About This Document
This report analyzes the June 2025 New England Journal of Medicine publication on Vertex's zimislecel therapy, which showed 83% of type 1 diabetes patients achieving insulin independence. It then compares this breakthrough with other cell therapies in development (Sana, CRISPR, Novo Nordisk) to provide families with a complete picture of the emerging treatment landscape. The analysis is divided into three sections: trial results, company comparisons, and implications for patients.
For those wanting to review the original research, the full NEJM paper is available here:
Stem Cell–Derived, Fully Differentiated Islets for Type 1 Diabetes.pdf
What Was Done - Detailed Treatment Specifications
The Zimislecel (VX-880) Treatment Protocol
- Cell Manufacturing: Pluripotent stem cells differentiated into fully functional pancreatic islets containing:
- Beta cells (produce insulin)
- Alpha cells (produce glucagon)
- Delta cells (produce somatostatin)
- Complete islet architecture mimicking natural pancreas
- Dose Details:
- Full dose: 0.8×10^9 cells (800 million cells)
- Half dose tested: 0.4×10^9 cells (400 million cells)
- Single infusion lasting 30-60 minutes
- Delivery Route: Portal vein catheterization (directly into liver blood supply)
- Immunosuppression Protocol:
- Induction therapy before infusion
- Lifelong maintenance with tacrolimus-based regimen
- Critical: No glucocorticoids (steroids) allowed - the 2 participants who received steroids had worse outcomes
Patient Selection Criteria
- Adults with T1D for average 22 years (range 7.8-47.4 years)
- Severe hypoglycemia unawareness (≥2 severe events/year)
- Failed all standard therapies including automated insulin delivery
- Undetectable C-peptide at baseline (no insulin production)
Detailed Results at 1 Year
Insulin Production Recovery
- C-peptide trajectory:
- Baseline: Undetectable (<13 pmol/L)
- Day 90: 424 pmol/L (meal-stimulated)
- Day 180: 1,036 pmol/L
- Day 365: 1,274 pmol/L