Application of factorial design to accelerate identification of CHO growth factor requirements.

To accelerate recombinant CHO media and process development, we describe a simple approach to integrating multiple tasks associated with these processes including initial media design, serum-free adaptation, stability analysis and first generation scale-up. Factorial design techniques and normal probability chart representation of the results were first applied to identify potent parental CHO cell growth factors in a lean basal medium. These results were then applied to identify a suitable manufacturing medium from a panel of commercial and proprietary media formulations. When this approach was applied to recombinant CHO cell line, rapid adaptation of the cell line to an appropriate production medium occurred during culture expansion in the presence of the identified growth factor(s). This approach allows media component screening to be naturally integrated into the adaptation and scale-up processes since components that have little or no relative effect on cell proliferation are selected against as the "best" cultures are moved forward. The rapidity of the adaptation process allowed cell line stability studies to be initiated relatively early in the development process, thus providing preliminary stability information by the time the "outgrowing" culture could be scaled to 100-L reactors some 30 days after adaptation commenced. The application of full factorial design techniques allowed us to calculate the maximum number of interaction effects, the interpretation of which we believe can provide insights into growth factor biology.