Executing Efficient Scale-up and Large-Scale Viral Vector Manufacturing

In this podcast, we spoke with Margherita Neri, Director of Vector Process Development, Milan Site at AGC Biologics, Andrew Laskowski, Global Product Manager Bioreactors at Cytiva and Andreia Pedregal, Upstream Applications Specialist Manager at Cytiva about large-scale viral vector manufacturing. Our conversation included discussions around scalability, AAV (adeno-associated virus) and lentivirus production platforms, adherent culture, and next generation bioreactor improvements. I began the interview by asking Margherita about her work at AGC Biologics. She explained that as the Director of the Vector Process Development Unit, her team is responsible for process development of large scale viral vector production for gene therapy applications. Her team is also the first point of contact for new clients. Next, we talked about the types of viral vector platforms that AGC Biologics operates. Margherita described that at their Milan site, they offer AAV (adeno associated virus) and lentiviral vector production platforms in adhesion and in suspension, at 50-to-200-liter scale with expansion planned for up to 1,000 liters. I then asked her about some of the differences between adherent cell culture and suspension cell culture paths to commercial manufacturing. Margherita said that the first consideration is that most clinical trials in gene therapy have been sustained with vector produced from adherent cells, typically via processes performed using Cell Factory™ or Cell STACK®. Now that those gene therapy products are being commercialized, manufacturers need to increase scale and demonstrate comparability using a minimal comparability exercise. So, systems that allow adherent scale up are very useful in this process. Suspension processes are appealing from a scalability point of view because historically they were used for traditional protein bioproductions which can be scaled up to 20,000 – 30,000 liters. Of course, this scale still needs to be demonstrated for vector production that is performed mainly using transient transfection at 200-500 liter scale for lentivirus and between 500-to-1,000-liter maximum scale for AAV. Margherita went on to say that another important aspect in comparability between adherent and suspension systems is quality of the vector in terms of impurity profiles. She said that with adherent processes, cells are attached to the growth support, and the levels of host cell protein and cell DNA are lower when compared to suspension processes. This is very important for lentiviral vector production that is used in vivo where the requirements for impurity levels are very challenging, especially considering that for lentiviral vectors there is currently no affinity step for purification. I followed up by asking her how AGC Biologics can help customers that want to stay in adherent culture to scale up from current processes, for instance, from flatware to larger-scale production. She explained that when customers ask for a scale increase, they usually offer the iCELLis™ platform. First, they demonstrate at small scale the feasibility of the transition from flatware to the iCELLis bioreactor using the iCELLis Nano bioreactor. Using the iCELLis Nano bioreactor, AGC Biologics has developed a full upstream and downstream process that is highly representative of their process using the full-scale iCELLis bioreactor. AGC Biologics can then propose that customers use the vector produced in the iCELLis scale-down model to perform a comparability study between a clinical vector and the future commercial or large-scale vector. This comparability should be based not only on the comparison of titers, residuals, and all the CQA, but also AGC Biologics suggests performing a test of cell transduction on the target cells (i.e. CD34 or T cells) and evaluation on these cells of transfection efficiency – vector copy number, residuals and functionality. I followed up by asking Margherita about whether the iCELLis system was scalable. She said that yes, in their experience the system is scalable, with some work required to perform the scale up from the iCELLis Nano bioreactor to the iCELLis 500 + bioreactor. They did a lot of experiments to verify the scalability from the iCELLis Nano to the iCELLis 500 +bioreactor. After these preliminary studies the productivity data in the full-scale runs was very comparable to the runs that were obtained in the iCELLis Nano. Next, I asked Andrew about any recent improvements that had been made to the iCELLis bioreactor. He explained that the iCELLis bioreactors have been commercially available for a little over ten years. The company has been launching new products and improvements to this family on an almost annual basis. For the iCELLis 500 bioreactor specifically, they launched a significant hardware upgrade in 2017 of the iCELLis 500 + and this upgrade allows the system to be implemented into GMP clean rooms much more easily. They have also continually upgraded the