penciclovir and lobucavir

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 microgram ml-1 after 24 h of incubation, 0.02 +/- 0.01 microgram ml(-1) after 48 h of incubation and 0.0016 +/- 0.001 microgram 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 microgram ml(-1) (24 h) and 1.0 +/- 0.2 microgram ml(-1) (48 h) vs 0.003 +/- 0.001 microgram ml(-1) (9 days) for adefovir, and 6.5 +/- 1.1 microgram ml(-1) (24 h) and 0.8 +/- 0.1 microgram ml(-1) (48 h) vs 0.03 +/- 0.02 microgram 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.

Topics: Acyclovir; Adenine; Antiviral Agents; Carcinoma, Hepatocellular; DNA, Viral; Guanine; Hepatitis B virus; Lamivudine; Organophosphonates; Organophosphorus Compounds; Tenofovir; Tumor Cells, Cultured

Several nucleoside analogues (penciclovir, lobucavir, dioxalane guanine [DXG], 1-beta-2,6-diaminopurine dioxalane [DAPD], L-FMAU, lamivudine) and acyclic nucleoside phosphonate analogues (adefovir, tenofovir) that are in clinical use, in clinical trials or under preclinical development for the treatment of hepatitis B virus (HBV) infections, were evaluated for their inhibitory effect on the replication of a la- mivudine-resistant HBV variant containing the methionine --> valine substitution (M550V) in the polymerase nucleoside-binding domain. The antiviral activity was determined in the tetracycline-responsive HepAD38 and HepAD79 cells, which are stably transfected with either a cDNA copy of the wild-type pregenomic RNA or with cDNA containing the M550V mutation. As expected, lamivudine was much less ( approximately 200-fold) effective at inhibiting replication of the M550V mutant virus than the wild-type virus. In contrast, adefovir, tenofovir, lobucavir, L-FMAU, DXG and DAPD proved almost equally effective against both viruses. A second objective of this study was to directly compare the antiviral potency of the anti-HBV agents in HepG2 2.2.15 cells (which are routinely used for anti-HBV drug-screening purposes) with that in HepAD38 cells. HepAD38 cells produce much larger quantities of HBV than HepG2 2.2.15 cells, and thus allow drug screening in a multiwell plate format. All compounds were found to be almost equally effective at inhibiting HBV replication in HepAD38 cells (as in HepG2 2.2.15 cells), except for penciclovir, which was clearly less effective in HepAD38 cells.

Topics: Acyclovir; Adenine; Antiviral Agents; Arabinofuranosylcytosine Triphosphate; Cell Line; Dioxolanes; DNA-Directed DNA Polymerase; DNA, Viral; Guanine; Hepatitis B virus; Humans; Organophosphonates; Organophosphorus Compounds; Purine Nucleosides; Tenofovir; Virus Replication

Mycophenolic acid [the active metabolite of the immunosuppressive agent mycophenolate mofetil (MMF)] and ribavirin were found to potentiate the anti-HBV activity of the guanine-based nucleoside analogues penciclovir (PCV), lobucavir (LBV) and 3'-fluorodideoxyguanosine (FLG) and diaminopurine dioxolane (DAPD). Ribavirin and mycophenolic acid are both inhibitors of inosine 5'-monophosphate dehydrogenase and cause a depletion of intracellular dGTP levels. It may be assumed that the 5'-triphosphorylated derivatives of the guanine-based nucleoside analogues, in the presence of reduced levels of dGTP, inhibit more efficiently the priming reaction as well as the reverse transcription and DNA-dependent DNA polymerase activity of the HBV polymerase. This assumption is corroborated by the observation that exogenously added guanosine reversed the potentiating effect of ribavirin and mycophenolic acid on the anti-HBV activity of the guanosine analogues. Our observations may have implications for those (liver) transplant recipients that receive MMF as (part of their) immunosuppressive regimen and that, because of de novo or persistent infection with HBV, need specific anti-HBV therapy.

Topics: Acyclovir; Antiviral Agents; Cell Line; Dideoxynucleosides; Dioxolanes; Drug Synergism; Filaggrin Proteins; Guanine; Guanosine; Hepatitis B; Hepatitis B virus; Humans; Mycophenolic Acid; Purine Nucleosides; Ribavirin; Virus Replication

The emergence of resistant hepatitis B virus (HBV), with mutations in the YMDD motif of the polymerase gene after treatment with lamivudine, is becoming an important clinical problem. In this study, susceptibility of wild-type and lamivudine-resistant HBV M552I, M552V, and L528M/M552V mutants to other reverse transcriptase inhibitors was investigated by transient transfection of full-length HBV DNA into human hepatoma cells. HBV DNA replication was monitored by Southern blot hybridization, which showed the presence of a single-stranded band (representative of the HBV replicative intermediates) in the drug-free, wild-type HBV-transfected cells. This band was diminished in the samples of wild-type HBV DNA treated with either lamivudine, adefovir, or lobucavir. The band intensities from the lamivudine-resistant mutants were not decreased by treatment with lamivudine, but were decreased by the treatments with adefovir or lobucavir. In contrast, penciclovir and nevirapine did not diminish the intensity of the single-stranded band of wild-type HBV or the lamivudine-resistant mutants. These results demonstrate that lamivudine-resistant HBV is susceptible to adefovir and lobucavir. Lamivudine-resistant HBV should be treated with adefovir or lobucavir, and combination therapy with lamivudine and adefovir/lobucavir may prevent the emergence of lamivudine-resistant HBV.

Topics: Acyclovir; Adenine; Carcinoma, Hepatocellular; Drug Resistance, Microbial; Guanine; Hepatitis B virus; Humans; Lamivudine; Mutagenesis, Site-Directed; Nevirapine; Organophosphonates; Reverse Transcriptase Inhibitors; Transfection; Tumor Cells, Cultured