Development of a safer stem cell-based diabetes therapy via suicide gene-mediated ablation of proliferative cells

Project Summary/Abstract Diabetes is an increasingly important health problem worldwide. In the 100 years since the discovery of insulin, tremendous advances have been made in the care of diabetic patients, including long-acting insulin formulations, insulin pumps, continuous glucose monitors, and wide array of pharmacologic agents that influence insulin secretion and sensitivity. Despite all of these advances, a majority of diabetic patients cannot achieve currently recommended targets for blood glucose control. Although transplantation of diabetic patients with donor-derived pancreatic islets or intact pancreas remains a rare procedure due to limited source material, these cell-based therapies are extremely effective in restoring blood glucose control. In order to make a cell-based therapy for diabetes available to more patients, Regenerative Medical Solutions (RMS) has developed a proprietary protocol for converting induced pluripotent stem cells (iPSC), a virtually unlimited cell source, into islet-like clusters of cells that include insulin-producing beta-like cells. These cells demonstrate functionality similar to primary beta cells both in vitro and after transplantation into diabetic mice, indicating their potential as a cell-based therapy for diabetes. However, as will all iPSC-based therapies, safety concerns remain: the transplantation of even a small number of proliferative cells in an iPSC-based product may result in undesired outgrowths or tumor formation at the graft site. To address this potential risk, Implant Therapeutics has developed a novel genetically modified iPSC line, FailSafeTM, in which the thymidine kinase gene is homozygously integrated downstream of the essential cell cycle regulatory gene CDK1. Treatment of FailSafeTM cells with the FDA-approved drug ganciclovir thus leads to selective elimination of actively proliferating cells. In this project, we will combine FailSafeTM iPSC and RMS’s proprietary protocol for the production of islet-like clusters of cells to demonstrate the potential of the combined product to produce a safer cell-based therapy for diabetes. First, we will define optimal conditions for the ablation of proliferating cells from islet-like clusters in culture. Next, we will demonstrate the safety and efficacy of the treated FailSafeTM clusters in a mouse model of diabetes. Together, these experiments will lay the foundation for the development of a cell-based therapy for diabetes with an improved safety profile compared to competing products.