An experimental antibody from Regeneron that blocks myostatin, the body's natural brake on muscle growth. It is being tested to help people keep muscle while they lose weight on semaglutide, after an earlier trial in age-related muscle loss. It is not approved for any use.
Trevogrumab is a fully human monoclonal antibody that binds myostatin, also called GDF8, and stops it from reaching its receptor. Myostatin is a circulating protein that tells muscle to limit its own growth, probably a holdover from times of food scarcity when muscle was an expensive tissue to maintain. Taking that brake off lets muscle fibers grow larger, and in mice the antibody increased muscle mass and force and prevented the wasting caused by immobilization or steroid treatment. In aged mice it also improved treadmill performance.
Antibody injected (1/6)
Trevogrumab, a fully human antibody, is injected and carried in the blood.
Myostatin is not the only brake. The same receptors also respond to activin A, and blocking both roughly doubles the muscle gain seen with myostatin blockade alone, which is why some trials pair trevogrumab with garetosmab, an anti-activin antibody. In obese mice and monkeys, blocking both signals prevented the muscle loss caused by GLP-1 drugs and increased fat loss at the same time. Whether more lean mass on a scan turns into more strength or better function in people is the question the human trials have to answer.
Trevogrumab is an experimental antibody being studied to preserve muscle in people who are losing weight. Its main trial, called COURAGE, gives it with or without a second antibody, garetosmab, on top of semaglutide to adults with obesity, and measures weight loss, fat loss, and how much lean mass is kept. An earlier phase 2 trial tested it for 3 months in 253 older adults with sarcopenia, the muscle loss of aging. Neither use is approved.
It is given by injection in trials run by its manufacturer, Regeneron, and only trial participants have received it. The COURAGE study has three parts, starting with healthy volunteers and moving to adults with obesity, with results expected after the study finishes. It is a monoclonal antibody, a large engineered protein, which puts it in a different manufacturing and regulatory world from the short peptides sold online. The sarcopenia trial finished in 2015, and the obesity program began in 2024.
Published human data are thin. A two-part randomized phase 1 trial in New Zealand gave single and repeated doses of the anti-myostatin antibody, an anti-activin antibody, or both to healthy postmenopausal women and men, with safety as the primary endpoint and thigh muscle volume and body composition as secondary endpoints. A phase 2 sarcopenia trial of 253 patients was completed in 2015, and the obesity trial began in 2024 and is no longer recruiting. Mouse and monkey studies supply most of the mechanistic evidence.
The central unknown is whether preserving lean mass during weight loss improves strength, mobility, or health, rather than just the numbers on a body scan. Results from COURAGE have not been peer reviewed or posted to the registry. Long-term safety of removing a growth brake that evolution kept in place is untested beyond trial durations. None of this evidence applies to any product sold under the trevogrumab name outside a trial.
In the phase 1 trial the main outcome was how many treatment-related adverse events occurred and how severe they were, through week 16 after a single dose and week 40 after repeated doses. Full safety results from the obesity program have not been published. The COURAGE record lists safety and tolerability as the aim of its first part in healthy volunteers, before the drug moves to people with obesity. Until those data are public, the side effect profile is unknown.
This compound is still in clinical trials. No regulator has approved it for any use.
Trevogrumab is investigational and has no approval from the FDA or any other regulator. It is available only inside Regeneron's clinical trials, and the obesity study is registered under NCT06299098. The sarcopenia trial, NCT01963598, was completed without any approval following. Anything sold online under this name has no link to the studied antibody.