Lec13 cells, a variant Chinese hamster ovary cell line, were used to produce human IgG1 that were deficient in fucose attached to the Asn 297 -linked carbohydrate but were otherwise similar to that found in IgG1 produced in normal Chinese hamster ovary cell lines and from human serum. Lack of fucose on the IgG1 had no effect on binding to human Fc␥RI, C1q, or the neonatal Fc receptor. Although no change in affinity was found for the His 131 polymorphic form of human Fc␥RIIA, a slight improvement in binding was evident for Fc␥RIIB and the Arg 131 Fc␥RIIA polymorphic form. In contrast, binding of the fucose-deficient IgG1 to human Fc␥RIIIA was improved up to 50-fold. Antibody-dependent cellular cytotoxicity assays using purified peripheral blood monocytes or natural killer cells from several donors showed enhanced cytotoxicity, especially evident at lower antibody concentrations. When combined with an IgG1 Fc protein variant that exhibited enhanced antibody-dependent cellular cytotoxicity, the lack of fucose was synergistic.

We have engineered two Chinese hamster ovary cell lines secreting different recombinant glycoproteins to express high levels of human beta1,4-galactosyltransferase (GT, E.C. 2.4.1.38) and/or alpha2, 3-sialyltransferase (ST, E.C. 2.4.99.6). N-linked oligosaccharide structures synthesized by cells overexpressing the glycosyltransferases showed greater homogeneity compared with control cell lines. When GT was overexpressed, oligosaccharides terminating with GlcNAc were significantly reduced compared with controls, whereas overexpression of ST resulted in sialylation of >/=90% of available branches. As expected, GT overexpression resulted in reduction of oligosaccharides terminating with GlcNAc, whereas overexpression of ST resulted in sialylation of >/=90% of available branches. The more highly sialylated glycoproteins had a significantly longer mean residence time in a rabbit model of pharmacokinetics. These experiments demonstrate the feasibility of genetically engineering cell lines to produce therapeutics with desired glycosylation patterns.

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