Chromatographic clarification overcomes chromatin-mediated hitch-hiking interactions on Protein A capture column

Protein A capture chromatography is a critical unit operation in the clearance of host cell protein (HCP) impurities in monoclonal antibody (mAb) purification processes. Though one of the most effective purification steps, variable levels of protein impurities are often observed in the eluate. Coelution of HCP impurities is suggested to be strongly affected by the presence of chromatin complexes (Gagnon et al., 2014; Koehler et al., 2019). We investigated the effect of removal of DNA complex and HCP reduction pre-Protein A on the HCP clearance performance of the Protein A capture step itself. We found that only reduction of DNA in the Protein A load consistently lowered HCP in the Protein A eluate. Reduction of HCP in the Protein A load stream did not produce a significant increase in the chromatography HCP clearance performance. These results are consistent across three different biosimilar therapeutic mAbs expressed by the same Chinese hamster ovary (CHO) cell line (i.e., CHO^BC ® of Polpharma Biologics). This result demonstrates that optimization of the mAb purification process utilizing Protein A as the primary capture step depends primarily on being able to effectively clear DNA and associated complexes early in the process, rather than trying to incorporate HCP reduction at the harvest cell culture fluid.