Antiviral activities of MCC-478, a novel and specific inhibitor of hepatitis B virus.

MCC-478 is a newly synthesized 2-amino-6-arylthio-9-phosphonomethoxyethylpurine bis(2,2,2-trifluoroethyl) ester derivative. MCC-478 showed a substantially higher (ca. 80-fold) anti-hepatitis B virus (HBV) activity than that of lamivudine, despite no significant anti-human immunodeficiency virus activity. Since the bis(2,2,2-trifluoroethyl) ester group was used to improve the oral bioavailability of the phosphonomethoxyethylpurine derivatives, two monoester derivatives and one phosphonic acid derivative were also evaluated. It was suggested that these hydrolyzed derivatives, which appeared in animals given MCC-478, have enough anti-HBV activity to contribute to efficacy in vivo. Furthermore, no apparent cytotoxic effects or reductions of mitochondrial DNA content by MCC-478 and its derivatives were observed. These results indicated that MCC-478 may be a new promising anti-HBV agent.