Bimagrumab: Research & Studies
Scientific evidence, clinical trials, and research findings
๐TL;DR
- โข3 clinical studies cited
- โขOverall evidence level: moderate
- โข7 research gaps identified
Research Studies
Effect of bimagrumab vs placebo on body fat mass among adults with type 2 diabetes and obesity: a phase 2 randomized clinical trial
Heymsfield SB, Coleman LA, Miller R, Rooks DS, Laurent D, Petricoul O, Praestgaard J, Swan T, Wade T, Perry RG, Gilberg F, Chen P (2021) โข JAMA Network Open
Landmark Phase 2 RCT of 75 adults with T2D and obesity (BMI 28-40) randomized to bimagrumab 10 mg/kg IV every 4 weeks or placebo for 48 weeks. Bimagrumab produced simultaneous fat mass loss (20.5%, -7.5 kg) and lean mass gain (3.6%, +1.70 kg) vs placebo (-0.5% fat, -0.8% lean). HbA1c improved by 0.76% from baseline. This dual body composition effect was unprecedented for a single therapeutic agent.
Key Findings
- Fat mass decreased 20.5% (-7.5 kg) with bimagrumab vs 0.5% with placebo at week 48
- Lean mass increased 3.6% (+1.70 kg) with bimagrumab vs decreased 0.8% with placebo
- HbA1c improved by 0.76% from baseline in the bimagrumab group
- Waist circumference decreased significantly compared to placebo
- Effects were independent of caloric restriction (both groups received diet and exercise counseling)
Limitations: Small sample size (n=75). Single dose level tested (10 mg/kg). 48-week duration may not capture long-term effects. Mostly male participants (60%). T2D population may not generalize to non-diabetic obesity.
Safety and efficacy of intravenous bimagrumab in inclusion body myositis (RESILIENT): a randomised, double-blind, placebo-controlled phase 2b trial
Amato AA, Sivakumar K, Gober N, David WS, Salajegheh M, Praestgaard J, Lach-Trifilieff E, Trendelenburg AU, Laurent D, Glass DJ, Roubenoff R, Tseng BS, Greenberg SA (2019) โข Lancet Neurology
The largest clinical trial in IBM (n=251) at 38 sites. Participants randomized 1:1:1:1 to bimagrumab 10, 3, or 1 mg/kg or placebo IV Q4W for 52 weeks. The primary endpoint (6-minute walk distance) was not met at any dose. Bimagrumab showed a good safety profile and increased lean mass, but failed to translate lean mass gains into functional improvement.
Key Findings
- Primary endpoint (6-minute walk distance) not met at any dose vs placebo at week 52
- Good safety profile across all dose levels relative to placebo
- Increased lean body mass was observed but did not correlate with improved physical function
- Self-reported physical functioning (sIFA) showed preservation at 10 mg/kg vs placebo
Limitations: Failed primary endpoint despite increased lean mass. Functional endpoints may not capture bimagrumab benefits in IBM. Disease heterogeneity and slow progression complicate trial design. 52-week duration may be insufficient for this slowly progressive disease.
Treatment of sarcopenia with bimagrumab: results from a phase II, randomized, controlled, proof-of-concept study
Rooks D, Praestgaard J, Hariry S, Laurent D, Petricoul O, Perry RG, Lach-Trifilieff E, Roubenoff R (2017) โข Journal of the American Geriatrics Society
Phase 2 proof-of-concept in 40 community-dwelling older adults (65+) with sarcopenia (gait speed 0.4-1.0 m/s). Participants received bimagrumab 30 mg/kg IV or placebo. Over 16 weeks, bimagrumab increased muscle mass and strength. Those with slow baseline walking speed showed improved mobility.
Key Findings
- Increased muscle mass and strength in sarcopenic older adults over 16 weeks
- Improved mobility in participants with slow baseline walking speed
- Well-tolerated in elderly population at 30 mg/kg dose
Limitations: Very small sample size (n=40). Short duration (16 weeks). Single dose level. Proof-of-concept only. No long-term follow-up data.
