Cidofovir in Renal Transplant Recipients With BKVN

This study will look at the safety, tolerability and effectiveness of cidofovir in kidney transplant patients who have been diagnosed with BK virus nephropathy (BKVN), a viral condition that can cause patients to reject transplanted kidneys. Up to 48 adult (age 18 years and older) kidney or pancreas transplant recipients with newly diagnosed BKVN will receive 1 of 3 cidofovir dose levels or placebo (non medicated substance) to identify the maximum tolerated dose. Dosing will be administered intravenously (by a tube running into a blood vessel). In addition to the screening visit, volunteers will actively participate for approximately 8-10 weeks with a single follow up phone call at 4 months. Blood samples, urine samples, eye exams and physical exams are included in study procedures.