Bimagrumab: Novel Medical Therapy for Inclusion Body Myositis, Sarcopenia, and Medication-Induced Lean Body Mass Loss

Bimagrumab is a monoclonal antibody that targets activin type II receptors, blocks myostatin and related proteins: it promotes muscle growth and prevents muscle loss, while causing weight loss. It has been effective in sporadic inclusion body myositis with promising results, a disease that had no previous effective therapy. It has also been studied in sarcopenia, leading to improved muscle mass and reduced fat mass. It has been very effective in obese patients with type 2 diabetes, leading to reduced fat mass, increased lean body mass, and improved insulin sensitivity. Subcutaneous administration is now as effective as intravenous dosing. It has improved muscle mass in patients with sarcopenia and posthip fracture recovery, while only showing minimal improvements in mobility and strength. It has recently been used in combination with semaglutide, a glucagon-like peptide-1 receptor agonist administered weekly as a subcutaneous injection for weight loss. Semaglutide reduces appetite, slows gastric emptying, and improves glucose regulation. As much as 40% of weight loss may come from lean body mass, primarily skeletal muscle, raising concerns about sarcopenia. Bimagrumab is a promising solution to counter the muscle-wasting effects of semaglutide. We review the development of bimagrumab, its mechanism of action, clinical trial results, and the safety profile. We compare the efficacy of the combination of bimagrumab and semaglutide to a dual incretin glucagon-like peptide-1 receptor agonist and glucose-dependent insulinotropic polypeptide (GIP) drug. Finally, we will show the superiority of bimagrumab to other myostatin inhibitors.