The demise of islet allotransplantation in the United States: A call for an urgent regulatory update

Legal and Regulatory Challenges for Emerging Regenerative Medicine Solutions for Diabetes

Regenerative medicine solutions for type 1 diabetes are a rapidly developing field of medical technology. To date, these solutions have been principally cell-based treatments and at present, in Europe, these therapies are regulated under European Union regulations for advanced therapy medicinal products. But now, new emerging technology combining cellular therapy with medical devices is under development. The potential of this novel hybrid model to create a bioartificial pancreas to treat type 1 diabetes is tantalizing. However, incorporating medical devices creates a further layer of regulatory complexity. This article seeks to expose the complexity of this legal and regulatory landscape and demonstrate how evolving technology could challenge the entire existing legal paradigm. We start by summarizing the status of the only established cell-based therapy-transplantation. We set out the regulation of cellular therapies, their classification, and the role of statutory bodies. We examine the bottleneck of therapies moving from bench to bedside, and we consider the additional challenges of products, which use a combination of cells and medical devices. Finally, we argue that for the potential of this rapidly growing area of technology to be realized a seismic shift in how we regulate frontier cellular therapies will be required.

Hypoimmune islets achieve insulin independence after allogeneic transplantation in a fully immunocompetent non-human primate

Allogeneic transplantation of pancreatic islets for patients with difficult-to-control diabetes mellitus is severely hampered by the requirement for continuous immunosuppression and its associated morbidity. We report that allogeneic transplantation of genetically engineered (B2M-/-, CIITA-/-, CD47+), primary, hypoimmune, pseudo-islets (p-islets) results in their engraftment into a fully immunocompetent, diabetic non-human primate wherein they provide stable endocrine function and enable insulin independence without inducing any detectable immune response in the absence of immunosuppression. Hypoimmune primary p-islets may provide a curative cell therapy for type 1 diabetes mellitus.

Development of electrochemical Zn2+ sensors for rapid voltammetric detection of glucose-stimulated insulin release from pancreatic β-cells

Diabetes is a chronic disease characterized by elevated blood glucose levels resulting from absent or ineffective insulin release from pancreatic β-cells. β-cell function is routinely assessed in vitro using static or dynamic glucose-stimulated insulin secretion (GSIS) assays followed by insulin quantification via time-consuming, costly enzyme-linked immunosorbent assays (ELISA). In this study, we developed a highly sensitive electrochemical sensor for zinc (Zn2+), an ion co-released with insulin, as a rapid and low-cost method for measuring dynamic insulin release. Different modifications to glassy carbon electrodes (GCE) were evaluated to develop a sensor that detects physiological Zn2+ concentrations while operating within a biological Krebs Ringer Buffer (KRB) medium (pH 7.2). Electrodeposition of bismuth and indium improved Zn2+ sensitivity and limit of detection (LOD), and a Nafion coating improved selectivity. Using anodic stripping voltammetry (ASV) with a pre-concentration time of 6 min, we achieved a LOD of 2.3 μg/L over the wide linear range of 2.5-500 μg/L Zn2+. Sensor performance improved with 10-min pre-concentration, resulting in increased sensitivity, lower LOD (0.18 μg/L), and a bilinear response over the range of 0.25-10 μg/L Zn2+. We further characterized the physicochemical properties of the Zn2+ sensor using scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Finally, we demonstrated the sensor's capability to measure Zn2+ release from glucose-stimulated INS-1 β-cells and primary mouse islets. Our results exhibited a high correlation with secreted insulin and validated the sensor's potential as a rapid alternative to conventional two-step GSIS plus ELISA methods.

