Muscle-sparing antibody may lessen lean tissue loss with tirzepatide weight-loss therapy

A small Nature Medicine trial found that adding the monoclonal antibody apitegromab to tirzepatide (a GLP-1–based obesity drug) did not change total weight loss but reduced lean mass loss to about 1.6 kg (3.5 lb), or 14.6% of total weight loss, versus 3.5 kg with tirzepatide plus placebo—a 55% greater retention of lean tissue. Most participants were women; the study was limited in size and duration, so larger, longer trials are needed to assess safety and real-world benefits. Researchers also emphasize maintaining physical activity to help preserve muscle mass during weight-loss therapy.