Lilly's bimagrumab-semaglutide combo posted a 17.8 kg weight loss at week 48
The Phase 2 obesity trial's posted results show high-dose bimagrumab plus semaglutide beat either drug alone, with results already public a year before this listing.
Executive Summary
- A completed Phase 2 obesity trial shows Eli Lilly's bimagrumab, an antibody that blocks a muscle-growth-limiting receptor, added weight loss on top of semaglutide rather than simply matching it.
- The combination's edge over semaglutide alone tests whether targeting muscle and fat biology separately from the incretin pathway can push weight loss past what GLP-1 drugs already deliver.
- The result lands in a field crowded with incretin-based obesity programs and thin on activin-pathway competitors, with bimagrumab's own follow-on combination trial already withdrawn once.
- The posted data give the combination a clinical rationale to advance, but Lilly has not disclosed a registrational plan or next-phase design for the pairing.
The trial
The 507-patient study (NCT05616013) tested bimagrumab, an antibody that blocks the activin receptor ACVR2B (a signaling pathway that limits muscle growth), alone and combined with semaglutide in adults with obesity or overweight. Enrollment ran from November 2022 with completion in June 2025, and results were posted to the registry on July 18, 2025. The primary endpoint was change from baseline in body weight at week 48. NCT05616013Safety and Efficacy of Bimagrumab and Semaglutide in Adults Who Are Overweight or ObeseNCT05616013
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
The result
At week 48, bimagrumab 30 mg/kg alone reduced body weight by 9.3 kg versus 3.3 kg for placebo, semaglutide 2.4 mg alone produced a 14.2 kg reduction, and the high-dose combination of both drugs produced a 17.8 kg reduction. All active treatment arms showed weight reductions against placebo (P<0.001). The combination arm's advantage over semaglutide alone, roughly 3.6 kg, is the finding that matters here: bimagrumab did not just replicate incretin-driven weight loss, it added to it. EliEli Lilly Results Posted for Phase 2 Trial of Bimagrumab and Semaglutide in ObesityJul 18, 2025
How it was done
The trial randomized participants across nine arms combining three semaglutide doses (none, 1.0 mg, 2.4 mg) with placebo or two bimagrumab doses (10 mg/kg, 30 mg/kg), given intravenously for bimagrumab and subcutaneously for semaglutide, with double-blinding on the bimagrumab/placebo assignment. The core treatment period ran 48 weeks, followed by an open-label extension to week 72 in which placebo and low-dose bimagrumab participants switched to the 30 mg/kg dose. Analysis used a mixed-model repeated-measures approach with country and sex as covariates. NCT05616013Safety and Efficacy of Bimagrumab and Semaglutide in Adults Who Are Overweight or ObeseNCT05616013
Competitive position
Obesity drug development is dominated by GLP-1 receptor agonists: Lilly's own tirzepatide and retatrutide, Novo Nordisk's semaglutide and CagriSema, and other incretin programs account for most of the active trials in the indication. Bimagrumab's mechanism, blocking the ACVR2B activin receptor, has one other Phase 2 comparator in the same target class, Novartis's bimagrumab study in type 2 diabetes, and no other industry trial pairs an activin-pathway drug with an incretin in obesity. Against a field where GLP-1 monotherapy already drives double-digit percentage weight loss, the bar this combination has to clear is durable separation from semaglutide alone, not merely matching it, and the posted 17.8 kg versus 14.2 kg gap clears that bar at 48 weeks.
Program history
Lilly, which acquired bimagrumab through its purchase of Versanis Bio in 2023, has one other bimagrumab trial in obesity still active (NCT06643728, pairing bimagrumab with tirzepatide) and one withdrawn: a bimagrumab-tirzepatide study in patients with obesity or overweight and type 2 diabetes was withdrawn in June 2025. The subject trial changed its primary completion date four times and its enrollment target three times over its run, a registry-churn pattern the operational model attributes to routine amendment activity rather than a threat to the result, since enrollment landed exactly at its 507-patient target with no shortfall. NCT05616013Safety and Efficacy of Bimagrumab and Semaglutide in Adults Who Are Overweight or ObeseNCT05616013
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.