Telbivudine exerts no antiviral activity against HIV-1 in vitro and in humans

BACKGROUND

HIV-HBV-coinfected individuals who need to be treated only for their HBV infection have limited therapeutic options, since most approved anti-HBV agents have a risk of selecting for drug-resistant HIV mutants. In vivo data are inconclusive as to whether telbivudine (LdT) may exert antiviral effects against HIV. Thus, we investigated in further detail the antiviral activity and the biochemical properties of LdT against HIV-1.

METHODS

To investigate the activity of LdT against HIV-1 in humans we analysed viral dynamics and genotypic and phenotypic resistance development in two HIV-HBV-coinfected individuals with no prior antiviral exposure. To investigate the activity of LdT against HIV-1 in vitro, LdT susceptibility for HIV-1 wild-type strains as well as drug-resistant strains was determined. Furthermore, we studied whether the 5'-triphosphate form of LdT (LdT-TP) can act as a substrate for wild-type HIV-1 RT.

RESULTS

In the two patients studied, LdT treatment did not result in a significant decline of HIV-1 RNA load nor in selection of genotypic or phenotypic resistance in HIV-1 RT. In vitro virological analyses demonstrated that LdT had no activity (50% effective concentration >100 μM) against wild type HIV and drug-resistant variants. Biochemical analyses demonstrated that LdT-TP is not incorporated by wild-type HIV-1 RT.

CONCLUSIONS

Based on the in vivo and in vitro evidence obtained in this study, we conclude that LdT has no anti-HIV-1 activity and is currently the only selective anti-HBV agent among the five FDA-approved nucleoside/nucleotide analogues for treatment of HBV infections in HIV-infected individuals.

Entecavir: a review of its use in the treatment of chronic hepatitis B in patients with decompensated liver disease

The oral deoxyguanosine nucleoside analogue entecavir (Baraclude®) has potent activity against hepatitis B virus (HBV) and a high genetic barrier to resistance. This article reviews the clinical efficacy and tolerability of entecavir in the treatment of chronic hepatitis B in patients with decompensated liver disease, as well as summarizing its pharmacological properties. Entecavir 1 mg/day was more effective than adefovir dipivoxil 10 mg/day in the treatment of patients with chronic hepatitis B and decompensated liver disease, according to the results of a randomized, open-label, multicentre trial. Patients were either nucleos(t)ide naive or lamivudine experienced. The reduction from baseline in HBV DNA levels at week 24 (primary endpoint) was significantly greater with entecavir than with adefovir dipivoxil. The proportion of patients with HBV DNA levels of <300 copies/mL was also significantly greater with entecavir than with adefovir dipivoxil at weeks 24, 48 and 96, as was the proportion of patients with ALT normalization. Entecavir 0.5 or 1 mg/day, tenofovir disoproxil fumarate 300 mg/day and a fixed-dose combination of emtricitabine/tenofovir disoproxil fumarate 200 mg/300 mg per day were effective in the treatment of chronic hepatitis B in patients with decompensated liver disease, according to the 48-week analysis of a randomized, double-blind, multicentre trial, primarily designed to examine tolerability endpoints. In this trial, over one-third of patients had received previous therapy with lamivudine for ≥6 months. The efficacy of entecavir in treatment-naive patients with HBV-related decompensated cirrhosis did not significantly differ from that seen in patients with chronic hepatitis B or compensated cirrhosis (compensated group), according to the results of a prospective, nonrandomized study. After 6 or 12 months of entecavir treatment, there were no significant differences between the decompensated and compensated groups in virological, biochemical or serological endpoints. In patients with decompensated cirrhosis, significant improvements from baseline in liver function were seen after 12 months of entecavir therapy. Oral entecavir was generally well tolerated in patients with chronic hepatitis B and decompensated liver disease, with most of the reported treatment-emergent adverse events consistent with decompensated liver disease. In the trial primarily designed to examine tolerability endpoints, there was no significant difference between patients receiving entecavir and those receiving tenofovir disoproxil fumarate with or without emtricitabine in terms of the proportion of patients experiencing tolerability failure or the proportion of patients with confirmed increases in serum creatinine levels of ≥0.5 mg/dL above baseline or confirmed serum phosphorus levels of <2.0 mg/dL at week 48 (co-primary endpoints). It has been suggested that the risk of lactic acidosis associated with oral nucleos(t)ide analogue therapy is increased in patients with highly impaired liver function. However, only one case of lactic acidosis was reported among entecavir recipients across two clinical trials in patients with chronic hepatitis B and decompensated liver disease. Moreover, small studies found that the risk of lactic acidosis was not increased in patients with chronic hepatitis B and decompensated liver disease who received entecavir, compared with patients with non-HBV decompensated liver disease. In conclusion, entecavir is a valuable agent for the first-line treatment of chronic hepatitis B in patients with decompensated liver disease.

