Characterization of a Novel Capsid Assembly Modulator for the Treatment of Chronic Hepatitis B Virus Infection

The standard of care for the treatment of chronic hepatitis B (CHB) is typically lifelong treatment with nucleos(t)ide analogs (NAs), which suppress viral replication and provide long-term clinical benefits. However, infectious virus can still be detected in patients who are virally suppressed on NA therapy, which may contribute to the failure of these agents to cure most CHB patients. Accordingly, new antiviral treatment options are being developed to enhance the suppression of hepatitis B virus (HBV) replication in combination with NAs ("antiviral intensification"). Here, we describe GS-SBA-1, a capsid assembly modulator (CAM) belonging to class CAM-E, that demonstrates potent inhibition of extracellular HBV DNA in vitro (EC₅₀ [50% effective concentration] = 19 nM) in HBV-infected primary human hepatocytes (PHHs) as well as in vivo in an HBV-infected immunodeficient mouse model. GS-SBA-1 has comparable activities across HBV genotypes and nucleos(t)ide-resistant mutants in HBV-infected PHHs. In addition, GS-SBA-1 demonstrated in vitro additivity in combination with tenofovir alafenamide (TAF). The administration of GS-SBA-1 to PHHs at the time of infection prevents covalently closed circular DNA (cccDNA) formation and, hence, decreases HBV RNA and antigen levels (EC₅₀ = 80 to 200 nM). Furthermore, GS-SBA-1 prevents the production of extracellular HBV RNA-containing viral particles in vitro. Collectively, these data demonstrate that GS-SBA-1 is a potent CAM that has the potential to enhance viral suppression in combination with an NA.

Zirconium Molybdate Nanocomposites’ Sensing Platform for the Sensitive and Selective Electrochemical Detection of Adefovir

Adefovir (ADV) is an anti-retroviral drug, which can be used to treat acquired immune deficiency syndrome (AIDS) and chronic hepatitis B (CHB), so its quantitative analysis is of great significance. In this work, zirconium molybdate (ZrMo₂O₈) was synthesized by a wet chemical method, and a composite with multi-walled carbon nanotubes (MWCNTs) was made. ZrMo₂O₈-MWCNTs composite was dropped onto the surface of a glassy carbon electrode (GCE) to prepare ZrMo₂O₈-MWCNTs/GCE, and ZrMo₂O₈-MWCNTs/GCE was used in the electrochemical detection of ADV for the first time. The preparation method is fast and simple. The materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammetry (CV). It was electrochemically analysed by differential pulse voltammetry (DPV). Compared with single-material modified electrodes, ZrMo₂O₈-MWCNTs/GCE showed a vastly improved electrochemical response to ADV. Moreover, the sensor complements the study of the electrochemical detection of ADV. Under optimal conditions, the proposed electrochemical method showed a wide linear range (from 1 to 100 μM) and a low detection limit (0.253 μM). It was successfully tested in serum and urine. In addition, the sensor has the advantages of a simple preparation, fast response, good reproducibility and repeatability. It may be helpful in the potential applications of other substances with similar structures.

Active site polymerase inhibitor nucleotides (ASPINs): Potential agents for chronic HBV cure regimens

Chronic hepatitis B virus (HBV) infection affects 240 to 300 million people worldwide. In the nucleus of infected hepatocytes, the HBV genome is converted to covalently closed circular DNA (cccDNA), which persists and serves as a transcriptional template for viral progeny. Therefore, a long-term cure for chronic HBV infection will require elimination of cccDNA. Although currently available nucleos(t)ide analogues (eg, tenofovir disoproxil fumarate, tenofovir alafenamide, entecavir) effectively control HBV replication, they are seldom curative (functional cure rate ∼10%) and require lifelong treatment for most patients. As such, antiviral agents with novel mechanisms of action are needed. Active site polymerase inhibitor nucleotides (ASPINs) noncompetitively distort the HBV polymerase active site to completely inhibit all polymerase functions, unlike traditional chain-terminating nucleos(t)ide analogues, which only target select polymerase functions and are consumed in the process. Clevudine, a first-generation ASPIN, demonstrated potent and prolonged HBV suppression in phase 2 and 3 clinical studies, but long-term treatment was associated with reversible myopathy in a small number of patients. ATI-2173, a novel next-generation ASPIN, is structurally similar to clevudine but targets the liver and demonstrates potent anti-HBV activity on and off treatment, and may ultimately demonstrate an improved pharmacokinetic and safety profile by significantly reducing systemic clevudine exposure. Thus, ATI-2173 is currently in clinical development as an agent for HBV cure. Here, we review the mechanism of action and preclinical and clinical profiles of clevudine and ATI-2173 to support the role of ASPINs as part of curative regimens for chronic HBV infection.

