Single chain FC polypeptides

An isolated monovalent polypeptide, comprising a single chain Fc polypeptide, and a monovalent binding domain;

• wherein the single chain Fc polypeptide N to C-terminal sequence is:
• a first CH2 domain linked via its C-terminus to an N-terminus of a first CH3 domain, and the first CH3 domain is linked at its C-terminus via at least one amino acid linker comprising repeat units of GSGGS (SEQ ID NO:92), GGGGS (SEQ ID NO:93), and GGGS (SEQ ID NO94) to the N-terminus of a second CH2 domain and the second CH2 domain linked at its C-terminus to the N-terminus of a second CH3 domain;
• wherein the single chain Fc polypeptide does not contain cysteine amino acid residues in a hinge region;
• wherein Fc domains in the single chain Fc polypeptide consist of two CH2 domains and two CH3 domains, wherein the first CH2 domain is intra-molecularly dimerised with the second CH2 domain and the first CH3 domain is intra-molecularly dimerised with the second CH3 domain within the single chain Fc polypeptide;
• wherein the two CH2 domains and the two CH3 domains form a functional Fc domain within the single chain Fc polypeptide via at least one linker of 15 to 50 or 30 to 130 amino acids in length, or combinations thereof;
• and
• wherein the single chain Fc polypeptide is linked at its N terminus to one biologically active molecule that is a monovalent binding protein selected from the group consisting of scFv, Fab, Fab', VHH, and Fv,
• with the proviso that when the single chain polypeptide Fc is linked to the biologically active molecule via a linker, the linker does not contain cysteine amino acid residues.