Cell therapy for type 1 diabetes (T1D) offers hope for restoring insulin production in a condition where autoimmune destruction of pancreatic beta cells requires lifelong insulin therapy. Severe hypoglycemic events (SHEs) and impaired hypoglycemic awareness remain challenges. Vertex Pharmaceuticals’ zimislecel (VX-880) trial results highlight progress. This article explores cell therapy’s trajectory, Vertex’s breakthrough, and ongoing research.

Vertex’s Zimislecel: A Breakthrough in T1D Cell Therapy

Vertex presented Phase 1/2 FORWARD-101 trial (NCT04786262) data at the American Diabetes Association 85th Scientific Sessions (June 20–23, 2025), published in The New England Journal of Medicine. Zimislecel, an allogeneic, stem cell-derived islet cell therapy, targets T1D patients with SHEs.

Key Findings

• Efficacy: All 12 patients with a full dose achieved HbA1c <7% and time in range >70%, eliminating SHEs. Ten of 12 (83%) reached insulin independence at one year, with detectable C-peptide showing restored insulin production.

• Safety: No serious adverse events tied to zimislecel occurred. Two unrelated deaths were reported. The safety profile matches the immunosuppressive regimen.

• Delivery and Mechanism: Zimislecel is infused into the hepatic portal vein. Islet cells engraft and produce insulin based on glucose levels. Immunosuppression prevents rejection.

Implications

Vertex’s results signal a transformative “off-the-shelf” therapy. The trial entered Phase 3, with enrollment set to finish by mid-2025. Regulatory submissions are planned for 2026. Vertex explores zimislecel for kidney transplant patients, expanding potential use.

The Broader Landscape of Cell Therapy for T1D

Cell therapy replaces lost beta cells with insulin-producing cells from allogeneic or autologous sources. Stem cell technology, genetic engineering, and immunoprotection drive innovation. Key approaches include:

1. Stem Cell-Derived Islet Cells: Human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs) create insulin-producing cells, like zimislecel.

2. Encapsulation Technologies: Devices shield cells from immune attack, allowing insulin and glucose exchange without immunosuppression.

3. Gene-Edited Cells: Modifications produce hypoimmune cells, potentially eliminating immunosuppression.

Challenges and Considerations

• Immunosuppression: Allogeneic therapies require lifelong immunosuppression, raising infection and cancer risks.

• Scalability: Producing consistent islet cells at scale is complex.

• Durability: Long-term cell function needs further study.

• Accessibility: High costs and regulatory hurdles may limit access.

Ongoing Clinical Trials in Cell Therapy for Type 1 Diabetes

Several trials advance cell therapy for type 1 diabetes beyond Vertex’s FORWARD-101. Below are key projects with updated status:

1. Sernova Corp – Cell Pouch System (NCT03513939)

   • Description: The Cell Pouch creates a vascularized environment for islet transplantation. The Phase 1/2 trial tests safety and efficacy in T1D patients with SHEs, using donor islets and, later, iPSC-derived islet-like clusters.

   • Status: As of May 2025, Cohorts A and B (12 patients) show insulin independence in 8 patients, with C-peptide production and HbA1c <7% in 9. Cohort C, testing a 10-channel pouch, continues. A trial with iPSC-derived clusters is planned for 2026.

   • Key Feature: The retrievable Cell Pouch supports islet survival for over 5 years without fibrosis.

2. CRISPR Therapeutics – VCTX211 (NCT05210530)

   • Description: VCTX211, a gene-edited, hESC-derived pancreatic endoderm therapy, aims to be immune-evasive, reducing immunosuppression needs. The Phase 1 trial assesses safety and tolerability in T1D patients.

   • Status: The trial is active, with completion expected in late 2025. No efficacy data are public. Safety and immune evasion are the focus.

   • Key Feature: Gene editing (e.g., B2M knockout, PD-L1/HLA-E expression) seeks to eliminate immunosuppression.

3. Sigilon Therapeutics – SIG-002

   • Description: SIG-002 uses iPSC-derived beta cells in Afibromer spheres to protect against immune attack while releasing insulin, targeting T1D without immunosuppression.

   • Status: As of 2025, SIG-002 is in late preclinical development. An IND application is planned for 2026 to start a Phase 1 trial. No trials are active.

   • Key Feature: Afibromer encapsulation offers a scalable, retrievable solution without immunosuppression.

4. ViaCyte (Vertex Pharmaceuticals) – PEC-Direct (NCT03163511)

   • Description: PEC-Direct uses hESC-derived pancreatic progenitor cells (PEC-01) in a perforated device for vascularization. The Phase 1/2 trial tests safety and efficacy in T1D patients with immunosuppression. The University of Chicago Medicine is a trial site.

   • Status: Interim data from 2023 showed 3 of 10 patients with C-peptide levels ≥0.1 nmol/L by month 6, improving glucose control and reducing insulin needs. The trial continues, but fibrosis is a challenge.

   • Key Feature: The open-device design aids vascular integration but requires immunosuppression.

5. Novo Nordisk and Aspect Biosystems – 3D-Printed Islet Therapy

   • Description: This program develops 3D-bioprinted pancreatic tissues with iPSC-derived insulin-producing cells, designed to be immunoprotective and scalable.

   • Status: As of April 2023, the program is in preclinical development, with an IND submission planned. Trials are expected in 2026 or later.

   • Key Feature: 3D bioprinting enhances tissue engineering for better cell viability and scalability.

Future Directions of Cell Therapy for Type 1 Diabetes

Vertex’s zimislecel success highlights cell therapy’s potential. Advances in immunoprotection (e.g., Sernova’s Cell Pouch, Sigilon’s Afibromer) and gene editing (e.g., CRISPR’s VCTX211) may reduce immunosuppression. Autologous iPSC therapies could minimize rejection but face scalability issues. Combining cell therapy with immunomodulation or beta-cell regeneration may improve outcomes. Regulatory and ethical issues, especially around hESCs, will shape progress.

Conclusion

Vertex’s zimislecel trial shows cell therapy for type 1 diabetes can achieve insulin independence in most patients. Efforts by Sernova, CRISPR Therapeutics, Sigilon, Vertex (ViaCyte), and Novo Nordisk/Aspect Biosystems tackle immunosuppression, scalability, and durability. As trials advance, cell therapy may redefine T1D treatment, reducing reliance on insulin.