ATA 842

**ATA 842** is a humanized monoclonal antibody that inhibits myostatin (MSTN, also known as growth/differentiation factor 8), a member of the TGF-beta superfamily that negatively regulates skeletal muscle growth. Developed initially by Amgen and later advanced by Atara Biotherapeutics, it promotes muscle hypertrophy and strength, as demonstrated in preclinical mouse models where 4-week treatment increased lean body mass by ~7-9%, gastrocnemius weight by 13-19%, grip strength by 15-20%, and reduced muscle triglyceride content in aged and high-fat diet-fed animals. It also improved insulin-stimulated glucose uptake and whole-body insulin sensitivity in old mice without affecting plasma lactate or causing lactic acidemia. The program reached IND-enabling preclinical studies, with global highest R&D status reported as Pending; it does not cross-react with GDF11.[1][2][5][9]