AbbVie has signed a definitive agreement to acquire Gilgamesh Pharmaceuticals' lead investigational candidate, bretisilocin, for up to $1.2bn, including an upfront payment and development milestones.

The therapy is undergoing clinical development for patients suffering from moderate-to-severe major depressive disorder (MDD).

Bretisilocin, a 5-hydroxytryptamine receptor 2A (5-HT2A) agonist and 5-HT releaser, has been designed to reduce the duration of psychoactive experience while maintaining therapeutic benefit.

Positive topline data from a Phase IIa study in MDD demonstrated statistically significant reductions in depressive symptoms compared with a low-dose active comparator.

AbbVie research and development executive vice-president, and chief scientific officer Roopal Thakkar stated: “The field of psychiatry represents one of the most challenging areas in medicine, with a significant need for innovative solutions.

“This acquisition underscores our commitment to broadening and enhancing psychiatric care by investing in novel treatment approaches with the potential to reach patients for whom other treatments have been ineffective. We look forward to advancing bretisilocin to late-stage clinical development.”

Gilgamesh will also establish a new entity, Gilgamesh Pharma, to retain its employees and other programmes such as its oral N-methyl-D-aspartate receptor antagonist blixeprodil (GM-1020).

The companies have confirmed that the deal is still subject to customary closing conditions.

Gilgamesh Pharmaceuticals CEO Jonathan Sporn stated: “AbbVie's leadership in neuroscience and commitment to advancing innovative treatments make them the ideal partner to advance bretisilocin rapidly forward while enabling Gilgamesh to continue pursuing our broader mission of developing novel, transformative therapies for complex mental health and neurological conditions.”  

This transaction builds upon their 2024 collaboration and option-to-license deal for next-generation psychiatric treatments, which will be transferred to Gilgamesh Pharma following the spin-out.