Glycoengineering of Therapeutic Antibodies with Small Molecule Inhibitors

Abstract

Monoclonal antibodies (mAbs) are one of the cornerstones of modern medicine, across an increasing range of therapeutic areas. All therapeutic mAbs are glycoproteins, i.e., their polypeptide chain is decorated with glycans, oligosaccharides of extraordinary structural diversity. The presence, absence, and composition of these glycans can have a profound effect on the pharmacodynamic and pharmacokinetic profile of individual mAbs. Approaches for the glycoengineering of therapeutic mAbs-the manipulation and optimisation of mAb glycan structures-are therefore of great interest from a technological, therapeutic, and regulatory perspective. In this review, we provide a brief introduction to the effects of glycosylation on the biological and pharmacological functions of the five classes of immunoglobulins (IgG, IgE, IgA, IgM and IgD) that form the backbone of all current clinical and experimental mAbs, including an overview of common mAb expression systems. We review selected examples for the use of small molecule inhibitors of glycan biosynthesis for mAb glycoengineering, we discuss the potential advantages and challenges of this approach, and we outline potential future applications. The main aim of the review is to showcase the expanding chemical toolbox that is becoming available for mAb glycoengineering to the biology and biotechnology community.

Keywords: antibody; chemical tools; glycan; glycoengineering; glycoform; glycosylation; immunoglobulin; inhibitor.

Figure 1

(A) Cartoon representation and 3D structure of the Fc domain of a typical IgG and its Fc N-glycan. The crystal structure is taken from PDB 4Q7D, colour code: wheat, protein backbone; green, N-glycan; red, glycosylation site N297. (B) Common biantennary complex-type N-glycans found on mature glycoproteins.

Figure 2

Key steps during eukaryotic N-glycan biosynthesis. Red boxes indicate inhibitors of individual enzymes (CAST: castanospermine; KIF: kifunensine; SWA: swainsonine; see Section 3.4).

Figure 3

Glycosidase inhibitors 1-deoxymannojirimycin, kifunensine, swainsonine, and castanospermine, and its prodrug celgosivir. The iminosugar motif is shown in red.

Figure 4

l-Fucose, the fucosyltransferase donor GDP-l-fucose, and fucosylation inhibitors discussed in the text. Relevant structural motifs are shown in red.

Figure 5

Galactosyltransferase inhibitors based on donor (top) or acceptor (bottom) substrate.

Figure 6

Sialyltransferase inhibitors.

Figure 7

Non-substrate-like inhibitor chemotypes.