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.
