Antiviral effects of lamivudine, emtricitabine, adefovir dipivoxil, and tenofovir disoproxil fumarate administered orally alone and in combination to woodchucks with chronic woodchuck hepatitis virus infection.

Adefovir dipivoxil (ADV) and tenofovir disoproxil fumarate (TDF) are nucleotide analogs that inhibit the replication of wild-type hepatitis B virus (HBV) and lamivudine (3TC)-resistant virus in HBV-infected patients, including those who are coinfected with human immunodeficiency virus. The combination of ADV or TDF with other nucleoside analogs is a proposed strategy for managing antiviral drug resistance during the treatment of chronic HBV infection. The antiviral effect of oral ADV or TDF, alone or in combination with 3TC or emtricitabine (FTC), against chronic woodchuck hepatitis virus (WHV) infection was evaluated in a placebo-controlled study in the woodchuck, an established and predictive model for antiviral therapy.

In vitro susceptibility of adefovir-associated hepatitis B virus polymerase mutations to other antiviral agents.

Background: Adefovir dipivoxil is a nucleotide prodrug approved for the treatment of chronic hepatitis B. During clinical trials, ADV-associated mutations were observed in 0, 3, 11, 18 and 29% of patients after 48, 96, 144, 192 and 240 weeks of therapy, respectively. Hepatitis B virus (HBV) polymerase mutations associated with virological breakthrough to ADV include rtA181V and rtN236T, which occur alone or in combination.

Intracellular metabolism and in vitro activity of tenofovir against hepatitis B virus.

Tenofovir is an acyclic nucleotide analog with activity against human immunodeficiency virus (HIV) and hepatitis B virus (HBV). Tenofovir disoproxil fumarate (tenofovir DF), a bis-alkoxyester prodrug of tenofovir, is approved for the treatment of HIV and is currently being developed to treat chronic hepatitis B. In this report, we further characterize the in vitro activity of tenofovir against HBV as well as its metabolism in hepatic cells.

Safety and efficacy of adefovir dipivoxil in patients infected with lamivudine-resistant hepatitis B and HIV-1.

Background/aims: Adefovir dipivoxil (10 mg once-daily) was added to antiretroviral therapy including lamivudine in 35 HIV/HBV co-infected patients.

Methods: Parameters evaluated included alanine aminotransferase (ALT), HBV DNA and serological markers, HIV-1 RNA, and CD4+ cell count.

Results: Twenty-nine patients (83%) completed 144 weeks.

Cross-resistance testing of next-generation nucleoside and nucleotide analogues against lamivudine-resistant HBV.

Several next-generation nucleoside and nucleotide analogues are currently in clinical development for the treatment of chronic hepatitis B. However, the efficacy of newer agents against lamivudine-resistant hepatitis B virus (HBV) has not been fully explored. To investigate this in vitro, we generated novel stable cell lines expressing HBV encoding the four major patterns of lamivudine resistance mutations (rtL180M+rtM204V, rtV173L+rtL180M+rtM204V, rtM204I and rtL180M+ rtM204I).

Long-term therapy with adefovir dipivoxil for HBeAg-negative chronic hepatitis B.

Background: Treatment with adefovir dipivoxil for 48 weeks resulted in histologic, virologic, and biochemical improvement in patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B. We evaluated the effect of continued therapy as compared with cessation of therapy.

Methods: One hundred eighty-five HBeAg-negative patients with chronic hepatitis B were assigned to receive 10 mg of adefovir dipivoxil or placebo once daily for 48 weeks (ratio, 2:1).

Antiviral effect of oral administration of tenofovir disoproxil fumarate in woodchucks with chronic woodchuck hepatitis virus infection.

Tenofovir disoproxil fumarate (TDF) is a nucleotide analogue approved for treatment of human immunodeficiency virus (HIV) infection. TDF also has been shown in vitro to inhibit replication of wild-type hepatitis B virus (HBV) and lamivudine-resistant HBV mutants and to inhibit lamivudine-resistant HBV in patients and HBV in patients coinfected with the HIV. Data on the in vivo efficacy of TDF against wild-type virus in non-HIV-coinfected or lamivudine-naïve chronic HBV-infected patients are lacking in the published literature.

Combinations of adefovir with nucleoside analogs produce additive antiviral effects against hepatitis B virus in vitro.

Combination therapies may be required for long-term management of some patients chronically infected with hepatitis B virus (HBV). Adefovir is a nucleotide analog that has similar activity against wild-type and lamivudine-resistant HBV. In contrast to lamivudine, clinical resistance to the prodrug adefovir dipivoxil emerges infrequently.

Persistence of cccDNA during the natural history of chronic hepatitis B and decline during adefovir dipivoxil therapy.

Background & Aims: Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is a unique episomal replicative intermediate responsible for persistent infection of hepatocytes. Technical constraints have hampered the direct study of cccDNA maintenance and clearance mechanisms in patients. The aim of this study was to develop a sensitive and specific assay for quantifying cccDNA in biopsy samples from chronic hepatitis B patients during different natural history phases and in patients undergoing antiviral therapy.

In vitro antiviral susceptibility of full-length clinical hepatitis B virus isolates cloned with a novel expression vector.

