AbbVie Acquires Gilgamesh Pharmaceuticals' Bretisilocin for $1.2B to Boost Depression Treatment

AbbVie has acquired the rights to bretisilocin, a novel psychedelic compound, from Gilgamesh Pharmaceuticals for up to $1.2 billion. The compound is being developed for treating major depressive disorder and has shown rapid and durable antidepressant effects in a phase II study. AbbVie has been on an acquisition spree in the neuroscience space to bolster its early-stage pipeline.

AbbVie Inc. (NYSE: ABBV) has entered into a definitive agreement to acquire Gilgamesh Pharmaceuticals Inc.'s lead investigational candidate, bretisilocin, in a deal valued at up to $1.2 billion. The agreement includes an upfront payment and potential milestone payments tied to the development and commercialization of the drug [1].

Bretisilocin, a novel psychedelic compound, is currently in Phase 2 development for the treatment of major depressive disorder (MDD). The compound is a short-acting serotonin (5-HT)2A receptor agonist and 5-HT releaser, designed to address the long duration of psychoactive experience observed in existing psychedelic compounds [3].

Positive topline results from a Phase 2a study of bretisilocin in MDD were recently announced, demonstrating a clinically impactful and statistically significant reduction in severity of depressive symptoms versus a low dose active comparator [3]. At Day 14, a single dose (10mg) of bretisilocin showed a robust antidepressant effect, with a -21.6 point change from baseline in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score compared to a -12.1 point change from baseline for the low dose (1mg) active comparator (p = 0.003) [3].

This acquisition aligns with AbbVie's ongoing strategy to expand its pipeline of innovative treatments in the neuroscience space. The company has been on an acquisition spree to bolster its early-stage pipeline, reflecting the growing interest in securing promising pharmaceutical candidates at various stages of development [2].

Under the terms of the agreement, AbbVie will acquire Gilgamesh's bretisilocin program for up to $1.2 billion, inclusive of an upfront payment and development milestones. Additionally, Gilgamesh will spin off a new entity, Gilgamesh Pharma Inc., to hold its employees and other programs [1].

References:
[1] https://news.abbvie.com/2025-08-25-AbbVie-to-Acquire-Gilgamesh-Pharmaceuticals-Bretisilocin,-a-Novel,-Investigational-Therapy-for-Major-Depressive-Disorder,-Expanding-Psychiatry-Pipeline
[2] https://www.geneonline.com/abbvie-to-acquire-gilgamesh-pharmaceuticals-bretisilocin-in-1-2-billion-deal/
[3] https://www.prnewswire.com/news-releases/abbvie-to-acquire-gilgamesh-pharmaceuticals-bretisilocin-a-novel-investigational-therapy-for-major-depressive-disorder-expanding-psychiatry-pipeline-302537266.html