By Jared Isaac, Eric Bishop, and Ken Hoffman, Cygnus Technologies
Host cell proteins (HCPs) co-purify with biological drug substances (DS) and pose potential risks for both patients and drug manufacturers. Regulatory authorities require that biopharmaceutical companies perform comprehensive assay qualification to demonstrate the suitability of HCP ELISAs prior to proceeding to clinical trials. ELISA is the gold standard method for monitoring HCP levels but it is limited with respect to the information it provides regarding which HCPs are present. Identification and quantification of HCPs by mass spectrometry (MS) is a powerful complementary method to ELISA, however drug substances often mask HCPs. In this study, CHO HCPs were identified by MS before and after antibody affinity extraction in a DS sample. We show that AAE followed by MS is a powerful HCP enrichment method that can identify unknown HCPs and enrich them by as much as 240-fold. ELISA and MS are orthogonal methods that provide data throughout biopharmaceutical drug purification processes to inform manufacturers about how to modify their manufacturing processes and DS purity.