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Korbutt GS. The International Xenotransplantation Association consensus statement on conditions for undertaking clinical trials of porcine islet products in type 1 diabetes—Chapter 3: Pig islet product manufacturing and release testing. Xenotransplantation 2009; 16: 223–228. © 2009 John Wiley & Sons A/S.This chapter provides recommendations on pig islet product manufacturing and release testing to scientific and corporate programs interested in future clinical studies using xenogeneic porcine pancreatic islet cell products for the treatment of type 1 diabetes.To facilitate control of manufacturing as well as reproducibility and consistency of product lots, the manufacturing process, and the manufacturing facility must be in compliance with current Good Manufacturing Practices regulations. Data must be provided to demonstrate that islet products can be consistently prepared that would meet basic lot release requirements. To facilitate product safety: (i) materials used in the manufacturing process, including the pig pancreas, must be free of adventitious agents; (ii) islets must be manufactured using aseptic processing; and (iii) final product must undergo tests for sterility, mycoplasma (if cultured) and endotoxin. Safety specifications for pig islet product release include a negative Gram stain and an endotoxin content of <5.0 EU/kg recipient body weight. Product post-release assessments must include sterility cultures on the final product. Because results for sterility are available only retrospectively, a plan of action must be in place for patient notification and treatment in case the sterility culture results are positive for contamination. Product characterization information must address important aspects of lot release testing such as identity/purity (cell composition), quantity [islet equivalents (IE), cell number] and potency (insulin secretory capacity, oxygen consumption rate corrected for DNA or transplant bioassay in immunoincompetent diabetic mice). This information is also critical to demonstrate manufacturing control and product consistency across multiple islet preparations (lots). Providing islet products containing an islet mass sufficient to restore euglycemia in trial participants (≥10 000 IE/kg) requires pooling of islets from multiple donor pancreata (two to four from adult donors and seven to 10 from neonatal donors). Demonstration of product consistency across products from individual pancreata would warrant release testing to be performed on a sample of the pooled product. As product development and clinical trials advance, the increasingly more detailed specifications of potency assays on adult porcine islet products are expected to be predictive of post-transplant glycemic control. The immaturity of fetal and neonatal porcine islet tissue precludes the use of in vitro insulin secretion as a potency test as part of lot release testing; another measure of potency appropriate to fetal and neonatal cells will need to be developed for product release testing and evaluation of aliquots of these products in mouse transplant bioassays should be performed to provide meaningful post-release information.