Bimagrumab Trial Results for Lean Mass and Weight Loss

What the Phase 2 Trial Found on Lean Mass

Bimagrumab reduced lean-mass loss when added to semaglutide during a 48-week phase 2 clinical trial. The study design was a double-blind, placebo-controlled phase 2 trial named BELIEVE that enrolled 507 participants across nine randomized groups. Participants completed a 48-week primary period, which was followed by a 24-week open-label extension to week 72.

Study arms discussed here are placebo, bimagrumab at 30 mg/kg administered intravenously every 12 weeks, semaglutide at 2.4 mg administered weekly, and a high-dose combination of bimagrumab 30 mg/kg plus semaglutide 2.4 mg.

Dual-energy x-ray absorptiometry (DXA) measured body composition throughout the trial. At week 48, participants receiving semaglutide alone had a lean-mass change of −3.9 kg. Participants in the bimagrumab 30 mg/kg group had a lean-mass change of +0.4 kg. Those assigned to the high-dose combination had a lean-mass change of −1.3 kg, representing a smaller lean-mass loss than semaglutide alone.

Weight and Fat Mass Results

Total weight and body fat decreased across all active medication groups at week 48. Total weight change at week 48 was −3.3 kg in the placebo group, −9.3 kg in the bimagrumab 30 mg/kg group, −14.2 kg in the semaglutide 2.4 mg group, and −17.8 kg in the high-dose combination group.

Fat mass change at week 48 was −8.6 kg with bimagrumab alone, −9.6 kg with semaglutide alone, and −15.6 kg with the high-dose combination. The trial report did not list fat mass or lean mass figures for the placebo group.

Side Effects and Discontinuations

Adverse events in the phase 2 trial frequently involved muscle spasms, gastrointestinal symptoms, and skin reactions. Muscle spasms occurred in 73.7% of participants receiving bimagrumab alone and 63.6% of those in the combination group. Diarrhea was documented in 49.1% of participants receiving bimagrumab alone and 49.1% of participants in the combination group. Acne occurred in 43.9% of participants receiving bimagrumab alone and 52.7% of those receiving the combination. Nausea was reported in 46.4% of participants in the semaglutide group and 49.1% of those in the combination group.

Discontinuations due to adverse events varied across the trial arms. In the bimagrumab groups, discontinuation rates ranged from 14.0% to 21.4%. In the semaglutide groups, discontinuations ranged from 3.6% to 8.8%. In the combination groups, discontinuations ranged from 5.3% to 12.5%. In the placebo group, discontinuations due to adverse events were 3.6%.

See also: GLP-1 side effects.

Limits the Authors Note

The trial authors identified several limitations in the design and clinical findings of the study. Semaglutide was administered as an open-label medication because no matched placebo existed. The authors also noted that the intravenous schedule may have contributed to early laboratory abnormalities observed in participants.

Body composition measurements relied on dual-energy x-ray absorptiometry (DXA) rather than magnetic resonance imaging (MRI) to measure changes in muscle. In addition, the trial did not show a significant improvement in grip strength or patient-reported outcomes. The authors noted that this absence of physical performance improvement may have been due to the broad population studied rather than a cohort selected for baseline functional deficits.

Investigational Status

Bimagrumab is an investigational drug and is not an approved treatment. The published study report evaluated an investigational antibody and did not cover regulatory approval status. Readers should check current regulatory status with official health authorities.

The study categorizes bimagrumab as a myostatin inhibitor.

Questions for a Clinician

Questions regarding weight loss medications and body composition can be discussed with a medical provider. Individuals exploring treatment options can review clinical trial data with a healthcare professional. A doctor can evaluate medical history, assess approved therapies, and discuss risks associated with investigational compounds. Individuals can arrange a clinician consultation to discuss personal health questions.