Vertex Pharmaceuticals has decided to pause clinical trials of its celebrated type 1 diabetes therapy, VX-880, after two participants receiving the treatment died. In a statement, Vertex clarified that the two deaths were “unrelated” to its experimental therapy. Nevertheless, the biotech firm has placed the study “on a protocol-specified pause, pending review of the totality of the data by the independent data monitoring committee and global regulators.”

Miriam Tucker of Medscape was the first to report the news.

In the race to find a cure for type 1 diabetes, VX-880 may be the world’s most promising lead. The therapy involves a transplant of new pancreatic islet cells that have been grown in a laboratory from pluripotent stem cells. These new lab-grown cells can sense blood sugar concentrations and secrete insulin, just like healthy natural islet cells, replacing the cells that are lost in the autoimmune attack that defines type 1 diabetes.

VX-880 is still in an early phase of experimentation — to date, only 14 patients have received the treatment. But the results have been spectacular. In June, when Vertex shared its latest data, we learned that two VX-880 patients had achieved true insulin independence, and every other patient had enjoyed significant improvements, including lower A1C, higher time-in-range, reduced insulin requirements, and freedom from severe hypoglycemia.

One of the two patients to achieve insulin independence, however, has now died. His name was Brian Shelton, and he was the face of Vertex’s innovation. Shelton, an Ohio resident originally from Brooklyn, was the first patient to receive VX-880 and the first to achieve insulin independence with it.

In late 2021, the New York Times declared that Shelton had been “may be the first person cured of the disease” with the new therapy. Many people in the diabetes world disagreed with this assessment — Shelton still required immunosuppressive drugs to protect his new islet cells, which introduces potentially significant side effects — but his results were nonetheless remarkable and well worth celebrating. In an interview with Good Morning America, Shelton stated that he considered himself “cured.”

Shelton’s obituary, which notes that he remained “independent of insulin injections until his death,” asks for any memorial contributions to be sent to the pioneering type 1 diabetes charity JDRF. Many people from the diabetes community have left comments on the page, thanking Shelton for his bravery and selflessness in offering to undergo this vital experiment. One woman stated, “I cannot thank you enough for giving me a reason to hope.”

Vertex is just now beginning Phase 1 trials of a related therapy named VX-264. This therapy will use the same lab-grown islet cells as VX-880, which have already proven so successful, but will encapsulate them in a physical device to shield them from the immune system. Ideally, the capsule would remove the need for immunosuppressive drugs, which not only cause side effects but can also be toxic to the implanted islet cells. If VX-264 succeeds — prior efforts to encapsulate islet cells have failed — some experts may consider it to be an authentic cure for type 1 diabetes. The trial is still recruiting volunteers in the United States, Canada, England, and the Netherlands.