Study details

Roughly 2 million Americans have type 1 diabetes, which occurs when the immune system destroys islet cells, a subset of which — called beta cells — secrete insulin. Without insulin, glucose is unable to enter cells. As a result, patients with type 1 diabetes have to carefully inject calibrated doses of the hormone to substitute for the insulin their body doesn't have.

For the study, researchers recruited patients who had a history of impaired awareness of low blood sugar that led to severe hypoglycemic episodes like seizure, coma, loss of consciousness, or a hospital visit.

This condition, called hypoglycemic unawareness, leaves patients with no warning when their glucose levels are falling. As a result, patients with this complication can suddenly pass out, have seizures, or die.

Once the patients started on zimislecel, they needed to take immune-suppressing drugs so their bodies wouldn't attack the new islet cells. This is the same protection against rejection that is needed after stem cell transplants from a deceased donor.

According to Trevor Reichman, director of the pancreas and islet transplant program at University Health Network in Toronto and first author on the study, participants started needing less insulin within a few months of being infused with the new islet cells and most patients stopped needing the hormone entirely at around six months.

Reichman added that patients' episodes of hypoglycemia went away within the first 90 days of treatment. A year later, 10 out of the 12 patients in the study no longer needed insulin while the other two required much lower doses.

"Although elimination of the need for exogenous insulin is desired, the results of this study show clinical benefits from the restoration of islet function, even in the absence of complete elimination of insulin therapy," the authors wrote in the study.

If the study continues showing positive results, the maker of the drug, Vertex Pharmaceuticals, expects to submit an application to FDA next year.

Discussion

Reichman said the study "represents for the first time that biologic replacement can be administered to patients with type 1 diabetes in a single safe and effective procedure with minimal risk to the recipient. This study has the potential to get us one step closer to a 'functional cure' for patients with type 1 diabetes."

However, patients in the trial had to stay on immune-suppressing drugs to keep their immune systems from destroying the new cells. Suppressing the immune system increases the risk of infections and, over time, can increase cancer risk, Hirsch said.

Jay Skyler, an endocrinologist at the University of Miami Miller School of Medicine, said he was "very encouraged" by the results, which he said were comparable to those achieved after successful islet cell transplants but without the same difficulty in finding suitable donor pancreases.

"This is really demonstrating that stem cell-derived islets could replace cadaver islets," Skyler said. "Now that they've shown that they can achieve the same as with islets, I think the next step would be trying to get a milder form of immunosuppression — immunomodulation, perhaps."

"What we need is for the next phase of this to expand to a much greater population of people with type 1 diabetes. You have to balance risk and benefit," Skyler added. "In the population they were using, there is tremendous benefit and they were able to essentially cure the susceptibility to severe hypoglycemia. But if you’re going to use it on a wider scale, you’re going to have to study it in a bit more detail, and they'll probably do that in the next study."