Japan Society of Hepatology Guidelines for the Management of Hepatitis B Virus Infection: 2019 update

The Drafting Committee for Hepatitis Management Guidelines established by the Japan Society of Hepatology published the first version of the Guidelines for the Management of Hepatitis B in 2013 (first English version in 2014), and has since been publishing updates to the Guidelines as new drugs become available, with the latest original Japanese version being Version 3.1. Herein, the Drafting Committee publishes the second English version that contains all the changes made since the first English version of the guidelines was published in 2014. This 2019 version covers: (i) the nucleos(t)ide analogs, tenofovir disoproxil fumarate and tenofovir alafenamide; (ii) updates to treatment recommendations and management of drug-resistant hepatitis B virus that reflect the new availability of these drugs; and (iii) new information about hepatitis B virus reactivation with each update. This latest update also contains information about treatment goals, indications for treatment and cessation of nucleos(t)ide analog therapy, most of which were covered by the first version.

Identification of a quadruple mutation that confers tenofovir resistance in chronic hepatitis B patients

BACKGROUND & AIMS

Tenofovir disoproxil fumarate (TDF) is one the most potent nucleot(s)ide analogues for treating chronic hepatitis B virus (HBV) infection. Phenotypic resistance caused by genotypic resistance to TDF has not been reported. This study aimed to characterize HBV mutations that confer tenofovir resistance.

METHODS

Two patients with viral breakthrough during treatment with TDF-containing regimens were prospectively enrolled. The gene encoding HBV reverse transcriptase was sequenced. Eleven HBV clones harboring a series of mutations in the reverse transcriptase gene were constructed by site-directed mutagenesis. Drug susceptibility of each clone was determined by Southern blot analysis and real-time PCR. The relative frequency of mutants was evaluated by ultra-deep sequencing and clonal analysis.

RESULTS

Five mutations (rtS106C [C], rtH126Y [Y], rtD134E [E], rtM204I/V, and rtL269I [I]) were commonly found in viral isolates from 2 patients. The novel mutations C, Y, and E were associated with drug resistance. In assays for drug susceptibility, the IC₅₀ value for wild-type HBV was 3.8 ± 0.6 µM, whereas the IC₅₀ values for CYE and CYEI mutants were 14.1 ± 1.8 and 58.1 ± 0.9 µM, respectively. The IC₉₀ value for wild-type HBV was 30 ± 0.5 µM, whereas the IC₉₀ values for CYE and CYEI mutants were 185 ± 0.5 and 790 ± 0.2 µM, respectively. Both tenofovir-resistant mutants and wild-type HBV had similar susceptibility to the capsid assembly modulator NVR 3-778 (IC₅₀ <0.4 µM vs. IC₅₀ = 0.4 µM, respectively).

CONCLUSIONS

Our study reveals that the quadruple (CYEI) mutation increases the amount of tenofovir required to inhibit HBV by 15.3-fold in IC₅₀ and 26.3-fold in IC₉₀. These results demonstrate that tenofovir-resistant HBV mutants can emerge, although the genetic barrier is high.

LAY SUMMARY

Tenofovir is the most potent nucleotide analogue for the treatment of chronic hepatitis B virus infection and there has been no hepatitis B virus mutation that confers >10-fold resistance to tenofovir up to 8 years. Herein, we identified, for the first time, a quadruple mutation that conferred 15.3-fold (IC₅₀) and 26.3-fold (IC₉₀) resistance to tenofovir in 2 patients who experienced viral breakthrough during tenofovir treatment.

Is Combination Antiviral Therapy Mandatory for Maintenance Therapy in Fully Suppressed Multidrug-Resistant Hepatitis B Patients?

