Strong and Selective Inhibitors of Hepatitis B Virus Replication among Novel N 4 -Hydroxy- and 5-Methyl-β- l -Deoxycytidine Analogues

Abstract

ABSTRACT Novel N 4 -hydroxy- and 5-methyl-modified β- l -deoxycytidine analogues were synthesized and evaluated as anti-hepatitis B virus (HBV) agents. Their in vitro efficiencies were investigated in HepG2.2.15 cells stably transfected with HBV. β- l -2′,3′-Didehydro-2′,3′-dideoxy-N 4 -hydroxycytidine (β- l -Hyd4C) was most effective in reducing secreted HBV DNA (50% effective concentration [EC 50 ], 0.03 μM), followed by β- l -2′,3′-dideoxy-3′-thia-N 4 -hydroxycytidine (EC 50 , 0.51 μM), β- l -2′,3′-dideoxy-N 4 -hydroxycytidine (EC 50 , 0.55 μM), and β- l -5-methyl-2′-deoxycytidine (EC 50 , 0.9 μM). The inhibition of the presumed target, the HBV DNA polymerase, by the triphosphates of some of the β- l -cytidine derivatives was also assessed. In accordance with the cell culture data, β- l -Hyd4C triphosphate was the most active inhibitor, with a 50% inhibitory concentration of 0.21 μM. The cytotoxicities of some of the 4-NHOH-modified β- l -nucleosides were dramatically lower than those of the corresponding cytidine analogues with the unmodified 4-NH 2 group. The 50% cytotoxic concentrations for β- l -Hyd4C in HepG2 and HL-60 cells were 2,500 μM and 3,500 μM, respectively. In summary, our results demonstrate that at least β- l -Hyd4C can be recommended as a highly efficient and extremely selective inhibitor of HBV replication for further investigations.