Addex Therapeutics Ltd. announced that it has extended its research collaboration agreement with Indivior PLC. As part of the extension, Indivior has committed $4 million of new funding to advance development of selected novel oral gamma-aminobutyric acid subtype B (GABAB) positive allosteric modulator (PAM) drug candidates discovered by Addex. The new funding will be used to prepare drug candidates for both Indivior's substance use disorder program and Addex's proprietary Charcot-Marie-Tooth type 1A neuropathy program, which are both expected to start IND enabling studies in 2022.

Activation of gamma-aminobutyric acid subtype B (GABAB) receptor, a Family C class of GPCR, is clinically & commercially validated. The generic GABAB receptor agonist, baclofen, is marketed for spasticity and some spinal cord injuries, and used for overactive bladder (OAB), but it is not commonly used due to a variety of side effects and rapid clearance. Potent, selective oral positive allosteric modulators (PAM) that potentiate GABA responses at the GABAB receptor, rather than an orthosteric agonist at the GABAB receptor like baclofen, only act when the natural ligand (GABA) activates the receptor, therefore respecting the physiological cycle of activation.

It has been proposed that PAMs produce less adverse effects and could lead to less tolerance than direct agonists (May and Christopoulos 2003; Langmead and Christopoulos 2006; Perdona et al. 2011; Urwyler 2011; Gjoni et al., 2008; Ahnaou et al).