title: Evaluation of leflunomide for the treatment of BK viremia and biopsy proven BK nephropathy; a single center experience.
abstract: BACKGROUND
  BK virus reactivation is a significant complication following renal transplantation that can result in graft failure. Reduction of immunosuppression and substitution of leflunomide for mycophenolate mofetil (MMF) has been used to treat this entity.
  
  
  OBJECTIVE
  To evaluate the use of leflunomide in BK viremia (BKV) and biopsy proven BK nephropathy (BKN) in kidney and kidney-pancreas transplant recipients.
  
  
  METHODS
  We retrospectively reviewed 28 kidney and kidney-pancreas transplant recipients who had received leflunomide for BKV from January 2006 to November 2012. Demographics, time to BKV diagnosis, biopsy findings, rejection episodes, and laboratory data were recorded.
  
  
  RESULTS
  The average (mean ± SD) time to BKV from time of transplant was 316.1 ± 368.0 days (62-1708 days). At time of diagnosis, 64% of patients had their maintenance immunosuppression reduced. The indications for leflunomide administration were; BKV and biopsy proven acute rejection (BPAR) (50%), biopsy proven BKN (18%), or persistent BKV (25%). Therapeutic levels (50-100 mcg/mL) were achieved in only 54% of patients, and 60% of them had required a leflunomide dose of at least 60 mg/day. BK virus was cleared from the serum on average of 151 ± 145.2 days (17-476 days). At study commencement, 29% of patients had remained on leflunomide due to persistent BKV.
  
  
  CONCLUSIONS
  In our study, most patients required at least a 60 mg daily dose of leflunomide to achieve therapeutic levels and to clear the virus compared to the standard 40 mg daily dose. Delaying therapy may result in progressive BKV and BKN.
authors.affiliation: Department of Pharmacy, SSM Saint Louis University Hospital, Saint Louis, Missouri, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Nesselhauf
authors.affiliation: Department of Pharmacy, Minneapolis VA Health Care System, Minneapolis, Minnesota, USA.
authors.forename: Jaclyn
authors.initials: J
authors.lastname: Strutt
authors.affiliation: Division of Nephrology, Saint Louis University, School of Medicine, Saint Louis, Missouri, USA.
authors.forename: Bahar
authors.initials: B
authors.lastname: Bastani
keywords: BK nephropathy; BK viremia; BK virus; Kidney transplant; Leflunomide; Polyomavirus