| abstract |
The present application provides specific sites for modifying antibodies or antibody fragments, by replacing at least one native amino acid in the constant region of a cysteine progenitor antibody or antibody fragment, which can be used as a binding site for a payload or for a linker-payload combination. In one embodiment, the antibodies are modified with cysteines at positions 152 and 375 of the heavy chain constant region, as defined by the European Union (EU) numbering format. In another embodiment, the antibodies are modified with cysteines at position 360 of the heavy chain constant region, and position 107 of the kappa light chain constant region, as defined by the European Union (EU) numbering format. . |