Vertex’s VX-264 Clinical Trial Fails to Produce Results & Ends Abruptly

The trial aimed to protect Vertex’s insulin-producing cell product from the immune system with a surgically implanted device — eliminating the need for immunosuppression drugs. Unfortunately, the device did not effectively protect those cells based on the participant’s C-peptide and blood glucose levels.

Here’s what you need to know.

Understanding VX-264

VX-264 uses Vertex’s manufactured and proprietary cell product, which has already proven to be highly effective in the VX-880 clinical trial — but VX-880 protects the cells with immunosuppression therapy.

VX-264 was an ambitious attempt to develop a functional cure for T1D by surgically implanting a protective device containing insulin-producing cells. The first participants in this clinical trial were enrolled in the summer of 2024, and the diabetes community has been waiting patiently to hear initial results. 

The Failure of VX-264

The Phase 1/2 study of VX-264 was conducted in two parts, labeled Part A and Part B. Participants in Part B of the study received the full dose of the investigational cell therapy along with Vertex’s surgically immunoprotective device. The success of this phase was based on:

• Changes in C-peptide levels (which indicate if the body is producing insulin)
• Blood glucose levels after eating
• The overall safety of the therapy 

While VX-264 was found to be generally safe and well tolerated, the press release says VX-264 failed to produce significant C-peptide levels–meaning the implanted cells were not producing insulin. 

Unfortunately, this suggests the immunoprotective device was not protecting the cells from the participant’s immune system. 

Due to these disappointing results, Vertex decided to end the VX-264 trial. 

VX-880 Continues Progress Under New Name: Zimislecel

While VX-264 will not continue, Vertex’s other promising T1D therapy, VX-880, is still on track. Now officially named Zimislecel, this therapy involves delivering the company’s proprietary stem cells via infusion into the hepatic portal vein. The hepatic vein is a major vein connected to the liver and is a common location for transplanting insulin-producing cells in T1D research.  

Unlike VX-264, Zimislecel requires standard immunosuppression to prevent the immune system from attacking the transplanted cells. For this reason, VX-880 is intended for people with frequent severe hypoglycemia. The long-term impact of immunosuppression therapy is simply not worth it for people who can live generally full lives with T1D. VX-880 is truly for those who are struggling to get through the day. 

As of December 2024, 11 out of 12 participants in the VX-880 trial were insulin-independent and no longer required daily insulin therapy. This is a big deal! The therapy is working.

The Zimislecel study is currently in the Phase 3 portion of its Phase 1/2/3 clinical trial. Vertex expects to complete enrollment and dosing in the first half of 2025. They definitely have big plans for Zimislecel—they’ve already shared plans to submit the drug for approval across multiple countries in 2026. They are also building a manufacturing plant in New Hampshire to mass-produce their cell therapy product.

If approved, Zimislecel could help an estimated 60,000 people across the U.S. and Europe who struggle to survive with T1D despite the best available care.

What’s Next?

While Vertex has not shared its next plans to develop a functional cure for T1D without immunosuppression drugs, we know Vertex is 100 percent committed to its mission. Hopefully, their remarkable team of experts and researchers is already plotting the next idea to protect their groundbreaking cell therapy product from the T1D immune system.