A method for improving protein A chromatography's aggregate removal capability

Protein A chromatography is generally less effective at removing antibody aggregates under typical conditions. We recently developed a method that can significantly improve Protein A's aggregate removal capability. This method involves adding calcium chloride/polyethylene glycol (PEG) or sodium chloride/PEG combination to wash and elution buffers. Each salt alone showed some resolution-enhancing effect when its concentration reaches a certain level, and this effect was significantly enhanced by the presence of PEG, which itself had no effect on resolution. The synergistic effect of salt and PEG results in almost complete separation of monomer from aggregates. For the particular case used for method development and demonstration, in comparison with the control run the optimized procedure reduces aggregates in elution pool from 20% to 3-4%. This new method, by facilitating aggregate removal at the capture step, improves the overall robustness of downstream process.