Neurosterix, Addex (NASDAQ: ADXN) spin-out, targets NTX-253 Phase 1 finish by Q2 2026

Rhea-AI Filing Summary

Addex Therapeutics reported that its spin-out company Neurosterix remains on track to complete a Phase 1 clinical study of NTX-253 for schizophrenia in Q2 2026. NTX-253 is an oral, potent, selective positive allosteric modulator of the muscarinic M4 receptor, aiming to treat schizophrenia by indirectly modulating dopamine signaling.

The Phase 1 program includes single ascending dose and multiple ascending dose components in healthy adults and adults with stable schizophrenia, assessing safety, tolerability, pharmacokinetics, food effects and cerebrospinal fluid exposure. Neurosterix, spun out of Addex in April 2024, raised $65 million in Series A financing, and Addex retains a 20% equity interest in the company.

Key Figures

Phase 1 completion target: Q2 2026 Neurosterix Series A financing: $65 million Addex equity stake in Neurosterix: 20% equity interest +2 more

5 metrics

Phase 1 completion target Q2 2026 Expected timing to complete NTX-253 Phase 1 study

Neurosterix Series A financing $65 million Raised in April 2024 spin-out financing round

Addex equity stake in Neurosterix 20% equity interest Ongoing ownership in spin-out company

MAD dosing duration 10 days Once-daily NTX-253 or placebo dosing in MAD phase

Antipsychotic withdrawal period up to eight days Duration prior to NTX-253 dosing for schizophrenia cohorts

Key Terms

positive allosteric modulator, single ascending dose, multiple ascending dose, cerebrospinal fluid, +1 more

5 terms

positive allosteric modulator medical

"NTX-253 is an investigational potent, selective, orally available positive allosteric modulator (PAM) of the muscarinic M4 receptor"

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.

single ascending dose medical

"The study includes both single ascending dose (SAD) and multiple ascending dose (MAD) components"

A single ascending dose is a method used in testing new medicines where small amounts are given to participants, gradually increasing each time to find the safest and most effective dose. For investors, it provides important information about a drug’s safety and potential, helping gauge the progress and prospects of a pharmaceutical development.

multiple ascending dose medical

"In the MAD phase, participants will receive once-daily oral dosing of NTX-253 or placebo for 10 consecutive days"

A multiple ascending dose is a method used in testing new medicines where small groups of people receive gradually larger amounts of the drug over time. This approach helps researchers find the safest and most effective dose without causing too many side effects. For investors, it signals ongoing steps in drug development that can impact a company's potential success or approval prospects.

cerebrospinal fluid medical

"evaluate NTX-253 concentrations in cerebrospinal fluid, providing early insight into central nervous system exposure"

A clear fluid that surrounds and cushions the brain and spinal cord, acting like a protective bath and cleanup system that removes waste and helps circulate nutrients. For investors, cerebrospinal fluid matters because it is a common source of diagnostic markers and a route for delivering or testing neurological drugs; changes in its composition can signal disease or affect a therapy’s development, approval prospects, and market value.

Phase 1 clinical study medical

"on track to complete its Phase 1 clinical study evaluating NTX-253 in Q2 2026"

A phase 1 clinical study is the first stage of testing a new drug or therapy in people to check safety, how the body handles the treatment, and appropriate dosing. Think of it as a cautious test drive with a small group to confirm the product won’t cause serious harm and to gather early clues about whether it might work; for investors, positive phase 1 results reduce risk, guide development timelines and costs, and make later-stage value more tangible.

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 23, 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 23, 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 23, 2026		/s/ Tim Dyer
		Tim Dyer
		Chief Executive Officer

EXHIBIT INDEX

Exhibit Number		Description
99.1		Press release dated April 23, 2026

EXHIBIT 99.1

Addex Spin-Out Company Neurosterix on Track to Complete Phase 1 Clinical Study of NTX-253 for Schizophrenia in Q2 2026

Ad Hoc Announcement Pursuant to Art. 53 LR 

Geneva, Switzerland, April 23, 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, today announced that its spin-out company, Neurosterix, is on track to complete its Phase 1 clinical study evaluating NTX-253 in Q2 2026. NTX-253 is an investigational potent, selective, orally available positive allosteric modulator (PAM) of the muscarinic M4 receptor being developed for the treatment of schizophrenia. The study is designed to generate a robust early-stage clinical data package assessing safety, tolerability, and pharmacokinetics (PK) across both healthy adult participants and those with stable schizophrenia.

The clinical study includes a multi-part, ascending-dose design intended to efficiently characterize NTX-253’s clinical profile and support subsequent patient-focused development. The study includes both single ascending dose (SAD) and multiple ascending dose (MAD) components, incorporating key translational elements such as food-effect and cerebrospinal fluid (CSF) assessments.

