The use of cells as a cryopreserved, readily available reagent has facilitated high-throughput screening of new drug candidates by bioassay. This practice is considerably less labor intensive and allows more flexibility in laboratory testing than traditional continuous cell culture. We have shown that this practice can be adapted to cell proliferation and reporter gene assay formats used in routine sample testing for determination of relative potency of commercial product in a Quality Control Laboratory. The ability to use the same, optimized population of cells provides consistency in an assay over time. Measures of assay performance to indicate maintenance of the validated state of a method and to determine benefit on variation in potency results were compared between cultured and cryopreserved (frozen ready-to-plate) cells. Control of the cellular component, which is the most variable aspect of most cell based potency assays, allowed detection of more minor contributors to variability. In a cell proliferation assay format, the final result was a highly precise bioassay (repeatability CV of 2%). An improvement in process capability (Cp) was noted when ready-to-plate cells were used in the studies completed over long periods of time.
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