Eli Lilly Halts Phase 2b Obesity Trial for Bimagrumab, Citing Strategic Reasons
Pharmaceutical giant Eli Lilly has unexpectedly withdrawn a phase 2b clinical trial for its obesity treatment bimagrumab, an asset acquired through its $1.9 billion acquisition of Versanis. The company cited "strategic business reasons" for the decision, which comes before any patients were enrolled in the study.
Trial Design and Objectives
The now-terminated trial was designed to evaluate bimagrumab both as a standalone treatment and in combination with Lilly's blockbuster GLP-1/GIP drug tirzepatide. The study aimed to enroll 180 participants with obesity or overweight individuals with Type 2 diabetes, featuring nine arms to test various regimens of the two drugs.
Bimagrumab, an antibody that binds to activin type II A and B receptors, works by blocking activin and myostatin signaling. This mechanism of action was expected to complement the effects of tirzepatide, which is the active ingredient in Lilly's approved drugs Mounjaro and Zepbound.
Timeline of Events
The trajectory of the trial's cancellation unfolded over several months:
- March 2025: Lilly initially filed to conduct the study.
- June 2025: The trial's status on ClinicalTrials.gov changed from "not yet recruiting" to "active, not recruiting."
- September 2025: Lilly updated the trial status to "withdrawn," confirming its termination.
Ongoing Research and Previous Results
Despite this setback, Lilly continues to explore bimagrumab's potential. A separate phase 2 trial investigating the combination of bimagrumab and tirzepatide in patients without diabetes is still actively enrolling participants.
The decision to withdraw the trial comes on the heels of promising data from a phase 2 study that tested bimagrumab in combination with Novo Nordisk's semaglutide (sold as Ozempic and Wegovy). Results presented at the American Diabetes Association's Scientific Sessions in June showed a "very striking difference" in the proportion of weight loss attributed to fat mass reduction when the drugs were combined.
In the semaglutide monotherapy arm, fat accounted for approximately 72% of weight loss. This figure increased to over 90% in the combination therapy group, highlighting the potential synergistic effects of combining bimagrumab with GLP-1 receptor agonists.
References
- Eli Lilly withdraws phase 2b trial of $1.9B obesity bet before starting enrollment
Eli Lilly has pulled the plug on a phase 2b obesity trial before enrolling a single patient, citing “strategic business reasons.” The study was designed to test bimagrumab, an asset Lilly acquired in its $1.9 billion Versanis buyout, as a single agent and in combination with blockbuster GLP-1/GIP drug tirzepatide.
Explore Further
What are the strategic business reasons that led Eli Lilly to halt the phase 2b trial for bimagrumab in combination with tirzepatide?
What are the potential implications of Eli Lilly's ongoing phase 2 trial for bimagrumab in combination with tirzepatide in non-diabetic patients?
How does bimagrumab's mechanism of action compare to other obesity treatments currently in clinical development or on the market?
What lessons can be drawn from the promising phase 2 results of bimagrumab and semaglutide in achieving greater fat mass reduction?
What is the potential market size and competitive landscape for bimagrumab as a combination therapy with GLP-1 receptor agonists like tirzepatide or semaglutide?