Clinical Applications of Ligand Traps Targeting Activin Type II Receptors

This review summarizes recent advances in ligand trap therapies targeting activin type II receptors [ActRIIA/ACVR2A and ActRIIB/ACVR2B], which serve as shared receptors for members of the TGF-β family, including activins, GDF11, and myostatin [MSTN]. These receptors mediate Smad2/3 signaling and play critical roles in hematopoiesis, vascular homeostasis, and muscle regulation. Two peptide-based ligand traps have recently received clinical approval: luspatercept [ActRIIB-Fc], an erythroid maturation agent, and sotatercept [ActRIIA-Fc], a novel therapeutic agent for pulmonary arterial hypertension [PAH]. Luspatercept primarily inhibits activin B and GDF11, thereby promoting late-stage erythropoiesis and demonstrating efficacy in anemia associated with conditions such as myelodysplastic syndromes [MDS] and β-thalassemia. Sotatercept binds activins and GDFs to rebalance Smad2/3 and Smad1/5/8 signaling, thereby improving vascular remodeling in PAH. Although both agents have failed to increase skeletal muscle mass in clinical trials consistently, they represent significant advances in the treatment of hematopoietic and vascular disorders. Future studies should focus on optimal dosing strategies, long-term safety, and potential synergistic effects when combined with other therapeutic modalities.