GPEX AND GENETIC STABILITY
Because of the genetic stability of GPEx generated cell lines, stability studies do not need to be performed as part of the
cell line selection process. Cell lines selected to master cell bank are chosen strictly based on protein expression and protein
quality. Once the master cell bank is produced, confirmation of cell line genetic stability is performed on the bank. Results
for 17 GPEx cell banks each producing a different protein are shown in Figure 4. The cell bank for each cell line was designated
as generation 0 for the purpose of the study. Cells were continuously cultured by serial passage from generation 0 to approximately
generation 40 or 60 depending on the study protocol. At the end of the experiment, samples of cells from the generation 0
cell bank and from the generation 40 or 60 culture were used for DNA and RNA isolation. Real-time PCR analysis of the DNA
showed no significant difference between the number of transgenes at generation 0 and generation 40 or 60 for any of the 17
banks. To examine the stability of mRNA expression, cell banks producing seven different antibodies were tested at generation
0 and 60. Heavy and light chain mRNA levels were estimated individually at the two time points for each of the cell lines.
No significant differences in heavy chain or light chain mRNA levels over the extended culture were observed (see Figure 5).
The GPEx method of gene insertion consistently produces genetically stable cell lines. The fact the gene inserts are single
copy make the method inherently more stable than any technique that results in more than one copy of the transgene inserted
at a single chromosomal location. This innate genetic stability of the cell lines allows biopharmaceutical development timelines
to be shortened 3–5 months by removing cell line stability screening from the critical path.
GREGORY T. BLECK, PHD, Research and Development Platform Lead- Biologics, Catalent Pharma Solutions, Middleton WI, Gregory.Bleck@catalent.com
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