bimagrumab (Eli Lilly and Company)

Bimagrumab (BYM338, LY3985863) is a fully human IgG1 lambda monoclonal antibody that acts as a dual antagonist of activin receptor type IIA (ActRIIA) and activin receptor type IIB (ActRIIB). Originally developed by Novartis in collaboration with MorphoSys, bimagrumab was licensed to Versanis Bio in 2021 and subsequently acquired by Eli Lilly in 2023. By binding to ActRIIA and ActRIIB, bimagrumab competitively blocks the binding of negative regulators of muscle mass, including myostatin (GDF-8), activin A, and GDF-11, thereby preventing downstream Smad2/3 signaling. This inhibition promotes skeletal muscle hypertrophy and reduces fat mass. Bimagrumab is currently in Phase II development for the treatment of obesity and overweight, both as a monotherapy and in combination with GLP-1 receptor agonists (such as semaglutide or tirzepatide) to preserve lean muscle mass during weight loss. It was previously investigated for sporadic inclusion body myositis, sarcopenia, and other muscle-wasting conditions, but development in those indications was discontinued.

Other names

anti-ActRIIA/ActRIIB antibodyanti-ActRIIA/IIB antibodyanti-activin receptor type IIA/IIB antibodybimagrumabαActRIIA/IIB ab