As GLP-1 drugs like semaglutide (Wegovy) and tirzepatide (Zepbound) are producing unprecedented weight loss, concern has arisen about the proportion (30-50%) of lost weight that is lean body mass vs fat mass.
Several drugs are in development aimed at preserving or building muscle mass when used in combination with GLP-1 medications for weight loss, including:
- Veru’s oral SARM enobosarm (phase 2b trial with semaglutide)
- Lilly’s IV antimyostatin bimagrumab (phase 2b trial with semaglutide)
- Scholar Rock’s IV antimyostatin apitegromab (phase 2 trial)
- Biohaven’s subcutaneous antimyostatin taldefgrobep alfa (phase 2 soon)
Early data shows enobosarm increased lean mass and decreased fat mass, especially in older adults at risk for muscle loss. But defining functional benefit endpoints is challenging.
Experts caution muscle mass isn’t everything – fat loss provides huge cardiometabolic benefits even with some lean mass loss. Safety of muscle drugs is also a concern.
Drug companies see combining muscle agents with GLP-1s as a major market opportunity as use of the weight loss medications expands.
In summary, pharmaceutical companies are developing muscle-preserving medications to potentially enhance the benefits of GLP-1 weight loss drugs, though their efficacy and safety profile remains to be proven.
