Bimagrumab
Bimagrumab (Anti-ActRII Monoclonal Antibody)
The muscle-preserving add-on
An investigational monoclonal antibody that blocks the activin type II receptor (ActRII), the brake on muscle growth. It does something incretins can't: in trials it reduced fat mass while *increasing* lean muscle. Its real role is as an adjunct to GLP-1/GIP therapy — which strips ~25–30% of lost weight as muscle — to protect lean mass. Clinic-administered IV; not yet approved.
Key Benefits
Reduces fat while increasing lean muscle — unique among weight agents
The logical add-on to protect muscle during GLP-1/GIP weight loss
BELIEVE Phase 2b evidence supports the fat-down/muscle-up effect
Especially relevant for a power/fast-twitch genetic phenotype
Once-monthly-class dosing as an IV biologic
Mechanism of Action
How Bimagrumab works
Bimagrumab works on the muscle-regulation axis, not the appetite axis:
- ActRII blockade — antibodies bind and block activin type II receptors, removing the myostatin/activin "stop-growing" signal on muscle, which lets muscle mass increase
- Fat loss + muscle gain — uniquely among weight agents, Phase 2 (BELIEVE) showed simultaneous fat-mass reduction and lean-mass gain, the opposite of the lean-mass cost of incretins
- Adjunct logic — GLP-1/GIP weight loss costs ~25–30% of the loss as muscle; bimagrumab is the rational lean-mass-preserving add-on, especially for people whose genetics make muscle worth protecting
- Clinic-administered — an IV biologic given in a clinical setting, not a self-injected peptide
Your Genetics & Bimagrumab
Genetic variants that affect your response
These SNPs determine how effectively Bimagrumab works for you specifically. A genetic peptide report identifies your variants before you start.
The R577X variant defines fast-twitch (power) versus endurance muscle. An RR (power/fast-twitch) phenotype is the kind of lean mass most worth protecting during weight loss — strengthening the rationale for a muscle-preserving adjunct like bimagrumab.
Myostatin is the growth brake bimagrumab releases. Variants altering myostatin tone set how much room there is for muscle gain when the activin/ActRII signal is blocked.
ACVR2B is the receptor bimagrumab blocks. Variation in receptor expression can influence the magnitude of the muscle-sparing and muscle-building response.
Which variants do you carry?
Upload your DNA data or order a kit to find out.
Evidence & Research
15+
Published studies
Animal studies and in vitro data with promising but limited clinical validation
Common Stacks
Bimagrumab is commonly combined with:
Frequently Asked Questions
What is bimagrumab used for?
Bimagrumab is an investigational antibody that blocks the activin type II receptor to reduce fat while preserving or increasing muscle. Its most logical use is alongside GLP-1/GIP weight-loss drugs, which otherwise cost a large fraction of lost weight as muscle.
How is it different from a GLP-1 drug?
GLP-1/GIP drugs reduce appetite and overall body weight — including muscle. Bimagrumab works on the muscle-regulation pathway instead, so it loses fat while protecting (or building) lean mass. They're complementary, not competing.
Is bimagrumab approved?
No. As of 2026 bimagrumab is investigational, supported by Phase 2b (BELIEVE) data. It is a clinic-administered IV biologic, not a self-administered peptide, and not an available prescription.
Learn More About Bimagrumab
Your next move
Two ways forward with Bimagrumab.
Not sure it's for you?
Will Bimagrumab work for your genes — and at what dose?
Your report scores Bimagrumab against your receptor, CYP and pathway variants — likely responder, non-responder, and a sensible starting dose — in minutes.
Analyze my DNA — $99