Assessment and Control of Host Cell Proteins in Biologics: Survey of Industry Practices and a Vision for Harmonization

ABSTRACT Host cell proteins (HCPs) are important process‐related impurities produced by the host organism during the manufacturing of biotherapeutics. Even trace amounts of these contaminants can be considered significant during drug development due to their potential impact on the quality, safety, and/or efficacy of the therapeutic. This article summarizes the findings of a survey conducted by the IQ DruSafe Impurities Safety Working Group (Biologics Impurities Subteam) concerning industry practices and challenges related to HCPs in biologic therapeutics. The survey addressed four key areas: the scope of HCP control challenges, practices for HCP control and monitoring, methods for qualification of HCP levels, and regulatory interactions. Results revealed both perceived risks and experienced impact from HCP impurities as well as analytical strategies for their identification and quantification. The article also presents current default limits being employed for total and individual HCP impurities, approaches for assessing the safety and immunogenicity risk of HCPs, and a summary of feedback from global health authorities. Overall, the survey results illustrate progress in HCP management across biologic drug development while underscoring persistent challenges. The findings point to emerging best practices informed by historical knowledge and also reveal areas where a harmonized approach may be justified. Identifying and addressing challenges will require sustained industry collaboration and ongoing engagement with regulatory authorities to ensure the continued advancement of safe, effective biologic therapeutics.