Type 1 diabetes has long stood as one of medicine’s most demanding chronic diseases. Unlike type 2 diabetes, which is often strongly linked to insulin resistance and metabolic factors, type 1 diabetes is primarily an autoimmune disease in which the immune system destroys the pancreatic beta cells responsible for producing insulin. Once these cells are lost, the body loses its natural ability to sense glucose and respond with precisely timed insulin secretion. For patients, this means a lifetime of external insulin, glucose monitoring, dietary calculation, fear of hypoglycemia, and long-term risk to the kidneys, eyes, nerves, heart, and blood vessels (NIDDK, 2025).
Modern insulin therapy has saved millions of lives. Continuous glucose monitors, insulin pumps, hybrid closed-loop systems, and improved insulin analogues have transformed care. Yet insulin replacement remains management, not restoration. It does not rebuild the lost biological system. It asks the patient and device to imitate what a healthy beta cell does naturally, minute by minute. The central scientific dream in type 1 diabetes has therefore remained simple but difficult: replace the missing beta cells and protect them from the immune system that destroyed the originals.
This is where cell therapy and gene therapy now converge.
The Logic of Cell Therapy
Cell therapy for type 1 diabetes is based on a direct biological idea: if the disease is caused by the loss of insulin-producing beta cells, then replacing those cells could restore endogenous insulin production. The earliest version of this approach has been pancreatic islet transplantation, in which islets from a deceased donor pancreas are infused into a patient, usually through the hepatic portal vein. These transplanted cells can engraft and produce insulin in response to glucose (NIDDK, 2026).
The clinical principle is already proven. In 2023, the U.S. Food and Drug Administration approved Lantidra, the first allogeneic pancreatic islet cellular therapy for adults with type 1 diabetes who have repeated severe hypoglycemia despite intensive diabetes management. In the clinical studies supporting approval, some patients achieved insulin independence for at least one year, and a subset remained insulin independent for more than five years (FDA, 2023). This approval was historically important because it showed that cellular replacement is not merely theoretical.
But donor islet transplantation has two major limitations. First, donor pancreases are scarce. There will never be enough high-quality donor islets to treat the global population of people with type 1 diabetes. Second, because the cells come from another person, patients require systemic immunosuppression to prevent rejection. Immunosuppressive drugs carry risks, including infection, malignancy, kidney toxicity, and other complications. In many patients, the burden of immunosuppression may outweigh the benefit of islet replacement (NIDDK, 2026).
Thus, the field needed two breakthroughs: an unlimited source of beta-like cells and a way to protect them from immune attack.
Stem-Cell-Derived Islets: Solving the Supply Problem
Stem-cell-derived islet therapy addresses the first problem: supply. Instead of relying on scarce deceased-donor pancreases, scientists can differentiate pluripotent stem cells into pancreatic islet-like cells capable of producing insulin. These cells can, in principle, be manufactured at scale, tested for quality, standardized, cryopreserved, and distributed as an “off-the-shelf” therapy.
One of the leading examples is zimislecel, formerly known as VX-880. Zimislecel is an investigational allogeneic, stem-cell-derived, fully differentiated insulin-producing islet cell therapy. In the FORWARD study, participants with type 1 diabetes, impaired hypoglycemia awareness, and severe hypoglycemic events received stem-cell-derived islets along with immunosuppression. Updated results published and presented in 2025 showed that all 12 full-dose participants with at least one year of follow-up demonstrated engraftment with glucose-responsive C-peptide production, achieved HbA1c and time-in-range targets, and remained free of severe hypoglycemic events from day 90 onward. Ten of 12 participants no longer required exogenous insulin at one year (Reichman et al., 2025).
This is one of the strongest human demonstrations so far that stem-cell-derived islets can restore meaningful endogenous insulin production in type 1 diabetes. However, zimislecel still requires chronic immunosuppression. Therefore, while it addresses the supply problem, it does not yet fully solve the immune problem.
Another important milestone came from autologous stem-cell-derived islet approaches. Wang and colleagues reported transplantation of chemically induced pluripotent stem-cell-derived islets in a patient with type 1 diabetes, with insulin independence beginning 75 days after transplantation and sustained endogenous insulin production reported thereafter (Wang et al., 2024). Autologous approaches may reduce alloimmune rejection because the cells originate from the patient. However, they may not fully eliminate the risk of recurrent autoimmunity, and individualized manufacturing may be expensive, complex, and difficult to scale.
The field is therefore moving toward a combined strategy: scalable stem-cell-derived beta cells plus genetic engineering for immune protection.