Managing hepatitis B/HIV co-infected: adding entecavir to truvada (tenofovir disoproxil/emtricitabine) experienced patients

BACKGROUND

Combination emtricitabine (FTC) or lamivudine (LAM) with tenofovir disoproxil (TDF) is the recommended first-line regime for treatment in chronic hepatitis B virus (HBV)/HIV co-infection. However, in those failing to suppress, few data exist regarding further management. In HBV/HIV co-infection, there are no published data describing outcomes when entecavir (ETV) is then added to TDF-based regimes in patients no longer suppressing their HBV. We report the first series of patients using ETV with truvada-based HAART in HBV/HIV co-infected patients with previous HBV therapy failure, including inadequate suppression.

METHODS

A prospective observational study.

RESULTS

Thirteen HIV/HBV co-infected patients (all male, hepatitis B e antigen positive and hepatitis B e antibody negative) were commenced on ETV in addition to background truvada. All patients were previously exposed to LAM or FTC and TDF (median 53 months, range 6−123). Seven patients had LAM monotherapy prior to TDF/LAM or FTC combination; the remaining six patients were exposed to FTC or LAM and TDF combination. Median time of follow-up was 74 weeks (range 16−159) and median HBV decline was 2.53 log(10) IU/ml (range 1.28−7.36). Thirty-eight percent of patients achieved undetectable HBV DNA level by the end of the study and eight of 13 (62%) achieved normal alanine aminotransferase (ALT) levels with median reduction −28 U/l (range −152 to 37). TDF was stopped in one patient because of renal toxicity. ETV was well tolerated with no change of estimated glomerular filtration rate during the study.

CONCLUSION

Entecavir can be considered in addition to TDF/FTC in HBV/HIV co-infected treatment-experienced patients failing to fully suppress their HBV viral load.

Entecavir: a review of its use in chronic hepatitis B

Entecavir (Baraclude), a nucleoside analogue, is rapidly phosphorylated to the active intracellular 5'-triphosphate form that inhibits replication of hepatitis B virus (HBV). Oral entecavir is approved in the US, EU and several countries worldwide for the treatment of chronic HBV infection in adults (> or =16 years of age) with evidence of active viral replication and persistently elevated serum ALT and/or AST levels, and/or histological evidence of active disease. In several randomized, double-blind, multicentre trials, oral entecavir was an effective and generally well tolerated treatment in nucleoside-naive and lamivudine-refractory adult patients with chronic HBV infection, irrespective of whether patients were hepatitis B e antigen (HBeAg)-positive or -negative. Furthermore, it was more efficacious, associated with a lower risk of resistance, and more cost effective than lamivudine in these patient populations, with both drugs having a similar tolerability profile. In the EARLY trial, entecavir was significantly more effective than and as well tolerated as adefovir dipivoxil therapy in nucleoside-naive patients. In addition, in a double-blind, multicentre trial, entecavir plus lamivudine-based highly active antiretroviral therapy (HAART) was more effective than placebo plus lamivudine-based HAART in patients co-infected with HBV and HIV. Although the exact position of entecavir relative to other agents, such as tenofovir disoproxil fumarate and adefovir dipivoxil, for the treatment of chronic HBV infection remains to be fully determined, an important aspect in this positioning is the emergence of drug resistance. Hence, entecavir therapy provides a valuable first-line option in nucleoside-naive patients with chronic HBV infection and is a useful alternative in lamivudine-refractory patients.

Pharmacokinetics of LB80331 and LB80317 following oral administration of LB80380, a new antiviral agent for chronic hepatitis B (CHB), in healthy adult subjects, CHB patients, and mice

LB80380, a dipivoxil ester prodrug of LB80331 (metabolite, LB80317), is a novel antiviral agent for chronic hepatitis B (CHB). The pharmacokinetics of LB80331/LB80317 were evaluated in two clinical studies and a study with mice. The clinical studies were dose-escalating pharmacokinetic studies with six healthy subjects per single-dose group and six CHB patients per repeated-dose group. The mouse study was designed to measure the amounts of the phosphorylated portions of LB80331 and LB80317 in the liver. In healthy subjects receiving a single dose of LB80380, the plasma level of LB80331 increased as the dose increased. Although a high-fat diet delayed the time to the maximum concentration in plasma (T(max)) of LB80331, the area under the concentration-time curve from time zero to infinity was similar between the subjects in the fasted group and those in the group who consumed a high-fat diet. In CHB patients, the mean T(max) of LB80331 was 1.0 to 2.0 h postdosing at steady state. The steady-state plasma concentration of LB80331 declined in a monoexponential manner, and the apparent elimination half-life was 2.5 to 3.3 h. The steady-state plasma concentration of LB80317 was maximum at 3 to 8 h postdoing and declined in a monoexponential manner; the apparent elimination half-life was 45 to 62 h at the 30- to 240-mg doses, while LB80317 was measurable in plasma only at higher doses of 120 and 240 mg after the administration of the first dose of LB80380. Forty percent of the amount of LB80331/LB80317 in the mouse liver was detected as the phosphorylated form. In conclusion, LB80380 is rapidly absorbed and converted to LB80331. LB80317 has a long half-life at steady-state, supporting the use of a once-daily dosing regimen. The ingestion of a high-fat diet delays the rate of absorption of LB80380 without affecting the extent of absorption.