VX-264: encapsulated stem-cell islets without immunosuppression
What this study tests
A Phase 1/2 trial of Vertex's stem-cell-derived islets sealed inside an immune-protective device, aiming to restore insulin production without lifelong immunosuppression. In March 2025 Vertex reported the treatment was generally well tolerated in this small study but did not raise C-peptide enough to help, and discontinued the program.
Editorial review: .
Registry checked: 2026-09-17. Registry’s own update: 2026-09-10.
Most recent recorded citation date: 2025-07-01. Only explicit date metadata is included; an undated citation may be newer. This does not mean every claim was reviewed on that date.
Trial status, labels and access can change between reviews. How we review the evidence · How to read the evidence
Evidence at a glance
- Who can enter the study?
- Adults aged 18–65 with type 1 diabetes for at least 5 years, on a stable diabetes treatment regimen, and using continuous glucose monitoring (CGM) for at least 4 weeks before screening. People with a prior islet, organ, or cell transplant were excluded. Registered eligibility ↗Enrollment criteria describe who may enter. They do not establish who was analyzed or the denominator for a reported result.
- Reported benefit and results
- In March 2025 Vertex reported that VX-264 was generally safe and well tolerated, but the study did not meet its efficacy endpoint: increases in C-peptide were not seen at the levels needed to deliver benefit. Vertex announced the program would not advance. No detailed per-participant numbers were published. In the 10 September 2026 update, checked on 16 September, ClinicalTrials.gov still lists ACTIVE_NOT_RECRUITING with actual enrollment 7 and estimated completion 12 March 2027 — that is remaining follow-up of the seven dosed people, not a restart. The trial status describes follow-up; the linked therapy remains discontinued.Read the result sources and their limitations →
- Important harms
- Read the reported results, safety discussion and original sources. A separate harms summary is not available; this does not establish safety.
- Research access and approval
- Study regions: United States, United Kingdom, European Union, Canada, Other regions. A trial listing does not establish product approval or current recruitment at a particular site. Check the study’s current entry requirements.
- What remains uncertain?
- Read the full discussion and original sources for study limitations. Planned endpoints and completion dates are not results.
Research status alone does not establish approval, clinical benefit or local availability. This record cites company or conference reports. Those sources may describe interim findings; their source type is shown in the source list.
Primary endpoints
- Safety and tolerability: number of participants with adverse events and serious adverse events (Day 1 through 24 months)
- Change in peak C-peptide during a mixed-meal tolerance test (MMTT), from baseline to Day 90 (Part B)
The full picture
What this trial tested and why it matters
VX-264 set out to answer one of the most important questions in the search for a type 1 diabetes (T1D) cure: can lab-grown insulin-producing cells be protected from the immune system without the powerful anti-rejection drugs that today's cell therapies require?1 According to Vertex, it used the same stem-cell-derived, fully differentiated islet cells as the VX-880 (zimislecel) program — but instead of infusing them into the liver with chronic immunosuppression, the cells were sealed inside a proprietary immunoprotective "channel array" device and surgically implanted.11 The device is meant to let glucose, oxygen, and insulin pass through while shielding the cells from immune attack, so recipients would not need lifelong immunosuppressant drugs.11
If it worked, this would be the "holy grail" version of a cell cure: durable insulin production while avoiding the additional risks of chronic immunosuppression. The device and cell treatment would still require their own safety evaluation.2
Who it was for and how it was designed
This was an open-label Phase 1/2 study (NCT05791201) in adults aged 18–65 who had lived with T1D for at least 5 years, were on stable treatment, and used a CGM.3 It enrolled a small safety-first cohort — 7 participants in the reported analysis — across roughly 16 sites in the United States, Canada, the United Kingdom, Germany, Italy, the Netherlands, and Switzerland.3 Dosing was staggered: lower-dose groups (Part A) before full-dose groups (Part B), with the two co-primary endpoints being safety and the change in peak C-peptide (a marker of the body's own insulin production) during a mixed-meal test at Day 90.3 The first participant was dosed in 2023.1
The key result
In a portfolio update on 28 March 2025, Vertex reported that VX-264 was generally safe and well tolerated, but the study did not meet its efficacy endpoint: the increases in C-peptide "were not observed at levels necessary to deliver benefit."42 In other words, the reported C-peptide response was insufficient to justify advancing this program. That statement does not establish long-term cell survival or safety. Vertex announced the program would not advance and said it would analyze the explanted devices to understand why.42
What it means and what's next
The encapsulation strategy did not meet the sponsor’s efficacy threshold. Oxygen delivery and foreign-body responses are challenges in this field, but the public update did not establish either as the cause of VX-264’s outcome.2 Importantly, the cells themselves are a separate question from the device: the non-encapsulated version (zimislecel) has been reported to restore insulin independence in some participants in other small Vertex studies.5 Finding a way to protect islet cells without chronic immunosuppression remains the field’s described "next frontier".5 VX-264’s negative result is a data point the cited review discusses in the context of better device oxygenation and alternative immune-evasion approaches.5
Registry follow-up
The registry update posted 10 September 2026 still lists active, not recruiting, with seven actual participants and estimated completion on 12 March 2027. That describes follow-up of this study, not a reversal of the sponsor’s decision to discontinue development.3
Sources
- [1]Vertex Pharmaceuticals. Vertex Doses First Patient in Phase 1/2 Trial of VX-264 in Type 1 Diabetes (coverage). *CGTLive* (2023) · Science journalism
Vertex Pharmaceuticals. Vertex Doses First Patient in Phase 1/2 Trial of VX-264 in Type 1 Diabetes (coverage). CGTLive (2023).
CGTLive. Vertex Doses First Patient in Phase 1/2 Trial of VX-264 in Type 1 Diabetes. CGTLive (2023).
- [2]Masson G. Vertex drops cell-device diabetes combo over poor phase 1 results. *Fierce Biotech* (2025) · Science journalism
Masson G. Vertex drops cell-device diabetes combo over poor phase 1 results. Fierce Biotech (2025).
- [3]ClinicalTrials.gov. A Study to Evaluate the Safety, Tolerability, and Efficacy of VX-264 in Subjects With Type 1 Diabetes Mellitus (NCT05791201). *U.S. National Library of Medicine* (accessed 2026) · Trial registry
ClinicalTrials.gov. A Study to Evaluate the Safety, Tolerability, and Efficacy of VX-264 in Subjects With Type 1 Diabetes Mellitus (NCT05791201). U.S. National Library of Medicine (accessed 2026).
- [4]Vertex Pharmaceuticals. Vertex Announces Program Updates for Type 1 Diabetes Portfolio. *Vertex Pharmaceuticals* (2025) · Manufacturer
Vertex Pharmaceuticals. Vertex Announces Program Updates for Type 1 Diabetes Portfolio. Vertex Pharmaceuticals (2025).
- [5]Advances in Cell Replacement Therapies for Diabetes. · Peer-reviewed study · 2025-07-01
Hering BJ, Rickels MR, Bellin MD, et al. Advances in Cell Replacement Therapies for Diabetes. Diabetes 74(7):1068-1077 (2025).