Chicago-Sep 17 – A new federally approved drug, designed to prevent rejection in kidney transplants, could open the door for an effective treatment of Type I diabetes, researchers at the University of Minnesota said.
Rapamune, an immunosuppressant manufactured by American Home Products’ Wyeth-Ayerst Laboratories, received FDA approval Wednesday. The drug is also known by its generic name sirolimus, or more commonly as rapamycin because it inhibits a key regulatory kinase involved in cell cycle progression called the target of rapamycin.
Although it is designed to work in conjunction with existing transplant drugs, like cyclosporin and prednesone, to help prevent acute organ rejection, it gives scientists the flexibility to build anti-rejection protocols that could work for cellular transplants as well.
That could be crucial for researchers at the University of Minnesota’s Diabetes Institute who have been looking for an effective way of injecting insulin-producing islet cells into diabetics. Up until now, doctors have been limited to fending off the body’s immune response using steroids or other diabetogenic drugs, which can actually cause diabetes.
Already the Institute has had some limited success with rapamycin. Four test subjects who recently received islet transplants using a rapamycin protocol have remained 100 percent insulin independent, the longest for 6 months. “This is very encouraging,” said the Institute’s associate director and head of the islet transplantation program, Bernhard Hering -one of the pioneers in the field.
Encouraging enough that the center plans to launch a larger, more comprehensive study in coming weeks.
The secret behind the protocol, lies in the fact that rapamycin can be combined with other drugs in a “synergistic regimen” that allows doctors to reduce the use of the other anti-rejection agents by up to 50 percent, Hering said. The drug has also allowed doctors to build a protocol without steroids.
“(Now we) can do transplants with the benefit of an effective protocol that prevents rejection in the absence of steroids,” he said. “The result is immediate and sustained reversal of Type I diabetes for islet transplantation.”
Islet transplantation has long been the Holy Grail of diabetes research. Currently, doctors must transplant the entire pancreas in order to get the benefit of the thimble’s worth of islets that actually produce insulin.
Although pancreas transplants have success rates in excess of 83 percent, it is an invasive procedure that will fall short of being a widespread cure due to the lack of organs.
Scientists hope that once an effective islet transplant protocol is in place, islet cells can either be taken from animal subjects or grown in the lab.
There are over 16 million diabetics in the U.S. and about 10 percent of them suffer Type I diabetes, meaning they require daily insulin injections to keep their blood sugar levels regulated. It is Type I diabetics who would most benefit from the procedure.
Although the Diabetes Institute is hopeful the rapamycin protocol will work, they don’t have all their eggs in one basket. Studies are also set to begin to judge the effectiveness of a new class of anti-rejection drugs called co-stimulatory blocking agents.
So, after decades of struggling to transplant islets with few immunosuppressant options, doctors suddenly have two alternatives that look very viable.
“It’s like in the 1950s when both Salk and Sabine discovered polio vaccines,” Hering says. “They both worked.”