Regeneron’s experimental drug trevogrumab reduced muscle loss associated with Novo Nordisk’s semaglutide by 50% in a study of patients with obesity. Trevogrumab inhibits myostatin, a protein linked to muscle loss, and researchers found that adding a 75-milligram dose preserved more than 70% of the muscle that would otherwise have been lost after 52 weeks, based on thigh measurements from magnetic resonance imaging scans. The trial included nearly 1,000 adults ages 18 to 65, with results presented at the European Association for the Study of Diabetes conference in Milan. In one 26-week analysis, semaglutide alone reduced lean muscle mass by 6.7%, compared with 3.3% for the 75-milligram trevogrumab combination and 4.7% for the 25-milligram dose. Regeneron said trevogrumab alone had a safety profile similar to semaglutide, with no unexpected side effects. A combination with the company’s garetosmab preserved more lean mass but caused more adverse events, including muscle spasms; two participants receiving higher doses of trevogrumab with garetosmab died during the first 26 weeks. Regeneron will not advance the triple combination and has selected a once-weekly 75-milligram trevogrumab dose for further studies, including a planned mid-stage trial in patients over 65.