Host cell proteins (HCP) constitute a major group of impurities for biologic drugs produced using cell culture technology. Even at nanogram per milligram concentrations of HCP to drug substance (DS), HCPs can elicit undesired immune response, interfere with drug safety and efficacy, or impact DS stability. A broadly-reactive HCP ELISA should be used during the purification processes to ensure removal of HCPs and to demonstrate process consistency and final DS purity. Regulatory authorities are requesting biopharmaceutical companies employ orthogonal methods…