FBL-140

FBL-140 is a human monoclonal antibody that acts as a dual antagonist of the activin type II receptors A and B (ActR2A and ActR2B). Developed by Fable Therapeutics, it is designed for the treatment of obesity and related metabolic comorbidities. The antibody aims to provide high-quality weight loss by facilitating fat mass reduction while preserving or increasing lean muscle mass, addressing a key limitation of current weight-loss therapies. FBL-140 was optimized using machine learning to achieve balanced, high-affinity binding to both receptor subtypes, which enhances its potency and allows for infrequent, low-volume subcutaneous dosing. Preclinical data in non-human primates and mice indicate a long half-life and high bioavailability, supporting a once-monthly or quarterly dosing schedule in humans.