Aim

The efficacy of tenofovir disoproxil fumarate (TDF) monotherapy as maintenance therapy in multidrug-resistant (MDR) hepatitis B virus (HBV) patients after complete virologic suppression (CVS) has not been well evaluated. We evaluated the efficacy of maintenance TDF monotherapy compared with conventional TDF plus entecavir combination therapy after CVS of MDR HBV.

Methods

In this single-center retrospective study, patients with MDR HBV who were previously treated with entecavir plus TDF combination therapy and achieved CVS were included. Patients were either maintained on entecavir plus TDF combination therapy or switched to TDF monotherapy after CVS. The primary endpoint was the virologic breakthrough, and secondary outcomes were liver cirrhosis (LC) or hepatocellular carcinoma (HCC) development. To overcome immortal time bias, time-varying Cox proportional hazard regression analysis was performed.

Results

A total of 201 patients were included, and 153 patients were maintained on entecavir plus TDF combination therapy (combination group); 48 patients were converted from combination therapy to TDF monotherapy (single group) after CVS. Five patients experienced a virologic breakthrough, one patient in the single group owing to poor transient compliance and four patients in the combination group (P = 0.51). One new case of LC developed in the single group; five cases of LC developed in the combination group (P = 0.35). No new HCC development occurred in the single group, while seven cases of HCC developments were noted in the combination group. However, these results were not statistically significant (P = 0.54).

Conclusions

For patients with suppressed HBV DNA, the efficacy of TDF monotherapy as maintenance therapy is comparable to that of entecavir plus TDF combination therapy.

Discovery of the Novel Entecavir-Resistant Hepatitis B Virus Reverse Transcriptase A181C Substitution From an Integrated Genotypic Analysis

Entecavir (ETV) is a first-line therapy for chronic hepatitis B virus (HBV), demonstrating potent suppression of HBV DNA and a high barrier to viral resistance. Previous studies revealed that ETV-resistant (ETVr) HBV DNA resulted from substitutions in the HBV reverse transcriptase (RT) at positions rtT184, rtS202, or rtM250 in combination with lamivudine resistance (LVDr) substitutions rtM204I/V±rtL180M. In vitro, viral variants exhibit varying degrees of ETV susceptibility and replication capacity depending on specific resistance substitutions. To explore the potential for additional pathways to ETVr, HBV RT sequences from 982 evaluable patients enrolled in 17 ETV clinical studies were analyzed. Thirty novel emergent substitutions at amino acid positions not previously associated with HBV nucleos(t)ide drug resistance were observed in at least 2 patients and were identified in patient-derived HBV with a wild-type, LVDr, or ETVr RT sequence. Phenotypic analysis of these substitutions indicated that they had no effect on ETV susceptibility. Phenotypic analysis was also performed on patient-derived HBV RT sequences from 10 LVD-naive and 13 LVD-experienced patients with virologic breakthrough and emergent novel substitutions while on ETV treatment. One LVD-experienced patient-derived HBV RT harboring LVDr substitutions rtL180M+rtM204V with rtA181C displayed reduced ETV susceptibility (122-fold greater than wild-type HBV) and remained susceptible to adefovir and tenofovir. HBV harboring the rtA181C substitution without LVDr substitutions rtL180M+rtM204V remained susceptible to inhibition by ETV, adefovir, and tenofovir, although cross-resistance to LVD and telbivudine was observed. Conclusion: An integrated genotypic analysis of HBV RT sequences from patients with chronic HBV treated with ETV led to the discovery of the novel ETVr substitution rtA181C. This substitution was always detected in combination with LVDr substitutions rtL180M+rtM204V in ETV-treated patients.

RIG-I enhances interferon-α response by promoting antiviral protein expression in patients with chronic hepatitis B

BACKGROUND

Interferon (IFN)-α is widely used for the treatment of chronic hepatitis B (CHB) infection due to the high rate of hepatitis B surface antigen (HBsAg) seroconversion. However, IFN-α treatment has a number of side effects. Thus, identification of molecular biomarkers to predict IFN-α therapeutic effect would be useful in the clinic. In this study, we aimed to investigate the role of retinoic acid-inducible gene-I (RIG-I) in prediction of IFN-α curative effect of CHB patients.

