Eli Lilly Halts Phase 2b Obesity Trial for Strategic Reasons

Eli Lilly has unexpectedly withdrawn a phase 2b obesity trial before patient enrollment began, citing "strategic business reasons." The study was designed to evaluate bimagrumab, an asset acquired through Lilly's $1.9 billion Versanis acquisition, both as a standalone treatment and in combination with the company's blockbuster GLP-1/GIP drug tirzepatide.

Trial Design and Initial Plans

The now-terminated study, initially filed in March, aimed to enroll 180 participants with obesity or overweight plus Type 2 diabetes. The trial was structured with nine arms to test various regimens of bimagrumab and tirzepatide, the active ingredient in Lilly's Mounjaro and Zepbound medications.

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, potentially offering a more comprehensive approach to weight management.

Timeline of Trial Status Changes

The trajectory of the trial's cancellation unfolded over several months:

1. March 2025: Lilly files to initiate the phase 2b study
2. June 2025: Trial status changed from "not yet recruiting" to "active, not recruiting"
3. September 2025: Final status update to "withdrawn" due to strategic business reasons

While Lilly has terminated this specific trial, it's worth noting that a separate phase 2 study investigating bimagrumab and tirzepatide in patients without diabetes is still actively enrolling participants, according to ClinicalTrials.gov.

Implications and Recent Data

The decision to withdraw the trial comes on the heels of promising data from a phase 2 study that tested bimagrumab in combination with semaglutide, Novo Nordisk's GLP-1 drug marketed as Ozempic and Wegovy. Results presented at the American Diabetes Association's Scientific Sessions in June demonstrated a significant increase in the proportion of weight loss attributed to fat when bimagrumab was combined with semaglutide.

Researchers reported that while fat accounted for approximately 72% of weight loss in patients taking semaglutide alone, this figure surpassed 90% in the combination cohort. These findings highlighted the potential synergistic effects of combining bimagrumab with GLP-1 receptor agonists.

Despite these encouraging results, Lilly's decision to halt the new trial raises questions about the company's strategic direction in the highly competitive obesity treatment landscape. The pharmaceutical giant has not provided further details regarding the reasoning behind the trial's termination or its plans for bimagrumab's future development.