Trevogrumab, Regeneron’s experimental myostatin inhibitor, substantially reduced the muscle patients lose while taking semaglutide, according to new clinical results reported on September 30, 2026. In the nearly 1,000-participant COURAGE study, a 75-mg trevogrumab regimen preserved more than 70% of the thigh muscle that otherwise would have been lost with semaglutide alone over 52 weeks, Reuters reported.
Myostatin is a protein linked to loss of muscle mass, and trevogrumab is an antibody designed to block it. The results speak to a known drawback of GLP-1 weight-loss drugs: some of the weight patients lose is lean muscle rather than fat.
Key Results From the COURAGE Trial
COURAGE is a randomized, double-blind Phase 2 trial that added trevogrumab, with or without a second antibody called garetosmab, to semaglutide in 999 adults with obesity. The main endpoints were percent changes in lean mass, fat mass and body weight, measured at 26 weeks in the first part of the study and at 52 weeks in the second.
At 26 weeks, patients taking semaglutide alone lost 6.7% of their lean muscle mass. Those who also took 75 mg of trevogrumab lost 3.3%, and those who took 25 mg lost 4.7%, Reuters reported. At 52 weeks, MRI scans of the thigh showed the 75-mg dose preserved more than 70% of the muscle that semaglutide alone would have cost.
A Medical Xpress summary of the study paper, which is in press at The Lancet, says trevogrumab cut semaglutide-associated lean mass loss by about 50% and thigh muscle volume loss by about 70% in an MRI substudy. When patients stopped semaglutide but kept taking trevogrumab, their muscle mass returned to its pre-study level, the company said, which suggests the drug could help rebuild lost muscle.
Why Muscle Preservation Matters During GLP-1 Treatment
A Regeneron executive told Reuters that patients on GLP-1 drugs lose about 30% of their weight as lean muscle, and that trevogrumab can prevent this. The greatest benefit, the executive added, could go to patients who start treatment with lower muscle mass. Interim COURAGE data that Regeneron released in June 2025 found that roughly 35% of semaglutide-induced weight loss came from lean mass.
Muscle supports strength, mobility and metabolic health, so clinicians watch the lean mass lost during rapid weight reduction, especially in older adults. Regeneron plans another mid-stage trial in patients over 65, a group where muscle loss is a particular concern.
Safety Findings and the Triple-Combination Setback
Adding garetosmab produced greater lean-mass preservation than trevogrumab alone, but it also caused a high rate of adverse effects, including muscle spasms. Regeneron said it will not move the triple combination forward. In the 2025 interim release, the company described semaglutide plus trevogrumab as generally well tolerated, while the triple combination had substantially higher discontinuations from tolerability issues and other adverse events.
What Regeneron Plans Next
Regeneron selected the 75-mg once-weekly dose of trevogrumab for further studies. Several caveats apply. COURAGE is a company-sponsored Phase 2 study, trevogrumab is still an investigational drug, and preserving lean mass on a scan does not by itself prove better strength or fewer falls. Larger and longer trials will need to show whether the muscle benefit translates into outcomes that matter to patients.
Obesity Drug Market Context: Acumen Research and Consulting Statistics
The data arrive as demand for obesity treatments keeps expanding. According to the Anti-Obesity Drugs Market report from Acumen Research and Consulting, the global market was worth USD 2.1 billion in 2022 and is projected to reach USD 8.2 billion by 2032, a CAGR of 14.6% from 2023 to 2032. North America led with more than 68% of market share in 2022, and Asia-Pacific is expected to grow at around 15% a year over the same period.
Acumen also reports that prescription drugs held the largest share by drug type in 2022, and it cites a 2022 research study finding that one in three U.S. adults has obesity. It lists rising obesity rates, advances in drug development and demand for effective weight management among the growth drivers, and names novel combination therapies as a market opportunity, a category that trevogrumab plus semaglutide fits. The report was last updated in September 2023 and uses a 2022 base year, so its figures predate the latest surge in GLP-1 demand.
For more on obesity treatments, read our explainer on Mounjaro versus Ozempic and Wegovy and our report on Novo Nordisk’s oral cardiometabolic drug-discovery deal with Orbis Medicines, or browse our pharmaceutical news section.
Key Facts at a Glance
- Drug: trevogrumab, an investigational anti-myostatin antibody from Regeneron
- Trial: COURAGE, a randomized, double-blind Phase 2 study in 999 adults with obesity
- Headline result: the 75-mg dose preserved more than 70% of thigh muscle otherwise lost with semaglutide over 52 weeks
- 26-week lean mass loss: 6.7% with semaglutide alone versus 3.3% with 75 mg of trevogrumab
- Setback: the triple combination with garetosmab will not advance because of adverse effects
- Next step: 75-mg weekly dose chosen, with a mid-stage trial in people over 65 planned
- Acumen market data: USD 2.1 billion in 2022 to USD 8.2 billion by 2032, a 14.6% CAGR
Frequently Asked Questions About Trevogrumab
What is trevogrumab?
Trevogrumab is an investigational antibody from Regeneron that blocks myostatin, a protein linked to muscle loss. It is being tested alongside semaglutide to preserve lean mass during weight loss.
How much muscle did trevogrumab preserve?
On MRI at 52 weeks, the 75-mg dose preserved more than 70% of the thigh muscle that semaglutide alone would have cost. At 26 weeks, lean mass loss was 3.3% with trevogrumab versus 6.7% with semaglutide alone.
Is trevogrumab approved?
No. It is investigational and has been tested in a Phase 2 trial. Regeneron has chosen a dose for further studies and plans a trial in patients over 65.
How large is the anti-obesity drugs market, according to Acumen?
Acumen Research and Consulting values the global market at USD 2.1 billion in 2022 and projects USD 8.2 billion by 2032, a CAGR of 14.6%, with North America holding more than 68% of the 2022 share.
This report is based on published trial coverage and company disclosures, and market figures are attributed to Acumen Research and Consulting. It is for information only and is not medical or investment advice.