Effect of pH, NaCl concentration, and mAb concentration of feed solution on the filterability of Planova™ 20N and Planova™ BioEX

Virus filtration is one of the most important steps in ensuring viral safety during the purification of monoclonal antibodies (mAbs) and other biotherapeutics derived from mammalian cell cultures. Regarding the various virus retentive filters, including Planova filters, a great deal of data has been reported on the virus retention capability and its mechanism. Along with the virus retention capability, filterability is a key performance indicator for designing a robust and high-throughput virus filtration step. In order to obtain higher filterability, optimization of the feed solution conditions, and filter selection is essential; however, limited data are available regarding the filtration characteristics of Planova filters. Furthermore, for Planova 20N and Planova BioEX, the virus retention characteristics were reported to differ due to their respective membrane materials and layer structures. Whether these filters differ in their filtration characteristics is an interesting question, but no comparative evaluations have been reported. In this study, the filterability of the two filters was investigated and compared using 15 feed mAb solutions of a single mAb selected by design of experiments with different combinations of pH, NaCl concentration, and mAb concentration. The filterability of Planova 20N was affected not only by the feed solution viscosity, but also by the mAb aggregate content of the feed mAb solution and mAb-membrane electrostatic interactions. In contrast, the filterability of Planova BioEX decreased under some buffer conditions. These findings and the established design spaces of these filters provide valuable insights into the process optimization of virus filtration.