“This thoughtfully constructed Phase 1 clinical study has been designed to deliver a comprehensive understanding of NTX-253’s safety and pharmacokinetic profile, while incorporating early patient data and CNS exposure metrics,” said Tim Dyer, CEO of Addex. “We believe the study’s integrated, comprehensive design will help to de-risk subsequent clinical studies and could accelerate development timelines as it combines healthy volunteer and patient data within a single Phase 1 program.

Comprehensive Phase 1 Study Design
Part 1: Single Ascending Dose (SAD)
Healthy adult participants will receive a single oral dose of NTX-253 or placebo across sequentially escalating dose cohorts. This phase includes a dedicated food-effect cohort to assess the impact of food on NTX-253 pharmacokinetics. A separate SAD cohort in healthy volunteers will evaluate NTX-253 concentrations in cerebrospinal fluid, providing early insight into central nervous system exposure and brain penetration.

Part 2: Multiple Ascending Dose (MAD)
In the MAD phase, participants will receive once-daily oral dosing of NTX-253 or placebo for 10 consecutive days, with sequential dose escalation. This phase is designed to evaluate safety, tolerability, and steady-state pharmacokinetics following repeated dosing.

Importantly, the MAD phase includes two dedicated cohorts of adults with stable schizophrenia, representing early clinical evaluation in the target patient population. Participants in these cohorts will have their antipsychotic medications withdrawn for up to eight days prior to dosing with NTX-253, enabling assessment of safety and PK in patients while maintaining clinical stability.

Neurosterix was spun-out of Addex in April 2024, raising $65 million in a Series A financing led by funds affiliated with Perceptive Advisors. Addex retains a 20% equity interest in Neurosterix.

About NTX-253 and M4 PAMs

The M4 muscarinic receptor is a validated target for treating schizophrenia and related disorders through indirect modulation of dopamine signaling. NTX-253 is a potent, selective, orally available PAM of M4 that fine-tunes muscarinic signaling with the potential to reduce psychosis symptoms while avoiding the movement disorders and metabolic complications associated with traditional dopamine antagonists. Preclinical studies demonstrate robust antipsychotic-like activity and a favorable safety profile, supporting progression into first-in-human clinical studies. Currently available antipsychotics typically target dopamine receptors, providing some success in ameliorating the positive symptoms of the disorder. However, targeting dopamine also can induce metabolic, cognitive, and motor side effects, limiting their therapeutic utility. Research suggest that M4 PAMs could indirectly modulate dopamine levels and induce antipsychotic activity without peripheral muscarinic side-effects seen with direct agonists. Highly selective M4 PAMs have been found to have robust antipsychotic-like effects in multiple rodent models and reverse multiple in vivo effects of psychomotor stimulants that induce increases in extracellular dopamine.

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 Neurosterix and NTX-253?

Addex Therapeutics announced that its spin-out Neurosterix is on track to complete a Phase 1 clinical study of NTX-253 for schizophrenia in Q2 2026, supporting early evaluation of safety, tolerability and pharmacokinetics in healthy adults and patients with stable schizophrenia.

What is NTX-253 and how is it intended to treat schizophrenia?

NTX-253 is an investigational, orally available, potent and selective positive allosteric modulator of the muscarinic M4 receptor. It aims to fine-tune muscarinic signaling, potentially reducing psychosis symptoms by indirectly modulating dopamine while avoiding movement and metabolic side effects seen with traditional dopamine antagonists.

How is the Phase 1 clinical study of NTX-253 designed?

The Phase 1 study uses single ascending dose and multiple ascending dose parts in healthy adults and adults with stable schizophrenia, assessing safety, tolerability and pharmacokinetics. It includes food-effect evaluation and cerebrospinal fluid sampling to understand central nervous system exposure and brain penetration of NTX-253.

What exposure will schizophrenia patients have to NTX-253 in this Phase 1 trial?

In the multiple ascending dose phase, adults with stable schizophrenia receive once-daily NTX-253 or placebo for 10 days. Their existing antipsychotic medications are withdrawn for up to eight days before dosing to evaluate safety and pharmacokinetics directly in the target patient population while maintaining clinical stability.

What is Addex Therapeutics’ relationship to Neurosterix and its financing?

Neurosterix was spun out of Addex Therapeutics in April 2024 and raised $65 million in a Series A round led by funds affiliated with Perceptive Advisors. Addex retains a 20% equity interest in Neurosterix, giving it exposure to potential upside from NTX-253 and other allosteric modulator programs.

What other programs and partnerships does Addex Therapeutics (ADXN) highlight?

Addex highlights dipraglurant, an mGlu5 negative allosteric modulator being evaluated for brain injury recovery, and a partnered GABAB PAM program with Indivior for substance use disorders. Addex is also advancing its own GABAB PAM program for chronic cough and holds investments in Neurosterix and Stalicla.

Filing Exhibits & Attachments

1 document

Press Releases

• EX-99.1 PRESS RELEASE 8.7 KB