Indivior Pharmaceuticals has ended its collaboration with Addex Therapeutics to develop positive allosteric modulators, returning rights to all PAM assets discovered through the partnership. Addex said the handback followed Indivior’s “rationalization of its research and development activities and the announcement of the planned merger of Indivior’s parent company with Supernus.”
The decision closes a relationship that began in 2018, when Indivior paid Addex $5 million upfront to collaborate on ADX71441 for addiction. That program did not pan out, but Indivior later chose to take responsibility for developing another compound from the partnership as a potential treatment for substance use disorder. That August 2024 extension had signaled continuing interest in Addex’s GABAB work, particularly because it came only months after Johnson & Johnson discontinued development of an Addex-partnered PAM following poor data in a phase 2 epilepsy trial.
What Returns To Addex
Addex said regaining the rights gives it “one of the broadest portfolios” targeting the GABAB receptor. CEO Tim Dyer said the company now has flexibility to advance the broader GABAB PAM portfolio independently, including the returned candidate for substance use disorders and its proprietary candidate in development for chronic cough.
Dyer said Addex can now evaluate several strategic options, including seeking new partnerships in the near term or advancing the programs further before partnering. That framing suggests the asset return is not only a setback in one collaboration but also a financing and partnering fork in the road for a smaller biotech trying to preserve optionality around multiple GABAB programs.
The Merger Context
For Indivior, the exit fits a pattern of pipeline pruning ahead of its planned combination with Supernus. In April, the company also ended a collaboration with Alar Pharmaceuticals on a sustained-release prodrug of buprenorphine after the phase 2 failure of its orexin-1 receptor antagonist for opioid use disorder. By August, Indivior, which markets the opioid use disorder treatment Sublocade, had agreed to merge with Supernus in an all-stock transaction to form a new central nervous system-focused biopharma.
The signal is less about one returned candidate than about how merger preparation can compress tolerance for partnered research programs that need more time or capital. For Addex, full ownership restores strategic control. For Indivior, the handback shows that pre-merger simplification can take precedence over maintaining longer-duration discovery alliances, even in therapeutic areas that remain central to the combined company’s stated central nervous system focus.
