Viruses can arise during the manufacture of biopharmaceuticals through contamination or endogenous expression of viral sequences. Regulatory agencies require "viral clearance" validation studies for each biopharmaceutical prior to approval. These studies aim to demonstrate the ability of the manufacturing process at removing or inactivating virus and are conducted by challenging scaled-down manufacturing steps with a "spike" of live virus. Due to the infectious nature of these live viruses, "spiking studies" are typically conducted in specialized biological safety level-2 facilities. The costs and logistics associated with these studies limit viral clearance analysis during process development and characterization. In this study, a noninfectious Minute Virus of Mice-Mock Virus Particle (MVM-MVP) was generated for use as an economical small virus spiking surrogate. An immunoglobin G containing solution was spiked with live MVM or MVM-MVP and processed through Planova nanofiltration units. Flux decay data was collected and particle reduction values were calculated from TCID and Immuno-qPCR analysis. The data indicated comparable filtration performance and particle reduction between infectious MVM and noninfectious surrogate, MVM-MVP. This proof of concept study suggests the feasibility of utilizing MVPs for predictive size-based viral clearance assessments during process development and characterization as an alternative to homologous infectious virus.
The production of biopharmaceutical products carries an inherent risk of contamination by adventitious viruses. Historically, these manufacturing processes have incorporated a dedicated virus filtration step to ensure product safety. However, challenging process conditions can lead to passage of small viruses to the permeate pool and an overall decrease in the desired virus logarithmic reduction value (LRV) for the process. The implementation of serial virus filtration has improved the robustness of such processes, albeit concerns about increased operating times and process complexity have limited its implementation. This work focused on optimizing a serial filtration process and identifying process control strategies to provide maximum efficiency while ensuring proper controls for process complexity. Constant TMP was identified as the optimal control strategy, which combined with the optimal filter ratio, resulted in a robust and faster virus filtration process. To demonstrate this hypothesis, data with two filters connected in series (1:1 filter ratio) are presented for a representative non‐fouling molecule. Similarly, for a fouling product, the optimal setup was a combination of a filter connected in series to two filters operated in parallel (2:1 filter ratio). The optimized filter ratios bring cost‐ and time‐savings benefits to the virus filtration step, thereby offering improved productivity. The results of risk and cost analyses performed as part of this study combined with the control strategy, offer companies a toolbox of strategies to accommodate products with different filterability profiles in their downstream processes. This work demonstrates that the safety advantages of performing filters in series can be achieved with minimal increases in time, cost, and risk.
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