AbbVie to Acquire Gilgamesh's Antidepressant Bretisilocin in $1.2 Billion Deal

AbbVie has agreed to acquire Gilgamesh Pharmaceuticals’ lead investigational therapy for major depressive disorder, bretisilocin, in a deal valued at up to $1.2 billion. Bretisilocin is a novel serotonin 5‑HT2A receptor agonist and serotonin releaser that delivers shorter psychoactive effects while offering enduring therapeutic benefits.

This acquisition extends AbbVie’s reach in psychiatric treatment development following a phase failure in schizophrenia—part of the company’s broader strategy to revitalize its neuroscience portfolio amid biosimilar pressures on its blockbuster Humira. Gilgamesh will spin off its remaining programs—including NMDA antagonist, ibogaine analog, and M1/M4 agonist pipelines—into a new company, Gilgamesh Pharma Inc.

This definitive agreement builds on an earlier partnership from May 2024 in which AbbVie paid an upfront $65 million and agreed to up to $1.95 billion in potential milestone and option payments to Gilgamesh for psychiatric-focused neuroplastogen research. Together, these moves reinforce AbbVie’s commitment to exploring psychedelic-inspired therapies as part of the growing mental health treatment landscape.