Gene Therapy as Immune Engineering
In type 1 diabetes, “gene therapy” does not usually mean correcting a single defective gene in the patient. Type 1 diabetes is not a classic monogenic disease. It involves genetic susceptibility, environmental triggers, immune dysregulation, beta-cell stress, and autoimmune destruction. Therefore, the most practical gene-therapy strategy is not to edit the patient’s genome directly, but to edit the therapeutic cells before transplantation.
This is ex vivo gene therapy: cells are engineered outside the body, tested, and then transplanted. The purpose is to make the cells survive.
The most important recent advance in this area is hypoimmune beta-cell transplantation. In 2025, Carlsson and colleagues reported in the New England Journal of Medicine the first human transplantation of genetically modified allogeneic donor islet cells into a patient with long-standing type 1 diabetes without immunosuppression (Carlsson et al., 2025). The patient received donor islets engineered to reduce immune recognition. The cells were modified using CRISPR-Cas12b and lentiviral transduction to create a hypoimmune profile.
The strategy involved three key immune-evasive modifications. First, B2M knockout reduced HLA class I expression, limiting recognition by CD8-positive cytotoxic T cells. Second, CIITA knockout reduced HLA class II expression, limiting antigen presentation to CD4-positive helper T cells. Third, CD47 overexpression provided a “don’t eat me” signal to macrophages and other innate immune cells. Together, these edits attempted to make transplanted beta cells less visible to both adaptive and innate immunity (Carlsson et al., 2025; Licht et al., 2025).
This was not a full clinical cure. The study used a low cell dose designed primarily to test safety, immune evasion, and survival, not to eliminate insulin use. But the result was conceptually profound: genetically engineered allogeneic beta cells survived and produced glucose-responsive insulin without immunosuppression. Follow-up data presented in 2026 reported continued C-peptide production at approximately 14 months, suggesting that hypoimmune islet cells can persist for more than a year in a human without systemic immune suppression (Sana Biotechnology, 2026).
This shifts the question from “Can transplanted beta cells survive without immunosuppression?” to “Can this be scaled, dosed, standardized, and made safe enough to treat many patients?”
Why the Carlsson Study Matters
The Carlsson study is important not because it instantly cures type 1 diabetes, but because it breaks a central assumption. For decades, beta-cell replacement was trapped in a cruel trade-off. A patient could receive donor islets and potentially regain insulin secretion, but only by accepting systemic immunosuppression. The immune system had to be weakened so the graft could live. Hypoimmune engineering suggests another path: instead of suppressing the whole patient, redesign the transplanted cells.
This distinction is ethically and medically important. A child or young adult with type 1 diabetes may live for decades. A therapy meant for broad use must be safer than lifelong immunosuppression. A future treatment that uses stem-cell-derived beta cells edited to avoid immune destruction could, in principle, offer the benefits of transplantation without the systemic toxicity of anti-rejection drugs.
This is why the field is now focused on combining the two major breakthroughs: stem-cell-derived islets for unlimited supply and gene editing for immune protection.
Encapsulation and Local Immune Protection
Gene editing is not the only immune-protection strategy. Encapsulation attempts to physically shield transplanted cells inside a semi-permeable material that allows oxygen, nutrients, glucose, and insulin to pass through while blocking immune cells. Local immunomodulation attempts to create a protective microenvironment around the graft without suppressing the entire immune system. These strategies may be used alone or in combination with gene-edited cells (NIDDK, 2026; Licht et al., 2025).
Encapsulation has conceptual elegance, but practical difficulties remain. Cells need oxygen and vascular support. Capsules can trigger fibrosis. If the barrier is too tight, cells may starve; if too loose, immune cells and inflammatory signals may enter. The challenge is not merely to hide cells, but to keep them alive, responsive, and safe for years.
Safety Questions
The promise of hypoimmune cell therapy is enormous, but so are the safety questions. HLA molecules are not useless decorations on a cell surface. They are central to immune surveillance. Cells with reduced HLA expression may be less visible to T cells, but that also raises concern about infection surveillance and malignant transformation. CD47 overexpression may protect cells from macrophage clearance, but excessive “don’t eat me” signaling is also relevant in cancer biology. Immune invisibility is useful only if it remains controlled (Shalaby et al., 2025; Licht et al., 2025).
Stem-cell-derived products also carry risks related to incomplete differentiation, residual proliferative cells, genomic instability, off-target gene editing, insertional effects from viral vectors, and long-term graft behavior. These risks can be reduced by careful manufacturing, release testing, suicide switches, selectable safety markers, and long-term surveillance, but they cannot be ignored.
