Understanding the effect of increased cell specific productivity on galactosylation of monoclonal antibodies produced using Chinese hamster ovary cells

Abstract Achieving optimal productivity and desired product quality of the therapeutic monoclonal antibody (mAb) is one of the primary goals of process development. Across the various mAb programs at our company, we observed that increasing the specific productivity (qp) results in a decrease in the % galactosylation (%Gal) level on the protein. In order to gain further insight into this correlation, cells were cultured under different process conditions such as pH or media osmolality or in the presence of supplements such as sodium butyrate. A range of qp and N-glycan profiles were obtained with the greatest changes observed under high pH (lower qp, higher %Gal), higher osmolality (higher qp, lower %Gal) or sodium butyrate (moderately higher qp, moderately lower %Gal) conditions. Abundance of individual glycan species highlighted different bottlenecks in the N-glycosylation pathway depending on the treatment condition. Transcriptomics analysis was performed to identify changes in gene expression profiles that correlate with the inverse relationship between qp and %Gal. Results showed downregulation of Beta-1,4-galactosyltransferase 1 (B4GalT1), UDP-GlcNAc and Mn2+ transporter (slc35a3 and slc39a8 respectively) for the high osmolality conditions. Significant downregulation of slc39a8 (Mn2+ transporter) was observed for the sodium butyrate condition. No significant differences were observed for any of the genes in the N-glycosylation pathway under the high pH condition even though this condition showed highest %Gal. Together, data suggests that different treatments have distinct complex mechanisms by which the overall glycan levels of a mAb are influenced. Further studies based on these results will help build the knowledge necessary to design strategies to obtain the desired productivity and product quality of mAbs.