AbbVie to Acquire Gilgamesh Pharmaceuticals' Bretisilocin, a Novel, Investigational Therapy for Major Depressive Disorder, Expanding Psychiatry Pipeline

Rhea-AI Summary

AbbVie (NYSE:ABBV) has announced a definitive agreement to acquire Gilgamesh Pharmaceuticals' lead asset bretisilocin (GM-2505), a novel psychedelic compound in Phase 2 development for major depressive disorder (MDD), for up to $1.2 billion in upfront and milestone payments.

The Phase 2a study demonstrated significant results, with bretisilocin showing a -21.6 point reduction in MADRS depression score versus -12.1 points for the comparator. The compound features a shorter duration of psychoactive experience while maintaining extended therapeutic benefits, addressing key limitations of existing psychedelic treatments.

As part of the deal, Gilgamesh will spin off into Gilgamesh Pharma Inc., retaining its employees and other programs, including its existing collaboration with AbbVie from 2024.

Positive

• None.

Negative

• High acquisition cost of $1.2 billion for an early-stage (Phase 2) asset
• Regulatory uncertainty in the emerging psychedelics drug space
• Complex transaction structure with spin-off requirements

Insights

Neuropharmacology Specialist

AbbVie's $1.2B acquisition of Gilgamesh's bretisilocin shows promising potential in depression treatment with shorter psychedelic experience duration.

This acquisition represents a significant advancement in psychedelic medicine for treating depression. Bretisilocin (GM-2505) addresses a critical limitation of existing psychedelic compounds - their lengthy psychoactive duration - while maintaining therapeutic efficacy. The Phase 2a results are particularly noteworthy, showing a -21.6 point change from baseline in MADRS scores compared to -12.1 for the low-dose comparator (p = 0.003). This 78.5% greater improvement is clinically meaningful in the depression treatment landscape.

What makes bretisilocin distinctive is its dual mechanism as both a 5-HT2A receptor agonist and serotonin releaser. Most current psychedelic compounds in development primarily target the 5-HT2A receptor alone. This dual-action approach may explain its robust efficacy while maintaining a shorter psychoactive window - solving one of the major practical barriers to psychedelic therapy implementation.

The safety profile appears promising with no serious adverse events reported in Phase 2a testing. For context, a change of >10 points on the MADRS scale is generally considered clinically significant, making the -21.6 point improvement particularly impressive for a single-dose treatment. Most conventional antidepressants require weeks of daily dosing to achieve comparable results and rarely demonstrate this magnitude of effect. If bretisilocin maintains this efficacy profile through larger trials, it could potentially represent a paradigm shift in depression treatment.

Pharmaceutical Business Analyst

AbbVie's acquisition of bretisilocin for up to $1.2 billion represents a strategic move into the emerging psychedelic medicine space, specifically targeting the large and underserved depression market. The deal structure is noteworthy - it's asset-specific rather than a complete company acquisition, allowing Gilgamesh to spin off its remaining pipeline and continue operations as Gilgamesh Pharma Inc.

This transaction builds upon an existing 2024 collaboration between the companies, suggesting a thoughtful, staged approach to partnership rather than an impulsive acquisition. For AbbVie, this acquisition complements their existing neuroscience portfolio while providing entry into the rapidly evolving psychedelic medicine sector without the full risk of acquiring an entire early-stage company.

The $1.2 billion valuation for a single Phase 2 asset indicates high confidence in bretisilocin's clinical and commercial potential. The milestone-based structure (upfront payment plus development milestones) aligns incentives while managing AbbVie's financial risk. This approach is becoming increasingly common for large pharma companies seeking to bolster pipelines without assuming the full risk of early-stage assets.

For Gilgamesh, this deal provides substantial capital while allowing continued development of their remaining pipeline. Significantly, they maintain the existing collaboration with AbbVie, suggesting a productive relationship and potential for future deals. This strategic choice to divest their lead asset while continuing operations shows disciplined portfolio management, particularly for a company at their stage of development.

• Gilgamesh's lead asset, bretisilocin (GM-2505), is a potential best-in-class psychedelic compound currently in Phase 2 development for the treatment of major depressive disorder (MDD).
• Bretisilocin is a novel, short-acting serotonin (5-HT)2A receptor agonist and 5-HT releaser.

NORTH CHICAGO, Ill. and NEW YORK, Aug. 25, 2025 /PRNewswire/ -- AbbVie (NYSE: ABBV) and Gilgamesh Pharmaceuticals Inc. ("Gilgamesh") today announced a definitive agreement under which AbbVie will acquire Gilgamesh's lead investigational candidate, currently in clinical development for the treatment of patients with moderate-to-severe major depressive disorder (MDD).

Psychedelic compounds, including 5-HT_2A receptor agonists, have gained recognition as potential treatments for mental health disorders, such as MDD, because of their demonstrated rapid, robust and durable antidepressant effects. However, existing agents in this class are hampered by their long duration of psychoactive experience.

Bretisilocin, a 5-HT_2A receptor agonist and 5-HT releaser, is a novel, next-generation psychedelic compound designed to address development challenges observed within this class of compounds. Bretisilocin has been shown to exert a shorter duration of psychoactive experience, while retaining an extended therapeutic benefit.

