Objective
Due to the selective destruction of the pancreatic-β cell islets by immune cells, strategies to transplant pancreatic islets were explored to treat Type-1 Diabetes (T1D). Chronic systemic immunosuppression is required for both commercially available intrahepatic allogeneic islet transplant-Lantidra® or the phase1/2 clinically successful stem cell-derived fully differentiated islet transplant technology-VX880®. Even the extra-hepatic transplantation of biomaterial coated pancreatic islets within cell pouch (Licensed by Sernova Corp) needs to be accompanied with chronic systemic immunosuppression. Acute-immune rejection of the β-cell islet transplant, increased pill/injection burden, frequent hospitalization, risk of secondary infections, off-target side effects, and cancer are drawbacks associated with systemic immunosuppression. Localized immunomodulation uniquely enabled by localized islet transplantation will lead to safer and more efficacious islet transplantation strategies overcoming the complexities of intra-hepatic islet-transplant and the risks associated with systemic immunosuppression. Prolonged drug administration at the transplantation site is required to achieve chronic graft survival. Therefore, objective 1 involves developing a novel injectable biomaterial-based platform eliciting long-term transplant site specific drug release. Polymeric nanoparticles to encapsulate hydrophobic drugs, and tethered hydrophilic antibodies using Fc-binding peptide to both polymeric microgels and the nanoparticle surface will be evaluated through nano-in-micro drug delivery platform (N/M DDS). To elicit a site-specific release at the site of transplantation the N/M DDS will incorporate domains that enable drug release mediated by biomaterial degradation in the presence of inflammatory enzymes enhancing the specificity of the proposed platform. Moreover, the objective will involve the optimization of the proposed platform using a risk-based approach to elicit long-term drug release kinetics for 30 days meeting the required drug concentrations at the transplant site. Objective 2 of the proposed research involves identifying and validating islet-friendly drug combinations to simultaneously target innate and adaptive immune cells by testing in cell-based (mechanisms of action) and animal-based (efficacy in preventing chronic allograft rejection) models. The ability of islet friendly drug in combination with large antibody to effectively decrease the activation of immune cells that contribute to islet graft rejection will be evaluated to confirm replacement for harmful steroid. The targeting potential and efficacy of the combination drug delivery platform will be evaluated using validated cell-based studies including cellular uptake, cellular retention, and release studies, and their efficacy in suitable cellular models. Finally, objective 3 will involve preliminary pre-clinical evaluation of the combination drug loaded N/M DDS co-transplanted with biomaterial coated or uncoated murine allogenic islets in the fat pad of mice to evaluate the N/M DDS retention at the graft site, reduced systemic adverse effects, and its potential to accomplish graft operational tolerance.
Background Rationale
The incidence of type 1 diabetes (T1D) cases has risen over the last 50 years and is currently at 50 per 100,000 people per year. The stressed pancreatic β-cells secrete inflammatory messengers (cytokines) and release different foreign proteins (neoantigens). These antigens and cytokines released by pancreatic β-cells activate innate and the adaptive immune cells. Therefore, immunotherapy targeting the cytokines, and innate and adaptive immune cells could slow the disease progression and β-cell mass destruction and have been explored clinically. Recently, an anti-CD3 antibody (Teplizumab) targeting adaptive immune cells was approved by the US FDA and anti-inflammatory agents have also shown promising results in clinical trials in slowing disease progression. In a few T1D patients with complete absence of insulin production, successful attempts to transplant intra-hepatic insulin producing pancreatic islets (USFDA approved cell-based therapy-Lantidra® by CellTrans and stem cell derived β-cells (Vox880®) by Vertex)) have been accomplished to reverse T1D along with daily systemic immunosuppresants for transplant protection. This eliminated the need for exogenous insulin injections; however, the systemic delivery of the immunosuppresants increases the patients’ susceptibility to secondary infections and cancer. While inflammatory blood-mediated reactions cause 50% intra-hepatic transplant loss, and difficulty in monitoring the transplanted cells and their retrieval during severe complications. Although the extra-hepatic localized insulin producing pancreatic β-cell islet transplants are safer and prevent a direct immune attack, the inflammatory protein and/or lipid-based signals shed by the transplanted pancreatic β-cells, which persists even when islets are encapsulated, leads to indirect immune attack (indirect alloresponse) and chronic rejection. Moreover, both intra- and extra-hepatic transplantation still require systemic immunosuppressants. Therefore, systemic immunosuppressant-free localized islet transplantation coupled with transplant site-specific immunomodulation could enable safe and efficacious T1D treatment.
