Effect of leflunomide and cidofovir on replication of BK-virus in an in vitro culture system

Background. Cidofovir and Leflunomide are used empirically in the treatment of BK virus nephropathy. The aim of this study is to quantify the antiviral activity of these drugs. Methods. BK virus was grown in a cell-culture system. The rate of viral replication in the presence or absence of the drug being tested was assessed using a quantitative polymerase chain reaction assay. Results. The inhibitory concentration, effective concentration, and selectivity index for Leflunomide are 39.7 +/- 6.9, 11.3 +/- 2.8, and 3.8 +/- 0.8 mug/mL, respectively. For Cidofovir, these indices were, respectively, 63.9 +/- 17.2, 36.3 +/- 11.7, and 2.3 +/- 0.8 mug/mL. Conclusions. The in vitro activity of Cidofovir and Leflunomide is modest, and the selectivity index is low. There is a need to develop more effective and less toxic anti-BK virus drugs for clinical use.