Brivaracetam

Ad Hoc Announcement Pursuant to Art. 53 LR Geneva, Switzerland, July 22, 2024 - 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, announced today that its partner Janssen Pharmaceuticals, Inc. (now known as J&J Innovative Medicine) has informed the company that it has discontinued development of ADX71149 (JNJ-40411813) in epilepsy. The partnership between the two companies remains ongoing while the full data set from the Phase 2 study of ADX71149 (JNJ-40411813) as an adjunctive epilepsy treatment is analyzed. The decision follows top-line Phase 2 data announced on April 29, 2024, showing that adjunctive ADX71149 (JNJ-40411813) administration in patients with focal onset seizures with suboptimal response to levetiracetam or brivaracetam did not achieve statistical significance for the primary endpoint of time for patients to reach baseline seizure count when ADX71149 was added to standard of care. “Following the Phase 2 study results in epilepsy, this decision was anticipated. We have had an excellent working relationship with Janssen for twenty years and will continue to work diligently to complete the analysis of the full Phase 2 data set to elucidate all learnings from the study,” said Tim Dyer, CEO of Addex. “Once we have that information in hand, we anticipate a decision on the future of this asset.” About the Study:ADX71149 is a selective metabotropic glutamate subtype 2 (mGlu2) receptor positive allosteric modulator (PAM). The multi-center Phase 2 study was designed to assess the efficacy, safety, tolerability, and pharmacokinetics of adjunctive ADX71149 administration in patients with focal onset seizures with suboptimal response to levetiracetam or brivaracetam. The primary objective of the study was to evaluate the efficacy of ADX71149 in combination with levetiracetam or brivaracetam using a time to baseline seizure count endpoint. Part 1 of the study evaluated the acute efficacy of ADX71149 over 4 weeks. Patients who did not reach their monthly baseline seizure count in Part 1 continued double-blind treatment during Part 2 until they reached their monthly baseline seizure count or 8 weeks, deemed the maintenance efficacy phase. More information on the study can be found with Clinicaltrials.gov identifier NCT04836559. About Glutamate mGlu2 Receptors and Epilepsy:Glutamate is the primary excitatory neurotransmitter in the brain and plays a key role in the initiation and spread of seizures. When activated, the mGlu2 receptor decreases the release of glutamate and consequently, helps to maintain neurotransmitter balance. In the presence of agonist-induced activation, positive allosteric modulation of mGlu2 receptors could result in the normalization of the excessive glutamate release seen during a seizure. Epilepsy remains a challenging unmet medical need, with a significant proportion of the patient population struggling in their day-to-day management of seizures. About the Collaboration:Under the research collaboration and license agreement, Addex granted Janssen Pharmaceuticals, Inc. an exclusive worldwide license to develop and commercialize mGlu2 PAM compounds. Addex is eligible for up to a total of €109 million in success-based development and regulatory milestone payments. In addition, Addex is eligible for low double-digit royalties on net sales of compounds developed under the agreement. 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, ADX71149 (mGlu2 positive allosteric modulator or PAM), developed in collaboration with Janssen Pharmaceuticals Inc., has completed several Phase 2 clinical studies, including in schizophrenia, anxious depression and, more recently, one in epilepsy patients. The Company’s second clinical program, dipraglurant (mGlu5 negative allosteric modulator or NAM), is under evaluation for future development in dyskinesia associated with Parkinson’s disease and post-stroke/TBI recovery. In Addex’s GABAB PAM partnership with Indivior, multiple drug candidates are advancing through clinical candidate selection for substance use disorder. Under the agreement with Indivior, Addex is advancing an independent GABAB PAM program for chronic cough. Addex also holds a 20% share in a private company, Neurosterix LLC which is advancing a portfolio of allosteric modulator programs including M4PAM for schizophrenia, mGlu7NAM for undisclosed psychiatric indications and mGlu2NAM 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, visit www.addextherapeutics.com. Contacts: Tim DyerChief Executive OfficerTelephone: +41 22 884 15 55PR@addextherapeutics.comMike SinclairPartner, Halsin Partners+44 (0)20 7318 2955msinclair@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 for the year ended December 31, 2023, as filed with the SEC on April 18, 2024, the final prospectus supplement and accompanying 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.

Following previously shared disappointing top-line phase 2 data, Janssen Pharmaceuticals (now J&J Innovative Medicine) has discontinued development of its glutamate mGlu2 receptor in epilepsy, according to partner Addex Therapeutics. The decision to halt the development of ADX71149 did not come as a surprise considering the data shared back in April . The multi-center phase 2 study tested the efficacy of ADX71149, an allosteric modulator of the mGlu2 receptor intended to regulate glutamate release in the brain. The trial involved 110 patients with focal onset seizures who had insufficient responses to standard-of-care seizure medications, levetiracetam or brivaracetam. The study did not achieve statistical significance for its primary endpoint — time for patients to reach baseline seizure count when ADX71149 was added to standard treatment. The partnership — inked in 2004 — remains ongoing while the full data set from the phase 2 study of ADX71149 as an adjunctive epilepsy treatment is analyzed. The longstanding partnership gave Janssen development and commercialization rights for mGlu2 PAM compounds, with Addex potentially receiving up to $116 million in milestone payments and royalties.