Rapamune (sirolimus/rapamycin), a new medication for preventing organ rejection, has significantly improved graft survival in two phase III clinical trials, the results of which were presented at the recent 17th World Congress of the Transplantation Society.
For the first time since the introduction of cyclosporine, the findings "have clearly demonstrated" the ability of a new drug to improve the longevity of grafts, said Barry D. Kahan, MD, PhD, of the University of Texas-Houston Health Science Center, who led the United States-based trial.
In the U.S. study, 719 recipients of kidney transplants at more than 40 centers received cyclosporine and prednisone along with either 5 mg of Rapamune daily, 2 mg of Rapamune, or azathioprine. Acute rejection episodes occurred in 10%, 15%, and 24% of patients, respectively.
Similar results occurred with the 576 patients who participated in the global study, which was conducted in Australia, the United States, Canada, and six European countries. In this study, the efficacy of 5 mg and 2 mg of Rapamune was compared to the effects of placebo, and all patients received cyclosporine and prednisone. Acute rejection occurred in 11% of patients who received 5 mg of Rapamune, 19% who received 2 mg of Rapamune, and 29% of patients treated with placebo.
"For transplant physicians and patients alike, these findings hold promise for an entirely new therapeutic approach," said lead investigator Allan S. MacDonald, MD, of Dalhousie University in Halifax, Nova Scotia. "The incidence of rejection in these two studies is the lowest ever reported in large-scale clinical trials."
Dr. MacDonald added that Rapamune holds promise for "modifying immunosuppressive therapies so they are significantly less toxic and result in greater graft survival."
A number of other findings presented at the congress, which was attended by about 4,000 medical professionals from 79 countries, attracted the attention of the press:
University of Pittsburgh researchers reported several studies in which they used altered dendritic cells in animal models to improve the acceptance of transplanted organs. The research indicates that "donor dendritic cells genetically modified to protect themselves are less likely to disappear quickly within a donor body before they have a chance to teach T cells to tolerate a new organ," said Angus Thomson, PhD, director of transplant immunology at the University of Pittsburgh.
Investigators at the University of Alberta and the University of Oslo said that studies are underway in humans to determine the ability of new genetically engineered compounds to induce immune system tolerance while protecting patients from viruses and bacteria. Use of such proteins also could reduce the side effects associated with immunosuppressive drugs.
Among recipients of liver transplants, those who have recurrent hepatitis C have the lowest quality of life and lowest level of physical functioning. While quality of life decreased 6% a year after transplantation in patients who developed hepatitis C, quality of life increased 16% in all other liver recipients, according to investigators at the VA Medical Center in Pittsburgh.
Patients have had to wait longer for donor livers in recent years, but survival rates also have improved, according to researchers at Massachusetts General Hospital in Boston. The waiting time averaged 122 and 241 days in a two groups of 72 patients each who underwent liver transplants in 1991 through 1993 and in 1994 through 1996, respectively. However, one-year survival was 68% in the first group and 89% in the second group.
A questionnaire distributed to 2,500 kidney recipients at 56 transplant programs in the United States showed that patient compliance is strongly related to the patient's age, beliefs about the importance of immunosuppressive drugs, and factors such as the amount of time since the transplant. Investigators at Montefiore Medical Center in the Bronx defined noncompliance as missing at least one dose of immunosuppressives in the four weeks before the study.
Another questionnaire, given to 96 high school students, demonstrated a lack of awareness among teenagers of the need for minorities to donate more organs. A total of 69% of white adolescents and 38% of nonwhites knew that African Americans wait longer for kidney transplants than whites. "It's interesting to note that the group most affected by the problem was less likely to believe there was a problem," Reuters news service said in a quote attributed to researcher Michele Pineda of the University of Washington in Seattle.
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