METHODS

A total of 65 CHB patients treated with pegylated IFN-α weekly for 48 weeks were enrolled. Real-time PCR was performed for detection of RIG-I and IFN-stimulated gene (ISG) expression. In vitro, the HepG2 cells were transfected with siRNA and levels of RIG-I and anti-HBV proteins were detected by western blot. The P-values were calculated in SPSS 18.0. The statistical significance level was accepted as P<0.05.

RESULTS

In this study, we found RIG-I expression in peripheral blood mononuclear cells was higher in responder than non-responder CHB patients treated with IFN-α therapy. In HBV-transfected HepG2 and Huh7 cells, RIG-I enhanced IFN-α response by promoting anti-HBV protein expression such as double-stranded RNA-dependent protein kinase (PKR), oligoadenylate synthetase (OAS), adenosine deaminase (ADAR1) and Mx protein. Knocking down of RIG-I could downregulate the expression of these proteins. Inhibited RIG-I expression by RIG-I siRNA deceased STAT1 phosphorylation.

CONCLUSIONS

Our results revealed RIG-I enhanced IFN-α response by promoting antiviral protein expression via the STAT1 pathway. RIG-I may be a new predictive factor for prediction of IFN-α efficacy in CHB patients.

Trends in hepatitis B virus resistance to nucleoside/nucleotide analogues in North China from 2009-2016: A retrospective study

Nucleos(t)ide analogues (NAs) are widely used in anti-hepatitis B virus (anti-HBV) therapy for effective inhibition of HBV replication. However, HBV resistance to NAs has emerged, resulting in virus reactivation and disease recurrence. Data on the current dynamics of HBV resistance are still rare in China. This study analysed 4491 plasma samples with HBV primary genotypic resistance mutations representative of the general HBV resistance situation in northern China from 2009-2016. We found that entecavir (ETV), representing 57.6% (12 713/22 060) of NA users in North China in 2016, has become the major NA for treating Chinese patients infected with HBV. Despite >50% of M204I/V±L180M among all HBV resistance cases annually and extensive exposure of patients to lamivudine (LAM), telbivudine (LdT) and adefovir dipivoxil (ADV), ETV resistance also showed a dramatically increased incidence, which rose to 17.1% in 2016. Moreover, A181T/V, ETV resistance mutations and multidrug resistance mutations were found more frequently in HBV genotype C compared with genotype B (21.2% vs. 8.5%, 12.4% vs. 7.9% and 5.9% vs. 3.0%, respectively), whereas M204I and N236T were more predominant in genotype B than genotype C (40.3% vs. 20.8% and 11.3% vs. 1.8%, respectively). In conclusion, we report the dynamic changes of HBV NA resistance mutation patterns and the current NA usage profile for anti-HBV treatment in North China over the past 8 years. These data provide valuable information on HBV NA resistance that is an important reference for clinicians to devise more effective treatment regimens for individual patients.

Hepatitis B virus rtA181T/sW172non-stop mutation may increase resistance fold to adefovir- and entecavir-resistant mutants compared to rtA181T/sW172* mutation

The study aimed to characterize rtA181T/sW172stop (*) and rtA181T/sW172non-stop mutations of hepatitis B virus (HBV). Total of 22,009 patients who visited Beijing 302 Hospital from 2007 to 2016 were enrolled. These patients all received nucleos(t)ide analogues (NAs) treatment and their serum samples were collected for sequence analysis of HBV reverse-transcriptase (RT) and S regions. The rtA181T mutation was detected in 5.37% (1182/22,009) of the patients' samples. The rtA181T-causative sW172*, sW172non-stop (sW172 L/S), and mixed sW172*/non-stop mutations occupied 82.91%, 7.70%, and 9.39%, respectively. The patients with rtA181T/sW172non-stop mutants had a higher HBV DNA level compared to those with rtA181T/sW172* mutants. 44.33% (524/1182) rtA181T-positive samples were detected with signature drug-resistant mutations, including 325 with adefovir-resistant mutation rtA181V/N236T, 57 with lamivudine-resistant mutation rtM204V/I, 99 with entecavir-resistant mutation rtM204V/I plus rt184/202/250 substitution(s), and 43 with multidrug-resistant mutation rtA181V/N236T + rtM204V/I ± rt184/202/250 substitution(s). The rtA181T/sW172non-stop mutation had a higher ratio of coexistence with adefovir-resistant mutation compared to rtA181T/sW172* mutation (42.86% vs. 24.59%, P < 0.05). rtA181T/sW172S + rtN236T and rtA181T/sW172L + rtN236T mutants exhibited higher HBV DNA production and adefovir resistance fold than that of rtA181T/sW172* + rtN236T mutant (98.02% and 85.5% vs. 42.1% in HBV DNA production, and 7.38-fold and 5.49-fold vs. 3.69-fold in half maximal effective concentration of wild-type strain); rtA181T/sW172L + rtS202G + rtM204V strain exhibited higher HBV DNA production and entecavir resistance fold than that of rtA181T/sW172* + rtS202G + rtM204V strain (50.98% vs. 34.49%, 524.00-fold vs. 69.33-fold). In conclusion, rtA181T/sW172non-stop mutation may increase resistance fold of adefovir- and entecavir-resistant mutants compared to rtA181T/sW172* mutation and might influence clinical presentation of NAs-treated patients.

