Patent ID: 8871912

Claim:
A heterodimeric fusion protein comprising first and second polypeptides, each comprising a CH3 domain mediating the heterodimerization of the first and second polypeptides, wherein each CH3 domain is a modified IgG CH3 domain substituted with corresponding amino acid residues from an IgA CH3 domain, wherein each modified IgG CH3 domain comprises substitutions selected from the group consisting of: Glu at Kabat position 347, His at Kabat position 349, Pro at Kabat position 354, Leu at Kabat position 359, Asn at Kabat position 360, Leu at Kabat position 362, Thr at Kabat position 364, Arg at Kabat position 370, Lys at Kabat position 390, Leu at Kabat position 392, Trp at Kabat position 394, Ala at Kabat position 395, Arg at Kabat position 397, Glu at Kabat position 399, Pro at Kabat position 400, Ala at Kabat position 405, Thr at Kabat position 407, Ile at Kabat position 409, and Arg at Kabat position 411; wherein the substitutions in the first and second polypeptides occur at different positions; and wherein heterodimerization of the modified IgG CH3 domains is enhanced compared to IgG CH3 domains without the substitutions.