Two people with type 1 diabetes have received stem cell-derived implants to treat their condition for the first time.

About 10 per cent of the 422 million people with diabetes worldwide have type 1. This is caused by the immune system destroying the islet cells in the pancreas that make insulin. For more than 15 years, researchers have been trying to find a way to replace these using stem cells.

Now Viacyte, a company in San Diego, California, is about to find out if it has succeeded. The firm's credit card-sized implant contains progenitor cells derived from stem cells. Once inside the body, they mature into islet cells. The implant sits just below the skin, in the forearm, for example, and is intended to compensate for the lost islet cells, releasing insulin when blood sugar levels get too high.

"If it works, we would call it a functional cure," says Paul Laikind of Viacyte. "It's not truly a cure because we wouldn't address the autoimmune cause of the disease, but we would be replacing the missing cells."

A similar device has already been safety tested in 19 people with diabetes, but the trial didn't use enough cells to treat the condition. Now Viacyte has inserted implanted devices containing more cells into two people with type 1 diabetes. A third person will also get the implant soon.

Once inside the body, pores in the outer fabric of the device allow blood vessels in to nourish the progenitor cells. Once these cells have matured, in around three months, they should be able to monitor blood sugar levels and release insulin as required.

The treatment could free people with type 1 diabetes from having to inject insulin, although they would need to take immunosuppressive drugs. "If successful, this strategy could really change the way we treat type 1 diabetes in the future," says Emily Burns of the charity Diabetes UK.