Multi-column continuous chromatography effectively improves the robustness of bind-elute mode chromatography in which a pre-elution wash is applied to reduce weakly bound impurities and charge variants.

Background: For the purification of monoclonal antibodies, we employed a wash step in the cation exchange (CEX) chromatography to reduce acidic charge variants. Although optimal wash conditions, determined under a specific loading density, ensured both effective reduction of charge variants and good process yield, applying the same wash conditions to runs where the loading density moderately deviated from the optimal value could result in insufficient reduction of charge variants or low step yield. This issue is particularly problematic with large-scale manufacturing, where the same wash condition (including buffer and volume) is applied across all runs, despite variations in loading density due to fluctuations in harvest titer. Objective: To address this problem, we intended to demonstrate that multi-column continuous chromatography could offer an effective solution. Methods: A multi-column setup was implemented, in which all runs except the final one were performed under optimal conditions to ensure both high product quality and yield. Results: The multi-column approach allowed for both effective charge variant reduction and achievement of good step yield. Although the final run might be conducted under suboptimal conditions, potentially compromising quality or yield, its impact is minimal, as it contributed only a small fraction to the total product, thereby exerting a limited effect on overall quality and yield. Conclusion: The current study successfully demonstrated the proof-of-concept using CEX chromatography. In fact, the multi-column strategy proposed here may provide a universal solution to the load-dependence issue in wash steps that is aimed at removing or reducing weakly bound impurities or charge variants in any type of bind-elute mode chromatography.