Dose is another issue. A small number of cells may demonstrate survival but not produce enough insulin. A curative dose must be large enough to regulate glucose but not so large that it creates safety or vascularization problems. The implantation site also matters. The liver has been widely used for islet infusion, but alternative sites such as the omentum, subcutaneous space, muscle, or abdominal rectus sheath are being explored because they may permit retrieval, imaging, or better control of the graft environment (Wang et al., 2024; Dong et al., 2025).
A Realistic View of “Cure”
It is tempting to call these advances a cure. That word should be used carefully. For an individual patient, insulin independence with stable glucose control may feel like a cure. Scientifically, however, a durable cure for type 1 diabetes would require long-term graft survival, stable glucose-responsive insulin secretion, freedom from severe hypoglycemia, freedom from immunosuppression, no tumor formation, no late immune escape, and reproducible benefit across diverse patients.
The field is not fully there yet. Lantidra is approved but limited by donor supply and immunosuppression. Zimislecel has shown strong clinical efficacy but still requires immunosuppression. Autologous stem-cell-derived islets are promising but complex. Hypoimmune edited islets may solve the immune problem, but the human evidence is still early and limited.
Still, the direction is unmistakable. Type 1 diabetes is moving from a disease managed only by external insulin toward a disease that may one day be treated by biological reconstruction.
Conclusion
Gene and cell therapy for type 1 diabetes represents one of the most hopeful frontiers in modern medicine. The field began with a simple insight: replace the cells the immune system destroyed. It then confronted two barriers: too few donor cells and immune rejection. Stem-cell-derived islets are beginning to solve the supply problem. Gene editing is beginning to solve the immune problem.
The most exciting future therapy may be an off-the-shelf, stem-cell-derived, gene-edited beta-cell product that can be transplanted once, survive without systemic immunosuppression, sense glucose, secrete insulin, and restore metabolic freedom. That future is not yet standard clinical reality. But it is no longer fantasy.
For a century, insulin has kept people with type 1 diabetes alive. The next century may be defined by something deeper: not merely replacing insulin from the outside, but restoring the living cells that make it from within.
References
Carlsson, P.-O., Hu, X., Scholz, H., Ingvast, S., Lundgren, T., Scholz, T., Eriksson, O., Liss, P., Yu, D., Deuse, T., Korsgren, O., & Schrepfer, S. (2025). Survival of transplanted allogeneic beta cells with no immunosuppression. New England Journal of Medicine, 393(9), 887–894. https://doi.org/10.1056/NEJMoa2503822
Dong, L., Cao, X., Mi, C., et al. (2025). Stem cell-derived islets — significant progress amidst ongoing challenges for type 1 diabetes. The Innovation Medicine, 3, 100149.
FDA. (2023). FDA approves first cellular therapy to treat patients with type 1 diabetes. U.S. Food and Drug Administration.
Herold, K. C., & Pober, J. S. (2025). Replacement of beta cells for type 1 diabetes. New England Journal of Medicine, 393, 917–921. https://doi.org/10.1056/NEJMe2507578
Licht, B. J. M., Duffy, G. P., & Levey, R. E. (2025). Engineering hypoimmune stem cell-derived beta cells. Stem Cell Research & Therapy, 16, 610. https://doi.org/10.1186/s13287-025-04745-0
National Institute of Diabetes and Digestive and Kidney Diseases. (2025). Type 1 diabetes. National Institutes of Health.
National Institute of Diabetes and Digestive and Kidney Diseases. (2026). Pancreatic islet transplantation. National Institutes of Health.
Reichman, T. W., Markmann, J. F., Odorico, J., Witkowski, P., Fung, J. J., Wijkstrom, M., Kandeel, F., de Koning, E. J. P., Peters, A. L., Mathieu, C., Kean, L. S., Bruinsma, B. G., Wang, C., Mascia, M., Sanna, B., Marigowda, G., Pagliuca, F., Melton, D., Ricordi, C., Rickels, M. R., & VX-880-101 FORWARD Study Group. (2025). Stem-cell-derived, fully differentiated islets for type 1 diabetes. New England Journal of Medicine, 393(9), 858–868. https://doi.org/10.1056/NEJMoa2506549
Shalaby, K. E., & Abdelalim, E. M. (2025). Hypoimmune stem cells and islets: hype or a true breakthrough in diabetes treatment? Cellular & Molecular Biology Letters, 30, 112. doi:10.1186/s11658-025-00786-8.
Wang, S., Du, Y., Zhang, B., et al. (2024). Transplantation of chemically induced pluripotent stem-cell-derived islets under abdominal anterior rectus sheath in a type 1 diabetes patient. Cell, 187, 6152–6164.e18. https://doi.org/10.1016/j.cell.2024.09.004
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