Human hypoimmune primary pancreatic islets avoid rejection and autoimmunity and alleviate diabetes in allogeneic humanized mice

Transplantation of allogeneic pancreatic donor islets has successfully been performed in selected patients with difficult-to-control insulin-dependent diabetes and impaired awareness of hypoglycemia (IAH). However, the required systemic immunosuppression associated with this procedure prevents this cell replacement therapy from more widespread adoption in larger patient populations. We report the editing of primary human islet cells to the hypoimmune HLA class I- and class II-negative and CD47-overexpressing phenotype and their reaggregation into human HIP pseudoislets (p-islets). Human HIP p-islets were shown to survive, engraft, and ameliorate diabetes in immunocompetent, allogeneic, diabetic humanized mice. HIP p-islet cells were further shown to avoid autoimmune killing in autologous, diabetic humanized autoimmune mice. The survival and endocrine function of HIP p-islet cells were not impaired by contamination of unedited or partially edited cells within the p-islets. HIP p-islet cells were eliminated quickly and reliably in this model using a CD47-targeting antibody, thus providing a safety strategy in case HIP cells exert toxicity in a future clinical setting. Transplantation of human HIP p-islets for which no immunosuppression is required has the potential to lead to wider adoption of this therapy and help more diabetes patients with IAH and history of severe hypoglycemic events to achieve insulin independence.

Pancreas Transplantation: Current Challenges, Considerations, and Controversies

Pancreas transplantation (PTx) reestablishes an autoregulating source of endogenous insulin responsive to normal feedback controls. In addition to achieving complete β-cell replacement that frees the patient with diabetes from the need to monitor serum glucose and administer exogenous insulin, successful PTx provides counterregulatory hormone secretion and exocrine function. A functioning PTx mitigates glycemic variability, eliminates the daily stigma and burden of diabetes, restores normal glucose homeostasis in patients with complicated diabetes, and improves quality of life and life expectancy. The tradeoff is that it entails a major surgical procedure and requisite long-term immunosuppression. Despite the high likelihood of rendering patients euglycemic independent of exogenous insulin, PTx is considered a treatment rather than a cure. In spite of steadily improving outcomes in each successive era coupled with expansion of recipient selection criteria to include patients with a type 2 diabetes phenotype, a decline in PTx activity has occurred in the new millennium related to a number of factors including: (1) lack of a primary referral source and general acceptance by the diabetes care community; (2) absence of consensus criteria; and (3) access, education, and resource issues within the transplant community. In the author's experience, patients who present as potential candidates for PTx have felt as though they needed to circumvent the conventional diabetes care model to gain access to transplant options. PTx should be featured more prominently in the management algorithms for patients with insulin requiring diabetes who are failing exogenous insulin therapy or experiencing progressive diabetic complications regardless of diabetes type. Furthermore, all patients with diabetes and chronic kidney disease should undergo consideration for simultaneous pancreas-kidney transplantation independent of geography or location.

Tissue engineering approaches and generation of insulin-producing cells to treat type 1 diabetes

Tissue engineering (TE) has become a new effective solution to a variety of medical problems, including diabetes. Mesenchymal stem cells (MSCs), which have the ability to differentiate into endodermal and mesodermal cells, appear to be appropriate for this function. The purpose of this review was to evaluate the outcomes of various researches on the insulin-producing cells (IPCs) generation from MSCs with TE approaches to increase efficacy of type 1 diabetes treatments. The search was performed in PubMed/Medline, Scopus and Embase databases until 2021. Studies revealed that MSCs could also differentiate into IPCs under certain conditions. Therefore, a wide range of protocols have been used for this differentiation, but their effectiveness is very different. Scaffolds can provide a microenvironment that enhances the MSCs to IPCs differentiation, improves their metabolic activity and up-regulate pancreatic-specific transcription factors. They also preserve IPCs architecture and enhance insulin production as well as protect against cell death. This systematic review offers a framework for prospective research based on data. In vitro and in vivo evidence suggests that scaffold-based TE can improve the viability and function of IPCs.

Type 1 diabetes and engineering enhanced islet transplantation

The development of new therapeutic approaches to treat type 1 diabetes mellitus (T1D) relies on the precise understanding and deciphering of insulin-secreting β-cell biology, as well as the mechanisms responsible for their autoimmune destruction. β-cell or islet transplantation is viewed as a potential long-term therapy for the millions of patients with diabetes. To advance the field of insulin-secreting cell transplantation, two main research areas are currently investigated by the scientific community: (1) the identification of the developmental pathways that drive the differentiation of stem cells into insulin-producing cells, providing an inexhaustible source of cells; and (2) transplantation strategies and engineered transplants to provide protection and enhance the functionality of transplanted cells. In this review, we discuss the biology of pancreatic β-cells, pathology of T1D and current state of β-cell differentiation. We give a comprehensive view and discuss the different possibilities to engineer enhanced insulin-secreting cell/islet transplantation from a translational perspective.

