Transplanted insulin-producing cells still working at 14 months, without immunosuppression

Type 1 diabetes is caused by the immune system destroying the body's own insulin-producing cells. Transplanting replacement islet cells from a donor has been technically possible for years, but it comes with a catch that has limited its use: a transplant from someone else triggers immune rejection, which means recipients need lifelong immunosuppressive drugs — trading one chronic condition's burden for the risks of another.

A case report published as a letter in the New England Journal of Medicine on 10 July describes an attempt to remove that trade-off entirely. One patient received donor islet cells that had been genetically engineered to evade immune detection, transplanted with no immunosuppressive drugs at all. Fourteen months later, the cells are still there, and they are still producing insulin [s1, s2].

What was transplanted, and how

The cells, known as UP421, are donor-derived human pancreatic islet cells modified using a "hypoimmune" gene-editing platform designed to make the cells invisible to both the recipient's normal immune rejection response and to the specific autoimmune process that causes type 1 diabetes in the first place [s2]. The underlying premise is that if transplanted cells can be edited to avoid detection by the immune system altogether, the immunosuppressive drugs used to prevent rejection become unnecessary.

The case, run as an investigator-sponsored study at Uppsala University Hospital in Sweden, involved a single patient with type 1 diabetes who received the modified islet cells via surgical transplantation into forearm muscle — a subcutaneous, non-organ transplant site chosen in part because it allows the graft to be monitored and imaged directly, unlike islets infused into the liver, the more conventional transplant site [s2]. No immunosuppressive medication was given at any point [s2].

What 14 months of follow-up showed

Before transplant, the patient's own insulin-producing capacity was effectively absent: C-peptide, a biomarker used as a proxy for the body's own insulin production, was undetectable both while fasting and during a mixed meal tolerance test [s2]. C-peptide is preferred over measuring insulin directly because it is co-secreted with the body's own insulin at a stable ratio and, unlike insulin, is not confounded by any injected insulin a patient with diabetes might be taking.

By 14 months, fasting and stimulated C-peptide levels remained comparable to what was measured earlier in the study and had, notably, exceeded the levels recorded at the 9-to-12-month mark [s2] — meaning graft function was not simply persisting but improving over that window. Between months 12 and 14, researchers also reported tighter glycemic control alongside the improved insulin secretion [s2]. Imaging using PET-MRI at the 52-week mark confirmed that islet cells were still physically present at the forearm transplant site [s2]. No safety issues were identified over the follow-up period [s2].

Why a single patient still matters

A case report describing one person's outcome is, by definition, not evidence that a therapy works in general. It cannot establish response rates, cannot characterize the range of outcomes across different patients, and cannot rule out that this particular patient's result reflects something unusual about their own biology rather than the therapy's general effectiveness. Those limitations are real and should not be minimized.

What a single, well-documented case can do is answer a narrower but still important question: does the core concept — immune-evading gene-edited cells surviving and functioning without any immunosuppression — hold up at all, beyond the short term where transplant success is easiest to achieve. Islet transplants, even immunosuppressed ones, often show early function that fades within the first year as rejection processes and other factors erode the graft. Sustained and improving function at 14 months, in the complete absence of immunosuppression, is a meaningfully longer and harder bar to clear than an early positive readout would have been.

Per-Ola Carlsson, the study's principal investigator at Uppsala University Hospital, framed the result against the broader unmet need in the field: "After a century of relying on insulin, people living with type 1 diabetes deserve more than incremental improvements" [s2]. Sana's chief medical officer, Gary Meininger, described the findings as demonstrating "the promise of our HIP-modified cells and their potential as a significant medical breakthrough" [s2] — language from the therapy's developer that should be read as a statement of the company's own assessment, not an independent verification of clinical significance.

What comes next

The company has said it plans to file an Investigational New Drug application and begin a Phase 1/2 trial as early as this year for a related, stem-cell-derived hypoimmune candidate, rather than the donor-derived primary islet cells used in this case [s2]. That distinction matters: primary donor islets are a limited resource that cannot be manufactured at scale, while a stem-cell-derived version could in principle supply far more patients — but it is also a different starting material, and durability data from this donor-cell case report does not automatically transfer to a stem-cell-derived product.

What to watch

Whether this single case is followed by additional patients in a formal, larger trial, which is the only way to establish how consistently this outcome replicates. Whether longer follow-up in this same patient shows continued stability, decline, or further improvement in graft function beyond 14 months. And whether the planned stem-cell-derived candidate shows comparable survival and function once it enters human testing. This article describes a single case report, not an approved or generally available treatment; it is not medical advice for anyone managing type 1 diabetes.

Sources

• [s1] Carlsson PO, Hu X, Scholz H, et al., "Long-Term Survival of Hypoimmune Allogeneic Islets without Immunosuppression," New England Journal of Medicine, 10 July 2026. https://doi.org/10.1056/nejmc2604408
• [s2] Sana Biotechnology, "Sana Biotechnology Announces Follow-On Publication in The New England Journal of Medicine (NEJM) Highlighting Groundbreaking Long-Term Data and Durability of Hypoimmune-Modified Islet Cell Transplantation Without Immunosuppression in Type 1 Diabetes," press release via BioSpace, 13 July 2026. https://www.biospace.com/press-releases/sana-biotechnology-announces-follow-on-publication-in-the-new-england-journal-of-medicine-nejm-highlighting-groundbreaking-long-term-data-and-durability-of-hypoimmune-modified-islet-cell-transplantation-without-immunosuppression-in-type-1-diabetes