Engineering T cells to Promote Islet Transplant

A. Specific Aims

Type 1 diabetes (T1D) is a progressive autoimmune disease which renders individuals incapable of regulating their blood glucose levels due to immune-mediated β cell destruction, resulting in loss of insulin production and many severe health complications that, if untreated, lead to death. Careful monitoring of blood glucose coupled with insulin injections have made T1D a chronic disease in which T1D individuals live ~ a decade less than their healthy counterparts.

Thus, a cure for T1D is highly desirable. Cell gene therapy has proven to be an effective way to treat recalcitrant diseases such as pediatric leukemia, where chimeric antigen receptor (CAR) expressing T cells achieve 90% complete response, putting many individuals into very long remissions1, but to date no engineered T cell therapies have been attempted to cure T1D in humans.

We propose to test the hypothesis that engineered T cells can enable islet transplant with minimal or no additional immunosuppression. Islet transplantation represents the best-case scenario to test the ability of engineered T cells to protect islet cells from immune attack and will likely lay the foundation by which strategies are developed to treat new onset T1D.

In islet transplant, MHC matching of donor and recipient rarely occurs, generating highly expressed, unique islet-specific HLA antigens that can be targeted by CAR engineered T regulatory cells (CAR Tregs) or T cells engineered to express molecules that suppress the immune system (T suppressor cells or Tsups). Additionally, through a comprehensive screening process, we have identified two targets, fibroblast activation protein (FAP) and dipeptidyl peptidase like 6 (DPP6), that are highly expressed on α and β cells and have limited expression elsewhere that could be used to treat recently diagnosed individuals, and all transplant recipients without the desired MHC mismatch.

In this proposal, we will further develop this toolbox to both develop better in vivo, preclinical models of T1D and new cell and gene therapies that will prevent, stall or reverse T1D.

Within the last decade, rapid progress made in T cell-based therapies makes it possible to consider such therapies for T1D. Following long-term remission of 3 cancer patients treated by CD19-specific CARs developed by the Center for Cellular Immunotherapies at Penn under the leadership of Carl June2, the CAR T cell revolution was launched. This early success drove considerable investment, empowering many institutions and companies to develop ways to improve both the safety and efficacy of, and reduce cost to produce engineered T cells.

Many of these innovations will also help enable cell and gene therapies for T1D, which is the overarching goal of this RFA. The ultimate goal of this application is to successfully treat three non- human primates (NHP) with engineered T cells after an islet transplant, which we predict will launch similar enthusiasm for T1D cell and gene therapy as the first three CD19-CAR recipients did for cancer CAR therapy.

To achieve this goal, an experienced team of investigators with complementary expertise will lead this proposal. This team, a transplant surgeon who helped pioneer islet transplantation as a T1D therapy (Naji), a veterinary physician with expertise developing NHP T regulatory cell therapy models (Duran-Struuck), and a cell and gene therapist with a track record of engineering T cells and developing first-in-human clinical trials (Riley), have been working closely together via Helmsley Foundation funding to obtain the preliminary data presented in this application.

This team is now is poised to immediately perform in vivo studies to test the ability of engineered T cell therapies to prevent, stall, or reverse T1D.

Aim 1. Engineer T Suppressor Cells (Tsups) to Facilitate Islet Transplant in Humanized Mouse Models. While T regulatory cells are potent immune suppressors, there are other promising ways to induce tolerance that may work as stand-alone therapies or synergize with CAR Tregs to protect β cell function.

We will explore using PD-L1, TGF-β1, and/or γ-aminobutiric acid (GABA) expressing cells targeted to the islet to mediate islet acceptance alone or in combination with CAR Treg approaches we developed using humanized mice.

Aim 2. Optimize T cell Approaches to Promote Islet Transplant in NHPs. To date our efforts have focused on developing NHP CAR Tregs to enable islet transplant.

We have optimized isolation, transduction, and expansion of NHP MHC-specific CAR T regulatory cells and are poised to start islet transplant experiments immediately. After we perform proof of principle experiments using CAR Tregs, we will prioritize future experiments based on the data obtained in Aim 1. A particularly exciting aspect of our studies is testing whether the ortho-IL-2 system developed by the Garcia Lab3 can work in non-human primates and support engineered Treg or other engineered T cell function and expansion while having no effect on endogenous effector cells.

If successful, these studies will form the basis and rationale for Phase I clinical trials in humans.