Evolution of drug-resistant mutations in HBV genomes in patients with treatment failure during the past seven years (2010-2016)

The objective of this study was to analyze the prevalence of drug-resistant HBV mutants in patients with treatment failure during the past seven years (2010-2016). 4055 HBV-infected patients who underwent HBV polymerase gene mutation test from 2010 to 2016 were enrolled. The nucleos(t)ide analogues (NAs) resistance mutation positions, including rtL180, rtA181, rtT184, rtS202, rtM204, rtI233, rtN236, rtI169, rtV173, and rtM250 were analyzed. Genotypic resistance mutations were detected in 30.8% (1248/4055) of the patients with treatment failure. Rates of drug-resistant mutations associated with LAM, ADV, ETV, and multidrug were 27.23% (1104/4055), 9.67% (392/4055), 3.69% (150/4055), and 0.79% (32/4055). Among the primary NA-resistant mutations, rtM204I (13.44%, 545/4055) occurred more frequently, followed by rtM204V, rtN236T, rtA181T, and rtA181V. For single-base mutations, rtL180M and rtA181V increased gradually during the past seven years, while rtM204I/V and rtN236T decreased after 2015. The development of drug-resistant mutations positively correlated with the consumption of ETV (r = 0.964, P = 0.002), and weakly correlated with that of LAM (r = 0.679, P = 0.109) and ADV (r = 0.429, P = 0.354). Moreover, single-base mutation rtA181V and multi-base mutations (rtL180M + M204I and rtL180M + M204V + M204I) were more common in HBV genotype C than those in genotype B (1.94% vs. 0.66%, 1.84% vs. 0.16%, 1.02% vs. 0.16%, respectively). NA-related mutations in HBV RT region increased in the past seven years, especially for LAM. Frequencies of rtL180M and rtA181T/V increased gradually in the past seven years, to which we should pay more attention.

Monotherapy with tenofovir disoproxil fumarate for multiple drug-resistant chronic hepatitis B: 3-year trial

Combination therapy has been recommended for the treatment of patients harboring multiple drug-resistant hepatitis B virus (HBV). However, we recently demonstrated that monotherapy with tenofovir disoproxil fumarate (TDF) for 48 weeks displayed noninferior efficacy to TDF plus entecavir (ETV) combination therapy in patients with HBV resistant to multiple drugs, including ETV and adefovir. Nonetheless, whether prolonged TDF monotherapy would be safe and increase the virologic response rate in these patients was unclear. Among 192 patients with HBV-resistance mutations to ETV and/or adefovir, who were randomized to receive TDF monotherapy (n = 95) or TDF/ETV combination therapy (n = 97) for 48 weeks, 189 agreed to continue TDF monotherapy (TDF-TDF group) or to switch to TDF monotherapy (TDF/ETV-TDF group) and 180 (93.8%) completed the 144-week study. Serum HBV DNA <15 IU/mL at week 48, the primary efficacy endpoint, was achieved in 66.3% in the TDF-TDF group and 68.0% in the TDF/ETV-TDF group (P = 0.80). At week 144, the proportion with HBV DNA <15 IU/mL increased to 74.5%, which was significantly higher compared with that at week 48 (P = 0.03), without a significant difference between groups (P = 0.46). By on-treatment analysis, a total of 79.4% had HBV DNA <15 IU/mL at week 144. Transient virologic breakthrough occurred in 6 patients, which was due to poor drug adherence. At week 144, 19 patients who had HBV DNA levels >60 IU/mL qualified for genotypic resistance analysis, and 6 retained some of their baseline resistance mutations of HBV. No patients developed additional resistance mutations throughout the study period.