Cell Therapy for Type 1 Diabetes: From Islet Transplantation to Stem Cells

The field of cell therapy of type 1 diabetes is a particularly interesting example in the scenario of regenerative medicine. In fact, β-cell replacement has its roots in the experience of islet transplantation, which began 40 years ago and is currently a rapidly accelerating field, with several ongoing clinical trials using β cells derived from stem cells. Type 1 diabetes is particularly suitable for cell therapy as it is a disease due to the deficiency of only one cell type, the insulin-producing β cell, and this endocrine cell does not need to be positioned inside the pancreas to perform its function. On the other hand, the presence of a double immunological barrier, the allogeneic one and the autoimmune one, makes the protection of β cells from rejection a major challenge. Until today, islet transplantation has taught us a lot, pioneering immunosuppressive therapies, graft encapsulation, tissue engineering, and test of different implant sites and has stimulated a great variety of studies on β-cell function. This review starts from islet transplantation, presenting its current indications and the latest published trials, to arrive at the prospects of stem cell therapy, presenting the latest innovations in the field.

A Worldwide Survey of Activities and Practices in Clinical Islet of Langerhans Transplantation

A global online survey was administered to 69 islet transplantation programs, covering 84 centers and 5 networks. The survey addressed questions on program organization and activity in the 2000–2020 period, including impact on activity of national health care coverage policies. We obtained full data from 55 institutions or networks worldwide and basic activity data from 6 centers. Additional data were obtained from alternative sources. A total of 94 institutions and 5 networks was identified as having performed islet allotransplantation. 4,365 islet allotransplants (2,608 in Europe, 1,475 in North America, 135 in Asia, 119 in Oceania, 28 in South America) were reported in 2,170 patients in the survey period. From 15 centers active at the start of the study period, the number of simultaneously active islet centers peaked at 54, to progressively decrease to 26 having performed islet allotransplants in 2020. Notably, only 16 centers/networks have done >100 islet allotransplants in the survey period. Types of transplants performed differed notably between North America and the rest of the world, in particular with respect to the near-absence of simultaneous islet-kidney transplantation. Absence of heath care coverage has significantly hampered transplant activity in the past years and the COVID-19 pandemic in 2020.

International Survey of Clinical Monitoring Practices in Pancreas and Islet Transplantation

BACKGROUND

The long-term outcomes of both pancreas and islet allotransplantation have been compromised by difficulties in the detection of early graft dysfunction at a time when a clinical intervention can prevent further deterioration and preserve allograft function. The lack of standardized strategies for monitoring pancreas and islet allograft function prompted an international survey established by an International Pancreas and Islet Transplant Association/European Pancreas and Islet Transplant Association working group.

METHODS

A global survey was administered to 24 pancreas and 18 islet programs using Redcap. The survey addressed protocolized and for-cause immunologic and metabolic monitoring strategies following pancreas and islet allotransplantation. All invited programs completed the survey.

RESULTS

The survey identified that in both pancreas and islet allograft programs, protocolized clinical monitoring practices included assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and donor-specific antibody. Protocolized monitoring in islet transplant programs relied on the addition of mixed meal tolerance test, continuous glucose monitoring, and autoantibody titers. In the setting of either suspicion for rejection or serially increasing hemoglobin A1c/fasting glucose levels postpancreas transplant, Doppler ultrasound, computed tomography, autoantibody titers, and pancreas graft biopsy were identified as adjunctive strategies to protocolized monitoring studies. No additional assays were identified in the setting of serially increasing hemoglobin A1c levels postislet transplantation.

CONCLUSIONS

This international survey identifies common immunologic and metabolic monitoring strategies utilized for protocol and for cause following pancreas and islet transplantation. In the absence of any formal studies to assess the efficacy of immunologic and metabolic testing to detect early allograft dysfunction, it can serve as a guidance document for developing monitoring algorithms following beta-cell replacement.

