Successful Treatment of BK Nephropathy with Tacrolimus and mTOR Inhibitors

Abstract

Background BK nephropathy (BKN) has increased its incidence in the last two decades. Moreover BKN is a relevant cause of graft dysfunction in kidney transplantation. The mTOR inhibitors (mTORi) have a well-known antiviral action and have been suggested as the best immunosuppression in the BKN. However Tacrolimus-free therapy could increases the risk of both, acute and chronic rejection. Since 2009 in our center in patients with BKN we conducted a protocol discontinuing Mycophenolate and decreasing Tacrolimus (TAC) dose in association with mTORi, both with target levels of 5 ng/mL. Aim Analyze the efficacy and safety of a TAC-mTORi based-immunosuppression regimen in BKN in kidney transplantation. Methods From 2007 to 2013 we diagnosed 22 BKN. Patients diagnosed since 2009 (n= 14, group 1) were treated beginning mTORi and decreasing TAC dose plus Mycophenolate withdrawal. The others 8 patients suffered a significant reduction of immunosuppression (group 2). We analyze renal function, plasma quantitative BK PCR, antiHLA antibodies levels, acute or chronic rejections and dialysis or dead at final follow-up. Results 22 patients (16 men, 6 women; mean age 46±19 years) were identified. The BKN was diagnosed at 7th month after transplantation (range 2-55). The medium duration of follow-up was 53 months (6-85). Baseline characteristics and evolution of two groups are listed in Table 1. Although group 1 had a greater immunologic risk (43% had suffered a previous acute rejection and had antiHLA antibodies versus 25% of acute rejection and 12.5% with antiHLA antibodies in group 2) and a higher plasma BK viral load at diagnosis, the renal function during follow-up was more favorable than patients from group 2. Neither acute nor chronic rejection episodes were diagnosis in group 1. Only one patient in each group started chronic dialysis at the end of the follow-up (52 and 85 months after BKN diagnosis). Conclusion An immunosuppression regimen based in TAC and mTORi is an effective and safety treatment in patients with BKN. This treatment reduces viral load and increases graft survival without increases the rejection risk.