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Phase 1/2TerminatedNCT02239354

VC-01: ViaCyte first-gen encapsulated stem-cell islets

First-in-human trial of stem-cell-derived pancreatic progenitor cells sealed inside an immune-protective implant (PEC-Encap / Encaptra) placed under the skin, aiming to replace insulin-making cells without lifelong anti-rejection drugs. Terminated for insufficient engraftment: a foreign-body scarring response around the device starved most cells of blood supply, though small numbers did mature into insulin- and glucagon-making islet cells. Its failure mode shaped every later encapsulation program.

Primary endpoints

  • Safety and tolerability: number of adverse events through the Month 24 visit
  • Efficacy: change in C-peptide (a marker of the implant's own insulin production) from baseline to Month 6

Results so far

The device was generally safe, with no off-target cell growth (no teratomas) and signs that it shielded the cells from immune attack without anti-rejection drugs. But engraftment was insufficient: a foreign-body scarring response walled off the implants and blocked blood vessels, so most cells died from lack of oxygen. Where vascularization did occur, cells matured into insulin-making beta cells and glucagon-making alpha cells that survived up to two years — proof the concept can work, but too rarely to lower insulin needs. The trial was terminated for "insufficient functional product engraftment." The registry recorded 19 enrolled (Cohort 1), 9 completing the study, and 114 adverse events, mostly tied to the surgical implant/explant procedures.

The full picture

What was tested and why it matters

A cure for type 1 diabetes needs two things: a renewable supply of insulin-making cells, and a way to keep them alive without a lifetime of anti-rejection drugs. VC-01 (also called PEC-Encap) attacked both at once. It packed pancreatic progenitor cells, grown at scale from human pluripotent stem cells, inside the Encaptra device — a sealed, cell-impermeable pouch implanted under the skin and designed to hide the cells from the immune system while letting glucose, oxygen, and insulin pass.1 If it worked, one off-the-shelf implant could replace the cells diabetes destroys, with no donor organ and no immunosuppression.2

Who it was for

This first-in-human study enrolled adults aged 18-55 who had lived with type 1 diabetes for at least three years and were on stable treatment.1 People with advanced complications or already on immune-suppressing drugs were excluded.1

Design

It was an open-label, non-randomized Phase 1/2 trial sponsored by ViaCyte with funding from California's stem-cell agency (CIRM), run in San Diego and Edmonton.1 Cohort 1 received small "sentinel" units for analysis plus larger therapeutic units, all without anti-rejection medication; a planned higher-dose Cohort 2 was never started.1 Nineteen people were enrolled and followed for up to two years.1 The main goals were safety (adverse events through Month 24) and whether the implant made its own insulin, measured by C-peptide.1

Key results

The device itself was reasonably safe — most adverse events were tied to the implant or removal surgery, no off-target tumors formed, and the pouch appeared to shield cells from immune rejection.3 But the cells largely did not survive. The body mounted a foreign-body scarring response around the device, walling it off and choking the blood supply, so most cells died of low oxygen.4 In the minority of units that did connect to blood vessels, cells matured into genuine insulin-making beta cells and glucagon-making alpha cells that persisted as long as two years — proof the approach can work in principle.3 It simply happened too rarely to reduce anyone's insulin needs, and the trial was terminated for "insufficient functional product engraftment."1

What it means and what's next

VC-01's central lesson — that an immune-protective barrier also blocks the blood vessels cells need to live — redirected the entire field.5 ViaCyte's own follow-on, PEC-Direct (VC-02), deliberately opened the device to let blood vessels in, trading immune protection for survival (and adding immunosuppression), and that version did produce regulated, meal-responsive C-peptide in patients.65 The harder goal VC-01 chased — protection without immunosuppression — drives later encapsulation programs such as Vertex's VX-264 and the gene-edited VCTX approaches.2

References

  1. ViaCyte, Inc. A Safety, Tolerability, and Efficacy Study of VC-01 Combination Product in Subjects With Type I Diabetes Mellitus (STEP ONE). ClinicalTrials.gov NCT02239354 (registry record, results posted 2022). https://clinicaltrials.gov/study/NCT02239354 ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8

  2. Mota Teixeira S, et al. Immune Evasion in Stem Cell-Based Diabetes Therapy — Current Strategies and Their Application in Clinical Trials. Biomedicines (2025). https://www.mdpi.com/2227-9059/13/2/383 ↩ ↩2

  3. ViaCyte. Two-year Data from ViaCyte's STEP ONE Clinical Trial Presented at ADA 2018. PR Newswire (2018). https://www.prnewswire.com/news-releases/two-year-data-from-viacytes-step-one-clinical-trial-presented-at-ada-2018-300671013.html ↩ ↩2

  4. Mota Teixeira S, et al. Immune Evasion in Stem Cell-Based Diabetes Therapy. Biomedicines (2025) — describes the foreign-body response to the VC-01 device and hypoxia-driven cell loss. https://www.mdpi.com/2227-9059/13/2/383 ↩

  5. Shapiro AMJ, Thompson D, Donner TW, et al. Insulin expression and C-peptide in type 1 diabetes subjects implanted with stem cell-derived pancreatic endoderm cells in an encapsulation device. Cell Reports Medicine (2021). https://doi.org/10.1016/j.xcrm.2021.100466 ↩ ↩2

  6. Ramzy A, Thompson DM, Ward-Hartstonge KA, et al. Implanted pluripotent stem-cell-derived pancreatic endoderm cells secrete glucose-responsive C-peptide in patients with type 1 diabetes. Cell Stem Cell (2021). https://doi.org/10.1016/j.stem.2021.10.003 ↩