“…Although qPCR-based assays have emerged as an important bioanalytical method for assessing the pharmacokinetics of human-cell-based medicinal products [ 4 , 5 , 16 , 21 ], the regulatory guidelines on the validation of bioanalytical methods released by the EMA, FDA, and ICH [ 24 , 25 , 26 , 27 ] focus on methods suitable for small- and large-molecule drugs such as chromatographic and ligand-binding assays. While the basic concepts and parameters of method validation described in these guidelines can be adapted to cell quantification via qPCR, in the absence of specific regulatory recommendations including definitive acceptance criteria for a validated qPCR assay, researchers must rely on published evidence from bioanalytical scientists, as well as recently issued best practice recommendations [ 15 , 20 , 42 ] and white papers from scientific networks [ 21 , 22 , 23 , 43 ].…”