Immune rejection drug shrinks rare tumors

BOSTON (Reuters) - The Wyeth drug Rapamune dramatically reduces rare growths known as angiomyolipomas after one year of treatment, but the benefits begin to fade if the transplant drug is discontinued, researchers reported on Wednesday.

A team led by Dr. John Bissler of Cincinnati Children's Hospital Medical Center tested the drug, usually used to stop the rejection of organ and tissue transplants, on 25 volunteers.

They found it typically reduced the volume of the growths by nearly 50 percent of the 20 patients who made it to the one-year mark.

But the treatment caused side effects, including mouth ulcers, diarrhea, upper respiratory infections and joint pain.

After a year the drug, also known as sirolimus or rapamycin, was stopped. A year later, the average tumor had grown back to 86 percent of its original size, they reported in the New England Journal of Medicine.

The study, which included researchers with drug company ties but was not sponsored by Wyeth, did not have a control group that received a placebo, so the drug's effectiveness is not proven.

The Bissler team said the treatment "also resulted in a high rate of adverse events." Half the volunteers saw their lipid levels go up. In four of the patients, Rapamune had to be stopped because of side effects, such as diarrhea.

They said further research is needed to determine the safety, effectiveness and best dose for the drug for patients who need to be treated over the long term for a slow, progressive disease.

All of the patients in the study had angiomyolipomas from tuberous sclerosis complex, a rare genetic disease, or lymphangioleiomyomatosis, a rare lung disease. They are usually treated with surgery.

Potential cures lie in the field of gene therapy or even in finding ways to prevent the genetic mutations that underlie the disease, noted Dr. Elahna Paul and Dr. Elizabeth Thiele of Massachusetts General Hospital in Boston.

"Since gene therapy and prophylaxis against somatic mutation are still in the realm of science fiction, physicians now caring for people with the tuberous sclerosis complex have turned to sirolimus," they wrote in a commentary.

Rapamycin interferes with the defective genes that cause the rare diseases.

(Editing by Maggie Fox)