Addex Therapeutics (NASDAQ: ADXN) posts robust GABAB PAM chronic cough results

Rhea-AI Filing Summary

Addex Therapeutics reported new preclinical data showing its novel GABAB positive allosteric modulator (PAM) produced robust anti-tussive, or cough-suppressing, activity in a non-human primate chronic cough model. The candidate significantly reduced citric acid-induced cough frequency with efficacy similar to baclofen.

Previously reported guinea pig data showed the same GABAB PAM reduced cough frequency, increased cough latency and did not show tolerance after sub-chronic treatment, with antitussive effects appearing superior to nalbuphine, baclofen, codeine and a P2X3 inhibitor. The compound also demonstrated better tolerability and a wider therapeutic margin than nalbuphine, baclofen or codeine, and similar tolerability to a P2X3 inhibitor based on respiratory rate.

Addex is advancing this GABAB PAM program for chronic cough alongside other allosteric modulator programs, including its lead candidate dipraglurant for brain injury recovery and partnered GABAB PAM development in substance use disorders.

Key Figures

Neurosterix equity stake: 20% equity interest

1 metrics

Neurosterix equity stake 20% equity interest Ownership in private spin-out Neurosterix LLC

Key Terms

positive allosteric modulator, GABAB receptors, chronic cough, orthosteric site, +2 more

6 terms

positive allosteric modulator medical

"novel gamma-aminobutyric acid sub-type B receptor (GABAB) positive allosteric modulator (PAM)"

A positive allosteric modulator is a drug-like molecule that attaches to a different spot on a biological target than the body’s own messenger, and increases the target’s response when that natural messenger is present—like turning up a volume knob rather than replacing the song. For investors, these agents can boost a therapy’s effectiveness or safety without directly activating the target, offering potential competitive advantage, clearer combination strategies, and distinct patent or regulatory value.

GABAB receptors medical

"GABAB receptors are widely expressed throughout the central and peripheral cough neural circuit"

chronic cough medical

"Chronic cough is a difficult to treat disease in need of novel therapeutics"

orthosteric site medical

"baclofen, a selective GABAB agonist, that binds the receptor within the GABA binding, orthosteric site"

IND enabling studies regulatory

"Indivior, has selected a GABAB PAM drug candidate for development in substance use disorders and has successfully completed IND enabling studies"

negative allosteric modulator medical

"dipraglurant (mGlu5 negative allosteric modulator or NAM), is under evaluation for future development"

A negative allosteric modulator is a drug or compound that binds to a site on a biological receptor different from where the body's natural molecule binds, and reduces the receptor's activity. Think of it as turning down the volume on a signal without cutting it off entirely. For investors, this mechanism can mean more selective effects, potentially fewer side effects, and distinct commercial and regulatory prospects compared with drugs that fully block or mimic a receptor.

Form 6-K: How Foreign Companies Report to the SEC →

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of April 2026

Commission File Number: 001-39179

Addex Therapeutics Ltd
(Translation of registrant's name into English)

Chemin des Mines 9,
CH-1202 Geneva,
Switzerland
(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.
Form 20-F [ X ]      Form 40-F [   ]

On April 21, 2026, the Registrant issued a press release, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

(c) Exhibit 99.1. Press release dated April 21, 2026

INCORPORATION BY REFERENCE

Exhibit 99.1 to this Report on Form 6-K shall be deemed to be incorporated by reference into the registration statement on Form F-3 (Registration No. 333-291644) of Addex Therapeutics Ltd and the registration statement on Form S-8 (Registration No. 333-255124 and No. 333-272515) of Addex Therapeutics Ltd (including any prospectuses forming a part of such registration statements) and to be a part thereof from the date on which this report is filed, to the extent not superseded by documents or reports subsequently filed or furnished.

RISK FACTORS

Our business faces significant risks. You should carefully consider all of the information set forth in this Report on Form 6-K and in our other filings with the United States Securities and Exchange Commission, or the SEC, including the risk factors related to our business set forth in our Annual Report on Form 20-F for the year ended December 31, 2024 filed with the Securities and Exchange Commission on May 15, 2025. Our business, financial condition, results of operations and growth prospects could be materially adversely affected by any of these risks. This report also contains forward-looking statements that involve risks and uncertainties. Our results could materially differ from those anticipated in these forward-looking statements, as a result of certain factors including the risks described in our Annual Report and our other SEC filings.

 

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

		Addex Therapeutics Ltd
		(Registrant)
Date: April 21, 2026		/s/ Tim Dyer
		Tim Dyer
		Chief Executive Officer

EXHIBIT INDEX

Exhibit Number		Description
99.1		Press Release dated April 21, 2026

EXHIBIT 99.1

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

Ad Hoc Announcement Pursuant to Art. 53 LR

Geneva, Switzerland, April 21, 2026 - Addex Therapeutics (SIX: ADXN and Nasdaq: ADXN), 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.

“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.”

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.

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.

About GABAB activation and chronic cough
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.

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 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 www.addextherapeutics.com

Contacts:

Tim Dyer
Chief Executive Officer
Telephone: +41 22 884 15 55
PR@addextherapeutics.com Mike Sinclair
Partner, Halsin Partners
+44 (0)7968 022075
msinclair@halsin.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.

FAQ

What did Addex Therapeutics (ADXN) announce about its chronic cough program?

Addex reported that its novel GABAB positive allosteric modulator showed robust anti-tussive activity in a non-human primate chronic cough model, significantly reducing citric acid-induced cough frequency with efficacy similar to baclofen but with a more favorable preclinical tolerability profile.

How does Addex’s GABAB PAM compare to existing chronic cough treatments?

In preclinical guinea pig studies, Addex’s GABAB PAM reduced cough frequency, increased cough latency and showed no tolerance, with antitussive efficacy appearing superior to nalbuphine, baclofen, codeine and a P2X3 inhibitor, while demonstrating better tolerability and a wider therapeutic margin than nalbuphine, baclofen or codeine.

Why is targeting the GABAB receptor important for chronic cough according to Addex (ADXN)?

Addex notes that GABAB receptors are widely expressed in the cough neural circuit, lungs and airways. Baclofen, a GABAB agonist, already clinically validates this target for chronic cough, but its use is limited by side effects, short half-life and loss of efficacy during chronic treatment.

What advantages does an allosteric modulator offer over an orthosteric GABAB agonist?

Addex explains that targeting an allosteric site on the GABAB receptor can provide higher selectivity, better tolerability and reduced risk of tolerance compared with orthosteric compounds like baclofen, which bind at the main GABA binding site and are associated with sedation and other side effects.

What other programs is Addex Therapeutics (ADXN) developing alongside its chronic cough candidate?

Addex is a clinical-stage company focused on small molecule allosteric modulators. Its lead candidate dipraglurant (mGlu5 NAM) is being evaluated for brain injury recovery, and a partnered GABAB PAM has completed IND-enabling studies for substance use disorders. Addex also holds a 20% equity interest in Neurosterix LLC.

How is Addex Therapeutics (ADXN) positioned in terms of collaborations and investments?

Addex reports a 20% equity stake in Neurosterix LLC, which is advancing M4 PAM and mGlu7 NAM programs, and has invested in Stalicla, a Swiss precision-medicine company for neurodevelopmental and neuropsychiatric disorders, complementing its internal allosteric modulator pipeline.

Filing Exhibits & Attachments

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Press Releases

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