Establishment of FUT8 knockout Chinese hamster ovary cells: An ideal host cell line for producing completely defucosylated antibodies with enhanced antibody‐dependent cellular cytotoxicity

Abstract
To generate industrially applicable new host cell lines for antibody production with optimizing antibody‐dependent cellular cytotoxicity (ADCC) we disrupted both FUT8 alleles in a Chinese hamster ovary (CHO)/DG44 cell line by sequential homologous recombination. FUT8 encodes an α‐1,6‐fucosyltransferase that catalyzes the transfer of fucose from GDP‐fucose to N‐acetylglucosamine (GlcNAc) in an α‐1,6 linkage. FUT8−/− cell lines have morphology and growth kinetics similar to those of the parent, and produce completely defucosylated recombinant antibodies. FUT8−/−‐produced chimeric anti‐CD20 IgG1 shows the same level of antigen‐binding activity and complement‐dependent cytotoxicity (CDC) as the FUT8+/+‐produced, comparable antibody, Rituxan. In contrast, FUT8−/−‐produced anti‐CD20 IgG1 strongly binds to human Fcγ‐receptor IIIa (FcγRIIIa) and dramatically enhances ADCC to approximately 100‐fold that of Rituxan. Our results demonstrate that FUT8−/− cells are ideal host cell lines to stably produce completely defucosylated high‐ADCC antibodies with fixed quality and efficacy for therapeutic use.

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