The Business of Biofabrication

Phase 1/2 Trial Demonstrates Glycemic Control
In an open-label Phase 1/2 segment of its ongoing pivotal study, Vertex Pharmaceuticals reported that all 12 participants achieved blood glucose levels within the American Diabetes Association’s recommended range at least one year after receiving a single infusion of its stem cell–derived islet cell therapy, zimislecel. Ten of those 12 patients were able to discontinue exogenous insulin entirely as of the data cutoff, marking a significant milestone in the pursuit of durable glycemic control for type 1 diabetes.

Product Composition and Administration
Zimislecel (formerly VX-880) consists of pluripotent stem cell–derived pancreatic islet cells that are differentiated in vitro to secrete physiologic levels of insulin and C-peptide. The cell suspension is delivered via a one-time infusion into the hepatic portal vein under interventional radiology guidance. To ensure engraftment and prevent immune rejection, patients initiate a chronic immunosuppressive regimen—typically combining tacrolimus and mycophenolate mofetil—immediately before and after infusion.

Safety Profile and Adverse Events
Because of the required immunosuppression, safety monitoring focuses on infection risk and hematologic effects. Most adverse events in the trial were mild or moderate and consistent with known immunosuppressive toxicities. The most common serious adverse event was neutropenia, observed in three patients; no serious events were attributed directly to the cell therapy itself. Two deaths previously reported in the trial were determined to be unrelated to zimislecel administration.

Regulatory Pathway and Next Steps
Enrollment in the Phase 1/2/3 trial is expected to complete this summer, positioning Vertex to potentially file for regulatory approval in 2026. The company is also actively researching alternative immunosuppressive regimens to broaden the therapy’s commercial reach, given that long-term immunosuppression may limit patient uptake.

Market Opportunity and Competitive Landscape
Type 1 diabetes affects approximately 3.8 million patients in the U.S. and Europe, with an estimated 60,000 experiencing life-threatening severe hypoglycemic events annually. Vertex is initially targeting this high-need subgroup. Currently, the only FDA-approved cell therapy for type 1 diabetes is Lantidra, which relies on donor-derived islet cells. Zimislecel’s stem cell–derived, “off-the-shelf” approach could address supply constraints and consistency issues inherent to donor sourcing.

Upcoming Milestones

• Completion of enrollment and dosing in the pivotal study: Summer 2025
• Regulatory submissions anticipated: 2026
• Data readouts on alternative immunosuppressive regimens: ongoing preclinical research

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About Vertex Pharmaceuticals
Vertex Pharmaceuticals is a global biotechnology company dedicated to the discovery and development of transformative medicines for serious diseases. With a deep expertise in genetic and cell therapies, Vertex advances research across cystic fibrosis, pain, and metabolic diseases, leveraging its internal capabilities and strategic partnerships to bring novel treatments to patients worldwide. Find more info here.