Long-term efficacy and safety of porcine islet macrobeads in nonimmunosuppressed diabetic cynomolgus macaques

Although human islet transplantation has proven to provide clinical benefits, especially the near complete amelioration of hypoglycemia, the supply of human islets is limited and insufficient to meet the needs of all people that could benefit from islet transplantation. Porcine islets, secreting insulin nearly identical to that of human insulin, have been proposed as a viable supply of unlimited islets. Further, encapsulation of the porcine islets has been shown to reduce or eliminate the use of immunosuppressive therapy that would be required to prevent rejection of the foreign islet tissue. The goal of the current study was to determine the long-term safety and efficacy of agarose encapsulated porcine islets (macrobeads) in diabetic cynomolgus macaques, in a study emulating a proposed IND trial in which daily exogenous insulin therapy would be reduced by 50% with no loss of glucose regulation. Four of six animals implanted with macrobeads demonstrated ≥ 30% reduction in insulin requirements in year 1 of follow-up. Animals were followed for 2, 3.5, and 7.4 years with no serious adverse events, mortality or evidence of pathogen transmission. This study supports the continued pursuit of encapsulated porcine islet therapy as a promising treatment option for diabetes mellitus.

Towards a Rational Balanced Pancreatic and Islet Allocation Schema

Allocation of donated organs for transplantation is a complex process that considers numerous factors such as donor, organ and candidate characteristics and practical issues such as geography. Whole pancreas and isolated islet transplantation are lifesaving for certain individuals with diabetes. Herein, we suggest a revised allocation schema that matches donor characteristics with candidate medical condition while allowing for geographic considerations. It is hoped that adoption of this schema will shorten allocation time, decrease organ waste and optimize the parity between organ donor characteristics and candidate state of health.

Pain resolution and glucose control in pediatric patients with chronic pancreatitis after total pancreatectomy with islet auto-transplantation

BACKGROUND

Chronic pancreatitis (CP) and acute recurrent pancreatitis (ARP) in pediatric patients are strongly associated with genetic mutations and lead to pan-parenchymal disease refractory to medical and endoscopic treatment. Our aim was to assess pain resolution and glucose control in patients with CP and ARP following total pancreatectomy with islet auto-transplantation (TPIAT).

METHODS

We retrospectively analyzed prospectively collected clinical data of 12 children who developed CP and ARP and underwent TPIAT when 21 years old or younger at the University of Chicago between December 2009 and June 2020. Patients with recurrent or persistent abdominal pain attributed to acute or chronic pancreatic inflammation and a history of medical interventions attempted for the relief of pancreatic pain were selected by a multi-disciplinary team for TPIAT. We followed patients post-operatively and reported data for pre-TPIAT, post-operative day 75, and yearly post-TPIAT.

RESULTS

All 12 patients experienced complete resolution of pancreatic pain. The overall insulin-independence rate after 1 year was 66% (8/12) and 50% (3/6) at 4 years. Shorter duration of CP/ARP pre-TPIAT, higher mass of islets infused, and lower BMI, BMI percentile, and BSA were associated with insulin-independence post-TPIAT.

CONCLUSIONS

TPIAT is a viable treatment option for pediatric patients with CP and ARP. Pediatric patients undergoing TPIAT for CP achieved resolution of pancreatic-type pain and reduced opioid requirements. The majority were able to achieve insulin-independence which was associated with lower pre-TPIAT BMI and higher islet mass transplanted (i.e., over 2000 IEQ/kg), the latter of which can be achieved by earlier TPIAT.

LEVEL OF EVIDENCE

Treatment study, Level IV.

