(522e) Virus Clearance during Downstream Purification of Protein Therapeutics

Virus clearance is an essential component of the downstream purification of biopharmaceutical products. Virus filtration flux and throughput are largely product, solution condition and filter specific due to (1) the intrinsic properties of the product including its charge, hydrophobicity and tendency for aggregation at specific solution conditions; (2) product-related foulants such as fragments and variants; (3) impurities such as host cell proteins (HCPs), DNA and spiked virus particles. Our virus filtration results indicate that insolvable aggregates are not likely the major cause for the fouling of virus filters at a product titer of ~10 g/L. Instead, product variants with higher molecular weight (MW) and stronger hydrophobicity are likely the dominant foulants during virus filtration. These variants commonly exist in protein feed streams during cell culture production. Analysis of the feed, filtrate and elution fractions indicate that these higher MW variants tends to form soluble aggregates which cause significant decay of the filtration flux.