Glycans of Antibodies as a Specific Site for Drug Conjugation Using Glycosyltransferases

Abstract

The therapeutic cargo molecules conjugated to a specific-site on a monoclonal antibody (mAb), called antibody-drug conjugates (ADCs), are becoming powerful tools in cancer treatment. Generally, the cargo molecules conjugated at the cysteine or lysine residue of the mAb, which generally results in a highly heterogeneous ADC. Therapeutic cargo molecules need to be conjugated in a site-specific manner to the mAb so that the bioefficacy of these molecules is not compromised. The mAb (IgG1) are N-glycosylated at the conserved residue Asn 297 , which is present in each heavy chain of the IgG1, near the CH2 domain of the Fc fragment. The mutant or wild-type glycosyltransferases transfer sugars with a chemical handle to the glycan molecule of IgG1, making the sitespecific linking of cargo molecules possible via the chemical handle, and, thus making the process an invaluable technique for the production of homogeneous ADCs.

Considerations for the Design of Antibody-Based Therapeutics

“…Similarly, postexpression glycan engineering allows for introduction of galactose and sialic acid residues that contain azide or ketone functionality. 61,226 This is achieved using glycosylating enzymes that naturally have, or are mutated to have, expanded substrate specificity. Finally, chemical oxidation of vicinal diols within glycan residues such as sialic acid introduces electrophilic aldehyde groups.…”

Straightforward Glycoengineering Approach to Site-Specific Antibody–Pyrrolobenzodiazepine Conjugates

“…3−6 Human immunoglobulins have a conserved glycosylation site in the CH2 domain of the heavy chain at position N297, making it an attractive target for generating site-specific antibody−drug conjugates. 7 However, since glycosylation is a heterogeneous post-translational modification, 8−10 remodeling of the glycan is often required before conjugation of the payload. Many reported strategies involve chemical drug conjugation following a multienzymatic process to install either natural or synthetic carbohydrate analogues, such as CMP-9-azido sialic acid and UDP-GalNAz derivatives (Figure 1), onto the antibody glycan.…”

Antibody and antibody derivatives as cancer therapeutics

“…Mild oxidation of native sugars provides a functional aldehyde that can be used to couple amine or hydrazine‐modified drug/linkers (Zhou et al, ). Alternatively, native sugars can be enzymatically remodeled using galactosyltransferase (Qasba, ) or fucosyltransferase (Okeley et al, ) to incorporate sugar analogs with more specific chemical handles. Nevertheless, the influence on antibody stability and effector function from any glycol modification should be carefully monitored.…”