Myostatin and activin pathway inhibitors

Myostatin and activin pathway inhibitors block signals that limit muscle growth, so muscle mass rises or is preserved. They are being tested to keep lean mass during weight loss with incretin drugs and in muscle-wasting diseases, and none is approved for these uses. Muscle cramps, injection-site reactions, and acne-like skin changes are among the reported effects, and some antibodies in this family raised concerns about bleeding and blood vessel changes. The key safety point is that long-term effects of switching off a growth brake are unknown.

• Trevogrumab