Patent ID: 6872393

Claim:
A single-chain antigen-binding polypeptide capable of site specific polyalkylene oxide conjugation, that comprises, (a) a first polypeptide comprising an antigen binding portion of a variable region of an antibody heavy or light chain; (b) a second polypeptide comprising an antigen binding portion of a variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides, wherein the single-chain antigen-binding polypeptide has at least one Cys residue which is capable of polyalkylene oxide conjugation, and has an antigen binding site, and wherein the Cys residue is located at a position selected from the group consisting of: (i) the amino acid position 11, 12, 13, 14 or 15 of the light chain variable region; (ii) the amino acid position 77, 78 or 79 of the light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of the heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 of the heavy chain variable region; and (v) combinations thereof; and wherein the single-chain antigen-binding polypeptide is monovalent or multivalent.