Bimagrumab dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
Bimagrumab is an antibody shot that takes the brake off muscle growth. In studies it took off fat while adding muscle. It is being tested with semaglutide.
Evidence grade for Bimagrumab: Moderate. The rule: at least one finished study in people, and at least 100 people who took it. The sum on this page: 2 completed trials, 507 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 507
- Human studies
- 2
- Found nothing
- 0
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
2 completed trials, 507 people given it
1 effects reported, 1 wanted, by people using it, not a trial
Goal pages: Fat loss and metabolism
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Bimagrumab is an antibody shot that takes the brake off muscle growth. It blocks a receptor that myostatin and activin use to hold muscle back. In studies it took fat off and put muscle on at the same time. It is being tested with semaglutide. It is not approved for weight loss.
What people take it for
- Keeping muscle while losing weight on a GLP-1 drug.
- Losing fat and gaining muscle at once.
What studies in people showed
The main study had 507 adults and ran 48 weeks. The high dose combo with semaglutide took off about 17.8 kg. Semaglutide alone took off about 14.2 kg. Bimagrumab alone took off about 9.3 kg. The dummy group lost about 3.3 kg. With semaglutide, 92.8 percent of what people lost was fat. On bimagrumab alone, lean mass went up 2.5 percent. An earlier study in adults with type 2 diabetes and obesity found they lost fat, gained lean tissue and handled blood sugar better.
What people report
Reports, not study results
The good
- In the studies on this page, people lost fat and kept or gained lean tissue.
The bad
- The studies on this page do not list side effects, and we have not collected user reports on this one yet.
Where these come from: The good line is from the two studies on this page. We have not collected forum or user reports for this drug yet.
My bottom line
This goes after the problem I care about most with weight drugs, which is losing muscle. It is still in testing. Until then, the muscle saver that works is lifting and eating enough protein.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Bimagrumab has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Losing weight507 people · 1 study
35 of the 36 indexed goals have no study of any kind behind Bimagrumab
No study in people, animals or cells on this page reports a result for these. That does not prove Bimagrumab does nothing for them. It does mean anything you have heard about Bimagrumab and one of these did not come from a study cited here.
Show full evidence
What is Bimagrumab?
Bimagrumab is an antibody shot that takes the brake off muscle growth. In studies it took off fat while adding muscle. It is being tested with semaglutide.
Bimagrumab is a lab-made antibody. It blocks activin type II receptors, which act like a brake on muscle growth. With the brake off, muscle can grow. In studies it cut body fat while adding muscle, which is rare for a weight loss drug. In a mid-stage study called BELIEVE, with 507 adults, people on bimagrumab plus semaglutide lost 22.1 percent of their weight, and 92.8 percent of what they lost was fat. People on bimagrumab alone lost 10.8 percent, and their lean mass went up 2.5 percent. It is still experimental for weight loss.
How does Bimagrumab work?
It blocks the activin type II receptors. That shuts off myostatin and activin, two signals that hold muscle back. The result is more muscle and less fat.
The evidence, in charts
Fig. 1a · how many people
507people, across 1 study in people cited here
| Study | People | Share |
|---|---|---|
| BELIEVE, Nature Medicine 2026 | 507 | 100% |
The whole total is one study of 507. Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 1 more study in people gives no headcount and is not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
All 2 sources here are studies in people.
- Study in people · done in people2100%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
Sources here come from just two years, 2021 and 2026.
Too few different years on this page to draw a timeline.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Biologic
- Molecule weight
- About 150 kDa (IgG1 monoclonal antibody; KEGG lists the full heavy and light chain sequences but no mass)
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
No amino acid sequence is on file for Bimagrumab, so none is drawn rather than guessed from a name.
The studies we cite
- Study in people2021Effect of bimagrumab vs placebo on body fat mass among adults with type 2 diabetes and obesity: a phase 2 randomized clinical trial
Blocking this muscle pathway stripped fat and added muscle at the same time. Adults with type 2 diabetes and obesity were treated for nearly a year. They lost fat, gained lean tissue, and their blood sugar handling improved. That combination is unusual and worth noticing, because most weight loss takes a chunk of muscle with it.
48 weeks of ActRII blockade produced significant fat-mass loss, lean-mass gain and metabolic improvement.
- Study in people2026Bimagrumab plus semaglutide alone or in combination for the treatment of obesity: a randomized phase 2 trial (BELIEVE)
Added to semaglutide, it took off more weight than semaglutide managed alone. 507 adults were treated for nearly a year. The high dose combination lost about 17.8 kg, semaglutide on its own about 14.2 kg, the muscle drug on its own about 9.3 kg, and the dummy group about 3.3 kg. In pounds that is roughly 39, 31, 20 and 7. This is a middle stage trial.
507 adults: weight change at 48 weeks was -17.8 kg for high-dose combination, -14.2 kg semaglutide alone, -9.3 kg bimagrumab alone, -3.3 kg placebo.
Common questions
Has Bimagrumab been tested in people?
Yes. 507 people given it across 2 completed trials cited here, 0 of which found nothing. Bimagrumab is an antibody shot that takes the brake off muscle growth. In studies it took off fat while adding muscle. It is being tested with semaglutide.
What is the Bimagrumab dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 2 completed trials, 507 people given it
Is Bimagrumab FDA-approved?
Investigational for obesity and body makeup (fat and muscle); the mid-stage BELIEVE study was published in 2026
Why combine bimagrumab with GLP-1 drugs?
GLP-1 drugs take off some muscle along with the fat. Bimagrumab builds muscle. So the two are being tested together, to keep muscle while people lose weight.