Depth filtration is an integrated part of downstream process and has major impact on viral vector purification process, but often deprioritized in the overall scope of viral vector manufacturing process optimization. The ever-increasing demand in lentiviral (LV) vectors owing to increase in dose for certain disease indications makes it inevitable to improve current manufacturing processes. Advances in upstream bioreactor systems and process intensifications have enabled cell densities of over 10⁶ cells/mL and created challenges for harvest unit operations. Owing to the large size of enveloped LV vectors and the physiochemical properties similar to DNA, poor clarification performance causes significant challenges for the subsequent chromatography-based purifications. As a result, development of robust and scalable harvest process that meets yield and quality attributes has become cumbersome and difficult, especially for LV in vivo therapeutic quality needs. In this study, we have systematically evaluated depth filtration systems to improve enveloped LV functional vector recovery. We found that an established depth filtration system that provided 94% LV functional recovery in defined Process A cell culture could be not be translated to intensified Process B cell culture, and hence become bottleneck for the purification performance in an intensified process. We demonstrated LV functional vector recovery improvement from 34% to 82% via filter train optimization for intensified suspension cell culture system (>10⁶ cells/mL and higher titer), while still maintaining loading throughput of >82 L/m² and turbidity <20 NTU. It was manifested that the two or three-stage depth filtration scheme is scalable and more suitable for high cell density culture at large scale LV manufacturing process.

Mukesh Mayani

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