Biopharmaceuticals are the largest group of drugs under development (1), and the demand for new and safe drug products is high. The most common bacterial and mammalian cell lines for production are Escherichia coli, Chinese hamster ovary (CHO) cells, and yeast. During a production bioprocess, a cell line expresses not only the molecule of interest, but also host-cell proteins (HCPs). They are considered to be impurities in a final drug product because they can affect the efficacy and safety of…