AbbVie to Acquire Gilgamesh Pharmaceuticals' Bretisilocin for Up to $1.2 Billion

AbbVie has agreed to acquire Gilgamesh Pharmaceuticals' bretisilocin, a novel therapy for major depressive disorder, for up to $1.2 billion. The Phase 2a study showed a significant reduction in depression score with a single 10mg dose. Gilgamesh will spin off into a new entity and retain its employees and other developmental programs. This acquisition expands AbbVie's psychiatry pipeline and addresses the need for innovative solutions in the field.

AbbVie Inc. (NYSE: ABBV) has announced a definitive agreement to acquire Gilgamesh Pharmaceuticals Inc.'s lead investigational candidate, bretisilocin, for up to $1.2 billion. The deal, which includes an upfront payment and development milestones, underscores AbbVie's commitment to expanding its psychiatry pipeline and addressing the significant need for innovative solutions in the field.

Bretisilocin, a novel, short-acting 5-HT2A receptor agonist and 5-HT releaser, is currently in Phase 2 development for the treatment of major depressive disorder (MDD). Recent Phase 2a study results demonstrated a clinically impactful and statistically significant reduction in depressive symptoms compared to a low-dose active comparator. A single 10mg dose 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 for the low-dose active comparator (p = 0.003) [1].

The acquisition also includes the option-to-license agreement between AbbVie and Gilgamesh Pharmaceuticals, which will be transferred to Gilgamesh Pharma Inc., a new entity that will retain employees and other developmental programs, such as the oral NMDA receptor antagonist blixeprodil (GM-1020) [2]. This transaction builds upon AbbVie and Gilgamesh's 2024 collaboration and option-to-license agreement for next-generation psychiatric treatments.

Roopal Thakkar, M.D., executive vice president, research and development, and chief scientific officer at AbbVie, 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."

Jonathan Sporn, M.D., chief executive officer at Gilgamesh Pharmaceuticals, added, "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."

The acquisition is subject to customary closing conditions and is expected to strengthen AbbVie's position in the rapidly evolving field of psychedelic therapies for mental health disorders.

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.pharmaceutical-technology.com/news/abbvie-signs-gilgamesh-bretisilocin/