Virus Filtration Development for Adeno-Associated Virus-Based Gene Therapy Products

Adeno-associated virus (AAV) vectors have become a leading platform for gene delivery. A major portion of gene therapy currently in clinical trials are AAV-based for a wide range of diseases. A commonly used method for AAV production is by mammalian or insect cell culture, with or without added viruses to introduce needed genetic elements for AAV production. There are potential risks of virus contamination from the production cell line, process residuals, or adventitious contamination in the production of biotherapeutics, including AAV-based gene therapy products; therefore, it is imperative to demonstrate that the drug substance manufacturing process has sufficient capability to clear process-related or adventitious viruses. In the AAV-based gene therapy manufacturing process, cell lysis, affinity chromatography, and ion exchange chromatography steps are often effective to inactivate or remove viruses. To increase the viral clearance robustness, virus filtration (VF) is increasingly recommended by regulatory agencies for gene therapy products as a dedicated viral clearance step in the downstream purification process. In the current study, two commercially available virus filters were evaluated in the context of AAV manufacturing. The filter throughput and process yield were assessed under different operational modes. Virus clearance performance was evaluated by spiking in Adenovirus type 5 (Adv-5) and Simian virus 40 (SV-40). The viral filters assessed in this study demonstrated manufacturable throughputs, acceptable process yields, and robust virus clearance capabilities for viruses greater than 40 nm.