Objective
The overall objective of the proposed study is to evaluate whether low-dose (LD) interleukin 2 (IL-2) plus insulin-like growth factor 1 (IGF1) synergizes to augment immune regulation as well as pancreatic beta cell fitness, representing a combination therapy to prevent type 1 diabetes (T1D). Functional deficiencies in both the IGF1 axis and IL-2 signaling pathway have been individually identified in T1D. Specifically, multiple T1D-associated genetic mutations lead to IL-2 signaling defects and promote autoimmunity. Moreover, we previously reported low levels of IGF1 in blood from T1D patients with IGF1 declining notably throughout the pre-T1D period in people who progressed to T1D diagnosis. Our goal is to normalize these deficiencies in subjects at risk for T1D development. Our recent publication demonstrates that combinatorial IGF1 and LD IL-2 treatment enhances regulatory T cell (Treg) proliferation in mice and in cultured human cells; however, the underlying mechanisms of action and efficacy toward T1D prevention remain unclear. The proposed studies are designed to address these questions using the non-obese diabetic (NOD) mouse model of T1D. Specifically, we will evaluate the influence of LD IL-2 plus IGF1 treatment in NOD mice on blood glucose control, diabetes progression, cellular organization within the pancreas, as well as frequencies, distribution, and function of various immune cell subsets. Next, we will pilot LD IL-2 combined with growth hormone [GH] or verapamil as potential alternatives to IGF1 infusion. We anticipate that treatment with GH or verapamil will increase circulating levels of IGF1 and that targeting the IGF1 axis indirectly will similar synergy with LD IL-2 for the expansion of Tregs. Thus, the proposed studies will leverage four FDA approved therapeutics to establish the efficacy of IGF1 enhancement on LD IL-2 treatment in the NOD model (directly with IGF1 treatment, and indirectly with GH and verapamil), with the potential to translate this combinatorial therapy as a means to overcome notable defects in both the IGF axis and IL-2 signaling pathways in T1D. If successful, these studies will be followed by a clinical trial in subjects with or at high-risk for developing T1D. Hence, we believe our proposal provides a path toward immediate clinical translation by using repurposed drugs in combination.
Background Rationale
Impairments in immune regulation have been suggested to contribute to the development of type 1 diabetes (T1D) and other autoimmune diseases. Hence, there is a need for drugs that can address T1D-specific defects within the pancreas to correct impairments in insulin production and restore immune regulation using viable Food and Drug Administration (FDA)-approved agents. Specifically, efforts to expand the beneficial immune cell subset, known as regulatory T cells (Tregs), without enhancing pro-inflammatory immune cell activities are of great interest for T1D prevention. At high doses, interleukin-2 (IL-2) is Food and Drug Administration (FDA)-approved as an anti-tumor biologic. Low dose (LD) IL-2 has been explored as a means to increase the number and enhance the function of Tregs in autoimmune diseases, including T1D, but unfortunately, these effects occur alongside off-target expansion of various unfavorable pro-inflammatory immune cell subsets. This highlights an unmet need for identification of additional factors that can enhance the impact of LD IL- 2 on the total Treg pool, allowing for efficacy with lower IL-2 doses and avoidance of off-target effects. We previously reported that blood levels of insulin-like growth factor-1 (IGF1) are deficient during pre-T1D. IGF1 is known to induce immune regulation and enhance fitness of the pancreas, making it an exciting candidate therapy for T1D. We recently published data demonstrating that IGF1 and LD IL-2 can synergize to promote expansion of Tregs, in the non-obese diabetic (NOD) mouse model of T1D and in human cell cultures. These data support the need for further investigation into the mechanisms of action and efficacy of IGF1 alone and in combination with LD IL-2 in the NOD animal model. We hypothesize that the addition of IGF1 to LD IL-2 treatment will directly expand Tregs while improving β-cell health, resulting in enhanced resistance to T1D onset. In addition, we propose to pilot two additional drug combinations: LD IL-2 plus growth hormone (GH) and LD IL-2 plus verapamil, representing strategies to potentially increase endogenous production of IGF1 in NOD mice without the known adverse effects of IGF1 infusion. GH is well established as an IGF1 induction agent, while verapamil’s effect toward IGF1 enhancement was discovered quite recently. Moreover, in a recent clinical trial, verapamil treatment preserved beta cell function in recent-onset T1D patients. Mechanistic studies of verapamil in T1D have focused primarily on its effect within the pancreas, and little is known about its effect on the immune system. We propose to address these knowledge gaps through dose-finding and cross-sectional mechanistic studies comparing GH + LD IL-2, verapamil + LD IL-2, and IGF1 + LD IL-2 combination treatment. The proposed combinatorial approach represents a uniquely innovative treatment strategy in that it leverages FDA approved drugs, which have never before been evaluated as a combination treatment for T1D.
