AbbVie to Acquire Gilgamesh’s Bretisilocin, Boosting Psychiatry Pipeline for Depression

AbbVie and Gilgamesh Pharmaceuticals have entered into a definitive agreement under which AbbVie will acquire Gilgamesh’s lead investigational candidate, bretisilocin, a next-generation psychedelic compound being developed for major depressive disorder (MDD). The deal is valued at up to $1.2 billion, including upfront and milestone payments.

Bretisilocin is a 5-HT2A receptor agonist and 5-HT releaser, designed to offer the rapid and durable antidepressant effects seen with psychedelic therapies, but with a shorter psychoactive duration—a key development challenge in the class.

Recent Phase 2a trial results showed that a single 10mg dose of bretisilocin led to a -21.6 point reduction in depression severity (measured by the MADRS scale) at Day 14, compared to a -12.1 point reduction for a 1mg active comparator, a statistically significant difference (p = 0.003). The treatment was well tolerated, with no serious adverse events reported.

“The field of psychiatry represents one of the most challenging areas in medicine,” said Dr. Roopal Thakkar, AbbVie’s EVP and Chief Scientific Officer. “This acquisition underscores our commitment to innovative approaches that can offer hope to patients with limited treatment options.”

As part of the transaction, Gilgamesh will spin off its remaining pipeline and employees into a new entity, Gilgamesh Pharma Inc. This includes other programs such as its oral NMDA receptor antagonist blixeprodil, a cardio-safe ibogaine analog, and a muscarinic M1/M4 agonist program. An existing collaboration and option-to-license agreement between AbbVie and Gilgamesh—originally signed in 2024—will transfer to Gilgamesh Pharma Inc.

Gilgamesh CEO Dr. Jonathan Sporn called AbbVie the “ideal partner” to advance bretisilocin into late-stage development, citing the company’s leadership in neuroscience and commitment to mental health innovation.

The transaction is subject to customary closing conditions and marks a significant step forward in AbbVie’s strategy to broaden its psychiatry and neuroscience portfolio.