Preclinical study design for evaluation of stem cell-derived cellular therapy products: a pathologist's perspective.

Despite-or perhaps because of-the rapid expansion of interest in stem cell-derived cellular therapy products, relatively few guidelines have been published to assist in the design of scientifically sound preclinical studies. The field is complex and wide ranging, and of necessity regulators tend to treat each project on a case by case basis. One of the core tenets remains the need to retain all tissues from the study, thereby allowing for further analysis of tissues should unexpected effects be seen in clinical studies; attempts to comply with this may result in an unmanageable financial burden. Judicious input from the pathologist at the earliest stages of study design may not only improve the scientific integrity of the study but also help to mitigate some of the cost. Careful animal selection, the development of robust cell markers, and justifiable triage of tissues based on phased tissue examination can all be discussed with the regulatory authorities at pre-pre-investigational new drug (IND) and pre-IND meetings to achieve optimal study design.