Simon Fradin1, Kerstin Hein1, and Helmut Kewes1 1Cevec Pharmaceuticals GmbH, Cologne, Germany Robert Glaser2, Ulrike Rasche2, and Ma Sha3 2Eppendorf Bioprocess Center Juelich, Germany; 3Eppendorf Inc., Enfield, CT, USA
Bioprocess development is usually carried out at small working volumes. This helps saving time and resources, because at small scale several experiments can be conducted in parallel, costs for media are kept low, and not much lab space is required to operate small-scale bioreactors. But in the course of biopharmaceutical development more material is needed for characterization, trial runs, and finally for commercialization. To maintain product yield and product quality while scaling up, bioprocess engineers usually aim to keep one or more process parameters constant across scales.
Stirred-tank bioreactors with similar vessel geometries and capabilities across scales simplify scale-up, as they allow keeping critical parameters constant. Parameters to describe the vessel geometry include impeller diameter, vessel diameter, liquid height and ratios thereof. Key engineering parameters related to scale-up include the tip speed, mixing time, volumetric mass transfer coefficient (kLa), and the power input/volume ratio (P/V). It depends on the process, which of these parameters is most important. Cevec Pharmaceuticals uses a unique human cell–based expression system (CAP Technology) in two product portfolios. One is the glyco-optimized CAP Go® cell line for tailor-made production of N- or O-glycosylated proteins, the other is the CAP GT cell platform for stable and transient industrial-scale production of recombinant adeno-associated viruses (rAAV), lentiviral, and adenoviral gene therapy vectors. In this study, researchers at Cevec aimed at scalingup a rAAV transient production process using CAP GT cells. When scaling up, they maintained constant P/V between vessels, which is one of the most prevalent strategies for scale-up.