CONCLUSION

TDF monotherapy was efficacious and safe for up to 144 weeks, providing an increasing rate of virologic response in heavily pretreated patients with multidrug-resistant HBV. (Hepatology 2017;66:772-783).

Efficacy and Safety of Tenofovir Disoproxil Treatment for Chronic Hepatitis B Patients with Genotypic Resistance to Other Nucleoside Analogues: A Prospective Study

Background:

Tenofovir disoproxil (TDF) is a promising salvage therapy for patients with chronic hepatitis B (CHB) who failed regimens of other nucleoside analogues (NAs). In this study, we aimed to investigate the clinical efficacy and safety of TDF monotherapy in Chinese CHB patients with genotypic resistance.

Methods:

A total of 33 CHB patients who had failed treatment with other NAs and had genotypic resistance were switched to TDF monotherapy for 48 weeks. Patients’ demographic data (age, sex, history of hepatitis B virus [HBV] therapy), laboratory testing results (hepatitis B e antigen [HBeAg] status, HBV DNA levels, alanine aminotransferase [ALT] levels, serum creatinine, urinary protein, genotypic assay), clinical symptoms, and liver color ultrasound examinations were collected for evaluation at day 0 (baseline) and the 12^th, 24^th, 36^th, and 48^th weeks after initiating treatment. Statistical analyses were carried out using rank sum test or rank correlation.

Results:

With regard to efficacy, the study found that all patients who switched to TDF monotherapy had undetectable HBV DNA levels after 48 weeks. In addition, patients with lower baseline HBV DNA levels realized earlier virological undetectability (r_s = 0.39, P = 0.030). ALT levels were normal in 30 of 33 patients (91%). HBeAg negative conversion occurred in 7 of 25 patients (28%), among whom HBeAg seroconversion (12%) and HBeAg seroclearance (16%) occurred. The time of complete virological response was significantly affected by the number of resistance loci (r_s = 0.36, P = 0.040). Concerning safety, the study found that no adverse events were observed during the 48 weeks.

Conclusion:

TDF monotherapy is an effective and safe salvage treatment for CHB patients who are resistant to other NAs.

Five-year efficacy and safety of tenofovir-based salvage therapy for patients with chronic hepatitis B who previously failed LAM/ADV therapy

BACKGROUND

Multidrug-resistant HBV continues to be an important clinical problem. The TDF-109 study demonstrated that TDF±LAM is an effective salvage therapy through 96 weeks for LAM-resistant patients who previously failed ADV add-on or switch therapy. We evaluated the 5-year efficacy and safety outcomes in patients receiving long-term TDF±LAM in the TDF-109 study.

METHODS

A total of 59 patients completed the first phase of the TDF-109 study and 54/59 were rolled over into a long-term prospective open-label study of TDF±LAM 300 mg daily.

RESULTS

Results are reported at the end of year 5 of treatment. At year 5, 75% (45/59) had achieved viral suppression by intent-to-treat analysis. Per-protocol assessment revealed 83% (45/54) were HBV DNA undetectable. Nine patients remained HBV DNA detectable, however 8/9 had very low HBV DNA levels (<264IU/mL) and did not meet virological criteria for virological breakthrough (VBT). One patient experienced VBT, but this was in the setting of documented non-compliance. The response was independent of baseline LAM therapy or mutations conferring ADV resistance. Four patients discontinued TDF, one patient was lost to follow-up and one died from hepatocellular carcinoma.

CONCLUSIONS

Long-term TDF treatment appears to be safe and effective in patients with prior failure of LAM and a suboptimal response to ADV therapy. These findings confirm that TDF has a high genetic barrier to resistance is active against multidrug-resistant HBV, and should be the preferred oral anti-HBV agent in CHB patients who fail treatment with LAM and ADV.

