On the use of glycoengineering methods for the generation of antibodies with enhanced effector functions

Glycosylation is a non-template driven cellular process wherein sugars are enzymatically attached to proteins or lipids. For IgG, the most abundant class of therapeutic antibodies, glycosylation at position N297 contributes extensively to the structure and dynamics of the antibody Fc region. Certain glycosylation motifs, including core-fucosylation, terminal galactosylation and terminal sialylation, impact the binding affinity with Fc-gamma receptors and therefore the capacity for antibodies to recruit immune cells in vivo. For therapeutic mAbs, the glycosylation motif is an important modulator of therapeutic antibody safety, stability and therapeutic efficacy. Glycoengineering enables the precise control or modification of antibody glycosylation for the targeted improvement of antibody effector functions. There are numerous approaches available depending on the target glycoform, including genetic manipulation of the cellular glycosylation genome, metabolic inhibition of glycosylation enzymes, in vitro enzymatic remodelling of glycans and complete replacement of whole chains via transglycosylation. The complexity of IgG glycosylation requires each strategy to be tailored depending upon the composition of the target glycan. In this work, we review the current glycoengineering landscape for directing antibody glycosylation during production, and for remodelling of antibody glycosylation in vitro following purification. Strategies for producing all clinically relevant glycoforms are reviewed in detail, providing a broad summary of the current and emerging options available.