General Requirements for Cell Lines

Nevertheless, there are general requirements applicable to cell lines used across different assays, including:

• Stay away from donor cells whenever possible. Primary cells are notoriously variable and often have poor viability and limited quantities won't support all formats of the assay.

• Verify legal permissions for cell use. When acquiring cells from universities, cell bank, or other organizations, consult your legal group before you invest your resources to develop the potency assay. Note that the same applies to cells received from the research department within your own organization. Often these cells have not been vetted for commercial use. Many cell lines are restricted to research and development purposes and cannot be utilized for releasing commercial products.

• Assess the biochemical stability of critical receptors or proteins in your cells. Many cells are phenotypically unstable and may dedifferentiate during passaging. Select cells, which can be passaged a minimum of 20 times without losing key functional attributes; stability at greater passage numbers (e.g. more than 50) are preferable.

• Plan that a significant amount of your development will center around the care and handling of your cells. For plate-based formats (such as 96-well or 384-well), prioritize plate homogeneity early in development. This assessment can include a combination of viability dyes and antibodies targeting critical receptors and does not necessarily require complete assay execution.

• Where feasible, consider using frozen-ready-to-use (FRTU) cells. Over the past two decades, there has been a transition toward cells that can be pipetted directly into assay plates and employed within a day. In contrast, traditional methods involve extensive passaging and culture periods prior to assay initiation. This single technology change has resulted in more QC friendly assays with greatly enhanced precision.