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Keywords:

  • adefovir;
  • HBV;
  • lamivudine;
  • penciclovir;
  • PMPA

In this work, we investigated the anti-hepatitis B virus (HBV) activity of lamivudine, adefovir, tenofovir, penciclovir and lobucavir after short-term (i.e. 24 or 48 h) or continuous (9 days) exposure of the HBV-containing cell line, HepG2 2.2.15, to these drugs. Lamivudine maintained significant anti-HBV activity when added for only 24 or 48 h to the cell cultures compared to when the drug was present for the whole period (9 days) on the cells, i.e. 50% effective concentration (EC50) values for the inhibition of HBV DNA synthesis were 0.07 ± 0.02 μg ml−1 after 24 h of incubation, 0.02 ± 0.01 μg ml−1 after 48 h of incubation and 0.0016 ± 0.001 μg ml−1 after 9 days of incubation. Similarly, the nucleoside phosphonate analogues, adefovir and tenofovir, retained significant anti-HBV activity when added for only a short period of time to the cells. The EC50 values were 12 ± 1 μg ml−1 (24 h) and 1.0 ± 0.2 μg ml−1 (48 h) vs 0.003 ± 0.001 μg ml−1 (9 days) for adefovir, and 6.5 ± 1.1 μg ml−1 (24 h) and 0.8 ± 0.1 μg ml−1 (48 h) vs 0.03 ± 0.02 μg ml−1 (9 days) for tenofovir. In contrast, penciclovir and lobucavir lost most of their anti-viral activity when present on the cells for 48 h or less.