Regeneron's trevogrumab cuts muscle loss in half when paired with semaglutide

One of the biggest criticisms of GLP-1 weight-loss drugs like Wegovy is that rapid weight loss often comes with significant loss of lean muscle mass — about 30% of total weight lost. Regeneron thinks it has a fix. Its experimental drug trevogrumab, a myostatin inhibitor, was shown to cut that muscle loss in half when used alongside semaglutide, according to data presented at the European Association for the Study of Diabetes conference in Milan.

In a mid-stage trial of nearly 1,000 patients (ages 18–65), those on semaglutide alone lost 6.7% of lean muscle mass over 26 weeks. Adding 75 mg of trevogrumab brought that figure down to just 3.3%. MRI scans of thigh muscle confirmed the drug preserved over 70% of muscle loss seen with semaglutide alone at 52 weeks. Notably, when patients stopped semaglutide but continued trevogrumab, their muscle mass rebounded to baseline — suggesting the drug may also help rebuild lost muscle.

By the Numbers:

• ~30% of weight lost on GLP-1s comes from lean muscle mass
• 75 mg trevogrumab reduced muscle loss from 6.7% → 3.3% over 26 weeks
• Over 70% of muscle mass preserved vs. semaglutide alone at 52 weeks
• Muscle-preserving therapies projected to reach $30 billion in annual sales by 2035

Why it matters: As GLP-1 drugs become a cornerstone of obesity treatment, preserving muscle mass — especially in older or frailer patients — is a critical unmet need. Trevogrumab's results position it as a promising next-generation add-on, with Regeneron planning further trials in patients over 65.