Using qPCR and ddPCR to study biodistribution of cell therapy products: a multi-site evaluation

Regenerative therapies employing cell therapy products (CTPs) have attracted considerable attention. Biodistribution (BD) evaluation of CTPs is mainly performed to clarify the cell survival time, engraftment, and distribution site. This evaluation is crucial for predicting the efficacy and safety profiles of clinical studies based on non-clinical BD study outcomes. However, no internationally unified method has been established for assessing cell BD after administration. Here, we aimed to standardize the BD assay method used for CTPs, conducting the following evaluations using the same protocol across multiple study facilities: (1) in vitro validation of quantitative polymerase chain reaction (qPCR) and droplet digital PCR (ddPCR) analyses using the primate-specific Alu gene, and (2) in vivo BD studies after the intravenous administration of human mesenchymal stem cells (hMSCs) to immunodeficient mice, commonly used in non-clinical tumorigenicity studies.