(64c) Breaking the Habit: Overcoming Acute Sensitivities of Antibody-Producing Mammalian Cell Lines to pH and Raw Materials

As part of a broad effort to understand and refine our existing scale-down bioreactor model for several monoclonal antibody producing CHO and NS0 cell lines, we examined several possible sensitivities including pH set-point and raw materials.  Initially, cells were grown at pH set-points ranging from 6.8 to 7.1 using the same bioreactor configuration.  As the pH increased, cells produced more lactate and alanine.  In addition, at lower pH set-points, ammonia production decreased.  Follow-up studies examined feed composition and feeding strategy in several different bioreactor scales.  We found that subsurface feed addition resulted in dramatic improvements in final antibody titer (~25%) while also reducing lactate production by more than 50%.  Similarly, we examined the impact of an animal-origin derived raw material in the performance of our scale-down model and were successful in re-creating large-scale trends in growth and productivity.  However, our scale-down model also exhibited tremendous variability, as replicate conditions diverged in performance.  Careful review of historical data suggested several avenues to explore including: cell bank source, age of media supplements, cleaning procedures, feeding strategy, agitation and sparging flow rates.  Several experimental blocks were constructed to investigate these factors and our results indicated the cell source, a single raw material and overall feeding strategy were most influential in terms of process variability.  Subsequent work has reduced the variability in our small-scale model while preserving the ability to re-create large-scale trends in performance.  Collectively, understanding these sensitivities has enabled us to improve our cell culture performance in terms of both productivity and robustness.