J&J-Partnered Addex Fails Phase II Epilepsy Study, Mulls Future of Candidate

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Pictured: Johnson & Johnson's business center in Switzerland/iStock, yuelan

Johnson & Johnson-partnered Addex Therapeutics on Monday announced that ADX71149, the companies’ investigational modulator of the metabolic glutamate subtype 2 receptor, did not meet its primary efficacy endpoint in a Phase II epilepsy study.

Addex and J&J subsidiary Janssen, which is in charge of development activities, did not provide specific data in their announcement. The partners only disclosed that the mid-stage trial “did not achieve statistical significance” for its primary endpoint of time to reach baseline seizure count when ADX71149 was used in the adjunctive setting.

Addex CMO Roger Mills said that the biotech is “disappointed” with the results of the Phase II study, and that the company is still conducting its analysis of the findings. “We will provide details on data from the full study when this analysis is completed and will work with our partner to determine next steps for the ADX71149 program.”

Monday’s topline readout comes from a Phase II randomized, double-blinded and placebo-controlled study that enrolled 110 patients who had focal onset seizures with poor response to levetiracetam or brivaracetam. The trial was designed to assess the efficacy, tolerability, safety and pharmacokinetics of ADX71149 when given as an add-on to standard of care.

Despite showing no significant efficacy advantage over placebo, ADX71149 was safe and well-tolerated in the mid-stage study, according to the companies.

ADX71149 is an investigational PAM of the metabotropic glutamate subtype 2 receptor, which is key to the release of the primary excitatory neurotransmitter glutamate and is central to initiation and spread of seizures. ADX71149’s mechanism of action allows it to normalize the neurotransmitter balance in the brain, potentially reducing the frequency of seizures in patients with epilepsy.

To advance ADX71149, Addex partnered with J&J which has assumed responsibility of development activities through its subsidiary Janssen. The pharma launched a Phase II study of the candidate in June 2021 and in September 2023 announced that the final patient in the first cohort had been randomized, with an early readout expected in the second quarter of 2024.

According to Monday’s announcement, Addex is entitled to up to approximately $117 million in success-based development and regulatory milestones, plus low double-digit royalties on net sales.

Reeling from the failure of ADX71149, Addex CEO Tim Dyer said on Monday that the biotech will channel its focus and resources to advance the rest of its positive allosteric modulator (PAM) programs. This includes the Indivior-partnered GABAB, “which is on track to select drug candidates for IND enabling studies in June for substance use disorder and chronic cough.”

Addex is also working on its one remaining clinical program dipraglurant, a negative allosteric modulator of the metabotropic glutamate receptor subtype 5, being developed for post-stroke sensorimotor recovery.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at tristan@tristanmanalac.com or tristan.manalac@biospace.com.

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