BIOTECHNOLOGY
Emma Zhao discusses how high-yield and high-throughput afucosylated mAb expression benefits therapeutic antibody efficacy
A ADVANCED NTIBODY SERVICES
Fig. 1. Antibody-dependent cellular cytotoxicity
A
n absence of fucose residues on the antibody Immunoglobulin γ (IgG) constant (Fc) region N-glycan moiety has been demonstrated to
increase the binding affinity to IgG-Fc- receptor (FcγR) IIIa. It results in increased antibody-dependent cellular cytotoxicity (ADCC) since this receptor is found on immune effector cells like natural killer cells. Sino Biological has established a proprietary FucoFree eukaryotic cell culture system for the custom expression of afucosylated mAbs. Te company provides high-yield and high-throughput antibody expression with >95% purity and low endotoxin level (<1 EU/mg).
HOW DOES THE ANTIBODY WORK TO ELIMINATE THE ANTIGENS? Targets are eliminated by immune cells recruited by antibodies that specifically bind to their antigen. Trough their effector functions, IgG antibodies mediate immunity and inflammation. Interactions between complement proteins and FcγR on myeloid and Natural Killer (NK)
cells are mediated by the Fc region of the IgG antibody. Te next step is antibody- dependent cellular cytotoxicity (ADCC), in which the NK cells lyse the target cells with antigens presented on the membrane surface. It is one of the major Fc-dependent effector functions of IgG. NK-cell mediated ADCC is mainly triggered by IgG-subclasses IgG1 and IgG3 through the FcγRIIIa. Targeted monoclonal antibody (mAb) therapy is a promising therapeutic approach for many cancer types. Te majority of mAbs that are approved for use in oncology treatments trigger ADCC. Patients with metastatic breast cancer who were given trastuzumab and a taxane responded better as FcgRIIIa antibody binding increased. One way to improve the binding is to design and engineer the Fc region on antibodies, such as afucosylation. Fucosyltransferase (FUT), which
regulates the fucosylation of O- and N-glycans, is crucial for numerous physiological and pathological
processes, including infection, cancer, and inflammation. Te N-glycans on the Fc portion of human IgG are typically heavily fucosylated (~90%). Low- to non-fucosylated monoclonal antibodies improves Fc_IIIa binding. Obinutuzumab, an afucosylated anti- CD20 antibody, has received approval to treat people with chronic lymphocytic leukemia because clinical trials have demonstrated its better efficacy.
HOW CAN THE FUCOSYLATION ON FC BE LOWERED? Te elimination of the fucose residues was initially achieved via a combination of chemical and enzymatic treatment of the mAb, a laborious process with high operational costs. α-1,6-fucosyltransferase (FUT8) is the gene responsible for the addition of the core fucose residues that catalyses the transfer of fucose from GDP-fucose to N-linked type complex glycopeptides (Fig. 2). Te key enzyme in N-glycan core fucosylation is FUT8. Due to advancements in gene editing
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