The present invention is directed to modified antibodies, including anti-TNFα antibodies, in which C-terminal amino acids of heavy chain sequences are modified from a native sequence of proline-glycine-lysine (“PGK”) to one that includes a proline positioned between the glycine and lysine, resulting in a C-terminal sequence of proline-glycine-proline-lycine (“PGPK”). The invention further provides methods of producing and using such antibodies.