What are the latest developments in islet transplantation?

Latest Developments in Islet Transplantation

The most significant recent development is the 2023 FDA approval of donislecel-jujn, the first allogeneic islet cell therapy in the United States, marking a paradigm shift from organ transplant regulation to cell therapy regulation for islet transplantation. 1

Regulatory and Clinical Approval Breakthrough

The U.S. regulatory landscape fundamentally changed in 2023 when donislecel-jujn received approval as a cell therapy rather than an organ transplant. This distinction is critical because it opens new pathways for manufacturing, quality control, and broader clinical implementation. Donislecel is specifically indicated for adults with type 1 diabetes who cannot achieve A1C goals due to repeated severe hypoglycemia despite intensive diabetes management and education. 1

Internationally, islet transplantation has already achieved approval and reimbursement status in several countries for treating problematic hypoglycemia in type 1 diabetes, based on phase 3 Clinical Islet Transplantation Consortium trials. 2

Clinical Outcomes and Efficacy

Primary Endpoints Have Evolved

Modern islet transplantation trials have shifted from insulin independence as the sole goal to a dual endpoint: achieving near-normal glycemic control (HbA1c <7.0%) combined with elimination of severe hypoglycemia. This reflects real-world clinical priorities focused on morbidity and quality of life. 2

Clinical trial data demonstrate:

• 82% of patients achieve the dual endpoint at 1 year post-transplant 2
• 70% maintain this benefit at 2 years 2
• 50% of recipients maintain insulin independence for 5 years 2

• 90% reduction in severe hypoglycemia incidence regardless of insulin independence status 2

Partial Graft Function Provides Substantial Benefit

A critical advancement in understanding is that even partial islet graft function (requiring continued insulin) significantly protects against problematic hypoglycemia and improves glycemic variability. 2 Continuous glucose monitoring studies confirm near-absence of time spent at glucose <70 mg/dL (<3.9 mmol/L), with minimal islet graft function sufficient to abrogate hypoglycemia <54 mg/dL (<3.0 mmol/L). 2

This finding is clinically transformative because it means patients benefit substantially even without complete insulin independence, expanding the therapeutic value beyond traditional success metrics.

Technical and Procedural Advances

Patient Selection Criteria

Islet transplantation's minimally invasive nature allows inclusion of:

• Older patients (>50 years) who would be ineligible for whole-pancreas transplant 2
• Patients with coronary artery disease 2
• Non-obese recipients (<30 kg/m²) requiring target islet dose ≥5,000 islet equivalents/kg from deceased donor pancreas 2

Most islet transplants are performed in non-uremic patients with type 1 diabetes experiencing problematic hypoglycemia and excessive glycemic lability. 2

Immunosuppression Requirements

Critical caveat: All recipients require lifelong immunosuppression to prevent graft rejection and recurrence of autoimmune islet destruction. 1 This necessitates careful risk-benefit assessment, as immunosuppressive therapy carries potential adverse effects that must be weighed against the morbidity of recurrent severe hypoglycemia and ketoacidosis.

Emerging Research Directions

Alternative Islet Sources

Alternative islet sources are currently under active investigation to address the fundamental limitation of donor organ shortage. 1 These include:

• Stem cell-derived insulin-producing cells 3, 4, 5, 6
• Porcine islet cells (xenotransplantation) 4
• Autologous islet transplantation following pancreatectomy 6

Novel Transplantation Strategies

Recent research focuses on:

• Biomaterial-based islet encapsulation to address immune rejection and hypoxia while providing optimal cell microenvironment 3, 4
• Alternative transplantation sites beyond traditional portal vein infusion, including subcutaneous space and mesenteric fat 4
• Targeting instant blood-mediated inflammatory reaction (IBMIR), the thrombo-inflammatory burst that destroys most transplanted islets within hours 7
• Combined cell therapies using mesenchymal stem cells/regulatory T cells with islet cells 4

Immune Tolerance Approaches

Cutting-edge research emphasizes:

• Pharmacological and cell-intrinsic interventions to modulate early immune responses 7
• Building immune-resilient microenvironments for durable graft function 7
• Novel immunosuppressive protocols and biomarkers for graft monitoring 8

Clinical Implementation Algorithm

For adults with type 1 diabetes and recurrent severe hypoglycemia despite optimized management:

1. Confirm indication: Inability to reach A1C goals due to repeated severe hypoglycemia despite intensive diabetes management and education 1

2. Assess eligibility:

   • Non-obese (BMI <30 kg/m²) 2
   • Willing to accept lifelong immunosuppression 1
   • No contraindications to immunosuppressive therapy

3. Consider timing:

   • Reserve for patients with recurrent ketoacidosis or severe hypoglycemia despite optimized glycemic management 1
   • For patients with simultaneous kidney transplant needs, consider simultaneous pancreas-kidney transplant (5-year graft survival >85%) 2

4. Set realistic expectations:

   • Primary goal is elimination of severe hypoglycemia and achievement of HbA1c <7.0% 2
   • Insulin independence is possible but not guaranteed (50% at 5 years) 2
   • Even partial graft function provides substantial protection against hypoglycemia 2

Common pitfall: Viewing insulin independence as the sole measure of success. Modern evidence demonstrates that even insulin-requiring recipients with partial graft function achieve similar reductions in hypoglycemia, glucose variability, and time spent hypoglycemic compared to insulin-independent recipients. 2