Prolonged localized delivery of immunomodulators upto several weeks/months at the transplant sites is essential to educate the immune cell-based onslaught coaxing transplanted graft survival through targeted immunomodulation. Simultaneous targeting of both innate and adaptive immune cells is more effective compared with only adaptive immune cell targeting strategy. Given that clinically approved immunomodulatory small drugs (majorly oil soluble) and biologics (majorly water soluble) have different solubility and molecular weight, their co-encapsulation and prolonged delivery from a single biomaterial-based delivery platform is challenging. We aim to design a strategic extra-hepatic transplantation coupled with transplant site immunomodulation elicited due to the released combination drugs from a single biomaterial platform called as Nano-in- micro drug delivery system (N/M DDS). The development and optimization of the N/M DDS for the combination delivery of small drugs and biologics using biocompatible and biodegradable biomaterials to accomplish protracted and controlled drug release would augment targeted immunomodulation at the extra-hepatic islet transplant site, avoid systemic effect of drugs, and significantly reduce the graft immunogenicity resulting in long-term euglycemia and T1D reversal. Additionally screening selected combinations of the immunomodulatory drugs encapsulated within the proposed N/M DDS would work in synergy to decrease direct and indirect alloresponses. Moreover, targeted intracellular drug delivery into innate and adaptive immune cells will lead to secondary intracellular depot augmenting prolonged drug delivery. The targeting efficiency and release kinetics would determine the efficacy of the developed combinatorial drug delivery platform to decrease the activation of innate and adaptive immune cells. A safer immunomodulatory regimen will be designed by replacement of harmful steroids with islet friendly small drug specifically targeting the innate immune cells. Whereas a biologic targeting the T-cells will elicit synergistic localized immunomodulation. The developed combinatorial drug loaded N/M DDS will be evaluated in different cell-based and animal-based models to evaluate their scalability and translational potential to T1D.
Description of Project
Around 9 million Type-1 Diabetes (T1D) cases were reported worldwide in 2017 as per the World Health Organization (WHO) with the majority from high-income countries. In 2021, 2 million Americans had T1D amongst which 304,000 were children. T1D is an autoimmune disease characterized by selective destruction and dysfunction of insulin-producing pancreatic islet cells due to constant attacks by various immune cells. Systemic administration of immunosuppressants can delay disease progression. In established T1D, daily glucose monitoring and exogenous insulin injections are needed. Suboptimal metabolic control, frequent hypoglycemia, skin reactions, and patient non-compliance are the drawbacks associated with exogenous insulin injection leading to long-term complications and poor quality of life. Alternatively, pancreatic islet transplantation through intrahepatic portal vein infusion (Lantidra® by CellTrans Inc) accompanied by systemic immunosuppression can lead to T1D reversal and improved quality of life in patients with severe T1D. Unfortunately, this islet transplant therapy is available only for 2% of T1D patients due to several limitations including instant blood-mediated inflammatory reactions (IBMIR) with more than 50% transplanted cell loss, difficulty in transplant cell monitoring and retrieval, and adverse effects of systemic immunosuppressants like organ toxicity, infection, and cancer.
