Figure 1.

Schematic diagram of the site-specific glycoconjugation for generating IgG1 m860-nAF ADC is illustrated. The native IgG1 m860 with desialylated N-glycan attached to Asn 297 of the CH2 domain (a close-up molecular surface view of a CH2 domain with carbohydrates in sticks) was treated with β-galactosidase to obtain a homogeneous G0F glycoform population. The fully degalactosylated IgG1 contains four GlcNAc residues per IgG1 molecule at the terminal positions available for the transfer of C2-keto-Gal from its UDP-derivative by Y289L-b4Gal-T1. The chemically reactive C2-keto-gal sugar handle is used to conjugate the drug molecule AF via a non-cleavable linker as shown.