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

Abstract

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. The antiviral effect of oral administration of TDF against chronic woodchuck hepatitis virus (WHV) infection, an established and predictive animal model for antiviral therapy, was evaluated in a placebo-controlled, dose-ranging study (doses, 0.5 to 15.0 mg/kg of body weight/day). Four weeks of once-daily treatment with TDF doses of 0.5, 1.5, or 5.0 mg/kg/day reduced serum WHV viremia significantly (0.2 to 1.5 log reduction from pretreatment level). No effects on the levels of anti-WHV core and anti-WHV surface antibodies in serum or on the concentrations of WHV RNA or WHV antigens in the liver of treated woodchucks were observed. Individual TDF-treated woodchucks demonstrated transient declines in WHV surface antigen serum antigenemia and, characteristically, these woodchucks also had transient declines in serum WHV viremia, intrahepatic WHV replication, and hepatic expression of WHV antigens. No evidence of toxicity was observed in any of the TDF-treated woodchucks. Following drug withdrawal there was prompt recrudescence of WHV viremia to pretreatment levels. It was concluded that oral administration of TDF for 4 weeks was safe and effective in the woodchuck model of chronic HBV infection.

FIG. 1.

Antiviral effect of oral TDF administration on serum WHV DNA in chronic WHV carrier woodchucks. Horizontal bars denote the 4-week treatment period. Log₁₀ changes in WHV viremia from baseline at week zero prior to TDF administration for individual woodchucks in each treatment group are displayed. WHVge, WHV genomic equivalents (virion or WHV DNA-containing virus particles).

FIG. 2.

Antiviral effect of oral TDF administration on serum WHV DNA and WHsAg, intrahepatic WHV replication and WHV RNA, and hepatic expression of WHcAg and of membranous and cytoplasmic WHsAg in individual chronic WHV carrier woodchucks. Woodchuck F5905 received TDF at a dose of 5.0 mg/kg/day for 4 weeks (left panels), whereas woodchuck F5865 was treated for 4 weeks with 15.0 mg/kg/day of TDF (right panels). Horizontal bars in the top panels denote the 4-week treatment period. Log₁₀ changes in WHV viremia and WHsAg antigenemia from baseline at week zero prior to TDF administration are shown in the top panels. WHVge, WHV genomic equivalents (virion or WHV DNA-containing virus particles); ODU, optical density units; WHV RI, hepatic WHV DNA replicative intermediates; WHsAg (mem), hepatic membranous WHsAg; WHsAg (cyt), hepatic cytoplasmic WHsAg. Levels of hepatic cellular DNA and RNA were quantified by hybridization to a commercial β-actin gene probe (Oncor, Inc., Gaithersburg, MD) by Southern or Northern blot hybridization techniques, respectively.

FIG. 3.

Antiviral effect of oral TDF administration on intrahepatic WHV replication in chronic WHV carrier woodchucks. Values for individual woodchucks in each treatment group are displayed in first five panels. Mean values for all of the experimental groups are compared in the last panel (vertical lines denote standard deviations). Each experimental group contained four woodchucks. The asterisk within the last panel indicates that the mean value of intrahepatic WHV replicative intermediates for woodchucks treated with TDF at a dose of 1.5 mg/kg/day was statistically different from placebo-treated control woodchucks at week 8 (P < 0.01). WHV RI, hepatic WHV DNA replicative intermediates. Levels of hepatic cellular DNA were quantified by hybridization to a commercial β-actin gene probe (Oncor, Inc., Gaithersburg, MD) by Southern blot hybridization techniques as described in the text.