Objective
Our objective is to advance the Endotope mRNA-LNP therapy for T1D towards the clinic. This involves optimizing and selecting the best autoantigen epitopes and lipid nanoparticle delivery vehicle for inducing tolerance in disease causing autoreactive T cells to prevent them from further attacking beta cells. Specifically, we aim to validate our novel approach of targeting and reprogramming stromal cells to present disease-relevant epitopes, screen for the most effective combination of epitopes, and translate aspects of our approach into a lead compound for use in clinical trials with T1D patients.
Background Rationale
T1D is an autoimmune disease characterized by the destruction of insulin-producing beta cells by autoreactive T cells, specifically CD4+ and CD8+ T cells, due to a breakdown in immune tolerance. Normally T cells that recognize components within the body, called antigens, are eliminated through a process called negative selection. However, in individuals with T1D, the process of immune tolerance malfunctions and allows T cells recognizing antigens from beta cells to escape. Current T1D treatments primarily focus on managing symptoms through life-long insulin injections, which do not address the underlying autoimmune pathology and can lead to complications like insulin resistance, hypoglycemia, and weight gain over time. Existing immunotherapies (teplizumab, rituximab), while more selective than broad immunosuppressants, still do not distinguish between pathogenic and beneficial immune cells, posing potential risks like opportunistic infections and malignancies. We are developing an antigen-specific immunotherapy to treat T1D, which delivers antigens to specialized cells that selectively engage autoreactive T cells only to reestablish immune tolerance while leaving the rest of the immune system intact. Antigen-specific tolerance can manifest through various mechanisms including elimination or exhaustion of autoreactive CD8+ T cells or conversion of autoreactive CD4+ T cells to regulatory T cells that actively suppress other autoreactive T cells targeting the pancreas without affecting other T cells that fight off infections. Another major advantage of inducing tolerance is the durability and curative potential of the therapy, as the immune system would be re-educated to no longer mount a response against beta cell autoantigens. To deliver the antigens, our approach utilizes mRNA encapsulated by lipid nanoparticles (LNPs). The Endotope mRNA encodes a curated combination of epitopes (sequences of peptides derived from antigens) that are specifically recognized by autoreactive CD4+ and CD8+ T cells, while the LNP protects mRNA from degradation and delivers it to be expressed at relevant sites throughout the body. Our mRNA constructs also include novel features that restrict the expression of epitopes to stromal cells and enhances the regulatory functions of these cells and their ability to engage autoreactive T cells. This differs from conventional antigen-specific approaches that usually target professional antigen-presenting cells (APCs) to engage T cells but carries the risk of further activating autoreactive T cells and exacerbating disease. Stromal cells lack the capacity to activate T cells and have been shown to have an important role in maintaining tolerance. By targeting stromal cells and expressing beta cell epitopes in non-inflamed tissue like the spleen and lymph nodes distant from the pancreas, the T cells are no longer activated when encountering the antigen and instead become tolerized. We have shown these approaches work as intended and certain forms of the treatment delay or prevent disease progression in a T1D mouse model.
