Host-cell proteins (HCPs) constitute an inevitable impurity of biopharmaceutical products originating from recombinant-cell culture. HCPs are a heterogeneous mix of different proteins, their specific characteristics depending on the kind of organism used as an expression platform, on the “destination” of the expressed recombinant product (extra- or intracellular), and on the corresponding purification approach (1–3). Contamination of a final drug substance with residual HCPs could lead to immunogenic reactions in some patients who receive the drug product (DP). So a reliable…