Challenges, highlights, and opportunities in cellular transplantation: A white paper of the current landscape

Although cellular transplantation remains a relatively small field compared to solid organ transplantation, the prospects for advancement in basic science and clinical care remain bountiful. In this review, notable historical events and the current landscape of the field of cellular transplantation are reviewed with an emphasis on islets (allo- and xeno-), hepatocytes (including bioartificial liver), adoptive regulatory immunotherapy, and stem cells (SCs, specifically endogenous organ-specific and mesenchymal). Also, the nascent but rapidly evolving field of three-dimensional bioprinting is highlighted, including its major processing steps and latest achievements. To reach its full potential where cellular transplants are a more viable alternative than solid organ transplants, fundamental change in how the field is regulated and advanced is needed. Greater public and private investment in the development of cellular transplantation is required. Furthermore, consistent with the call of multiple national transplant societies for allo-islet transplants, the oversight of cellular transplants should mirror that of solid organ transplants and not be classified under the unsustainable, outdated model that requires licensing as a drug with the Food and Drug Administration. Cellular transplantation has the potential to bring profound benefit through progress in bioengineering and regenerative medicine, limiting immunosuppression-related toxicity, and providing markedly reduced surgical morbidity.

Update on islet cell transplantation

PURPOSE OF REVIEW

Chronic diabetes-related complications continue to exert a rapidly growing and unsustainable pressure on healthcare systems worldwide. In type 1 diabetes, glycemic control is particularly challenging, as intensive management substantially increase the risk of severe hypoglycemic episodes. Alternative approaches to address this issue are required. Islet cell transplantation offers the best approach to reduce hypoglycemic risks and glycemic lability, while providing optimal glycemic control. Although ongoing efforts have improved clinical outcomes, the constraints in tissue sources and the need for chronic immunosuppression limit the application of islet cell transplantation as a curative therapy for diabetes. This review provides an update on islet cell transplantation, focusing on recent clinical experience, ongoing research, and future challenges.

RECENT FINDINGS

Current evidence demonstrates advances in terms of long-term glycemic control, improved insulin independence rates, and novel approaches to eliminate chronic immunosuppression requirements after islet cell transplantation. Advances in stem cell-based therapies provide a promising path towards truly personalized regenerative therapies, solving both tissue supply shortage and the need for lifelong immunosuppression, enabling widespread use of this potentially curative treatment. However, as these therapies enter the clinical realm, regional access variability and ethical questions regarding commercialization are becoming increasingly important and require a collaborative solution.

SUMMARY

In this state-of-the-art review, we discuss current clinical evidence and discuss key aspects on the present and future of islet cell transplantation.

Arguments against the Requirement of a Biological License Application for Human Pancreatic Islets: The Position Statement of the Islets for US Collaborative Presented during the FDA Advisory Committee Meeting

The Food and Drug Administration (FDA) has been regulating human islets for allotransplantation as a biologic drug in the US. Consequently, the requirement of a biological license application (BLA) approval before clinical use of islet transplantation as a standard of care procedure has stalled the development of the field for the last 20 years. Herein, we provide our commentary to the multiple FDA’s position papers and guidance for industry arguing that BLA requirement has been inappropriately applied to allogeneic islets, which was delivered to the FDA Cellular, Tissue and Gene Therapies Advisory Committee on 15 April 2021. We provided evidence that BLA requirement and drug related regulations are inadequate in reassuring islet product quality and potency as well as patient safety and clinical outcomes. As leaders in the field of transplantation and endocrinology under the “Islets for US Collaborative” designation, we examined the current regulatory status of islet transplantation in the US and identified several anticipated negative consequences of the BLA approval. In our commentary we also offer an alternative pathway for islet transplantation under the regulatory framework for organ transplantation, which would address deficiencies of in current system.

US food and drug administration (FDA) panel endorses islet cell treatment for type 1 diabetes: A pyrrhic victory?

Allogeneic islet transplantation is a standard of care treatment for patients with labile type 1 diabetes in many countries around the world, including Japan, the United Kingdom, Australia, much of continental Europe, and parts of Canada. The United States is now endorsing islet cell treatment for type 1 diabetes, but the FDA has chosen to consider islets as a biologic that requires licensure, making the universal implementation of the procedure in the clinic very challenging and opening the manufacture of islet grafts to private companies. The commercialization of human tissues raises significant legal and ethical issues and ironically leads to a situation where treatments developed as a result of the scientific and economic efforts of academia over several decades become exploited exclusively by for-profit entities.

