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TYPE 1 DIABETES · RESEARCH ANALYSIS

Islet Therapy and Type 1 Diabetes: How Close Are We to a Cure?

An investigation of the clinical evidence, the risks behind the headlines, and the implications for people living with diabetes for decades.

By Staff Writer · October 6, 2026

Research reviewed through October 6, 2026. Clinical findings and regulatory decisions are distinguished from company forecasts and editorial analysis.

The promise—and the condition attached

For someone who has lived with type 1 diabetes for 30 or 40 years, the possibility of making insulin again carries extraordinary weight. It could mean fewer calculations before meals, less fear of going low overnight, and greater freedom to exercise or travel. Islet-cell therapy has already made insulin independence possible for selected patients. The central question is whether that freedom can be made durable, safe, and widely available.

In June 2023, the U.S. Food and Drug Administration approved Lantidra, a deceased-donor islet therapy for a narrowly defined group of adults. In 2025, a separate stem-cell-derived treatment produced insulin independence in 10 of 12 full-dose participants at one year. These are substantive clinical advances, but neither finding establishes a permanent cure available to everyone with type 1 diabetes. [1, 3]

The most accurate description of current success is a functional cure while the transplanted cells work: sufficient biological insulin production to remove the need for injected insulin. That does not necessarily eliminate the autoimmune disease, remove the need for medication, or repair damage accumulated before treatment. The distinction determines what patients can reasonably expect.

What is being transplanted?

Pancreatic islets are small clusters of hormone-producing cells. Their beta cells produce insulin, the hormone that helps regulate blood glucose. In type 1 diabetes, immune destruction of beta cells leaves the person dependent on replacement insulin. Islet therapy supplies new insulin-producing cells rather than trying to make injected insulin act more naturally. [14]

Donor-islet treatment ordinarily places purified cells into the liver through its portal vein. A catheter delivers the cells, which can establish an insulin-producing graft. This is less extensive than whole-pancreas transplantation, but it remains an invasive medical procedure. Researchers are also testing other implantation sites. [14]

There are several distinct approaches: cells isolated from deceased donors; islets manufactured from stem cells; personalized cells made by reprogramming a patient’s own tissue; and cells modified or enclosed to resist immune attack. These are different products with different levels of evidence. A successful trial of one does not establish that the others work. [3, 6, 7, 9]

The approved option: what Lantidra actually proved

Lantidra, or donislecel-jujn, was approved for adults unable to approach their target HbA1c because of repeated severe hypoglycemia despite intensive diabetes management and education. Severe hypoglycemia means a low-glucose episode requiring help from another person. Approval was not a recommendation for routine transplantation in everyone who uses insulin. [1]

The FDA’s approval announcement described two nonrandomized studies totaling 30 participants, who received up to three infusions. Twenty-one went without insulin for at least one year: 11 for one to five years and 10 for more than five years. Five never achieved insulin independence. These outcomes demonstrate a meaningful possibility, rather than a guaranteed result. [1]

For patients, the practical lesson is that years without injections can be achievable, but the treatment may require repeat procedures and continuing anti-rejection medication. A donor-cell product also depends on donated pancreatic tissue. It cannot automatically solve the supply problem for the much larger population living with type 1 diabetes. [2, 12]

The risk behind the insulin-free headline

Lantidra’s prescribing information reports serious adverse reactions in 27 of the 30 participants, or 90%, during follow-up that varied widely in duration. Twenty-six experienced infections, and malignancy events were reported in 11. Two deaths occurred during follow-up. These figures cannot be interpreted as a uniform annual risk or directly compared with a different trial. They nevertheless belong beside the efficacy figures whenever the treatment is discussed. [2]

Complications include bleeding, liver injury, and portal-vein problems from administration. Immunosuppression brings additional risks, including serious infection and cancer. In eight participants, stopping immunosuppression led to loss of graft function and, when achieved, insulin independence. Continued glucose monitoring remains necessary, and insulin must be used or restarted when required. [2]

Editorial assessment: for a person experiencing repeated life-threatening lows, these risks may be acceptable. For someone managing safely with modern insulin treatment, the same trade-off may be much less attractive. Insulin independence is an important outcome, but overall health and survival matter more than whether a pump can be removed.

