Cysteine/cystine chemistry in the culture medium plays an important role in maintaining consistent antibody product quality during manufacturing. An imbalance can result in extensive protein cysteinylation, reduced productivity and the formation of tri-sulfides from the insertion of a sulfur atom into the disulfide bonds of all IgG subclasses. Cysteine/cystine chemistry can also influence the IgG2 disulfide isomer ratios of A, A/B, and B-forms. To identify the response of tri-sulfide formation, disulfide isomers and cysteinylation to culture conditions a series of response surface DOEs were run in bench-scale reactors and the Ambr bioreactor system. Factors included media and feed cysteine/cystine concentrations, pH and temperature. Results indicated that cysteinylation, tri-sulfide formation and IgG2 disulfied isomers could all be controlled by choosing the appropriate culture conditions without decreasing productivity. Surprisingly, N-terminal truncation caused by protease activity also demonstrated a response to these conditions. We observed decreased proteolysis as well as increased overall productivity by re-balancing cysteine/cystine concentrations and increasing the culture pH. Our ongoing studies are investigating the effects of divalent cations and the removal of oxygen during formulation and storage of cell culture medium before IgG manufacturing.

Process conditions that control cysteine/cystine associated product quality attributes

253rd National Meeting (2017)

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