The triple combination of tenofovir, emtricitabine and efavirenz shows synergistic anti-HIV-1 activity in vitro: a mechanism of action study

<p>Abstract</p> <p>Background</p> <p>Tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) are the three components of the once-daily, single tablet regimen (Atripla) for treatment of HIV-1 infection. Previous cell culture studies have demonstrated that the double combination of tenofovir (TFV), the parent drug of TDF, and FTC were additive to synergistic in their anti-HIV activity, which correlated with increased levels of intracellular phosphorylation of both compounds.</p> <p>Results</p> <p>In this study, we demonstrated the combinations of TFV+FTC, TFV+EFV, FTC+EFV, and TFV+FTC+EFV synergistically inhibit HIV replication in cell culture and synergistically inhibit HIV-1 reverse transcriptase (RT) catalyzed DNA synthesis in biochemical assays. Several different methods were applied to define synergy including median-effect analysis, MacSynergy^®II and quantitative isobologram analysis. We demonstrated that the enhanced formation of dead-end complexes (DEC) by HIV-1 RT and TFV-terminated DNA in the presence of FTC-triphosphate (TP) could contribute to the synergy observed for the combination of TFV+FTC, possibly through reduced terminal NRTI excision. Furthermore, we showed that EFV facilitated efficient formation of stable, DEC-like complexes by TFV- or FTC-monophosphate (MP)-terminated DNA and this can contribute to the synergistic inhibition of HIV-1 RT by TFV-diphosphate (DP)+EFV and FTC-TP+EFV combinations.</p> <p>Conclusion</p> <p>This study demonstrated a clear correlation between the synergistic antiviral activities of TFV+FTC, TFV+EFV, FTC+EFV, and TFV+FTC+EFV combinations and synergistic HIV-1 RT inhibition at the enzymatic level. We propose the molecular mechanisms for the TFV+FTC+EFV synergy to be a combination of increased levels of the active metabolites TFV-DP and FTC-TP and enhanced DEC formation by a chain-terminated DNA and HIV-1 RT in the presence of the second and the third drug in the combination. This study furthers the understanding of the longstanding observations of synergistic anti-HIV-1 effects of many NRTI+NNRTI and certain NRTI+NRTI combinations in cell culture, and provides biochemical evidence that combinations of anti-HIV agents can increase the intracellular drug efficacy, without increasing the extracellular drug concentrations.</p

Circulating microRNAs in sera correlate with soluble biomarkers of immune activation but do not predict mortality in ART treated individuals with HIV-1 infection: A case control study

Introduction: The use of anti-retroviral therapy (ART) has dramatically reduced HIV-1 associated morbidity and mortality. However, HIV-1 infected individuals have increased rates of morbidity and mortality compared to the non-HIV-1 infected population and this appears to be related to end-organ diseases collectively referred to as Serious Non-AIDS Events (SNAEs). Circulating miRNAs are reported as promising biomarkers for a number of human disease conditions including those that constitute SNAEs. Our study sought to investigate the potential of selected miRNAs in predicting mortality in HIV-1 infected ART treated individuals. Materials and Methods: A set of miRNAs was chosen based on published associations with human disease conditions that constitute SNAEs. This case: control study compared 126 cases (individuals who died whilst on therapy), and 247 matched controls (individuals who remained alive). Cases and controls were ART treated participants of two pivotal HIV-1 trials. The relative abundance of each miRNA in serum was measured, by RTqPCR. Associations with mortality (all-cause, cardiovascular and malignancy) were assessed by logistic regression analysis. Correlations between miRNAs and CD4+ T cell count, hs-CRP, IL-6 and D-dimer were also assessed. Results: None of the selected miRNAs was associated with all-cause, cardiovascular or malignancy mortality. The levels of three miRNAs (miRs -21, -122 and -200a) correlated with IL-6 while miR-21 also correlated with D-dimer. Additionally, the abundance of miRs -31, -150 and -223, correlated with baseline CD4+ T cell count while the same three miRNAs plus miR- 145 correlated with nadir CD4+ T cell count. Discussion: No associations with mortality were found with any circulating miRNA studied. These results cast doubt onto the effectiveness of circulating miRNA as early predictors of mortality or the major underlying diseases that contribute to mortality in participants treated for HIV-1 infection

Entecavir (ETV) therapy in chronic hepatitis B patients previously treated with adefovir (ADV) with incomplete response on-treatment or relapse off-treatment

Background: The primary aims of antiviral therapy for the treatment of chronic hepatitis B (CHB) are the suppression of viral replication and remission of liver disease. However, a significant proportion of CHB patients treated with adefovir (ADV) have a suboptimal response to treatment, increasing the risks of disease progression and development of resistance. Due to the absence of cross-resistance in vitro, entecavir (ETV) therapy is recommended in patients not responding to ADV. Methods: Study ETV-079 was a randomized, open-label study comparing the viral kinetics, efficacy and safety of ETV (0.5 mg/day) with ADV (10 mg/day) in nucleoside-naive HBeAg(+) patients. After 48 weeks of treatment, patients from both arms of this study were eligible to enroll in the rollover study ETV-901 and receive treatment with ETV (1.0 mg/day). Results: Eighteen of the 24 ADV-treated patients who enrolled in ETV-901 from ETV-079 either failed to achieve undetectable HBV DNA (PCR<300 copies/mL) or relapsed following ADV therapy and were subsequently switched to ETV. Among the patients who relapsed off-treatment between ETV-079 and -901, the treatment gap ranged from 1–128 days. At entry into ETV-901, the median HBV DNA for the whole group was 6.31 log10 copies/mL. Median exposure to ETV (1.0 mg) in ETV-901 was 46 weeks, and all 18 patients currently remain on study therapy. At Week 24, the mean reduction in HBV DNA was −4.54 log10 copies/mL and 8/16 (50%) achieved HBV DNA <300 copies/mL. Nine patients had reached Week 48 in ETV-901; all had reductions in HBV DNA to <104 copies/mL and 8/9 (89%) had HBV DNA <300 copies/mL. Genotypic resistance testing was not performed. The safety profile of ETV in these ADV-experienced patients remained consistent with the previously reported experience. Conclusions: The majority of patients who had incomplete virological response or experienced virological relapse following ADV treatment in study ETV-079 had rapid reductions in HBV DNA when switched to ETV in study ETV-901. HBV DNA levels continued to decline to <300 copies/mL in the majority of patients between 24 and 48 weeks of ETV treatment.link_to_subscribed_fulltex