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๐Research Gaps & Future Directions
- โขNo Phase 3 registration trial completed for any indication (IBM RESILIENT was Phase 2b/3 but failed primary endpoint)
- โขBELIEVE Phase 2b combination data with semaglutide demonstrates concept but Phase 3 confirmation needed
- โขLong-term safety beyond 48-52 weeks not well characterized
- โขOptimal dosing for obesity/body composition indication not fully established
- โขEffects on reproductive hormones and fertility not comprehensively studied despite TGF-beta superfamily involvement in reproduction
- โขCardiovascular outcome data lacking despite metabolic improvements
- โขOne tirzepatide combination trial terminated by Lilly in 2025 for strategic reasons, creating uncertainty about development path
Research Overview#
Bimagrumab has an extensive clinical trial program spanning multiple indications. Unlike most entries on this site, bimagrumab has been evaluated in well-designed, multi-center, placebo-controlled clinical trials with hundreds of participants. The evidence base is substantially stronger than most peptides, though no indication has yet progressed to regulatory approval.
Body Composition and Obesity#
Phase 2 RCT in T2D and Obesity (JAMA Network Open 2021)#
Heymsfield et al. (PMID 33439265) conducted the landmark study that repositioned bimagrumab from rare disease to metabolic medicine.
Design: 75 adults with T2D and BMI 28-40, randomized to bimagrumab 10 mg/kg IV Q4W or placebo for 48 weeks with diet and exercise counseling.
Key Results:
| Outcome | Bimagrumab | Placebo |
|---|---|---|
| Fat mass change | -20.5% (-7.5 kg) | -0.5% (-0.18 kg) |
| Lean mass change | +3.6% (+1.70 kg) | -0.8% (-0.4 kg) |
| HbA1c change | -0.76% | Not significant |
| Waist circumference | Significantly reduced | Not significant |
The simultaneous fat loss and lean mass gain was unprecedented for a single therapy. Most weight loss interventions (including GLP-1 agonists) cause 20-40% of weight loss to come from lean mass.
BELIEVE Phase 2b Combination Trial#
The BELIEVE trial evaluated bimagrumab alone and in combination with semaglutide in 507 adults with overweight or obesity.
Key Results:
| Treatment | Total Weight Loss | Fat Mass Loss | Lean Mass Change |
|---|---|---|---|
| Bimagrumab alone | -10.8% | 100% from fat | +2.5% lean mass |
| Semaglutide alone | -15.7% | 71.8% from fat | -7.9% lean mass |
| Combination | -22.1% | 92.8% from fat | -2.6% lean mass |
The combination preserved 67% more lean mass compared to semaglutide alone while achieving greater total weight loss. This addresses one of the key concerns with GLP-1 agonist therapy: excessive loss of lean mass.
Inclusion Body Myositis#
RESILIENT Phase 2b/3 (Lancet Neurology 2019)#
Amato et al. (PMID 31397289) conducted the largest-ever IBM trial at 38 sites with 251 participants.
- Primary endpoint: 6-minute walk distance at week 52 -- NOT MET at any dose
- Safety: Good profile across all dose levels
- Lean mass: Increased but did not translate to functional improvement
- Patient-reported outcomes: Preserved at the 10 mg/kg dose
The IBM failure was pivotal in Novartis's decision to license bimagrumab to Versanis Bio and shift focus to metabolic disease.
Sarcopenia#
Proof-of-Concept (JAGS 2017)#
Rooks et al. (PMID 28653345) showed that bimagrumab 30 mg/kg increased muscle mass and strength in 40 sarcopenic older adults. A larger Phase 2 study subsequently confirmed lean mass gains but functional endpoints were mixed.
Evidence Quality Assessment#
| Evidence Criterion | Assessment | Details |
|---|---|---|
| Study design | Phase 2 RCTs | Multiple well-designed clinical trials |
| Publication quality | High | JAMA Network Open, Lancet Neurology |
| Sample sizes | Moderate-Large | 40-507 participants across studies |
| Mechanism | Well-defined | ActRII blockade, Smad2/3 inhibition |
| Body composition effects | Strong | Consistent fat loss + lean mass gain |
| Functional outcomes | Mixed | IBM failed; sarcopenia mixed |
| Safety profile | Well-characterized | Muscle spasms, diarrhea, acne |
| Regulatory approval | None | No approved indications |
Critical Assessment#
Bimagrumab represents a compelling proof-of-concept for ActRII blockade in body composition modification:
- Unique mechanism: The only therapy demonstrating simultaneous fat loss and lean mass gain across multiple clinical trials
- GLP-1 combination: The BELIEVE data addresses the critical clinical need for muscle preservation during GLP-1 agonist therapy
- IBM lesson: Increased lean mass does not automatically translate to improved function, highlighting the gap between surrogate and clinical endpoints
- Commercial uncertainty: Despite promising data, one Lilly combination trial was terminated in 2025, and the path to regulatory approval remains unclear
Related Reading#
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