Islet transplantation in extrahepatic sites like the omentum and the subcutaneous tissues when coupled with systemic immunosuppressants enhances the safety of the procedure because of the capability to retrieve the islet transplant. Although delayed, the immune attack is still persistent despite chronic systemic immunosuppression causing immune rejection of extra-hepatic islet transplants, which could be triggered and exacerbated by transplant site inflammation. Moreover, the islet graft functionality is susceptible to the harmful effects of non-specific immunosuppresive steroids. Localized extra-hepatic co-transplantation of pancreatic β-cell islet transplant and immune cell-specific immunomodulators will promote local immune protection and retrievability (if needed) of the islet graft. A combination of drugs specifically targeting the primary/innate and secondary/adaptive immune cells responsible for islet rejection locally will be an appropriate strategy to prevent acute and chronic rejection of locally transplanted pancreatic islet grafts at the extrahepatic sites without compromising systemic immunity and critical organ function.
Clinically approved immunomodulators include combinations of hydrophilic antibodies and hydrophobic/hydrophilic small molecules. Delivery of these immunomodulatory drugs is challenging because of low drug solubility/permeability and limited transplant site bioavailability after systemic delivery coaxing frequent administration and reducing patient compliance. Given the challenges associated with the existing immunomodulators, designing an injectable, localized combinatorial drug delivery platform to eliminate the drawbacks will improve drug bioavailability at the transplant site, reduce transplanted cell immunogenicity, and eliminate the need for frequent systemic injections. Therefore, my research goal involves the strategic design of a biocompatible and biodegradable drug delivery platform for long-term combinatorial delivery of repurposed steroid-free small molecules and biologics targeting innate and adaptive immune cells to eventually accomplish operational tolerance and long-term transplanted islet survival. To enable combination drug delivery while also eliciting spatial and temporal release, the biomaterial platform will incorporate a modular design containing polymeric nanoparticles to encapsulate hydrophobic drugs and microgels that can encapsulate large hydrophilic drugs. To enhance the specificity of drug release at the local site of immune attacks against islets only when needed, the biomaterial carriers will be designed to elicit inflammation-triggered drug delivery. The innovation of the drug-biomaterial platform I propose to develop lies in its ability to co-deliver different types of drugs (small hydrophobic versus large hydrophilic antibody-based) within one platform and to cause protracted delivery without chemically modifying the drugs to be delivered. The developed drug delivery platforms will be evaluated in different cell-based and animal-based models and explored for their scalability and translational potential to T1D.
Anticipated Outcome
In the proposed postdoctoral research work, I aim to develop a novel platform for the combinatorial delivery of small drugs and biologics that target activated innate and adaptive immune cells simultaneously (at the same time and within the same platform), and gradually and locally decrease the immunogenicity (visibility to the immune system) of the transplanted islet allograft. Given the confined small extra-hepatic space for implantation of islet transplant and the need for combination drugs at the transplant sites for effective immunomodulation, the optimized nano-in-micro drug delivery platform (N/M DDS) is expected to have the ability to incorporate small drugs and biologics with different physicochemical properties and prolong their release from N/M DDS upto 30 days. This will be facilitated due to the modular design of N/M DDS incorporating different polymers to make small drug-loaded nanoparticles which will be embedded within biologic-loaded microparticles, strategically designed based on the affinity of the combination drugs. Localized immunomodulation should be attained only in the presence of inflammatory enzymes or proteins to restrain the activation of immune cells. Therefore, the N/M DDS has been crosslinked using inflammatory enzyme sensitive peptide and is expected to elicit degradation-based diffusion of small drugs and biologic, facilitate their long-term release, and prevent large amounts of drug release all at once. As stated in the background and summary the immune response against the transplanted pancreatic β-cells involves the complex interplay of cytokine-mediated innate and adaptive immune cell activation. Therefore, I anticipate identifying and appropriately targeting the key role players involved in the immune onslaught of islet transplants. Based on the N/M DDS evaluation using laboratory-based cell lines, and small and large animals, I expect to identify the required synergy, and efficacy ultimately affecting the dose reduction of administered small drugs and biologics. Moreover, I anticipate the combinatorial drug and biologic encapsulated N/M DDS to elicit minimal off-target side effects. The N/M DDS platform is expected to release the small drug and biologic for 30 days and/or until the attainment of operational tolerance. The appropriate selection of a small drug as a replacement to clinically approved yet harmful steroids along with a T-cell specific biologic of known safety profile which will be encapsulated within the N/M DDS, I expect the combinatorial drug loaded N/M DDS platform will show large safety profile. Lastly, the research proposal aims to reduce the severity of T1D by building on the capability of transplanted islets to secrete glucose-stimulated insulin while decreasing the pill burden/injections by localized combination delivery of anti-rejection drugs with significant reduction in systemic effects thereby improving the quality of life. To conclude, the benefit-to-risk ratio is expected to increase using the optimized localized combinatorial drug-loaded N/M DDS alongside extra-hepatic islet transplantation.