Why pancreatic islets should be regarded and regulated like organs

There are strong reasons to say that pancreatic islets are organs before they are isolated and that they should be considered to be organs once transplanted. Thus, taking into account how much we have learned about the structure and function of islet micro-organs, it seems highly illogical to on one hand consider autologous islets be regulated as organ transplants and alloislets to be regulated with the very restrictive rules used for cell transplantation. It is particularly problematic that this policy has led to restrictions that have made it next to impossible for transplants of alloislets to be carried out in the US, which is a very sad situation for the country that made so many of the advances that brought islet transplantation to the clinic.

Islets Transplantation at a Crossroads - Need for Urgent Regulatory Update in the United States: Perspective Presented During the Scientific Sessions 2021 at the American Diabetes Association Congress

Clinical islet allotransplantation has been successfully regulated as tissue/organ for transplantation in number of countries and is recognized as a safe and efficacious therapy for selected patients with type 1 diabetes mellitus. However, in the United States, the FDA considers pancreatic islets as a biologic drug, and islet transplantation has not yet shifted from the experimental to the clinical arena for last 20 years. In order to transplant islets, the FDA requires a valid Biological License Application (BLA) in place. The BLA process is costly and lengthy. However, despite the application of drug manufacturing technology and regulations, the final islet product sterility and potency cannot be confirmed, even when islets meet all the predetermined release criteria. Therefore, further regulation of islets as drugs is obsolete and will continue to hinder clinical application of islet transplantation in the US. The Organ Procurement and Transplantation Network together with the United Network for Organ Sharing have developed separately from the FDA and BLA regulatory framework for human organs under the Human Resources & Services Administration to assure safety and efficacy of transplantation. Based on similar biologic characteristics of islets and human organs, we propose inclusion of islets into the existing regulatory framework for organs for transplantation, along with continued FDA oversight for islet processing, as it is for other cell/tissue products exempt from BLA. This approach would reassure islet quality, efficacy and access for Americans with diabetes to this effective procedure.

Post-Hoc Analysis of a Randomized, Double Blind, Prospective Study at the University of Chicago: Additional Standardizations of Trial Protocol are Needed to Evaluate the Effect of a CXCR1/2 Inhibitor in Islet Allotransplantation

A recent randomized, multicenter trial did not show benefit of a CXCR1/2 receptor inhibitor (Reparixin) when analysis included marginal islet mass (>3,000 IEQ/kg) for allotransplantation and when immunosuppression regimens were not standardized among participating centers. We present a post-hoc analysis of trial patients from our center at the University of Chicago who received an islet mass of over 5,000 IEQ/kg and a standardized immunosuppression regimen of anti-thymocyte globulin (ATG) for induction. Twelve islet allotransplantation (ITx) recipients were randomized (2:1) to receive Reparixin (N = 8) or placebo (N = 4) in accordance with the multicenter trial protocol. Pancreas and donor characteristics did not differ between Reparixin and placebo groups. Five (62.5%) patients who received Reparixin, compared to none in the placebo group, achieved insulin independence after only one islet infusion and remained insulin-free for over 2 years (P = 0.08). Following the first ITx with ATG induction, distinct cytokine, chemokine, and miR-375 release profiles were observed for both the Reparixin and placebo groups. After excluding procedures with complications, islet engraftment on post-operative day 75 after a single transplant was higher in the Reparixin group (n = 7) than in the placebo (n = 3) group (P = 0.03) when islet graft function was measured by the ratio of the area under the curve (AUC) for c-peptide to glucose in mixed meal tolerance test (MMTT). Additionally, the rate of engraftment was higher when determined via BETA-2 score instead of MMTT (P = 0.01). Our analysis suggests that Reparixin may have improved outcomes compared to placebo when sufficient islet mass is transplanted and when standardized immunosuppression with ATG is used for induction. However, further studies are warranted. Investigation of Reparixin and other novel agents under more standardized and optimized conditions would help exclude confounding factors and allow for a more definitive evaluation of their role in improving outcomes in islet transplantation. Clinical trial reg. no. NCT01817959, clinicaltrials.gov.