Correlative N-Glycan and Charge Variant Analysis of Cetuximab Expressed in Murine, Chinese Hamster and Human Expression Systems

A well-defined and controlled glycosylation pattern is important to maintain quality and safety of therapeutic proteins. Glycosylation is strongly dependent on the host cell line used for recombinant protein expression. Cetuximab, which is produced in mouse myeloma cells has been shown to harbour Fab glycans, which contain non-human like features and hence, can potentially cause an immunogenic response in patients. In light of the advent of biosimilar and biobetter development, we produced cetuximab variants in human embryonic kidney (HEK293) and Chinese hamster ovary (CHO) cells. A combination of orthogonal chromatographic modes such as hydrophilic interaction, size exclusion and strong cation exchange chromatography with various detection strategies was employed to characterise the three different cetuximab variants and to compare the in-house produced HEK and CHO variants with the reference drug product. While Fc galactosylation and sialic acid content of the drug product and the HEK variant were highly similar, the CHO product showed lower galactosylation on Fc glycans and a comparatively low sialic acid content in the Fab region. The elevated high-mannose content of CHO cetuximab also suggests potential rapid clearence from circulation. The combination of multiple chromatographic separation modes has proven powerful for the characterisation of expression system dependent protein quality attributes such as N-glycosylation.