Modulating tyrosine sulfation of recombinant antibodies in CHO cell culture by host selection and sodium chlorate supplementation.

Abstract

Tyrosine sulfation is a post-translational modification found on many surface receptors and plays an important role in cell-cell and cell-matrix interactions. However, tyrosine sulfation of therapeutic antibodies has only been reported very recently. Because of potential potency and immunogenicity concerns, tyrosine sulfation needs to be controlled during the manufacturing process. In this study, we explored methods to modulate antibody tyrosine sulfation during cell line development and upstream production process. We found that tyrosine sulfation levels were significantly different in various Chinese hamster ovary (CHO) cell lines due to differential expression of genes in the sulfation pathway including tyrosylprotein sulfotransferase 2 (TPST2) and the sulfation substrate transporter SLC35B2. We also screened chemical inhibitors to reduce tyrosine sulfation in CHO culture and found that sodium chlorate could significantly inhibit tyrosine sulfation while having minimal impact on cell growth and antibody production. We further confirmed this finding in a standard fed-batch production assay. Sodium chlorate at 16mM markedly inhibited tyrosine sulfation by more than 50% and had no significant impact on antibody titer or quality. These data suggest that we can control tyrosine sulfation by selecting CHO cell lines based on the expression level of TPST2 and SLC35B2 or adding sodium chlorate in upstream production process.