A weak anion exchange (AEX) resin is utilized as the first polishing chromatography unit operation in a recombinant protein purification process. Clearance of product-related variants across this anion exchanger is shown to be dependent on the difference in net charge imparted by biochemical modifications as measured by isoelectric focusing (cIEF). Thus, a mechanism emerges wherein product-related variants with a higher net-negative charge (and, consequently, higher affinity for the AEX ligand) displace product-related variants with a lower net-negative charge during the load phase. Additionally, the pH of the wash and elution buffers is shown to have a substantial impact on clearance of these variants. The development of this mechanistic understanding – through Quality by Design (QbD) principles during small-scale process characterization – led to establishment of the proven acceptable ranges (PAR) of various critical process parameters (CPP) for this unit operation in the commercial manufacturing process.

Employment of QbD principles to control charge variants with anion exchange chromatography

249th National Meeting (2015)

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