Regulatory aspects of clinical xenotransplantation.

Xenotransplantation attracted interest from regulatory authorities, particularly after the demonstration of pig-to-human transmission of porcine endogenous retrovirus (1996). This added to the risk of a product, resulting in a Guidance of the US Food and Drug Administration (2003). This addresses the full flow chart in product manufacturing, starting with the designated pathogen-free status of the source animal; and special aspects regarding the recipient like informed consent and monitoring for infectious pathogens. Also archiving of records from the donor and recipient, as well as storage of samples is described. The European Medicines Agency issued a Guideline on xenogeneic cell therapy products (2009). Cell-based medicinal products are subject to specific regulations and directives, which apply also to xenogeneic products: the xenotransplant guidances/guidelines are an addition to these regulations. Noteworthy, acellular products like heart valves and decellularized cornea are not considered a cell therapy product, but rather a medical device with its own regulation. WHO issued relevant documents, especially about safety, and the International Xenotransplantation Association published consensus documents, a.o., addressing preclinical efficacy requirements before entering clinical trials. This manuscript presents an overview of the regulatory framework, with special focus on cell therapy products necause these are expected to reach the market first (i.e., pancreatic islets, hepatocytes and cellularized cornea); major illustrations are from the European situation. Albeit being complex, the regulation of xenotransplant products does not form a block in product development, but rather supports the introduction of efficacious and safe products to meet the medical need.