Stem-cell-derived islets: a milestone, with unfinished work
What the 2025 zimislecel human study showed, what insulin independence means, and why immune protection and long-term safety remain essential.
By The Diabetes Guide editorial project · Updated 30 Sept 2026
On this page
Scientists can grow islet-like cells from stem cells. Early studies show they can make insulin in people, with immune-suppressing medicine.
Step 1: What is replaced
The new cells sense sugar and release insulin, replacing what was lost.
For example: Replacing a burned-out bulb, but the wiring problem remains.
Step 2: What the study showed
A phase 1–2 study reported 10 of 12 full-dose participants free of insulin at a year. It was small and had serious side effects.
For example: A promising test drive of a prototype car.
Step 3: What is unknown
How long the cells last, safety without immune drugs, cost and access.
For example: We know it starts, but not how far it will go.
Remember: It is promising, and it is not yet a routine cure.
The full story
Want more? Below is the detailed version with the real science words. It is fine to skip it.
What is being replaced?
Stem cells can be guided to develop into islet-like cells, including cells that secrete insulin in response to glucose. The objective is to replace a missing physiological capability. This does not automatically switch off the immune process that caused Type 1.
The 2025 human evidence
A phase 1–2 zimislecel report included 14 participants with at least one year of follow-up. Among 12 full-dose participants, 10 were insulin independent at day 365. The study involved selected adults with severe hypoglycemia and required immunosuppression. Analyses were interim and not prespecified; serious adverse events occurred, including neutropenia, and two deaths were reported. These features prevent treating the result as an estimate for everyone with Type 1. 1
What the finding supports
The study supports the possibility that manufactured islets can engraft and restore meaningful insulin secretion. Engraftment means transplanted cells establish themselves and function in the recipient. C-peptide provides evidence of endogenous secretion, while insulin independence is a separate clinical outcome.
What it does not establish
It does not establish lifelong cell survival, freedom from immune-suppressing drugs, safety in broad populations, affordability, or reliable access. A successful trial participant is not evidence that manufacturing and care systems can serve millions of people.
Type 1 research: solve several problems together
Preserve. Immune modulation can preserve function or delay progression in selected people.
Read every step in a list
- Preserve. Immune modulation can preserve function or delay progression in selected people.
- Replace. Donor or stem-cell-derived islets can supply insulin-producing cells.
- Protect. Immune rejection and recurrent autoimmunity require durable solutions.
- Scale safely. Long-term safety, reliable manufacturing, cost and access remain essential.
Immune protection is a separate problem
Gene editing and encapsulation try to protect cells in different ways. A 2025 single-participant study of edited donor islets reported glucose-responsive secretion without immunosuppression over short follow-up. Donor cells in that study were not the same product as stem-cell-derived zimislecel. These approaches must not be conflated. 2
Where donor transplantation fits
Donor islet therapy and pancreas transplantation establish that replacing function can work, but donor supply, procedure risks and immunosuppression limit who can benefit. The FDA's Lantidra approval is for selected adults with difficult severe hypoglycemia; it is not a general replacement for contemporary insulin management. 3
The next questions
Can cells survive safely for many years? Can protection avoid systemic immune suppression without compromising oxygen supply or tumor surveillance? Can production be consistent and affordable? These are measurable research questions. Assigning a date for a universal cure would outrun the evidence.
Trace the evidence
Sources and further reading
1.Stem Cell–Derived, Fully Differentiated Islets for Type 1 Diabetes (opens in a new tab)
Reichman et al.; New England Journal of Medicine · 2025 · Early human study
Who was studied, limits and source check
Population: Selected adults with T1D, severe hypoglycemia and impaired awareness
Sample: 14 with ≥12-month follow-up; 12 at full dose
Limitations: Small, uncontrolled interim analysis; required immunosuppression; serious adverse events and deaths occurred. Not a routine cure.
Source checked 2026-09-30. See the original publication for full methods.
2.Survival of Transplanted Allogeneic Beta Cells with No Immunosuppression (opens in a new tab)
Carlsson et al.; New England Journal of Medicine · 2025 · Early human study
Who was studied, limits and source check
Population: One adult with long-standing T1D
Sample: 1 participant; 12-week reported follow-up
Limitations: Single participant, low cell dose and short follow-up. Does not demonstrate generalizable insulin independence.
Source checked 2026-09-30. See the original publication for full methods.
3.FDA approves first donor islet cellular therapy for selected adults with T1D (opens in a new tab)
US Food and Drug Administration · 2023 · Regulatory
Who was studied, limits and source check
Population: Adults with T1D and repeated severe hypoglycemia despite intensive management
Sample: 30 in two nonrandomized single-arm studies
Limitations: Selected population, donor constraints and risks of infusion and immunosuppression. Approval does not establish universal cure.
Source checked 2026-09-30. See the original publication for full methods.
Source checking is an editorial literature check, not independent medical review. This page is for learning. It cannot diagnose you or make a treatment plan. Evidence labels describe the cited claims, not the whole topic.
What does “Preliminary” mean?
Early results. They need to be repeated. Like a first test drive of a new car.
Keep reading
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Type 1
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Type 2
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