Analyses of drug susceptibility and replication capacity for clinical HBV isolates have been hampered by the limitations of available in vitro culture systems. Site-directed mutagenesis has been used to study the effects of point mutations in recombinant laboratory HBV strains, however, the validity of such analyses are compromised since mutations are removed from their natural genetic context. Here we report the development of a new plasmid vector that facilitates the cloning and expression of full-length HBV genomes amplified from the sera of chronic hepatitis B patients.

Selection of a hepatitis B virus strain resistant to adefovir in a liver transplantation patient.

Background/aims: In contrast to lamivudine, adefovir dipivoxil (ADV) therapy is associated with delayed and infrequent selection of drug resistant hepatitis B virus (HBV).

Methods: A 52 year-old man was treated with lamivudine for an HBV recurrence on his liver graft. A viral breakthrough was observed and the patient received ADV.

Adefovir dipivoxil therapy for lamivudine-resistant hepatitis B in pre- and post-liver transplantation patients.

Three-hundred and twenty-four patients were enrolled in an open-label, multicenter, international study in which pre- and post-liver transplantation (LT) patients with recurrent chronic hepatitis B (CHB) and evidence of lamivudine-resistant HBV were treated with adefovir dipivoxil 10 mg once daily. In the pre- and post-LT cohorts, 128 and 196 patients were treated for a median duration of 18.7 and 56.

The hepatitis B virus polymerase mutation rtV173L is selected during lamivudine therapy and enhances viral replication in vitro.

Therapy of chronic hepatitis B virus (HBV) infection with the polymerase inhibitor lamivudine frequently is associated with the emergence of viral resistance. Genotypic changes in the YMDD motif (reverse transcriptase [rt] mutations rtM204V/I) conferred resistance to lamivudine as well as reducing the in vitro replication efficiency of HBV. A second mutation, rtL180M, was previously reported to partially restore replication fitness as well as to augment drug resistance in vitro.

Resistance to adefovir dipivoxil therapy associated with the selection of a novel mutation in the HBV polymerase.

Background & Aims: Adefovir dipivoxil effectively inhibits both hepatitis B virus (HBV) replication and disease activity in patients with chronic hepatitis B. Resistance to treatment was not observed in 2 recent large placebo-controlled 48-week studies with this drug. The aim of this study was to characterize adefovir resistance in a patient who developed clinical and virologic evidence of breakthrough during a 96-week course of treatment.

Hepatitis B virus genotypes and virologic response in 694 patients in phase III studies of adefovir dipivoxil1.

Background & Aims: Hepatitis B virus (HBV) genotype may influence disease progression and antiviral response. We therefore analyzed the frequency and distribution of genotypes in patients from 2 multinational phase III studies of adefovir dipivoxil. Antiviral efficacy of adefovir dipivoxil 10-mg therapy was examined with respect to HBV genotype, hepatitis B e antigen (HBeAg) serostatus, and race.

Week 48 resistance surveillance in two phase 3 clinical studies of adefovir dipivoxil for chronic hepatitis B.

Seven hundred nucleoside treatment-naive patients were enrolled in two phase 3 trials of adefovir dipivoxil (ADV) for the treatment of chronic hepatitis B. To monitor for the emergence of potential adefovir resistance mutations over the first 48 weeks, all intent-to-treat patients (467 ADV-treated and 228 placebo patients) were included in a prospectively defined, treatment-blinded, virology substudy. The study protocol mandated genotypic analysis for all patients with detectable hepatitis B virus (HBV) DNA by Roche Amplicor polymerase chain reaction (PCR) at baseline and week 48, and in vitro phenotypic analyses for patients with conserved site substitutions in HBV polymerase or 1.

Adefovir dipivoxil for the treatment of hepatitis B e antigen-positive chronic hepatitis B.

Background: In preclinical and phase 2 studies, adefovir dipivoxil demonstrated potent activity against hepatitis B virus (HBV), including lamivudine-resistant strains.

Methods: We randomly assigned 515 patients with chronic hepatitis B who were positive for hepatitis B e antigen (HBeAg) to receive 10 mg of adefovir dipivoxil (172 patients), 30 mg of adefovir dipivoxil (173), or placebo (170) daily for 48 weeks. The primary end point was histologic improvement in the 10-mg group as compared with the placebo group.

Adefovir dipivoxil for the treatment of hepatitis B e antigen-negative chronic hepatitis B.

Background: Adefovir dipivoxil, a nucleotide analogue, demonstrated clinically significant antiviral activity in patients with chronic hepatitis B in phase 1 and 2 clinical trials.

Methods: We randomly assigned 185 patients with chronic hepatitis B who were negative for hepatitis B e antigen (HBeAg) to receive either 10 mg of adefovir dipivoxil or placebo once daily for 48 weeks in a 2:1 ratio and a double-blind manner. The primary end point was histologic improvement.

Resistance surveillance in chronic hepatitis B patients treated with adefovir dipivoxil for up to 60 weeks.

Current therapies for chronic hepatitis B virus (HBV) infection do not provide adequate long-term control of viral replication in the majority of patients. Monotherapy with nucleoside analogs, such as lamivudine and famciclovir, is effective for short periods but results in the emergence of drug-resistant HBV in a substantial number of patients within 1 year of therapy. Adefovir dipivoxil (ADV) has demonstrated clinical activity against wild-type and lamivudine-resistant HBV, but it is unclear whether resistance mutations will emerge after long-term therapy with this drug.