhibitory neurotransmitter GABA activates ionotropic (GABAA) and metabotropic (GABAB) types of receptors. GABAB receptors are widely expressed throughout the central and peripheral cough neural circuit as well as in the lungs and airways. Activating GABAB receptors to treat chronic cough has been clinically validated with baclofen, a selective GABAB agonist, that binds the receptor within the GABA binding, orthosteric site. Baclofen is used off-label to treat chronic cough patients, but its wider use is limited due to serious side effects including sedation, short half-life and gradual loss of efficacy during chronic treatment. Targeting an allosteric site of the receptor encompasses many advantages, including higher selectivity, better tolerability and lack of tolerance compared to an orthosteric compound.</p>  <p><b>About Addex Therapeutics</b></p>  <p align="justify"><a href="https://www.globenewswire.com/Tracker?data=1O9Ugb07lLu1EXydV_jV3EeLb4SlAtREr3mqnAZMdi4y_t4uNfAzW-4wAporOz1rI8IlHlYmhIFqUV3r3CjFyGsOezDhEb4tV3MBYPCNkiE=" rel="nofollow" target="_blank">Addex Therapeutics</a> 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 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.</p>  <p align="justify">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 <a href="https://www.globenewswire.com/Tracker?data=pcM0QJcUQyqPMeY1YYqFZhwberC3FDHXbvyQmuCRUXRgmelPccmxYRN1pIPswIM-c1gL4yzM9xJf--1ugw4aKyp2lTkezEdYJhn4EeuZaur_xOKvTIVfqJJuFNj9J8SH" rel="nofollow" target="_blank">www.addextherapeutics.com</a></p>  <p><b>Contacts:</b></p> <table style="border-collapse: collapse; width:377pt; border-collapse:collapse ;"><tr><td style="width:264.87px;;vertical-align: top ; ">Tim Dyer<br></br>Chief Executive Officer<br></br>Telephone: +41 22 884 15 55 <br></br><a href="mailto:PR@addextherapeutics.com" rel="nofollow" target="_blank"><u>PR@addextherapeutics.com</u></a> </td><td style="width:237.8px;;vertical-align: top ; ">Mike Sinclair<br></br>Partner, Halsin Partners<br></br>+44 (0)7968 022075<br></br><a href="mailto:msinclair@halsin.com" rel="nofollow" target="_blank"><u>msinclair@halsin.com</u></a> </td></tr></table> <p align="justify"><b>Addex Forward Looking Statements:</b></p>  <p align="justify">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&#39;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.</p> <img alt="" class="__GNW8366DE3E__IMG" src="https://www.globenewswire.com/newsroom/ti?nf=MTAwMTE3Njg1MiM0MDIzNzc4MjYjMjAwMjU4Ng=="></img> <br></br><img alt="" src="https://ml-eu.globenewswire.com/media/YzhlYTc1YjQtOGJiMi00YTIyLTk4ZjEtZjQ5YjgzNDhmNTI3LTEwMTQxNTktMjAyNi0wNC0yMS1lbg==/tiny/Addex-Therapeutics.png" referrerpolicy="no-referrer-when-downgrade"></img><p><a href="https://www.globenewswire.com/NewsRoom/AttachmentNg/e6c12443-4244-46f9-909c-5ab241bbea41"><img src="https://ml-eu.globenewswire.com/media/e6c12443-4244-46f9-909c-5ab241bbea41/small/logo-jpg.jpg" border="0" width="150" height="75" alt="Primary Logo"></img></a></p>

Addex Therapeutics announced robust anti-cough activity of its new GABAB PAM drug in non-human primates, suggesting potential as a chronic cough treatment. This breakthrough could positively impact investor sentiment and elevate ADXN's market position owing to the drug's favorable side-effect profile compared to existing therapies.

Addex GABAB PAM Candidate Demonstrates Robust Anti-Tussive Activity in Non-Human Primate Chronic Cough Model

AI Summary

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Trading Thesis

Market-Moving

Key Facts

Companies Mentioned

Research Analysis

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