Advances in Functional Cures: A Comprehensive Evaluation of Tegoprubart and the Islet Cell Transplantation Trial

Tegoprubart and Islet Cell Transplantation

The recent clinical progress of tegoprubart, a targeted monoclonal antibody developed by Eledon Pharmaceuticals, represents a significant paradigm shift in this field. By selectively blocking the CD40 ligand (CD40L) pathway, tegoprubart provides a mechanism to protect transplanted islet cells without the nephrotoxicity and neurotoxicity associated with traditional calcineurin inhibitors, such as tacrolimus. For individuals with type 1 diabetes (T1D), the restoration of endogenous insulin production through islet cell transplantation represents a potential functional cure. However, the success of this procedure has historically been limited by the systemic toxicity of required immunosuppressive regimens.  Recent data indicates that by replacing traditional calcineurin inhibitors with tegoprubart, transplant recipients can achieve insulin independence with a significantly improved safety profile.

Why Insulin Isn't a Biological Cure

Type 1 diabetes is characterized by the autoimmune destruction of insulin-producing beta cells within the pancreatic islets, leading to a lifelong dependence on exogenous insulin. While modern technology, including continuous glucose monitors (CGM) and automated insulin delivery (AID) systems, has improved the lived experience of patients, these tools do not constitute a cure. Many individuals, particularly those with long-standing disease, develop hypoglycemia unawareness in a life-threatening condition where the physiological warning signs of low blood sugar are no longer perceived.

For this high-risk population, islet cell transplantation offers a method to restore endogenous glucose regulation. The procedure involves isolating islets from a deceased donor pancreas and infusing them into the portal vein of the recipient’s liver. However, the success of these transplants depends entirely on the ability to prevent the recipient's immune system from rejecting the donor cells.

Clinical Impact of CNI Toxicity

The modern era of islet transplantation began in 2000 with the introduction of the Edmonton Protocol. This regimen achieved a milestone by eliminating the use of glucocorticoids, which are known to be directly toxic to beta cells and to cause severe insulin resistance. However, the Edmonton Protocol relied heavily on calcineurin inhibitors (CNIs), specifically tacrolimus (Prograf). While tacrolimus is highly effective at preventing acute rejection, its chronic use is associated with a cascade of metabolic and physiological complications.

Tacrolimus works by inhibiting calcineurin, a phosphatase involved in the activation of T-cells. Unfortunately, calcineurin is also vital for the healthy function of other organs and the islet cells themselves. Chronic CNI therapy often results in "CNI-associated nephrotoxicity," where the drug causes progressive damage to the kidneys, sometimes leading to renal failure. Furthermore, tacrolimus is linked to hypertension, neurotoxicity (including tremors and cognitive changes), and the development of post-transplant diabetes mellitus, as it can impair the insulin secretion of the very islets it is meant to protect. This "toxic" trade-off has limited the widespread adoption of islet transplantation, confining it to only the most severe cases of brittle diabetes.

Table 1: Edmonton Protocol vs Tegoprubart Regimen

Feature	Edmonton Protocol (Traditional)	Tegoprubart Regimen (Investigational)
Primary Immunosuppressant	Tacrolimus (Calcineurin Inhibitor)	Tegoprubart (Anti-CD40L Antibody)
Mechanism of Action	Broad intracellular signaling inhibition	Targeted costimulatory blockade
Kidney Impact	High risk of nephrotoxicity	No evidence of kidney damage; may improve function
Islet Impact	Potential direct toxicity to beta cells	Non-toxic; promotes islet survival and engraftment
Administration	Daily oral pills with blood level monitoring	Intravenous infusion every 3 weeks
Common Side Effects	Tremors, hypertension, hair loss, kidney decline	Generally well-tolerated; mild adverse events

Story of Tegoprubart

Tegoprubart, formerly known as AT-1501, was invented by scientists at the ALS Therapy Development Institute (ALS TDI), a nonprofit biotech focused on Amyotrophic Lateral Sclerosis. In 2011, researchers at ALS TDI began investigating the CD40L pathway as a means to dampen the chronic neuroinflammation associated with the progression of ALS and Alzheimer’s disease. To facilitate the capital-intensive process of clinical trials, ALS TDI established Anelixis Therapeutics as a for-profit clinical-stage company. In 2019, Anelixis successfully completed Phase 1 trials in healthy volunteers and patients with ALS, demonstrating the safety of the antibody. In November 2020, Anelixis was acquired by Novus Therapeutics, which changed its name to Eledon Pharmaceuticals in January 2021 to reflect its commitment to the development of tegoprubart across multiple indications. While tegoprubart met its primary endpoints for safety and target engagement in a Phase 2 ALS trial in 2022, its potential to revolutionize the field of organ and cell transplantation became the company's primary focus.

