On Jun. 20, 2025, Vertex Pharmaceuticals announced publication of updated data from the Phase 1/2 portion of the Phase 1/2/3 FORWARD-101 clinical trial of zimislecel (VX-880), an investigational stem cell-derived, fully differentiated islet cell therapy, in people with type 1 diabetes (T1D) with impaired hypoglycemic awareness and severe hypoglycemic events (SHEs).

The data are from 12 patients who received the full dose of zimislecel as a single infusion and were followed for at least one year, as of October 2024. Results from the study to date continue to demonstrate the transformative potential of zimislecel with consistent and durable patient benefit with longer follow-up.

All 12 participants: Demonstrated engraftment with glucose-responsive endogenous C-peptide production, which was durable through one year of follow-up; Achieved the ADA targets of HbA1c <7% and time in range of >70%; Were free of SHEs from day 90 onwards; Had a reduction in exogenous insulin use (mean reduction in daily insulin dose: 92%); 10/12 (83%) no longer required exogenous insulin at Month 12; and Achieved the Phase 1/2 primary endpoint of elimination of SHEs with HbA1c <7%.

Zimislecel continues to be generally well tolerated. Most adverse events (AEs) were mild or moderate, and there were no serious AEs related to zimislecel treatment. As previously reported, two patient deaths occurred, both unrelated to treatment with zimislecel. The safety profile is generally consistent with the immunosuppressive regimen used in the study, the infusion procedure, and complications from long-standing diabetes.

Zimislecel (VX-880) is an investigational allogeneic stem cell-derived, fully differentiated, insulin-producing islet cell therapy manufactured using proprietary technology. Zimislecel is being evaluated for patients who have T1D with impaired hypoglycemic awareness and severe hypoglycemia. Zimislecel has the potential to restore the body’s ability to regulate glucose levels by restoring pancreatic islet cell function, including glucose-responsive insulin production. Zimislecel is delivered by an infusion into the hepatic portal vein and requires chronic immunosuppressive therapy to protect the islet cells from immune rejection. The zimislecel trial has expanded to additional sites that are currently active and enrolling in the U.S., Canada and Europe.