The drug rapamycin could be widely used to prevent transplant rejection. Rapamycin appears to give a better chance of long term acceptance of an organ graft than many other treatments currently available. Drugs currently used need to be taken continuously after the transplant and often cause side effects, but still lead to long-term rejection of the transplant. The general shortage of donor organs means that it is essential that as many as possible of those transplanted are accepted by the body and not rejected. The largest single group of those waiting for transplants currently are those who have previously suffered organ rejection. Kidney transplants are also infinitely preferable to costly and time consuming dialysis.

One of the largest transplant studies ever carried out was done in the U.S. to test the effectiveness of rapamycin. 700 kidney transplant patients were monitored whilst being given 2mg/day or 5mg/day of rapamycin or azathioprine along with cyclosporin and prednisone (standard immunosuppressive therapy). The actual loss of the transplanted organ was lowest in the patients on the lower dose of 2mg per day - only 2% compared with 6% in the control group. Overall, patients treated with rapamycin showed a 60-70% reduction in acute rejection.

Researchers have long been looking for ways to introduce tolerance of a transplanted organ so that the body's immune system will ignore the transplant, but still protect the body against infection.

Facts about organ transplants:

Currently, more that 66,000 people are awaiting lifesaving organ transplants in the United States. Tens of thousands more need tissue transplants.

In the United States, as many as 20 people will die each day without receiving the lifesaving organ transplant that they need

Kidneys are one organ that can be donated by living donors. Segments of livers and lungs can also be transplanted from living donors.

Kidneys are the most commonly transplanted organ.

Table showing statistics on cadaveric Kidney waiting list for the United States:

The information above gives an indication of the shortage of organs for donation, given the size of the waiting list and the increase between the two years. This shows the huge potential for a drug such as rapamycin, as with such a shortage, those organs that are available are valuable and must not be wasted by being rejected. A greater number of accepted organs would also shorten waiting lists, as there would be less patients waiting having previously experienced organ rejection.

Graft and patient survival rates for Kidney transplants performed in the United States.

The table above shows that although survival rates for the transplant are high for a 3-month period, the percentage drops markedly after three years. This would mean a further transplant would be nescessary after this period, which may not be possible given the shortage of donor organs. It is in the long-term acceptance of organ grafts that it is thought rapamycin could be effective.

For more statistics about organ transplants see http://www.oosn.com/Stats.htmand

http://207.239.150.13/tpd/UserCriteria/getOrgan.asp

Cancer

Rapamycin could also be used in the treatment of cancer, although more research is needed in this area.