Viral clearance in biopharmaceutical manufacturing: Current strategies, challenges, and future directions

Viral safety remains a fundamental requirement in the manufacturing of monoclonal antibodies (mAbs), particularly due to the widespread use of mammalian cell lines susceptible to both endogenous and adventitious viral contamination. This review provides a comprehensive overview of current viral clearance strategies integrated into downstream processing (DSP), highlighting the mechanisms, performance, and practical implementation of key unit operations. Chromatographic methods, including Protein A affinity, ion exchange (CEX and AEX), hydrophobic interaction (HIC), and mixed-mode chromatography (MMC), contribute to virus removal to varying extents, depending on virus type, resin chemistry, and process conditions. Anion exchange membranes have demonstrated high log reduction values (LRVs), especially for small non-enveloped viruses, while mixed-mode resins enhance removal through dual-mode interactions. Dedicated viral inactivation steps, such as low-pH incubation and detergent treatment, remain effective against enveloped viruses, with the use of stabilizing agents like arginine and extremolytes increasingly adopted to preserve product quality. Virus filtration continues to represent the most robust barrier to small viruses, though its performance depends on parameters such as filter material, fouling tendency, and viral load. Emerging solutions, such as activated carbon filtration and membrane chromatography, offer scalable, orthogonal alternatives compatible with disposable and continuous processing formats. Notably, viral clearance strategies have been successfully incorporated into continuous downstream workflows, including multicolumn capture, inline inactivation, and extended-duration filtration. Collectively, these advances support the transition toward more flexible, efficient, and sustainable viral safety frameworks, paving the way for next-generation biomanufacturing platforms.