In certain aspects the disclosure provides soluble single arm heteromeric polypeptide complexes comprising an extracellular domain of a type I serine/threonine kinase receptor of the TGF beta family or an extracellular domain of a type II serine/threonine kinase receptor of the TGF beta family. In some embodiments the disclosure provides soluble single arm polypeptide complexes comprising an extracellular domain of a type II receptor selected from: ActRIIA ActRIIB TGFBRII BMPRII and MISRII. In some embodiments the disclosure provides soluble single arm polypeptide complexes comprising an extracellular domain of a type I receptor selected from: ALK1 ALK2 ALK3 ALK4 ALK5 ALK6 and ALK7. Optionally the soluble complex is a heterodimer. In certain aspects such soluble polypeptide complexes may be used for the treatment or prevention of various TGF beta associated conditions including without limitation diseases and disorders associated with for example cancer muscle bone fat red blood cells metabolism fibrosis and other tissues that are affected by one or more ligands of the TGF beta superfamily.
