Bimagrumab

Human clinical Weight Loss & Metabolism 2 sources

Bimagrumab is a fully human monoclonal antibody that binds to activin type II receptors (ActRIIA and ActRIIB). By blocking the binding of negative regulators of muscle growth like myostatin and activin A, it promotes significant skeletal muscle hypertrophy while simultaneously reducing fat mass. Research has explored its potential for treating muscle-wasting disorders, obesity, and type 2 diabetes.

01Dosing reference

Amount

10-30 mg/kg (in clinical trial settings)

Frequency

Once every 4 weeks

Cycle

Administered via intravenous (IV) infusion under medical supervision in clinical trials

Reference figures, not a recommendationThese values reflect amounts described in the literature and vendor documentation this database indexes. Use the reconstitution calculator to convert them into syringe units.

02Mechanism of action

Activin type II receptor (ActRII) blockade

Bimagrumab binds competitively to ActRIIA and ActRIIB receptors on cell membranes.

Inhibition of myostatin and activin signaling

This prevents the Smad2/3 intracellular signaling pathway that normally inhibits muscle protein synthesis and promotes fat accumulation.

Muscle hypertrophy and fat loss

The dual action leads to increased lean muscle mass and improved metabolic profiles, making it a candidate for sarcopenia and obesity treatments.

03Human evidence

Significant increase in lean mass and decrease in fat mass in overweight/obese adults with type 2 diabetes.

A phase 2 clinical trial showed that multiple doses over 48 weeks led to substantial fat loss and muscle gain compared to placebo.

Increased muscle volume in patients with sporadic inclusion body myositis (sIBM).

Early trials showed promise for muscle growth, though a larger Phase 2b/3 trial (RESILIENT) did not meet its primary functional endpoint for improving 6-minute walk distance.

04Preclinical evidence

Enhanced skeletal muscle mass and improved insulin sensitivity in animal models.

Studies in mice and cynomolgus monkeys demonstrated robust muscle hypertrophy and metabolic benefits.

Prevention of glucocorticoid-induced muscle atrophy.

Rodent models showed that ActRII blockade could protect against muscle wasting induced by dexamethasone.

05What is known vs. unknown

Reasonably established

Bimagrumab is a monoclonal antibody, not a traditional short-chain peptide.
It works by blocking ActRII receptors, preventing myostatin and activin from inhibiting muscle growth.
Clinical trials have demonstrated its unique ability to simultaneously increase lean muscle mass and decrease fat mass.
It has been investigated for obesity, type 2 diabetes, and muscle-wasting diseases like sIBM.

Unknowns & limits

Long-term safety and efficacy in broader populations remain under investigation.
The exact mechanisms driving the profound fat loss are still being elucidated, though increased muscle metabolic rate plays a role.
It failed to meet primary functional endpoints in some muscle-wasting disease trials despite increasing muscle mass.

06Safety & regulatory context

Regulatory statusBimagrumab is an investigational drug and is not FDA-approved for any indication. In clinical trials, it has generally been well-tolerated, but reported side effects include muscle spasms, diarrhea, and mild acne. Because it is a biologic (monoclonal antibody), it is administered via intravenous (IV) infusion rather than subcutaneous injection. Its use outside of approved clinical trials is strictly prohibited and potentially unsafe.

07Compared with Follistatin

Bimagrumab vs. Follistatin

Key difference

Bimagrumab is a monoclonal antibody that blocks the ActRII receptors directly, whereas Follistatin is a naturally occurring protein that binds to and neutralizes myostatin and other TGF-beta family members before they reach the receptor.

When researchers discuss each

Bimagrumab is discussed in the context of targeted pharmaceutical interventions for obesity and muscle wasting, while Follistatin is often discussed in gene therapy research and natural regulation of muscle growth.

08Glossary

Myostatin

A protein produced by muscle cells that acts as a negative regulator of muscle growth.

Monoclonal Antibody

A lab-made protein designed to bind to a specific target in the body, such as a receptor on a cell surface.

Hypertrophy

The enlargement of an organ or tissue from the increase in size of its cells, commonly referring to muscle growth.

09Knowledge check

Q1What is the primary mechanism of action for Bimagrumab?

Q2Which unique combination of effects has Bimagrumab demonstrated in clinical trials for obesity?

Q3Which interpretation best reflects the clinical trial findings for Bimagrumab in muscle-wasting disease (for example, sIBM)?

Q4According to the dossier, what is the key mechanistic difference between Bimagrumab and Follistatin?

Q5Which statement about Bimagrumab's regulatory and safety context is supported by the dossier?

10Sources

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Research and educational use onlyNothing on this site is medical advice, a prescription, or a recommendation for human use. Compounds documented here are research chemicals. Consult a qualified clinician before making any health decision.