Effect of Cell Culture Environment on the Stability of IgG1

As the biopharmaceutical industry has matured, there have been significant advances in the production of cell culture titres. However, it is hard to predict the effect that bioprocessing advances have had on antibody stability. This project explored the effects of the cell culture itself on IgG1, with particular focus on the quantities of IgG1 that are being unaccounted for as a consequence of the IgG1 interacting with components of the exogenous media. Analysis conducted on GS null CHO CAT-S cell culture runs, with five IgG1s spiked in at the inoculation stage at a variety of concentrations, indicated that IgG1 loss is occurring at rates ranging from 7.14% to 21.50%, regardless of concentration. Type of IgG1 was identified as the primary predictor of IgG1 loss, with media composition and feed strategy as a secondary predictor. Links were identified between the type of feed strategy used and the number of non-viable cells in the cell culture runs. This potentially indicates that a factor leading to IgG1 loss in culture is related to an internal component of the cells that is released into the exogenous media following lysis of the cell. Additional analyses were conducted in order to identify potential mechanisms that could be leading to IgG1 loss. These analyses indicated that a portion of the IgG1 is removed with the centrifuged cellular debris. Successful attempts at re solubilising this IgG1 suggest that the IgG1 is precipitating out of solution and may be recoverable. The work in this thesis highlights that a greater quantity of IgG1 is potentially being lost as a consequence of the cell culture process than was previously understood and that additional analyses, to improve bioprocessing, should focus on analysis of the cellular debris.