Mechanistic Insights into Aggregation Form Elimination of Cation Exchange Membrane Chromatography

In the field of monoclonal antibody (mAb) therapeutics, protein aggregates can significantly impact drug safety and efficacy. In standard industrial production, downstream purification processes often rely on cation-exchange chromatography (CEX) as a robust method for removing aggregates with a binding–elution mode using resin. However, this conventional approach can paradoxically trigger aggregate formation, which creates a critical bottleneck in production for certain molecules. In this study, experimental comparison revealed that switching to cation-exchange membrane chromatography effectively avoided the net HMW increase observed with the resin-based process. We hypothesize that mass transfer in conventional resins relies on diffusion, which leads to a non-uniform distribution of the sample within the column. This heterogeneity can cause localized regions of extremely high concentrations, thereby inducing aggregation for concentration-sensitive molecules. Most importantly, it suggests membrane chromatography as a promising solution for purifying concentration-sensitive proteins, avoiding the net HMW increase even under high-concentration processing conditions. It should be noted that this study was performed with a single concentration-sensitive IgG1 molecule, and the proposed mechanism remains a working hypothesis; applicability to molecules with different pI values or binding behaviors requires further evaluation.