Host cell proteins (HCPs) originate from host organisms that are used to produce biopharmaceutical products. They are in-process contaminants that must be minimized during downstream process operations. According to regulatory agencies, the maximum permitted level of total HCP in a biopharmaceutical product is 100 ng per mg (100 ppm) (1). HCPs can decrease drug efficacy and pose a risk to patient safety because they can bring on undesirable immune responses. Thus, HCPs are a critical quality attribute that should be…