Trevogrumab: Regeneron's Muscle-Saving Drug for GLP-1 Users

What is trevogrumab, and can it stop the muscle loss that comes with Ozempic, Wegovy or Zepbound? Trevogrumab is an experimental antibody from Regeneron that blocks myostatin, the body's "stop growing" signal for muscle. In the Phase 2 COURAGE trial, reported on October 1, 2026, adding it to semaglutide 2.4 mg cut lean mass loss at one year and saved about 70% of thigh muscle on MRI. It did not add extra weight loss. It is not approved, and you can only get it in a clinical trial.

Here is what the trial found, what garetosmab is, how it compares with Lilly's bimagrumab, and what you can do about muscle today.

What is trevogrumab and what does it do?

When you lose weight, some of what you lose is lean mass: muscle, organs, water and bone. On GLP-1 drugs, that share can be large. In the first COURAGE results, Regeneron reported that about 33% of the weight people lost on semaglutide alone was lean mass.

Trevogrumab (lab name REGN1033) is a monoclonal antibody. It binds to myostatin, also called GDF8. Myostatin is a protein your body makes to keep muscle from growing too much. Blocking it lets muscle hold on, even while you eat less. The idea is simple: let the GLP-1 drug take fat, and let trevogrumab protect muscle.

Muscle matters for more than looks. It drives strength, balance and blood sugar control, and it is harder to rebuild after 50. Our guide to sarcopenia on GLP-1 explains why.

Trevogrumab COURAGE trial results

COURAGE is a 52-week Phase 2 trial in adults with obesity (BMI of 30 or more). It has two parts. The lower-dose part tested trevogrumab 25 mg or 75 mg added to semaglutide 2.4 mg, compared with semaglutide plus placebo. These are the numbers Regeneron released on October 1, 2026, at the EASD meeting. The full paper is in press at The Lancet.

Two things stand out:

• Muscle was protected. The 75 mg dose cut lean mass loss by about 40% at one year on DXA scans. On MRI, which measures muscle itself rather than all lean tissue, the saving was close to 70% at both doses.
• Weight loss did not improve. Regeneron said the lower doses "did not meaningfully enhance" weight loss over semaglutide alone. The win was in what kind of weight came off, not how much.

People with low lean mass at the start (a sarcopenia definition from the FNIH) lost more lean mass on semaglutide alone and had numerically more preserved with trevogrumab. Regeneron has not released those numbers yet.

One caution: the trial measured body tissue, not strength, walking speed or falls. A drug can save muscle on a scan without proving it makes people stronger. That will need bigger trials.

Trevogrumab and garetosmab: the three-drug arm

Garetosmab is a second Regeneron antibody. It blocks activin A, another signal that holds muscle back. The higher-dose part of COURAGE tested semaglutide plus trevogrumab 200 mg or 400 mg, and a "triplet" arm that also added garetosmab.

The triplet looked strongest on paper: more weight loss and almost all of it fat. But more people in that arm quit because of side effects, and two people in it died. One death had an undetermined cause in a person with several heart risk factors. The other was cardiac arrest in a person with known heart disease. Regeneron said it has not found that the drugs caused either death. These safety signals are why the newest results focus on trevogrumab alone.

Trevogrumab side effects

From the published results so far:

• Lower doses (25 mg, 75 mg): 77% had at least one side effect, versus 82% on semaglutide plus placebo. The most common were nausea, constipation, diarrhea and vomiting, the usual GLP-1 effects.
• Earlier 26-week results: muscle spasms, fatigue, headache and reflux were among the side effects seen in at least 5% of people in some arm. Most were mild to moderate.
• Triplet arm: more stopped treatment for side effects, and two deaths, as above.

No regulator has reviewed trevogrumab's safety. Long-term effects are unknown.

Bimagrumab vs trevogrumab and garetosmab

Regeneron is not alone. Eli Lilly is testing bimagrumab, an antibody that blocks activin type II receptors. That one target covers signals from both myostatin and activin, so it works a bit like trevogrumab and garetosmab together.

In Lilly's BELIEVE trial, published in Nature Medicine in 2026, bimagrumab plus semaglutide led to more fat loss and less lean mass loss than semaglutide alone. The two companies' drugs have never been tested head to head.

Can you buy trevogrumab?

No. Searches like "trevogrumab for sale" and "trevogrumab peptide" are rising, but:

• Trevogrumab is not approved by the FDA, the EMA or any other agency.
• Regeneron does not sell it. You can only get it by joining a clinical trial.
• The real drug is a large antibody made in living cells, not a small peptide. Vials sold online under this name are unknown products with no quality checks.

This is the same pattern we saw with black-market retatrutide. If you are curious about trials, ask your doctor or search ClinicalTrials.gov. Regeneron says it plans a new Phase 2 trial in older adults with obesity and low muscle mass or strength.

What to do about muscle loss on GLP-1 today

A muscle drug may come one day. Until then, the tools with the best evidence are free:

• Hit a daily protein target. Many experts suggest about 1.2 to 1.6 grams per kilogram of goal body weight, but your needs depend on your health, so check with your care team. See how much protein you need on GLP-1.
• Lift something, 2 to 3 times a week. Strength training is the main signal that tells your body to keep muscle. Start with a beginner strength program.
• Watch the trend, not just the scale. If your weight drops fast but your strength falls too, tell your prescriber.

This is the exact problem Sharpy was built for. It gives you one protein target, one 20-minute workout and one Shape Score each day, so you can see if you are losing fat and keeping muscle.

The bottom line

Trevogrumab is the clearest sign yet that drug makers see muscle loss as the next problem to solve on GLP-1s. In COURAGE it cut lean mass loss on semaglutide without changing weight loss, and its side effects looked similar to semaglutide alone at lower doses. It is still years from any approval, and the three-drug version raised safety questions. For now, protein and strength training do the job, and Sharpy keeps both on track every day.

Sources

• Phase 2 COURAGE Trial Confirms Trevogrumab Prevents Lean Mass and Muscle Loss During GLP-1 Receptor Agonist-induced Weight Loss, Regeneron, October 1, 2026
• Results from Phase 2 COURAGE Trial (26-week data), Regeneron, September 17, 2025
• Bimagrumab plus semaglutide for the treatment of obesity: a randomized phase 2 trial (BELIEVE), Nature Medicine, March 2026
• ClinicalTrials.gov