Adjusting Cell Line Stability Study to Unfold Final Clone Selection
Traditional cell line stability study requires at least 60-generation cell passage and fed-batch evaluation between the pre-MCB (PCB) and the cells after stability passage (referred to as “PDL60”). The entire cell line stability takes almost 2 months, depending on the doubling time of the cell line. In the context of an aggressively accelerated CMC timeline, fitting in a full-length 12-week cell line stability could be particularly challenging. On the other hand, the instability of the final MCB clone, should it occur, could be devastating to the CMC plans. Therefore, however low risk of instability a cell line has, some degrees of the intelligence of the cell line stability should be acquired before deciding on the selection of the final MCB clone.
Empirically, loss of productivity usually occurs without selection pressure sustaining (data not shown). To evaluate the cell line stability as quickly as possible, selection pressure was removed as early as permissible by the actual needs of cells from other aspects, such as clone screening and bioreactor evaluation, and the cells were continuously passaged for approximately 30 PDLs before fed-batch inoculation. Most of the clones displayed stable productivity (Fig. 5). A single-cell genetic stability test was also performed with the clone candidates to further probe the potential risks of cell line instability (He et al., 2012).