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 low dose active comparator, as measured by the Montgomery-Åsberg Depression Rating Scale (MADRS) total score. At Day 14, a single dose (10mg) of bretisilocin demonstrated robust antidepressant effect with a -21.6 point change from baseline in MADRS total score compared to a -12.1 point change from baseline for the low dose (1mg) active comparator (p = 0.003). Bretisilocin was well tolerated with no serious adverse events.

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

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

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, as part of the transaction, Gilgamesh will spin off a new entity that will operate under the name Gilgamesh Pharma Inc. to hold its employees and other programs, including its oral NMDA receptor antagonist blixeprodil (GM-1020), cardio-safe ibogaine analog, M1/M4 agonist program and existing collaboration with AbbVie. The transaction is subject to customary closing conditions.

This transaction builds upon AbbVie and Gilgamesh's 2024 collaboration and option-to-license agreement to advance the development of next-generation therapies for the treatment of psychiatric disorders. This option-to-license remains in effect and will be transferred to Gilgamesh Pharma Inc. in connection with the spin-out.

Advisors

For AbbVie, Covington & Burling LLP is acting as legal counsel. For Gilgamesh, Centerview Partners LLC is acting as exclusive financial advisor and Ropes & Gray LLP is acting as legal counsel. 

About AbbVie

AbbVie's mission is to discover and deliver innovative medicines and solutions that solve serious health issues today and address the medical challenges of tomorrow. We strive to have a remarkable impact on people's lives across several key therapeutic areas including immunology, oncology, neuroscience and eye care – and products and services in our Allergan Aesthetics portfolio. For more information about AbbVie, please visit us at www.abbvie.com. Follow @abbvie on LinkedIn, Facebook, Instagram, X (formerly Twitter) and YouTube.

About Gilgamesh Pharmaceuticals

Gilgamesh Pharmaceuticals is a clinical-stage neuroscience biotech developing innovative, best-in-class new chemical entities that transform the treatment paradigm of psychiatric diseases, moving away from symptom management towards rapid-acting and durable therapies. Gilgamesh designs therapies acting through precedented mechanisms, which are optimized for safety, efficacy, and patient access. Gilgamesh is advancing a diverse portfolio of programs, including blixeprodil (GM-1020), an oral NMDA receptor antagonist that is completing a Phase 2a study in Major Depressive Disorder in 2025. Learn more about the company's therapeutic pipeline at https://www.gilgameshpharmaceutical.com/. Follow Gilgamesh Pharmaceuticals on LinkedIn and X.

Forward-Looking Statements 

Some statements in this news release are, or may be considered, forward-looking statements for purposes of the Private Securities Litigation Reform Act of 1995. The words "believe," "expect," "anticipate," "project" and similar expressions and uses of future or conditional verbs, generally identify forward-looking statements. AbbVie cautions that these forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially from those expressed or implied in the forward-looking statements. Such risks and uncertainties include, but are not limited to, challenges to intellectual property, competition from other products, difficulties inherent in the research and development process, adverse litigation or government action, changes to laws and regulations applicable to our industry, the impact of global macroeconomic factors, such as economic downturns or uncertainty, international conflict, trade disputes and tariffs, and other uncertainties and risks associated with global business operations. Additional information about the economic, competitive, governmental, technological and other factors that may affect AbbVie's operations is set forth in Item 1A, "Risk Factors," of AbbVie's 2024 Annual Report on Form 10-K, which has been filed with the Securities and Exchange Commission, as updated by its Quarterly Reports on Form 10-Q and in other documents that AbbVie subsequently files with the Securities and Exchange Commission that update, supplement or supersede such information. AbbVie undertakes no obligation, and specifically declines, to release publicly any revisions to forward-looking statements as a result of subsequent events or developments, except as required by law.

 

AbbVie Media: Liz Tang, Ph.D. Liz.Tang@abbvie.com    Gligamesh Media: media@gilgameshpharmaceutical.com

AbbVie Investors: Liz Shea Liz.Shea@abbvie.com    Gilgamesh Investors: Laszlo Kiss, Ph.D. laszlo@gilgameshpharmaceutical.com

 

 

View original content to download multimedia: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

SOURCE AbbVie

FAQ

What is the value of AbbVie's acquisition of Gilgamesh's bretisilocin?

AbbVie will acquire bretisilocin for up to $1.2 billion, which includes upfront payment and development milestones.

What are the Phase 2a clinical trial results for bretisilocin in treating depression?

A single 10mg dose showed a -21.6 point reduction in MADRS depression score at Day 14, compared to -12.1 points for the low dose comparator, with statistical significance (p=0.003).

How does bretisilocin differ from other psychedelic treatments for depression?

Bretisilocin is designed to have a shorter duration of psychoactive experience while maintaining extended therapeutic benefits, addressing a key limitation of existing psychedelic treatments.

What happens to Gilgamesh Pharmaceuticals after the ABBV acquisition?

Gilgamesh will spin off into a new entity called Gilgamesh Pharma Inc., which will retain employees and other programs, including the oral NMDA receptor antagonist and existing AbbVie collaboration.

What is bretisilocin's mechanism of action for treating depression?

Bretisilocin is a novel 5-HT2A receptor agonist and 5-HT releaser, designed as a next-generation psychedelic compound for treating major depressive disorder (MDD).