Researchers at UCSB have released a new study on the immunosuppressive drug rapamycin as a potentially effective treatment for kidney disease.

The study, released on Jan. 25, has found more evidence to add to past research that rapamycin may be effective in treating autosomal dominant polycystic kidney disease, or ADPKD, which is life-threatening and affects 12 million people worldwide.

Previous studies have indicated that rapamycin is successful in decreasing kidney cyst growth in mice with ADPKD, but the new study indicates that the drug may also benefit humans.

According to Jonathan Shillingford, UCSB project scientist and first author of the paper, the study has added human relevance to the testing of rapamycin.

Thomas Weimbs, associate professor of biology and the director of the research laboratory, explained how the researchers were able to apply the findings to humans.

“In our study, we have used a mouse model with the same gene that is affected in most human patients and it turned out to be just as effective as the drug was in mouse models, which suggests that it has a very high likelihood of reducing kidney disease in patients,” Weimbs said. “This is not clinical data, but it makes it all the more likely that clinical data might come out positive; it is a justification for doing these clinical trials, and it gives everybody great hope.”

According to Shillingford, while rapamycin is approved as an immunosuppressant and is currently used to help prevent rejection of newly transplanted organs, researchers are waiting on the results of five clinical studies taking place around the world to determine the safety and effectiveness of rapamycin as an ADPKD treatment.

Greg Germino, associate professor of nephrology at Johns Hopkins University and co-author of the paper, explained how rapamycin came to be considered as a potential ADPKD treatment.

“The drug targets a key signaling pathway that is widely functional within the body,” Germino said. “Because the pathway is ubiquitously expressed, the drug may affect numerous cell types. In ADPKD, the cyst cells may depend on the activity of this pathway for their survival and proliferation more than normal, adjacent renal epithelial cells, hence explaining their greater sensitivity to drugs like rapamycin.”

The discovery has given great hope to the ADPKD community. Dwight Odland, coordinator of the Los Angeles Chapter of the Polycystic Kidney Disease Foundation and an ADPKD patient himself, said he knows firsthand how crippling the disease can be.

“In addition to the fact that more than half of ADPKD patients will experience renal failure and require dialysis or a transplant to save their lives, there are many common side effects such as high blood pressure, aneurysms, heart disease, diabetes, acute and chronic pain, and anemia,” Odland said. “These side effects can often end a patient’s life before kidney failure occurs. Either way, both the quality and quantity of life suffers to a great degree for anyone with ADPKD.”

While ADPKD threatens patients with a serious list of side effects, rapamycin unfortunately also holds similar dangers because of its effectiveness as an immunosuppressant.

“Rapamycin is not without its side effects,” Shillingford said. “People who take the drug can get infections that the body can’t readily deal with because their immune system is depressed. It’s a wanted side effect with regard to immunosuppression, but an unwanted side effect with regard to ADPKD. At the end of the day, the benefits have to outweigh the side effects of the drug.”

According to Germino, potential side effects can include slow-healing wounds, lipid abnormalities, proteinuria and other immunosuppressive effects.

Though rapamycin has its risks, there are currently no other known treatments for ADPKD, so the possibility that the drug may prove effective in slowing or reversing cyst growth is still a significant source of hope for the medical community.

According to Weimbs, ADPKD progresses slowly, so many patients’ kidneys are not damaged enough to fail and would thus benefit from cyst-shrinking treatment.

Odland also maintains that though the drug is not a cure, it would, if approved, be a huge step in improving patients’ lives.

“If rapamycin is proven to be safe and effective in shrinking ADPKD cysts, it would be wonderful,” Odland said. “If rapamycin can shrink the cysts and prevent them from growing too large, that should either delay or eliminate the need for dialysis or transplant in most ADPKD patients. Dialysis and transplantation are very hard on the body and cause other serious side effects. Outside of a cure, any treatment to delay or avoid end stage renal failure would be the best possible news for ADPKD patients.”