For research and educational purposes only. Not medical advice.

Bimagrumab Reference

Educational, not medical advice reference for Bimagrumab: Fat Loss, Hormonal; regulatory status, evidence posture, source review, and schedule n…

Plain English

What it is
Bimagrumab is a lab-made antibody, a large protein medicine given by an IV drip in studies. It blocks a receptor called ActRII that normally puts the brakes on muscle growth. It is still experimental and is not approved by the FDA.
What people use it for
In trials, researchers are testing it to help people lose body fat while keeping, or even gaining, muscle. The newer interest is pairing it with GLP-1 weight-loss shots so people hold on to more muscle while they slim down.
What the science shows
In a phase 2 study of adults with type 2 diabetes and obesity, people on bimagrumab lost a large share of their body fat and actually gained a little lean mass, while a placebo group barely changed. A later phase 2 trial that combined it with a GLP-1 drug showed more total weight loss than the GLP-1 alone, and most of that loss was fat rather than muscle.
The catch
It is not approved anywhere and is only given by IV in supervised trials, so there is no real consumer version. Common side effects were muscle cramps and diarrhea, plus temporary bumps in pancreas and liver blood tests. One late-stage program was shut down, and long-term safety is still unknown.

Reference summary

Human phase 2 trial evidence. A placebo-controlled phase 2 trial in adults with type 2 diabetes and obesity (75 participants, 48 weeks) showed about a 20 percent reduction in total body fat with a small gain in lean mass, a large drop in waist circumference, and improved HbA1c, versus near-zero changes on placebo. The phase 2b BELIEVE trial (507 participants, Eli Lilly) combined intravenous bimagrumab with subcutaneous semaglutide and reported greater total weight loss than semaglutide alone (about 22 percent versus 16 percent for the top groups at 72 weeks), with most of the weight lost coming from fat and better lean-mass preservation. It removes a natural brake on muscle and acts on fat tissue rather than suppressing appetite. It remains investigational.

Regulatory and posture

Categories
Fat Loss, Hormonal
Aliases
BYM338, anti-ActRII monoclonal antibody, activin type II receptor blocker
Evidence posture
human - Investigational biologic, not FDA-approved. Given by IV in trials only, with no legitimate consumer supply; all amounts listed are trial references.
Regulatory status
Investigational. Bimagrumab is a monoclonal antibody that blocks activin type II receptors (ActRII). It is NOT FDA-approved and is not approved in any market; all uses are investigational. Originally developed by Novartis as BYM338, licensed to Versanis Bio in 2021 for obesity and body composition, and acquired by Eli Lilly in 2023. It is given by intravenous infusion in supervised trials only, with no legitimate consumer supply.
Content review status
investigational verified

Selected public sources

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