Fat loss
Bimagrumab + semaglutide
The trial combination that separates fat loss from lean-mass loss. An antibody against type II activin receptors, given intravenously every twelve weeks, alongside weekly semaglutide.
At a glance
- What is in it
- Sold as
- Separate vials
- The evidence
- BELIEVE, Phase 2, NCT05616013, n=507, 48 weeks with an open-label extension to week 72. Least-squares mean absolute weight change: −9.3 kg on bimagrumab 30 mg/kg, −14.2 kg on semaglutide 2.4 mg, −17.8 kg on the combination, −3.3 kg on placebo, all P<0.001. Adverse events: muscle spasms, diarrhoea, acne.Combination-specific research is limited. Treat each compound’s evidence as separate unless a study of the combination itself is named here, and review the complete plan with a qualified clinician.
Not runnableBimagrumab is an intravenous antibody given every 12 weeks in a clinical setting. Nobody self-administers this, and it is not obtainable. It is here as the pharmacological answer to the lean-mass question, not as something to run.
Running this stack, with the schedule, the vials it takes and a log of what you took, happens in the app: Claritide for iPhone.
Why people explore it
Common reasons for exploring it
- Anyone who wants to understand what the lean-mass problem looks like when a drug developer attacks it directly
Where clinician input matters
- Everyone, as a protocol. This is education. There is no version of this you can run at home.
The science
Read the compound mechanisms
Type II activin receptors mediate signalling from myostatin and activin, which restrain muscle growth. Blocking those receptors with an antibody removes the brake, increasing muscle mass and reducing fat mass. That is the opposite direction of travel from an incretin, which reduces both, and it is why the combination arm of the BELIEVE trial is the interesting one.
Semaglutide mimics GLP-1, a hormone your gut releases after eating, with 94% homology to the human peptide. Activating GLP-1 receptors in the brain reduces appetite and increases fullness. It slows gastric emptying, so meals feel filling for longer. And it both increases insulin secretion and reduces glucagon secretion in a glucose-dependent way, which is why the same molecule treats type 2 diabetes. A C18 fatty di-acid chain at position 26 binds it to albumin, which is what stretches the half-life to about a week; position 8 is modified to resist the DPP-4 enzyme that clears natural GLP-1 in minutes. It is a single-receptor drug. That is the difference from tirzepatide and retatrutide, and it is why its weight-loss figure is smaller.
Commonly researched ranges
- Bimagrumab10 or 30 mg/kg
- Semaglutide1.0 or 2.4 mgPrescription
| Compound | Amount | Frequency | Timing |
|---|---|---|---|
| Bimagrumab | 10 or 30 mg/kg | Every 12 weeks | Intravenous infusion, in a clinical setting |
| SemaglutidePrescription | 1.0 or 2.4 mg | Once weekly | Subcutaneous |
- Bimagrumab: An antibody, not a peptide. There is no self-administration route and no product to obtain.
- Semaglutide: The trial arms used both doses.
- Duration
- 48 weeks in the trial, with an open-label extension to week 72.
Mixing each compound
Not established in available literature. Use the figures printed on your own vial.
Not established in available literature. Use the figures printed on your own vial.
Week by week
Semaglutide
- Week 1–16
Escalation through four steps. Nausea is most likely here and settles: it affected 44% of people against 16% on placebo, and it is the reason the schedule climbs slowly rather than starting at the target.
- Week 17
Maintenance dose reached, 2.4 mg or 1.7 mg weekly depending on what it was prescribed for.
- Week 60–68
Weight loss flattens around here. STEP 1 showed 14.9% mean reduction at 68 weeks on 2.4 mg, against 2.4% on placebo.
What it costs
- Bimagrumab: Not established in available literature
- Semaglutide: $349–1349 per month
The combined figure excludes Bimagrumab, for which our sources publish no price.
Cautions
- This is a Phase 2 result, not a treatment. Bimagrumab is not approved for anything.
- The reason to know about it: a BMJ network meta-analysis found tirzepatide produced the largest fat-mass reduction at −25.7% and also the largest lean-mass reduction at −8.3%. This combination is the pharmacological attempt to separate those two numbers. Resistance training and protein intake are the version of that attempt you can actually act on.
- Reported adverse events in the trial were muscle spasms, diarrhoea and acne.
Absence from this list does NOT mean safety. It means lack of research.
Every stack here is free to read, and it stays free. Your own schedule, vials and log live in the app: Claritide for iPhone.