Objective
Islet cell transplantation using isolated and purified human allogenic islet cells has been shown to offer a transient “cure” for type 1 diabetes. However, the broader application of this procedure has been limited due to the significant loss of transplanted islets during the peritransplant period as result of innate immune response resulting in poor long-term function. Based on our preliminary studies, we propose to improve the efficacy of islet transplant by minimizing islet cell loss using TAK-242, a clinically tested small molecule inhibitor of TLR4. Our objectives are to 1) test the efficacy of TAK-242 administration on the survival and function of allogeneic islet grafts using a diabetic mouse model, 2) compare efficacy of systemic administration of TAK-242 versus localized delivery from the islet surface using allogeneic islet grafts, and 3) test the efficacy of TAK-242 administration on the survival and function of allogeneic islet grafts using a novel dissected peritoneal pouch transplant site. The long-term goal of this project is to initiate Phase I/II clinical trials of allogenic islet transplants into T1D patients using TAK-242 to suppress innate immune response and improve long term islet graft function. If successful, this objective will significantly lessen the number of deceased donor pancreases and islet tissue required for clinical islet cell transplantation.
Background Rationale
Type 1 diabetes results from autoimmune destruction of pancreatic β-cells leading to loss of endogenous insulin production and hyperglycemia. Although this condition is now commonly managed through the administration of exogenous insulin, there are still adverse events and long-term health care risks associated with this method due to spiking blood concentrations and absence of counterbalancing hormones to provide tight glucose control. Transplantation of allogeneic islets to replace beta-cell mass is a promising cell replacement therapy to regain natural release of counterbalancing hormones to achieve normoglycemia by glucose-sensing islet cells. Intraportal infusion of purified allogeneic islets invokes an acute inflammatory response that destroys 25-75% of islet mass within days leading to poor engraftment. This response is largely attributed to damage associated molecular patterns (DAMPs) released from damaged islet tissue as a result of islet isolation procedures that active innate immune toll-like receptors (TLR). We have identified TLR4 as a key mediator of the acute innate response and have shown that its inhibition can improve islet graft function in a syngeneic transplant model. Our preliminary data indicate that the TLR4-mediated inflammatory response can also initiate elements of the adaptive immune response. We hypothesize that TLR4 plays a major role in mediating innate and adaptive immune response against allogeneic islets. We propose to inhibit TLR4 as an upstream target to minimize innate immune response observed during the peri-transplant phase. While several reported approaches to block TLR4 are not clinically translatable, we have selected a clinically tested small molecule TAK-242 for this purpose.
Description of Project
Islet cell transplantation is a promising cell replacement therapy for type 1 diabetes to restore blood glucose to a naturally regulated state. Three main hurdles that limit its widespread use include 1) the limited availability of donor islet tissue, 2) long-term graft function, and 3) adverse side effects of immunosuppressants required to protect the graft from immune rejection. Recent progress in producing stem-cell derived islets in vitro has resulted in reversal of type 1 diabetes in clinical trials. However, this source of cells is also susceptible to immune rejection and requires immunosuppression for function and survival. This project identifies the toll-like receptor 4 (TLR4) signaling pathway as a novel target to inhibit activation of inflammatory and alloreactive immune response against transplanted islets. We propose to evaluate a clinically tested TLR4-selective inhibitor resatorvid (TAK-242) to suppress innate and adaptive responses to islet allografts to improve longevity and graft function in a diabetic mouse model. We will also pilot studies to utilize “click chemistry” to link the TAK-242 compound to the surface of islets ex vivo to produce a localized drug-releasing product at the graft site to enhance drug specificity and efficacy. Finally, we will test the efficacy of TAK-242 suppression of alloimmune reactivity to islets using a novel dissected peritoneal pouch transplant site developed by scientists and surgeons at our transplant center. This alternative site allows larger doses of cell replacement product with lower risk of thrombosis using the conventional portal vein delivery method. At the completion of this 3-year project, we expect to produce refined cGMP- and clinically- compatible methodologies to deliver larger and more effective doses of allogeneic resistant donor islets to recipients that will not require adverse doses of conventional immunosuppressants. This would open pathways for widespread use of islet cell replacement procedures by improving the efficacy and duration of islet grafts and extending its potential to improve and protect stem-cell derived islets to reverse type 1 diabetes.
Anticipated Outcome
We anticipate that selective inhibition of TLR4 by TAK-242 administration will improve islet graft survival and function of allogeneic islet grafts to reverse diabetes in a diabetic mouse model for up to 60 days. Based on our preliminary data, these improvements are expected to be matched or enhanced by systemic administration of TAK-242 versus localized delivery from the islet surface using allogeneic islet grafts. We predict that approaches of TAK-242 delivery using a dissected peritoneal pouch transplant site will produce equally efficacious results upon defining islet cell dose curves to optimize ratios of islet cell tissue volume to drug delivery and localized drug release. From these results we will devise cGMP- and clinically- compatible methodologies for translating these results to deliver larger and more effective doses of allogeneic resistant islets for potential testing of these methodologies to reverse type 1 diabetes in clinical trials.
Relevance to T1D
Type 1 diabetes results from immunological destruction and loss of pancreatic islet beta cells. The proposed research aims to identify targets and methodologies to replace islet cells and restore normal blood glucose concentrations in type 1 diabetes individuals. Current islet cell procedures require global immunosuppressant drugs that have toxic effects on islet cells leading to adverse side effects including loss of islet function. The severity of these beta cell toxic effects has hampered the broad use of this procedure. We have identified a selective target TLR4 to potently suppress islet allograft immunoreactivity without global immunosuppression. If successful, the proposed methodologies of targeted inhibition of immune response and drug delivery could eventually replace conventional global immunosuppressant regimens. This would essentially unlock the doors to avenues of more widespread use of clinical islet cell replacement therapies to reverse type 1 diabetes.