Tenofovir treatment in patients with lamivudine-resistant hepatitis B mutants strongly affects viral replication

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. Oncedaily treatment for 48 weeks with ADV plus 3TC or TDF plus FTC significantly reduced serum WHV viremia levels from the pretreatment level by 6.2 log 10 and 6.1 log 10 genome equivalents/ml serum, respectively, followed by TDF plus 3TC (5.6 log 10 genome equivalents/ml), ADV alone (4.8 log 10 genome equivalents/ml), ADV plus FTC (one survivor) (4.4 log 10 genome equivalents/ml), TDF alone (2.9 log 10 genome equivalents/ml), 3TC alone (2.7 log 10 genome equivalents/ml), and FTC alone (2.0 log 10 genome equivalents/ml). Individual woodchucks across all treatment groups also demonstrated pronounced declines in serum WHV surface antigen, characteristically accompanied by declines in hepatic WHV replication and the hepatic expression of WHV antigens. Most woodchucks had prompt recrudescence of WHV replication after drug withdrawal, but individual woodchucks across treatment groups had sustained effects. No signs of toxicity were observed for any of the drugs or drug combinations administered. In conclusion, the oral administration of 3TC, FTC, ADV, and TDF alone and in combination was safe and effective in the woodchuck model of HBV infection.Chronic infection with the hepatitis B virus (HBV) is a major public health problem and is responsible for 1.2 million deaths per year worldwide (64). It is estimated that more than 2 billion people have serological evidence of previous or current HBV infection, and over 350 million people are chronic carriers of HBV (64). Carriers of HBV are at high risk of developing chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma (HCC). Although safe and effective prophylactic vaccines against HBV are available, improvements in drug and/or immunotherapeutic strategies for the treatment of chronic HBV infection are still needed. Therapy with alpha interferon and nucleoside analogs alone or in combination can be effective against HBV; however, side effects of interferon and the emergence of nucleoside-resistant mutants often limit treatment outcomes (34).Lamivudine (3TC) was the first nucleoside analog licensed for the treatment of chronic HBV infection. Although 3TC is safe and effective, its therapeutic value is limited by the timedependent development of drug-resistant HBV mutants (32

mentioning

confidence: 55%

mentioning

confidence: 99%

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

Menne

Butler

George

et al. 2008

“…Multiple small investigator studies have demonstrated that the 300-mg dose of tenofovir DF approved for HIV also VOL. 50, 2006 IN VITRO METABOLISM AND ANTI-HBV ACTIVITY OF TENOFOVIR 2475 on May 9, 2018 by guest http://aac.asm.org/ results in a potent antiviral suppression of serum HBV DNA (Ͼ4 log 10 reduction in serum HBV copies/ml) in coinfected patients (5,23,28,29). The in vitro data presented here have confirmed that tenofovir inhibits HIV and HBV by similar mechanisms (competitive inhibition of DNA polymerization) and that tenofovir DF has potent cell-based anti-HBV activity (EC 50 , 0.02 M).…”

Section: Discussionmentioning

confidence: 99%

Intracellular Metabolism and In Vitro Activity of Tenofovir against Hepatitis B Virus

Delaney

Ray

Yang

et al. 2006

229

191

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. We show that tenofovir is efficiently phosphorylated to tenofovir diphosphate (TFV-DP) in both HepG2 cells and primary human hepatocytes. TFV-DP has a long intracellular half-life (95 h) and is a potent and competitive inhibitor of HBV polymerase (K i ‫؍‬ 0.18 M). Tenofovir has a 50% effective concentration of 1.1 M against HBV in cell-based assays, and potency is improved >50-fold by the addition of bis-isoproxil progroups. Tenofovir has previously demonstrated full activity against lamivudine-resistant HBV in vitro and clinically. Here we show that the major adefovir resistance mutation, rtN236T, confers three-to fourfoldreduced susceptibility to tenofovir in cell culture; the clinical significance of this susceptibility shift has not yet been determined. The rtA194T HBV polymerase mutation recently identified in tenofovir DF-treated HIV/ HBV-coinfected patients did not confer in vitro resistance to tenofovir as a single mutation or in a lamivudineresistant viral background. Overall, the antiviral and metabolic profile of tenofovir supports its development for the treatment of chronic hepatitis B.

“…Tenofovir disoproxil fumarate, a prodrug of the AMP analog tenofovir, has activity against both HBV and HIV and is approved for treatment of HIV. Although tenofovir disoproxil fumarate is not approved for use against HBV, it has been used to effectively treat lamivudine-resistant HBV in HIV-coinfected patients (28,31,38). Several other compounds, including MCC-478, L-FMAU [1-(2-fluoro-5-methyl-␤-L-arabinofuranosyl)uracil], and Val-␤-L-2Ј-deoxycytidine (a valyl prodrug of ␤-L-2Ј-deoxycytidine), are also in earlier stages of clinical development for the treatment of chronic hepatitis B (19,20,37).…”

Section: 2002mentioning

confidence: 99%

Combinations of Adefovir with Nucleoside Analogs Produce Additive Antiviral Effects against Hepatitis B Virus In Vitro

Delaney

Yang

Miller

et al. 2004

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. Based on its clinical efficacy and low frequency of resistance, adefovir dipivoxil may form an important component of combination regimens. We therefore investigated the in vitro antiviral efficacy of combinations of adefovir with other nucleoside analogs (lamivudine, entecavir, emtricitabine [FTC],and telbivudine [L-dT]) and the nucleotide analog tenofovir. Using a novel stable cell line that expresses high levels of wild-type HBV, we assayed the antiviral activity of each drug alone and in combination with adefovir. All two-drug combinations resulted in greater antiviral effects than treatments with single agents and could be characterized as additive by the Bliss independence model. Analysis using the Loewe additivity model indicated that adefovir exerted additive antiviral effects when combined with lamivudine, FTC, or L-dT and moderately synergistic effects when combined with entecavir or tenofovir. There was no evidence of cytotoxicity with any of the drugs when used alone or in combination at the tested doses. Hepatitis B virus (HBV) is a small hepatotropic DNA virus that is able to establish chronic infection in humans.Chronic HBV infection can last a lifetime, causing persistent hepatitis that frequently progresses to more-severe liver disease. Currently, three agents are approved for the treatment of chronic hepatitis B: alpha interferon (IFN-␣), lamivudine, and adefovir dipivoxil. IFN-␣, a cytokine with immunomodulatory and antiviral activity, is effective in only one third of indicated patients and is associated with significant side effects. Lamivudine, a cytosine analog in the unnatural levorotary (L) conformation, produces potent reductions in viremia (9) but is hampered by the emergence of viral resistance in approximately 20% of patients per year (23).Adefovir dipivoxil, an oral prodrug of the AMP analog adefovir, is the most recently approved anti-HBV therapeutic. Adefovir dipivoxil therapy produces a rapid decline in viremia in patients infected with wild-type or lamivudine-resistant HBV (2, 17, 24). Unlike lamivudine, resistance to adefovir dipivoxil emerges infrequently. During clinical trials, the adefovir resistance mutations rtN236T and A181V were observed in samples from Ͻ2% of patients who received 96 weeks of therapy and in Ͻ4% of patients after 144 weeks of therapy (1, 39; X. Qi, A.