Type 1 Diabetes: Is Insulin Independence Possible With Stem Cell-Derived Islet Cells?

A Development Awaited for Decades

Type 1 diabetes is a chronic disease caused by autoimmune destruction of pancreatic beta cells, requiring lifelong insulin from outside the body.

Despite modern medical advances, 75% of people with diabetes do not reach the blood glucose targets recommended by the American and European diabetes associations. These targets are:

• HbA1c below 7%

• Daily blood glucose between 70–180 mg/dL for at least 70% of the time.

In other words, 3 out of every 4 patients struggle to keep blood glucose at the desired level despite treatment.

Even the most advanced systems, such as automated insulin pumps, do not eliminate severe hypoglycemia risk. A treatment restoring physiological insulin production could therefore transform clinical diabetes care.

On June 20, 2025, the New England Journal of Medicinepublished the groundbreaking VX-880-101 FORWARD study addressing this issue. It investigated whether a single portal-vein infusion of fully differentiated pancreatic islet cells (zimislecel), produced in the laboratory from stem cells obtained from another healthy donor (allogeneic), could restore insulin production in patients with type 1 diabetes.

🧪 FORWARD Study Design and Participants

• Study type: Phase 1-2, open-label, single-arm, multicenter
• Participants: 14 patients (12 received full-dose zimislecel), with diabetes for 7.8–47.4 years, HbA1c > 7%, a history of severe hypoglycemia, and impaired hypoglycemia awareness
• Administration: Portal-vein infusion of 0.8 × 10⁹ cells as a single dose of zimislecel
• Follow-up: At least 12 months (ongoing study, with 5-year follow-up planned)
• Immunosuppression: Long-term protocol without glucocorticoids (cortisone)

📊 Main Findings: A Revolution in Numbers

• Mean HbA1c reduction: 1.81%
• Mean time in range: 93.3%
• Mean insulin dose reduction: 92%

These data show that the islet cells acquired and sustained physiological function.

The graph aboveshows glucose levels over time in 12 patients with type 1 diabetes who received zimislecel.

• Before treatment (baseline): Mean post-meal glucose (at 90 minutes) was very high (338 mg/dL), while fasting glucose was 177 mg/dL .
• On day 90 after treatment: These values fell to 209 mg/dL and 141 mg/dL, respectively.
• On days 180, 270, and 365: Glucose levels became even more stable:
  • At the end of 1 year, fasting glucose was 123 mg/dL,
  • and glucose at 90 minutes was 129 mg/dL .

These data show that zimislecel improves glucose control rapidly and sustainably.

⚠️ Safety Findings

• Most common adverse effects: diarrhea, headache, mouth sores, neutropenia
• Serious adverse effects:
  • Neutropenia in 3 patients → hospitalization
  • 2 deaths:
    • Cryptococcal meningitis (steroid use contrary to protocol)
    • Worsening of preexisting dementia

Most adverse effects were related to immunosuppression. No serious toxicity specific to zimislecel was observed.

💡 What Does This Study Mean?

• Physiological insulin production can be restored.
• Glucose control beyond that achieved with automated insulin systems can be obtained.
• Islet transplantation without reliance on an organ donor is possible.
• Promising for high-risk patients unable to reach clinical targets.

Zimislecel's potential could open the door to cell therapies not only for type 1 diabetes but also for other endocrine diseases.

🔭 Conclusion and Future Perspective

This first clinical study of VX-880 (zimislecel) showed that stem cell-derived islet cells can function successfully in the human body. However, these are early results; larger, controlled, long-term studies are needed. Phase 3 data will be decisive in the FDA approval process.

Where Are VX-880 (Zimislecel) Clinical Trials Being Conducted?

The clinical study of VX-880 (zimislecel) is being conducted by US-based Vertex Pharmaceuticals and is currently active at 27 centers across Europe and North America . Centers nearest Türkiye include university hospitals and transplant centers in cities such as Milan, Dresden, Geneva, Leiden, and London .

The clinical trial evaluating VX-880 (zimislecel), VX-880-101 FORWARD , is currently in phase 1/2/3 and remains active.

• Start date: March 2021
• Planned completion date: June 2030
• Target enrollment: 52 people
• Current status: The study appears active and recruiting .

The study enrolls individuals with type 1 diabetes, at least two severe hypoglycemic episodes, and at least 5 years of insulin use , aged 18–65 years. Participants must use a continuous glucose monitor (CGM).

📌 The study evaluates whether insulin production can be restored by administering a single zimislecel infusion followed by glucocorticoid-free immunosuppressive treatment to a group of patients.

Patients with type 1 diabetes and a history of severe hypoglycemiamay contact these centers for eligibility assessment. Suitable candidates may enter a program involving a single zimislecel infusion and long-term follow-up.

📎 Access the trial's official registration page here: NCT04786262 – ClinicalTrials.gov

📩 You can also request detailed information from Vertex's medical information service (medicalinfo@vrtx.com) or directly from the relevant centers.

This research represents a critical step toward understanding the safety and efficacy of stem cell-based islet transplantation.