Mechanism of Action: The Precision Shield

The therapeutic advantage of tegoprubart lies in its highly specific mechanism of action. It is a humanized monoclonal antibody that selectively inhibits the CD40 ligand (CD40L). The interaction between CD40L and its receptor, CD40, which is expressed on B-cells and antigen-presenting cells, is a critical "second signal" or costimulatory pathway required for a robust immune response. Unlike traditional immunosuppressants that broadly disable the immune system, tegoprubart blocks a specific costimulatory pathway required for immune cell "crosstalk". By silencing this signal, it prevents the immune system from identifying the donor islets as foreign enemies. This targeted approach also promotes the polarization of regulatory T-cells (Tregs), which help the body tolerate the new cells.

Clinical Outcomes and Engraftment Data

The most significant update on the Eledon trial came in March 2026, when Dr. Piotr Witkowski presented data from the fully enrolled 12-patient cohort at the ATTD conference. The results demonstrated an unprecedented level of success for a CNI-free regimen in islet transplantation. The cohort, which had an average time since transplant of approximately eight months, showed rapid and sustained improvement in glycemic control. Of the 10 patients who were more than four weeks post-transplant, 100% achieved complete insulin independence. This means they were able to stop all external insulin injections and pump therapy. Furthermore, these patients achieved an average HbA1c of approximately 5.35%, effectively normalizing their blood sugar levels to a range seen in individuals without diabetes. A critical finding presented by Dr. Witkowski was that tegoprubart appeared to enhance islet engraftment.

Safety and Tolerability

Tegoprubart demonstrated a highly favorable safety profile. Critically, there was no evidence of the kidney damage (nephrotoxicity), high blood pressure, or neurological side effects typically seen with tacrolimus. The trial reported no evidence of nephrotoxicity, hypertension, or neurotoxicity. Patients did not experience the tremors, metabolic disturbances, or cardiovascular stressors that often compromise the quality of life after a transplant. Adverse events related to immunosuppression were successfully managed by adjusting the dose of the ancillary medication, mycophenolic acid. This suggests that tegoprubart could enable access to islet cell transplantation for a much broader group of individuals living with T1D, including those who already have existing kidney dysfunction.

Conclusion: A New Paradigm for Functional Cures

The results of the Eledon trial and the clinical success of tegoprubart represent a significant milestone in the quest to cure type 1 diabetes. By moving away from the "toxic" legacy of the Edmonton Protocol and embracing targeted immunomodulation, researchers have demonstrated that it is possible to achieve insulin independence with a high safety margin. The University of Chicago pilot study has not only restored the natural blood sugar regulation of its participants but has also provided a blueprint for future therapies that prioritize the long-term health of the patient and the graft. As Eledon Pharmaceuticals moves toward regulatory engagement with the FDA and plans for larger, multicenter Phase 3 trials, the potential for tegoprubart to become a cornerstone of standard care in transplantation grows. The transition from managing diabetes with technology to curing it with cellular therapy is no longer a distant hope, but a rapidly approaching reality.

References

Akturk, H. K., Waterman, L. A., & Cobry, E. C. (2025). Revolutionizing diabetes care: From tech to therapeutics. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy, 18, 4675–4682. https://doi.org/10.2147/DMSO.S580423

Mbaye, E. H. A., Scott, E. A., & Burke, J. A. (2025). From Edmonton to Lantidra and beyond: Immunoengineering islet transplantation to cure type 1 diabetes. Frontiers in Transplantation, 4, 1514956. https://doi.org/10.3389/frtra.2025.1514956

Witkowski, P. (n.d.). Islet diabetes patient stories. https://www.pwitkowski.org/islet-diabetes-patient-stories

ALS Therapy Development Institute. (n.d.). Tegoprubart (AT-1501). Retrieved April 30, 2026, from https://www.als.net/tegoprubart/

ClinicalTrials.gov. (2023, November 9). A study of tegoprubart for the prevention of rejection in patients receiving a kidney transplant (NCT06126380). U.S. National Library of Medicine. https://clinicaltrials.gov/study/NCT06126380

Eledon Pharmaceuticals. (2024, January 17). Eledon announces clinical progress of tegoprubart for the prevention of rejection in kidney transplantation. https://ir.eledon.com/news-releases/news-release-details/eledon-announces-clinical-progress-tegoprubart-prevention

ClinicalTrials.gov. (2024, February 21). Islet transplantation in type 1 diabetes using tegoprubart (NCT06305286). U.S. National Library of Medicine. https://clinicaltrials.gov/study/NCT06305286

Eledon Pharmaceuticals. (2024, June 21). Eledon Pharmaceuticals announces positive initial data from subjects in a phase 1b trial of tegoprubart in patients undergoing islet transplantation. https://ir.eledon.com/news-releases/news-release-details/eledon-pharmaceuticals-announces-positive-initial-data-subjects

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Eledon Pharmaceuticals. (2026, March 16). Eledon announces updated data from investigator-initiated islet transplant trial of tegoprubart in patients with type 1 diabetes at UChicago Medicine [Press release]. https://ir.eledon.com/news-releases/news-release-details/eledon-announces-updated-data-investigator-initiated-islet

Iapoce, C. (2026, March 16). Tegoprubart enables insulin independence in type 1 diabetes islet transplant study. HCP Live. https://www.hcplive.com/view/tegoprubart-enables-insulin-independence-in-type-1-diabetes-islet-transplant-study

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