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Background: There is no effective therapy for BK virus (BKV) nephropathy (BKVN). Cyclosporine A (CsA) has a lower immunosuppressive effect than tacrolimus. In vitro studies have shown that CsA inhibits BKV replication. The present study aimed to evaluate the effectiveness of switching from tacrolimus to low-dose CsA in renal transplant recipients with BKVN. Methods: Twenty-four patients diagnosed with BKVN between January 2015 and December 2016 were included. Tacrolimus was switched to low-dose CsA, and patients were followed for 24 months. Primary end points were BKV clearance in blood and graft. Secondary end points were urine specific gravity, serum creatinine, and graft loss. Results: The viremia in all patients cleared at a mean of 2.7 ± 2.0 months after switching to CsA. Urine specific gravity at 3 months after switching to CsA increased significantly compared with that at diagnosis (P=0.002). The timing and trend of urine specific gravity increase was consistent with the timing and trend of blood and urine viral load decrease. Repeated biopsies at a median of 11.2 months (range: 9.1–12.5 months) after switching to CsA showed that 8 patients (42.1%) were negative for BKV, and 11 patients (58.9%) had a decrease in BKV load (P<0.001). There was no statistical difference in the serum creatinine level between the time of diagnosis and 24 months of CsA therapy (P=0.963). The graft survival rate was 100%. Only two patients (8.3%) suffered from acute rejection. Conclusion: Switching from tacrolimus to low-dose CsA may be an effective therapy for BKVN. [ABSTRACT FROM AUTHOR]