The present disclosure provides compositions and methods for inhibiting activity of TGFß superfamily ligands, particularly ligands such as GDF8, GDF 11, activin A, activin B, activin C and activin E, in vertebrates, including rodents, primates, and particularly in humans. The compositions of the disclosure contain protein complex/fusion comprising a heteromeric Fc interaction pair to which a follistatin related polypeptide is covalently or non-covalently associated. The compositions maybe used to treat or prevent diseases or disorders that are associated with abnormal activity of a follistatin-related polypeptide and/or a follistatin ligand.