Relevance to T1D
Type 1 diabetes (T1D) is an autoimmune disease characterized by the selective destruction of insulin-producing pancreatic β-cells due to constant attacks by innate and adaptive immune cells. It is associated with various short-term complications including diabetic ketoacidosis, hypoglycemia, skin reaction, visual and psycho-social, and long-term complications including retinopathy, neuropathy, nephropathy, coronary artery-, cerebrovascular, and peripheral vascular diseases. Clinical studies have shown that the disease can be delayed in pre-diabetic patients using immunotherapy including antibodies targeting inflammatory cytokines and cellular receptors, steroids, and pro- to anti-inflammatory innate and adaptive immune cells converting small molecules. However, when these therapies are stopped, the disease slowly progresses leading to islet cell destruction and loss of insulin secretion. Established T1D cases rely on disease management through glucose monitoring and programmed exogenous insulin injections. However, insulin injections do not provide sufficient metabolic control to avoid long-term complications of hyperglycemia, frequent and unaware hypoglycemia, lipodystrophy, and chronic wounds. To this end, complete reversal can be established with islet transplantation in patients with severe T1D. Transplantation of primary islets (Lantidra® by Celltrans Inc), stem cell-derived -cells (Vox880® by Vertex Pharmaceuticals), or extra-hepatic conformally coated pancreatic islets transplant within cell pouch (Licensed by Sernova Corp) require chronic systemic immunosuppression. Systemic immunosuppression is associated with general immunodeficiency, which risks include secondary infections and cancer, and off-target side-effects, including critical organ toxicity. Moreover, the treatment for patients with T1D who have developed secondary complications suffers from a high pill/injection burden, thereby -reducing patient compliance. Therefore, the existing islet transplantation strategies still need improvement for chronic graft survival devoid of systemic adverse effects to increase the applicability of beta-cell replacement in all patients with T1D.
The novelty of the proposed research lies in the identification and targeted inhibition of activated immune cells and immunological markers responsible for initiation and progression toward chronic rejection of islet allografts transplant. It further involves an amalgamation of novel formulation technology and disease biology to overcome the challenges with the existing therapies. To accomplish localized immunomodulation evading encapsulated islet recognition and immune activation, combination immunotherapy is desirable. Administration of clinically approved combination drugs using a common platform is challenging due to their differential physicochemical properties and half-life which increases the number and frequency of injections. The majority of the immunomodulatory antibodies used in cell transplantation suffer from rapid clearance increasing the dose and dosage. Moreover, the encapsulated islet graft site has a limited volume to accommodate several immunomodulators incorporated within separate nano- or microcarriers. Therefore, I plan to develop a nano-in-microgel drug delivery platform (N/M DDS) using biomaterials capable of encapsulating both hydrophobic drugs (in nanoparticles) and large hydrophilic antibodies drugs (in microgels) and eliciting site-triggered release. Moreover, the ability of the platform to elicit long-term drug delivery will lead to a reduction in dose and dosage. Ultimately, prolonged immunomodulation at the encapsulated pancreatic islet transplant site will lead to reduced immunogenicity and will promote long-term graft survival. Additionally, the development of the novel drug delivery platform can also be utilized to subcutaneously deliver combination drugs with rapid access to the draining lymph nodes and immunomodulation in pre-T1D cases.