In an international clinical trial, a new drug that selectively blocks immune responses has proved as effective in preventing acute kidney transplant rejection as cyclosporine, the standard anti-rejection treatment. Patients who took the experimental drug, a co-stimulatory blocker called belatacept (LEA29Y), also had better kidney function and experienced less of the toxic side effects associated with standard anti-rejection drugs, including kidney damage, high blood pressure and high cholesterol.In the August 25 issue of The New England Journal of Medicine, researchers report on the safety and efficacy of belatacept during a randomized phase II clinical study of 218 patients, conducted at 22 centers in the United States, Canada and seven European countries. Flavio Vincenti, MD, of the University of California, San Francisco, and Christian Larsen, MD, of Emory University in Atlanta, were co-principal authors of the study.The results mark an important step toward proving the value of a new type of treatment based on blocking the immune system’s reaction to a transplanted organ without hampering the body’s ability to fight diseases and infections, according to Vincenti, clinical professor of medicine and surgery at UCSF and a kidney transplant specialist at UCSF Medical Center.