Addex Therapeutics and Indivior have extended their research agreement for the drug discovery of novel oral gamma-aminobutyric acid subtype B (GABAB) positive allosteric modulator (PAM) drug candidates for treating substance use disorders.

The new agreement will extend until 30 June 2024, and Addex will receive SFr2.7m ($3m) from Indivior for drug research and discovery. Furthermore, Addex will retain exclusive rights to an independent GABAB PAM programme for treating chronic cough.

The agreement started in 2018, with an initial upfront payment of $5m and milestone-based payments of up to $330m. The companies have extended the partnership multiple times with additional payments from Indivior.

Addex CEO Tim Dyer said: “We are excited to continue working closely with Indivior in this promising application of our allosteric modulator discovery platform."

The generic versions of GABAB receptor agonists (baclofen) have been used to treat alcohol use disorder, Charcot-Marie-Tooth disease type 1A (CMT1A), chronic cough, and pain.

Addex also raised $5m in funding for providing a cash runway to achieve development milestones for drug partnerships with Janssen and Indivior, as per the 5 April 2023 press release.

Addex's ADX71149, a PAM of metabotropic glutamate receptor 2 (mGlu2 PAM), developed in collaboration with Janssen Pharmaceuticals, is in a Phase IIa proof of concept clinical trial (NCT04836559) for the treatment of epilepsy.

Following a review of cohort I data by the Independent Interim Review Committee in May 2023, the companies plan to continue the study. The study’s cohort I has progressed to Part II and cohort II is currently recruiting patients.

Other investigative drugs for substance use disorder treatment include Phase I/II (NCT05322954) Revive Therapeutics’ oral psilocybin for the treatment of methamphetamine use disorder (MUD) and Phase III Almatica Pharma’s ALM-006.