Addex Regains Full Global Rights to GABAB PAM Portfolio as Indivior Exits Collaboration
核心洞察
Addex Therapeutics (搜索) has regained full global rights to all GABAB positive allosteric modulator assets discovered under its research collaboration with Indivior, ending a partnership that began in 2018.
Indivior returned the rights after rationalizing its R&D activities ahead of the planned merger of its parent company with Supernus Pharmaceuticals, and no milestone payments were triggered.
The returned portfolio includes a small-molecule GABAB PAM candidate for substance use disorders (搜索) that completed IND-enabling studies, plus a wholly owned chronic cough (搜索) program ready for IND-enabling development.
Addex Therapeutics (搜索) has regained full global rights to all GABAB positive allosteric modulator (PAM) assets discovered under its research collaboration with Indivior UK Limited, the Geneva-based clinical-stage biopharmaceutical company announced on September 25, 2026. The reversion ends a partnership that began in 2018, when Indivior paid Addex $5 million upfront to collaborate on a PAM called ADX71441 for the treatment of addiction.
The original agreement had included up to USD 330 million in potential milestone payments, but Addex said no milestones were triggered before the rights reverted. Indivior handed back the assets following what Addex described as Indivior's "rationalization of its research and development activities and the announcement of the planned merger of Indivior's parent company with Supernus Pharmaceuticals, Inc."
Returned Assets and Portfolio Scope
The returned portfolio includes an unnamed small-molecule GABAB PAM candidate for substance use disorders (搜索) that completed IND-enabling studies under Indivior. Addex also retains a separate wholly owned GABAB PAM program for chronic cough (搜索), which the company said is ready to enter IND-enabling development.
The termination gives Addex full ownership of the returned development candidate and the freedom to pursue therapeutic indications beyond those originally contemplated under the agreement. Combined with the wholly owned chronic cough (搜索) program, the returned asset gives Addex what it describes as one of the broadest portfolios targeting GABAB receptor (搜索) biology. The company said the portfolio may have potential applications across substance use disorders (搜索), chronic cough, pain, overactive bladder, neurodevelopmental disorders, and other conditions in which modulation of GABAB signaling has demonstrated therapeutic promise.
"These GABAB PAM assets reflect years of world-class research in allosteric modulation and build on a biological approach clinically validated by baclofen," said Tim Dyer, CEO of Addex Therapeutics (搜索). "By regaining the rights to the development candidate selected by Indivior, we now have the flexibility to advance our broader GABAB PAM portfolio independently. This includes the returned candidate for substance use disorders (搜索) and our proprietary candidate in development for chronic cough (搜索)."
Dyer added that the company "can now evaluate a range of strategic options, including seeking new partnerships in the near term or advancing the programs further before partnering."
The GABAB PAM Mechanism
GABA is the main inhibitory neurotransmitter in the central and peripheral nervous systems and acts through two major receptor classes: the ionotropic GABAA receptor and the metabotropic GABAB receptor (搜索). GABAB receptors are widely expressed throughout the nervous system and play an important role in regulating neuronal excitability and neurotransmission.
The therapeutic potential of GABAB receptor (搜索) activation has been clinically demonstrated with baclofen, a selective GABAB receptor agonist that binds to the orthosteric GABA binding site. Baclofen is approved for the treatment of spasticity, including spasticity associated with multiple sclerosis and spinal cord injury, and has been clinically investigated and used off-label across a broader range of neurological and neuropsychiatric disorders, including alcohol use disorder and alcohol withdrawal, cocaine use disorder, gastroesophageal reflux disease, and reflux-associated chronic cough (搜索).
According to Addex, broader use of baclofen is constrained by aspects of its pharmacological and pharmacokinetic profile, including sedation and other central nervous system side effects, as well as the potential for reduced efficacy during chronic treatment. GABAB PAMs offer an alternative approach: rather than binding to the orthosteric GABA-binding site, they bind to a distinct allosteric site and enhance the receptor's response to endogenous GABA. This mechanism is intended to preserve the physiological and activity-dependent nature of GABAB receptor (搜索) signaling. By enhancing the effects of endogenous GABA, GABAB PAMs have the potential to provide greater pathway selectivity, improved tolerability and a reduced propensity for tolerance compared with direct orthosteric agonism.
Preclinical Data in Chronic Cough
In April 2026, Addex reported preclinical antitussive activity for its chronic cough (搜索) candidate in both a non-human primate model and a bleomycin-induced idiopathic pulmonary fibrosis-related cough model.
Broader Pipeline and Prior Setbacks
Addex's broader pipeline includes the Phase 2-ready mGlu5 negative allosteric modulator dipraglurant, which is being evaluated for development in brain injury recovery, including post-stroke and traumatic brain injury recovery. The company also holds a 20% equity interest in Neurosterix US Holdings LLC (搜索), a private spin-out advancing allosteric modulator programs including an M4 PAM for schizophrenia, psychosis and mood-related disorders, and a mGlu7 NAM for mood disorders. Addex has additionally invested in Stalicla (搜索), a private Swiss company pursuing a precision medicine approach for neurodevelopmental and neuropsychiatric disorders.
The rights reversion follows a difficult period for Addex-partnered programs. Johnson & Johnson discontinued development of an Addex-partnered PAM over poor data in a phase 2 epilepsy trial, and the earlier ADX71441 addiction program did not pan out. Indivior's August 2024 decision to take on responsibility for developing a second compound emerging from the partnership had been a show of faith in Addex at that time.
Indivior has also jettisoned another collaboration, a sustained-release prodrug of buprenorphine with Alar Pharmaceuticals (搜索), in April, as the company reeled from the phase 2 failure of its orexin-1 receptor antagonist for opioid use disorder.