Strategies for removing two "problematic" host cell proteins, using an "end-to-end" approach

Host cell proteins (HCPs) are critical process-related impurities of recombinant protein biopharmaceuticals that have the potential to impact product safety and efficacy. In this study, two residual HCPs, heat shock protein 90 beta and perilipin-4-like, produced from a CHO cell line, were identified during the development of a late-stage platform Immunoglobulin G subclass 1 (IgG1) monoclonal antibody process. A risk assessment was performed that included identification of HCPs, homology with their human protein counterparts, and prior non-clinical and clinical experience. The outcome deemed these two species as "problematic" and target levels were established to guide approaches for removal. Given the high productivity of the upstream and downstream platform processes, the goal was to explore conditions that minimize deviations from the platform. An end-to-end approach was performed that evaluated downstream levers, including Protein A washes, polishing chromatography operational parameters, and exploration of depth filter media. Upstream levers were also explored, evaluating effects of temperature shift and modulation of iron and citrate to help control levels of both HCP species. The results presented in this study demonstrated the upstream and downstream conditions achieved effective removal of the two HCP species to meet drug substance targets.