The stem-cell breakthrough: zimislecel

Reichman and colleagues’ 2025 New England Journal of Medicine study examined zimislecel, formerly VX-880, a stem-cell-derived islet therapy. Among 12 full-dose participants with at least one year of follow-up, 10 were insulin-independent at day 365. All 12 achieved HbA1c below 7% and freedom from severe hypoglycemic events during the specified evaluation period. Immunosuppression was required. [3]

The safety record must accompany that result. Across the reported study population, serious neutropenia—a low count of infection-fighting white blood cells—occurred in three participants. Two deaths were reported: one from cryptococcal meningitis and one from progression of preexisting neurocognitive impairment. The manufacturer reported that neither death was attributed to the cell product itself; that distinction does not erase the risks of the overall treatment regimen. [3, 4]

The scientific advance is the prospect of a reproducible manufactured source of functioning islets. The evidentiary limit is equally clear: a small, selected study with a one-year headline outcome cannot establish lifetime durability or suitability for the general diabetes population. An 83% trial result is not an individual patient’s guaranteed probability of success.

Where the program stands in 2026

Old timelines should not be mistaken for current availability. Vertex reported in May 2026 that dosing had resumed after an internal manufacturing analysis. Its August 2026 update said the phase 1/2/3 zimislecel study continued enrolling and dosing patients, with updated program timelines expected later in the year. The sources reviewed for this article describe zimislecel as investigational; they do not establish an FDA marketing approval. [5]

The same August release described FDA clearance of an investigational new drug application for VX-017 and plans for an early-stage trial. Permission to conduct a study is different from permission to sell an approved treatment. Sponsor announcements are useful for development status, but forecasts are not substitutes for published clinical outcomes. [5]

The personalized-cell case: remarkable, but incomplete

Wang and colleagues reported a different approach in Cell in 2024. In a preliminary report involving one woman, investigators reprogrammed her own cells, produced islets, and implanted them beneath the abdominal rectus sheath. She became insulin-independent beginning 75 days after transplantation, with results reported through one year. [6]

A crucial qualification is that she was already taking immunosuppressive medication after liver transplantation. The experiment therefore could not establish that personalized islets would survive the autoimmune process without immune protection. Using one’s own cells may address donor mismatch, but it does not automatically remove the original immune attack on beta cells. [6]

This is a real patient example with impressive results. It remains a one-patient early-stage finding, rather than proof that a broadly available, medication-free personalized cure has arrived.

Can the cells survive without anti-rejection drugs?

Carlsson and colleagues reported in the New England Journal of Medicine in 2025 that genetically modified donor islets transplanted into the forearm muscle of a man with long-standing type 1 diabetes survived and produced glucose-responsive insulin without immunosuppression. At 12 weeks, investigators reported no immune response against the edited cells and no serious adverse events. This was a single-patient report. [7]

A 2026 follow-up letter reported findings through 14 months supporting continued beta-cell function and lack of an immune response to the graft. That extends the observation substantially beyond the initial report. It still does not establish that recipients generally become insulin-independent, that protection lasts for decades, or that rare safety problems have been excluded. [8]

Another strategy is encapsulation: a protective barrier intended to allow nutrients and insulin to pass while limiting immune attack. Its engineering demands are substantial. Vertex announced in March 2025 that efficacy results from its VX-264 cells-plus-device program did not support further clinical advancement. This setback demonstrates why a compelling concept needs successful human data. [9]

Editorial assessment: reliable insulin production without systemic immunosuppression could change the benefit-risk calculation for many more patients. The field must still demonstrate both adequate glucose control and safe long-term survival of immune-protected cells. Neither goal can be assumed from a short proof-of-concept study.

