Twenty of 23 patients were able to go off insulin treatment for an average of 31 months; 12 of those have maintained this state, while 8 relapsed and began taking low doses of insulin. The researchers also measured levels of C-peptide, a by-product of insulin production that is used as an indicator of how much insulin is being manufactured in the pancreas. Burt explains that even on a “honeymoon” period, C-peptide levels will decrease in diabetics, but for patients in this study, “C-peptide levels kept going up and hit their maximum at two to three years.”
A stem-cell transplant would only be effective in newly diagnosed patients who still have some beta cells left to preserve. Some patients have also achieved insulin independence with an experimental treatment that involves transplanting insulin-secreting cells from a donor. However, these patients require immunosuppressive drugs to keep their immune systems from rejecting the donor cells. “This is the first treatment that, after one treatment, patients are on no insulin and require no medications,” Burt says.
Gordon Weir, head of islet transplantation at Joslin Diabetes Center in Boston, says that the results are impressive and that the treatment is “clearly having some effect on the natural course of the type 1 diabetes,” but it’s still too soon to declare this a permanent cure. Furthermore, he says that excitement about the results should be tempered by concerns about the potential dangers of the treatment and confusion about how the stem-cell transplant is actually working. In this study, two patients developed pneumonia because of the treatment; three others later experienced hormonal disorders, and nine patients developed a sperm deficiency.
Weir points out that the treatment regimen involved many drugs–including powerful chemotherapy agents–which may also have affected the diabetes. “We don’t actually know the stem cells had anything to do with this result,” he says. Weir hopes that the trial will spur further studies on the role of the stem cells and ways to make the treatment safer. Burt and his colleagues are now awaiting FDA approval for a randomized trial that would provide more rigorous data about the benefit of this treatment for diabetes.