The drug is rapamycin, also called sirolimus, and is currently used as an immunosuppressant, to help prevent rejection of a new, transplanted kidney.
Over 600,000 people in the U.S., and 12 million worldwide, are affected by the inherited kidney disease known as ADPKD, short for autosomal-dominant polycystic kidney disease. In the U.S., the number of individuals affected by ADPKD is greater than the number affected by cystic fibrosis, muscular dystrophy, hemophilia, Down's syndrome, and sickle cell anemia combined. The disease is characterized by the proliferation of cysts that eventually debilitate the kidney, causing kidney failure in half of all patients by the time they reach age 50.
Currently no treatment exists to prevent or slow cyst formation, and most ADPKD patients require kidney transplants or life-long dialysis for survival, explained Thomas Weimbs, director of the laboratory where the discovery was made. Weimbs is assistant professor in the Department of Molecular, Cellular and Developmental Biology at UCSB.
The scientists studied the effects of rapamycin on mice. "When we administered rapamycin to mice with PKD and looked at their kidneys afterwards, we were absolutely amazed," said Weimbs. "The kidneys were smaller, had smaller cysts and had retained their function."
"We have known the genetic mutations that cause PKD for over a decade," explained Weimbs. "The genetic mutations are located in the gene for the polycystin-1 protein. Unfortunately, the function of polycystin-1 has remained poorly understood, which has made it difficult to devise a treatment strategy for this disease."