Inhibition of hepatitis B virus by a novel L-nucleoside, 2′-fluoro-5-methyl-β-L-arabinofuranosyl uracil

Abstract

2′-Fluoro-5-methyl-β-L-arabinofuranosyl uracil (L-FMAU) was discovered to have potent antiviral activity against hepatitis B virus (HBV). L-FMAU was more potent than its D-enantiomer and produced dose-dependent inhibition of the viral DNA replication in 2.2.15 cells (human HepG2 cells with the HBV genome), with a 50% inhibitory concentration of 0.1 μM. There was no inhibitory effect on HBV transcription or protein synthesis. In the 2.2.15 cell system, L-FMAU did not show any toxicity up to 200 μM, whereas the n-enantiomer was toxic, with a 50% inhibitory concentration of 50 μM. Repeated treatments of HepG2 cells with L-FMAU at a 1 μM concentration for 9 days did not result in any decrease in the total mitochondrial DNA content, suggesting that a mode of toxicity similar to that produced by 2′,3′-dideoxycytidine is unlikely. Also at concentrations as high as 200 μM, L-FMAU did not adversely affect mitochondrial function as determined by lactic acid production by L-FMAU-treated hepatoma cells. L-FMAU was metabolized in the cells to its mono-, di-, and triphosphates. A dose-dependent inhibition of HBV DNA synthesis by L-FMAU triphosphate was observed in the DNA polymerase assays with isolated HBV particles, suggesting that the mode of action of this compound could involve viral polymerase. However, L-FMAU was not incorporated into the cellular DNA. Considering the potent inhibition of the viral DNA synthesis and the nontoxicity of L-FMAU towards the host DNA synthetic machinery, this compound should be further explored for development as an anti-HBV drug.