<br/>Monoclonal antibodies (mAbs) are often produced in mammalian cell lines, potentially resulting in the introduction of adventitious viruses in the drug substance. Anion exchangers (AEX) are one of the main workhorses for the removal of viruses in mAb processes. However, viral removal is currently not a well understood process, and process development for AEX is often done via a combinatorial approach to achieve an acceptable viral clearance safety factor; this approach has sometimes led to suboptimal clearance. The goal of this study was to advance the fundamental understanding of the virus removal mechanism in flow-through AEX, which could provide a more guided approach to process development for AEX or the antecedent step in order to achieve a more favorable overall viral clearance. A design of experiment (DOE) approach was employed for this experiment by tuning key process parameters such as pH, conductivity and protein loading, while keeping buffer species and protein concentrations constant. Three mAbs with different biophysical properties were tested against these parameters. Ion exchange theory suggests that an increase in pH and a decrease in conductivity will promote virus binding to the AEX resin. It was observed that the two mAbs with higher pI did not yield higher virus removal with higher pH. Furthermore, a mild conductivity increase led to increased virus removal for all the mAbs studied. This departure from expected behavior may arise from the fact that traditional norms in ion exchange theory accounts only for a binary interactions between the virus and resin. With the introduction of the mAbs an additional two interactions are added: mAb-resin and mAb-virus interactions. The change in pH and/or conductivity may disrupt the mAb-virus interactions and weaken the mAb-resin interactions, leading to the unusual clearance trends. These results suggest that the molecule’s biophysical properties are the most significant determining factor for virus removal by AEX due to the mAb-virus interactions, which cannot be quantified solely by isoelectric point. Accounting for these interactions through molecular modeling could provide a deeper understanding of the AEX virus removal mechanism and may enable predictive viral clearance in the future.<br/>

Design of experiment approach to a mechanistic understanding of viral removal in anion exchange chromatography

2019 Spring National Meeting

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