What decades of follow-up tell us

A 2022 Lancet Diabetes & Endocrinology report followed 255 recipients treated in Edmonton over a 20-year program. Estimated insulin independence declined from 61% at one year to 32% at five years, 20% at ten years, and 8% at twenty years. These are time-to-event estimates, not evidence that every participant was observed for twenty years. [10]

The study also found sustained graft survival in many recipients. Working cells and complete insulin independence are different outcomes: a graft can still offer value after supplementary insulin becomes necessary. The cohort reflects donor-islet practice across earlier treatment eras; its long-term percentages should not be presented as predictions for a newer stem-cell product. [10]

Of particular relevance to long-time patients, recipients with sustained graft survival had a median diabetes duration of 33.5 years at baseline. That supports the possibility of benefit after decades of disease. It does not show that waiting longer improves outcomes; the comparison was observational and affected by patient selection. [10]

What this means for long-time diabetics

The greatest immediate benefit may be protection from dangerous lows. A 2016 multicenter trial involving 48 adults found that 87.5% achieved HbA1c below 7% without severe hypoglycemia at one year; 52.1% were insulin-independent. However, kidney filtration declined on immunosuppression, and bleeding and infection occurred. The study supports transplantation for selected patients whose severe hypoglycemia persists despite expert care. [11]

Quality of life is another measurable outcome. NIDDK reported that participants in related research experienced substantial improvements even when they continued taking insulin. Relief from severe hypoglycemia and its associated fear appeared central to those gains. For someone who has organized a lifetime around avoiding a low, partial restoration of insulin production can have value beyond the number of injections eliminated. [13]

Consider three hypothetical patients; these are illustrations, not reported trial participants. A 55-year-old diagnosed in childhood who has repeated episodes requiring rescue despite specialist treatment may have a strong reason to seek transplant evaluation. A 45-year-old with safe glucose control using an automated insulin-delivery system may face a less favorable trade-off if immunosuppression is required. A kidney-transplant recipient already taking anti-rejection drugs has a different starting point, although an added islet procedure still requires individual assessment. [11, 12]

Existing complications deserve separate attention. Improved glucose regulation may help prevent or slow further damage, but these studies do not establish reversal of advanced blindness, kidney failure, coronary disease, or established neuropathy. A person who becomes insulin-independent still needs appropriate eye, kidney, cardiovascular, and foot care. That is a clinical implication of the evidence’s limits, not a claim that transplantation repairs every consequence of diabetes. [12]

For someone with vulnerable kidneys, the potential benefit of steadier glucose must be weighed against medication toxicity. Duration of diabetes alone cannot answer the eligibility question. Current health, hypoglycemia history, insulin requirements, and capacity to manage follow-up all affect the decision. The meaningful question is whether treatment improves that individual’s total health outlook.

The access question—and the evidence still needed

A therapy cannot transform population health merely by working in a research center. Donor supply, manufacturing consistency, specialist capacity, repeat treatment, insurance coverage, and continuing monitoring will determine who can receive it. No universal price or coverage promise can be inferred from the studies reviewed here. Manufactured cells may ease scarcity, but that prospect does not itself establish affordability. [5, 12]

Future reports should disclose how many patients were treated, how many remained in follow-up, how long insulin independence lasted, and what happened to those whose grafts failed. Outcomes should include severe hypoglycemia, glucose time in range, medication burden, kidney function, infections, cancer, and quality of life. Larger studies and longer surveillance are particularly important for immune-modified or stem-cell-derived products.

The evidence supports a carefully bounded conclusion: replacing lost islets can restore insulin production in people who have lived with type 1 diabetes for decades. For selected patients, it can provide years without injected insulin and meaningful relief from dangerous hypoglycemia. The next advance must make that benefit durable and safe enough to reach a much wider population.

Patients considering treatment should ask an endocrinologist or specialist transplant center about approved indications and registered clinical trials. Insulin should never be stopped in anticipation of a cure; adjustment after transplantation requires supervision. This article provides research analysis, not an individualized treatment recommendation.

References and further reading

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