Enzymatic Glycoprotein Modification for Stable Antibody Conjugates

The patent introduces an enzyme (galactosyltransferase) as an intermediary to catalyze the formation of a stable beta-galactoside linkage between the protein and the sugar derivative. This enzymatic approach replaces the direct chemical conjugation while maintaining high selectivity, and the resulting glycosidic bond is inherently more stable against hydrolysis and retro-Michael reactions compared to maleimide linkages.

The patent changes the chemical parameters of the conjugation reaction by using a sugar derivative with specific functional groups (thiol, halogen, sulfonyloxy) at defined positions on the galactose ring. This allows the formation of a stable glycosidic bond while incorporating reactive handles for subsequent conjugation, thus achieving both stability and functionality.

The patent utilizes the natural glycosylation machinery of the host cell to automatically attach the modified sugar to the protein's N-linked glycan. This self-service approach eliminates the need for manual cysteine engineering and site-specific modification, as the glycosylation process naturally occurs at defined sites during protein expression, providing inherent site-specificity without additional protein engineering complexity.

The patent employs galactosyltransferase as an intermediary enzyme that specifically recognizes and modifies terminal GlcNAc residues on N-linked glycans. This enzymatic approach provides precise site-specific conjugation at glycosylation sites without requiring protein engineering, as the enzyme naturally targets specific glycan structures.

The patent replaces the copper-catalyzed click chemistry mechanism with an enzymatic mechanism (galactosyltransferase-catalyzed glycosylation). This substitution eliminates the need for toxic copper catalysts and harsh reaction conditions, thereby preventing protein damage and reducing immunogenicity while maintaining high conjugation efficiency through enzymatic catalysis.

The patent changes the reaction conditions from harsh chemical parameters (copper catalyst, organic solvents, extreme pH) to mild physiological parameters (aqueous buffer, physiological pH, ambient temperature). The enzymatic reaction proceeds under gentle conditions that preserve protein integrity and avoid immunogenic modifications.

The patent introduces galactosyltransferase as a selective intermediary that specifically targets terminal GlcNAc residues on N-linked glycans. This enzymatic mediator ensures that conjugation occurs only at defined glycosylation sites, providing batch-to-batch consistency and manufacturing precision while maintaining ease of conjugation through a single-step enzymatic reaction.

The patent applies conjugation locally at specific glycosylation sites on the protein rather than randomly across all lysine residues. The galactosyltransferase enzyme selectively modifies terminal GlcNAc residues at N-linked glycan sites, ensuring uniform and predictable conjugation patterns that improve batch consistency while maintaining simplicity.