Description of Project
Type 1 diabetes (T1D) results from the autoimmune destruction and dysfunction of insulin-producing beta cells within the pancreatic islets. Accordingly, T1D patients experience severe hyperglycemia that requires lifelong management with exogenous insulin. Since its discovery as a lifesaving intervention over 100 years ago, many advances in insulin formulation and mode of delivery have been made, improving quality of life and longevity for people living with T1D. Even still, the vast majority of T1D patients are unable to achieve American Diabetes Association recommended glycemic targets and face significant risk of long-term complications. Hence, there is a need for therapies directed at the underlying disease mechanisms in order to prevent, slow, or halt T1D progression. One such strategy involves the expansion of an immune cell subset known as regulatory T cells (Tregs) in order to constrain destruction mediated by autoreactive and pro-inflammatory immune cells. We previously demonstrated that combination treatment with low-dose (LD) interleukin 2 (IL-2) and insulin-like growth factor 1 (IGF1) promotes the expansion of human Tregs in a cell culture dish. Moreover, we recently demonstrated Treg expansion in the non-obese diabetic (NOD) mouse model of T1D following treatment with IL-2 antibody complex (IAC) + IGF1; however, IAC cannot be readily translated to human trials. Here, we propose to evaluate LD IL-2 + IGF1 for the ability to expand Tregs and prevent autoimmune diabetes in NOD mice. We expect that this combination therapy will synergistically modulate the immune compartment and preserve pancreatic insulin production, altogether preventing diabetes onset. However, given the high cost and known adverse effects associated with infusion of unbound IGF1 in human patients, there is a need to evaluate alternative strategies to increase endogenous IGF1 production. Growth hormone (GH) and verapamil (a blood pressure medication) have both been demonstrated to increase serum levels of IGF1 in human patients with verapamil offering additional benefits toward the preservation of beta cell function in T1D. Accordingly, we propose pilot studies using GH and verapamil as potential alternatives to IGF1 treatment, to determine if one or both of these agents similarly synergizes with LD IL-2 to promote Treg proliferation. Importantly, this strategy will evaluate four drugs, each of which have regulatory approval in the U.S. and Europe for use in other disease settings, to target known defects associated with T1D. Hence, we envision that a pilot trial of a combination therapy with LD IL-2 plus IGF1, GH, or verapamil could be promptly initiated following the successful completion of the studies proposed herein, accelerating progress toward a means to delay, or perhaps even prevent T1D onset in at-risk individuals.
Anticipated Outcome
Based on our published and preliminary data, we expect that insulin-like growth factor-1 (IGF1) and low dose (LD) IL-2 will increase the number of beneficial regulatory T cells (Tregs) and that the combination will outperform the individual agents to prevent disease in the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). We further hypothesize that treatment with growth hormone (GH) or verapamil will raise serum levels of IGF1, ultimately synergizing with LD IL-2 to promote Treg expansion in mice, similar to what we have observed with IGF1. If successful, we anticipate GH or verapamil will be utilized (rather than IGF1) for subsequent preclinical studies and future pilot trials in humans given that GH and verapamil are both more affordable and more widely used in clinics. Previous studies have shown that LD IL-2 can effectively prevent diabetes when treatment is initiated in very young NOD mice and given for an extended period of time. By adding IGF1 (or GH or verapamil) to a shorter IL-2 duration, as proposed here, we expect to observe a synergistic effect compared to either agent alone. We also expect that IGF1 will create optimal conditions for growth of insulin producing beta cells within the pancreas and condition additional immune cells, known as macrophages, within the pancreas toward a distinct anti-inflammatory subtype, enabling tissue repair. Taken together, we expect to find improved blood glucose control, reduced diabetes incidence, and less inflammation within the pancreatic islets following LD IL-2 + IGF1 combinatorial treatment of NOD mice. The comprehensive examination of immune cells proposed in this study will identify undesired off-target stimulation that can be addressed in future studies through dose response curves or implementation of biomaterials engineered delivery systems. Finally, if the proposed research is successful, the resulting data will support the initiation of phase 1 pilot trials in humans with recent-onset T1D.
Relevance to T1D
The proposed research is directly relevant to type 1 diabetes (T1D) as our aim is to validate therapeutic targets and mechanisms to prevent the disease in a preclinical research setting. The proposed studies will leverage U.S. Food and Drug Administration (FDA) approved therapeutics to establish the efficacy of insulin-like growth factor-1 (IGF1) enhancement on low dose (LD) IL-2 treatment in the non-obese diabetic (NOD) model, with the potential to translate this combinatorial therapy as a means to overcome notable defects in both the IGF axis and IL-2 signaling pathways in T1D. IL-2 has been used to as a monotherapy for cancer and in LD forms for the treatment of various autoimmune diseases. Growth hormone (GH) and IGF1 are very familiar to pediatric endocrinologists providing a direct pathway for therapeutic translation with these agents for use in restoring immune tolerance in T1D. Recent studies have also demonstrated efficacy of verapamil (an antihypertensive calcium channel blocker) toward the preservation of IGF1 and β-cell function in individuals with T1D. While LD IL-2 has been explored in experimental settings for the treatment of T1D, it has never been evaluated in combination with IGF1, which has multiple anti-diabetogenic mechanisms of action, making this an attractive approach to mitigate islet autoimmunity. If successful, we expect that the proposed preclinical studies will be followed by a phase 1 clinical trial in subjects with or at high-risk for developing T1D. The populations who stand to benefit the most from these studies are those with stage 1-2 T1D who have not yet reached the criteria for stage 3 T1D diagnosis. However, it is possible that the combination treatment evaluated herein will have additional benefit in patients with recent-onset T1D, particularly if combined with additional methods to replace or restore functional beta cell mass.