Description of Project
In T1D, autoreactive CD4+ and CD8+ T cells drive disease progression through recognition of antigens expressed by insulin producing beta cells leading to their destruction. In healthy individuals, T cells that can target self-antigens are eliminated through a process called central tolerance. Due to a variety of factors including genetic predisposition, cellular stress, and other environmental triggers, autoreactive T cells from T1D patients can evade tolerance. The Endotope platform represents a next-generation approach that can precisely target these cells and induce effective and long-lasting antigen-specific immune tolerance to preserve the remaining beta cells. Unlike conventional broad immunosuppression, which carries significant risks of opportunistic infections and malignancies, our strategy targets only the autoreactive T cells that cause disease, leaving the rest of the immune system intact. Our core innovation involves encoding multiple disease relevant epitopes including a signaling domain that allows for efficient processing and presentation to both CD4+ and CD8+ T cells. The epitopes are encoded as mRNA and encapsulated in lipid nanoparticles (LNPs). Other crucial elements of our mRNA construct prevent expression in professional antigen-presenting cells (APCs) but allows for epitope expression in stromal cells while enhancing their regulatory functions. Professional APCs act as sentinels for pathogens by sampling antigens in the body and will present them to T cells to coordinate an immune response. Although professional APCs are highly efficient at processing antigens and engaging T cells, they can be inadvertently activated by the delivery system and become incapable of inducing tolerance or even accelerate disease progression. Since stromal cells inherently lack major signals necessary for pathogenic T cell activation, they are ideally suited for inducing tolerance. By targeting stromal cells, we have generated preliminary data demonstrating tolerance induction specifically in autoreactive T cells from a mouse model of T1D. An early version of the Endotope construct was also able to significantly delay disease progression and even prevent disease completely in some treated mice. This proposal would help further improve the treatment and optimize our therapy for human T1D patients. First, we plan to carefully validate the mRNA element that restricts expression in professional APCs and the reprogramming capabilities of the factors that improves regulatory functions of stromal cells. This detailed characterization will inform the selection of the most effective factors to promote sustained tolerance. Another portion of proposed research will focus on optimizing the selection of autoantigen epitopes and the dosing regimen. Our construct design already incorporates a diverse array of epitopes from multiple beta cell antigens. The broad epitope coverage ensures we can engage the widest possible range of autoreactive T cells and can lead to tolerance induction of autoreactive T cells not covered by our epitopes through a process called linked suppression. Screening various combinations of epitopes will help us determine the critical types of epitopes and combinations required to induce tolerance and further refine our construct. Finally, to bridge these findings to a human relevant therapy, we will validate human versions of the construct using human cells and mice with a human immune system that contain autoreactive T cells similar to those found infiltrating beta cells in T1D patients. These studies will aim to validate the presentation of epitopes in human system and also test the in vivo reprogramming of human autoreactive T cells by mRNA-LNPs. Ultimately, we will obtain a final candidate that we can proceed with to clinical trials.
Anticipated Outcome
The primary anticipated outcome of this research project is the identification and optimization of a lead mRNA-LNP candidate for our T1D therapy, preparing it for IND-enabling studies. This comprehensive effort will involve optimizing key parameters to achieve robust and durable tolerance induction in autoreactive T cells with no impact on non-diseased immune cells. We anticipate gaining a deeper understanding of how stromal cell targeting and reprogramming contribute to tolerance, which types of epitope are most effective, the optimal dosing strategy for durable protection, while validating the human version of this construct using in vitro and in vivo systems. This work is crucial for supporting and accelerating our efforts towards future clinical trials in individuals living with T1D, bringing us closer to a potentially transformative therapeutic solution.
Relevance to T1D
Type 1 diabetes currently requires life-long, frequent insulin injections to manage blood glucose levels, a treatment that does not address the underlying autoimmune cause. This regimen often leads to challenges like insulin resistance, hypoglycemia, and other long-term complications, severely impacting patients' quality of life. Our antigen-specific immune therapy offers a preventative treatment approach, particularly for early-onset or new-onset patients, aiming to halt or prevent disease progression by inducing immune tolerance. This could allow remaining pancreatic beta cells to continue secreting endogenous insulin, potentially transforming the current treatment paradigm and alleviating the need for constant glucose monitoring and exogenous insulin administration. Furthermore, for patients with little to no remaining beta cells, our approach has the potential to synergize with emerging stem cell therapies that aim to replenish insulin-producing cells. By inducing immune tolerance, Endotope's therapy could protect newly transplanted or regenerated autologous beta cells from autoimmune destruction, a significant challenge currently facing cell replacement therapies. This precision medicine approach, targeting autoreactive T cells without broad immune suppression, could lead to a safe and potentially curative therapy for T1D.