Early Translational I
Type I diabetes (T1D) is marked by a deficiency of the insulin-secreting beta cells within the pancreas. Because insulin is required for glucose homeostasis, these patients develop high blood glucose, which leads to acute symptoms of frequent urination, unquenchable thirst, weight loss, lethargy and eventually death. The most prevalent method of treatment for T1D is daily injection of recombinant insulin, which increases significantly the long-term survival rate of patients. Unfortunately, insulin injection does not always prevent the extreme glucose excursions experienced by these patients. Therefore, end-stage patients usually develop diabetic kidney diseases and require dialysis, and eventually kidney transplantation. In addition, some patients develop autonomic neuropathy that can lead to dangerous and frequent episodes of hypoglycemic coma, a condition in which people no longer experience the warning symptoms of low blood glucose levels. As a result of these complications, patients become increasingly home-bound and their quality of life is greatly diminished. Transplantation of pancreatic islets from cadaveric donors provides a beneficial cell-replacement therapy for these patients; however, there is an insufficient number of donor organs, which has greatly limited this procedure to a very small number of patients. A possible alternative source of cells for islet transplantation could be developed from human embryonic stem cells (hESCs), which offer a potentially unlimited source of human, pancreatic beta cell-like cells. In this early translational research proposal, we propose to characterize and enrich a population of glucose-responsive, insulin-producing and secreting (GRIS) cells generated from hESCs in culture that are devoid of inappropriate cell types and of undifferentiated hESCs, which may give rise to tumors when transplanted. We will use a mouse model of diabetes to test the ability of culture-generated, hESC-derived GRIS cells to survive and function in secreting insulin in response to an increase in blood glucose in transplantation recipients. We will also establish a robust assay to detect a small number of undifferentiated hESCs and develop a process to eliminate undifferentiated hESCs before transplantation, should any remain in the final cell preparation. In summary, this project will generate comprehensive efficacy and safety data for our hESC-derived GRIS cells in mouse models of diabetes. Our long-term goals include testing our cellular product in large animal models as the last step before Phase I clinical trials in humans.
Statement of Benefit to California:
Currently, it is estimated that there are more than 1.5 million Americans, including 140,000 Californians with Type 1 diabetes (T1D). Ten to fifteen percent of these patients have advanced forms of the disease and these numbers are expected to rise. Thus, approximately 14,000 to 12,000 Californians could benefit from allogeneic islet transplantation or stem cell-replacement therapy. In addition, it is estimated that a quarter of the Medicare budget is spent on diabetes-related care (including both T1D and T2D), which is a financial burden to State and Federal health care programs, and the taxpayers who support them. The development of a stem cell-replacement therapy for T1D will ease the burden of the long-term, intensive care required for advanced T1D patients.
The goal of this proposal is to advance a development candidate for the treatment of type 1 diabetes by refining a protocol for differentiation of human embryonic stem cells (hESC) into populations of glucose-responsive, insulin producing and secreting cells (GRIS). When transplanted into patients, such cells are envisioned to replace the beta cell function that has been lost due to disease. In the first aim, the investigators propose to derive GRIS cells from hESCs by adapting a protocol from their previous work in mice, characterizing the resulting derivatives, and enriching for those populations with relevant functionalities. The resulting cells will be tested for survival and efficacy in a mouse model of diabetes. In the second aim, the applicants propose to eliminate undifferentiated hESCs from the GRIS populations by establishing a robust in vivo teratoma assay to detect small numbers of these undesired cells, and by developing a cytolytic monoclonal antibody procedure to remove them prior to transplantation. The reviewers agreed that the rationale for using hESCs to develop an unlimited source of GRIS cells is very strong, particularly as cell therapy approaches have already been validated in clinical studies of islet transplantation, and no reasonable alternatives have yet been identified for the treatment of type I diabetes. While the research plan was thought to be logical and sound, the reviewers noted several technical limitations that could effectively reduce the utility this approach. For example, the described differentiation protocol relied on embryoid body formation, slow asynchronous induction and a GRIS cell purification strategy based on largely nonspecific parameters. These shortcomings suggest that this method would be impractical for clinical development in terms of timeline and scalability. Furthermore, the experiments to assess the functionality of the purified cells were thought to be lacking in rigor and depth, particularly in terms of quantifying key physiological parameters such as C-peptide levels and glucose responsiveness. The proposal also lacked the level of detail needed to assess the feasibility of the cytolytic antibody strategy. Thus, while intrigued by the premise, the reviewers were uncertain as to whether the described levels of cell killing would be sufficient for clinical consideration, particularly as there was little discussion of alternative strategies that might become necessary should the antibody not function as predicted. Reviewers appreciated the technical skills and qualifications of the principal investigator. Several were concerned, however, about the lack of demonstrable track record in terms of leadership and large project management. In general, while the research team and environment were thought to be adequate, most reviewers agreed that the team would be well served by greater input from collaborators with hands on product development experience and/or extensive interaction with the FDA. In summary, the reviewers felt that the proposed research addressed an important topic, possessed a compelling rationale and represented a logical course of investigation. However, their overall enthusiasm was significantly diminished by a number of technical and practical deficiencies. These weaknesses, combined with the applicants’ inexperience with the challenges of product development, suggest that the results of this effort would be premature and inadequate for a robust translational program.