Geneva-based Addex Therapeutics (Nasdaq: ADXN) has regained full global rights to its GABAB positive allosteric modulator (PAM) portfolio from Indivior, ending a collaboration that began in 2018. The agreement had included up to USD 330 million in potential milestone payments, but Addex said no milestones were triggered before the rights reverted.
The returned portfolio includes an unnamed small-molecule GABAB PAM candidate for substance use disorders that completed IND-enabling studies under Indivior. Addex also retains a separate wholly owned GABAB PAM program for chronic cough that the company said is ready to enter IND-enabling development.
GABAB PAMs enhance the receptor’s response to endogenous GABA rather than directly activating it. Addex has positioned the approach as a way to modulate GABAB signaling while potentially improving tolerability relative to direct receptor agonism.
In April 2026, Addex reported preclinical antitussive activity for its chronic cough candidate in both a non-human primate model and a bleomycin-induced idiopathic pulmonary fibrosis-related cough model. The company said it will now evaluate strategic options for the returned portfolio, including seeking new partners or advancing the programs further before partnering.