Potency can be described as the quantitative measure of biological activity, that is, the ability of an Advanced Therapy Medicinal Product (ATMP) to elicit the intended effect necessary for clinical efficacy. Potency testing is part of the quality control strategy necessary for batch release and is required for market approval application of an ATMP. Thus, it is crucial to develop a reliable and accurate potency assay. As a prerequisite for potency assay development, it is essential to define the mode of action of the product and thereby also the relevant biological activity that should be measured. The establishment of a potency assay should be initiated already during early product development followed by its progressive implementation into an ATMP's manufacturing, quality control and release process. Potency testing is indispensable for clinical use with a wide range of applications. A potency assay is a valuable tool to determine the product's stability, detect the impact of changes in the manufacturing process on the product, demonstrate quality and manufacturing consistency from batch to batch, estimate clinical efficacy and define the effective dose. This chapter describes the requirements and challenges to be considered for potency assay development and the importance of a well-established potency assay for clinical use.
Keywords: ATMP; Assay development; Biological activity; Cell therapy; Clinical efficacy; Clinical use; Potency assay; Quality control; Stability testing; Surrogate marker.
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