Myostatin, also called GDF-8, is a protein that inhibits muscle growth. It is produced naturally in the body and its production increases with age. Various induced or natural conditions leading to myostatin deficiency result in increased muscle mass and strength in normal animals and have been shown to treat or prevent a range of muscle wasting conditions.

Studies in mouse models of Duchenne show reduced fibrosis and adipose tissue replacement in muscles of mice treated with myostatin inhibitors.

Two new myostatin inhibitors are in development for Duchenne.

A phase II clinical trial of PF-06252616, sponsored by the pharmaceutical company Pfizer, is ongoing.

A phase II clinical trial of an anti-myostatin called Adnectin (BMS 986089), sponsored by the pharmaceutical company Bristol Myers Squibb (BMS), has also recently been started in children with Duchenne.