*Purpose: Over the past 10 years, our center has utilized various strategies in managing BK viremia in our kidney transplant recipients. Reducing immunosuppression (IMS) in a step-wise manner has been the primary strategy in managing BK viremia. When this was insufficient, adjunctive therapies, such as cidofovir, leflunomide, and/or intravenous immunoglobulin (IVIG) have also been utilized.

The purpose of the study is to evaluate the clearance of BK viremia in kidney transplant recipients following IMS reduction alone or in conjunction with cidofovir, leflunomide, or IVIG.

*Methods: This is a single-center, retrospective, observational study at a large academic medical center. Kidney transplant recipients transplanted between September 1, 2009 and December 31, 2018 and developed BK viremia are included in this study. Patients less than 18 years old at time of transplant were excluded. The primary outcome is clearance of BK viremia and secondary outcome is development of BK nephropathy.

*Results: A total of 116 patients were screened for inclusion and 81 patients were included: 41 patients with reduction in IMS only and 40 patients requiring adjunctive therapies (7 patients received cidofovir, 26 patients received leflunomide, 2 patients received IVIG and 5 patients received more than 1 adjunctive therapy). Clearance of BK viremia occurred in 90% (37/41) of patients with IMS reduction alone. Clearance of BK viremia in patients requiring adjunctive therapy after IMS reduction, occurred in 29% (2/7) who received cidofovir, 92% (24/26) who received leflunomide, 50% (1/2) who received IVIG, and 60% (3/5) who received 2 adjunctive treatment strategies. BK nephropathy occurred in 2.4% (1/41) of patients with IMS reduction alone and in 38% (15/40) of those requiring adjunctive therapy (28.6% (2/7) in the cidofovir group, 31% (8/26) in the leflunomide group, 50% (1/2) in the IVIG group, and 80% (4/5) in patients who received more than 1 adjunctive treatment).

*Conclusions: Reducing IMS in a step-wise manner as the primary strategy for managing BK viremia is effective in clearing BK viremia. Utilization of alternative strategies with cidofovir, leflunomide, or IVIG demonstrate some effectiveness in the clearance of BK viremia in situations where reduction in IMS alone is not effective.

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