Site specific biological coupling of engineered antibodies and Enzymatic method

Glutamine residues naturally exist in the Fc region of each heavy chain of the McAb. After deglycosylation at position 295, glutamine residues are coupled through MTGase mediated reaction to produce a uniform ADC with Dar = 2. In order to improve the efficiency, the linker with branched chain can be coupled to double the Dar, and the mutation of asparagine at position 297 to glutamine can also increase the DAR.

NBE therapeutics developed S-based Staphylococcus aureus transpeptidase A-mediated coupling. Their strategy uses transpeptidase a (srtA) to cut the amide bond between threonine and glycine residues in the motif of lpxtg (X = any amino acid) pentapeptide. It then catalyzes the coupling of glycine related payloads with the newly formed C-terminal to form peptide bonds at physiological temperature and pH.