Efficacy of long-term tenofovir-based rescue therapy in patients with chronic hepatitis B refractory to nucleoside/nucleotide analogs

BACKGROUND

Few studies have investigated the efficacy of long-term tenofovir disoproxil fumarate (TDF)-based rescue therapy in patients with chronic hepatitis B refractory to nucleoside/nucleotide analogs.

METHODS

We retrospectively analyzed 40 Japanese patients with chronic hepatitis B refractory to nucleoside/nucleotide analogs who received TDF-based rescue therapy [TDF monotherapy, TDF plus lamivudine (LAM) combination therapy, or TDF plus entecavir (ETV) combination therapy] followed up for a median of 45 months (range 14-99 months). Viral response, changes in hepatitis B surface antigen levels from the baseline, and viral breakthrough during therapy were analyzed.

RESULTS

The proportion of patients with undetectable serum hepatitis B virus (HBV) DNA levels (less than 2.1 log copies per milliliter) (viral response) during TDF-based rescue therapy was 68, 78, 85, 88, 83, 81, 88, and 100 % at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 years respectively. There were no differences in the viral response rate between the TDF plus LAM group and the TDF plus ETV group. The mean reduction from the baseline in hepatitis B surface antigen levels in patients with LAM-resistant HBV was greater than the reductions in patients with adefovir dipivoxil (ADV)-resistant or ETV-resistant HBV at 2 and 3 years (P = 0.024, and P = 0.025 respectively). However, two patients with ADV- or ETV-resistant HBV at the baseline developed viral breakthrough during TDF-based rescue therapy.

CONCLUSIONS

Long-term therapy with a TDF-based rescue regimen demonstrated high viral suppression in patients in whom LAM plus ADV combination therapy, ETV plus ADV combination therapy, or ETV monotherapy had failed. However, patients with ADV- or ETV-resistant HBV at the baseline may develop viral breakthrough and resistance, and careful follow-up is advised.

Management of Antiviral Resistance in Chronic Hepatitis B

The primary goal of therapy for chronic hepatitis B (CHB) is to prevent liver disease progression. Hepatitis B surface antigen (HBsAg) seroclearance or seroconversion is regarded as an optimal endpoint to discontinue treatment. However, HBsAg seroclearance occurs very rarely with nucleos(t)ide analog (NUC) treatment, and long-term, almost indefinite, NUC treatment is required for the majority of patients. In patients with drug-resistant hepatitis B virus (HBV), a combination of tenofovir disoproxil fumarate (TDF) and entecavir (ETV), which is currently regarded as the strongest combination therapy against HBV, would be potentially safe to prevent the emergence of additional HBV resistance mutations. However, long-term tolerance data are lacking, and cost may be an issue for combination therapies. Several recent, well-designed, randomized controlled trials have shown that TDF monotherapy provides similar antiviral efficacy compared with the combination of TDF and ETV. Furthermore, no additional HBV resistance mutations emerged during TDF monotherapy for up to 96 weeks. Considering a comparable antiviral efficacy, extremely low risk of TDF-resistance, lower cost, and better safety potential, TDF monotherapy would be a reasonable choice for the treatment of drug-resistant patients with CHB.

Tenofovir alafenamide demonstrates broad cross-genotype activity against wild-type HBV clinical isolates and maintains susceptibility to drug-resistant HBV isolates in vitro

Tenofovir alafenamide (TAF) is a novel prodrug of tenofovir (TFV). This study evaluated the antiviral activity of TAF against wild-type genotype A-H HBV clinical isolates as well as adefovir-resistant, lamivudine-resistant, and entecavir-resistant HBV isolates. Full length HBV genomes or the polymerase/reverse transcriptase (pol/RT) region from treatment-naïve patients infected with HBV genotypes A-H were amplified and cloned into an expression vector under the control of a CMV promoter. In addition, 11 drug resistant HBV constructs were created by site-directed mutagenesis of a full length genotype D construct. Activity of TAF was measured by transfection of each construct into HepG2 cells and assessment of HBV DNA levels following treatment across a range of TAF concentrations. TAF activity in vitro was similar against wild-type genotype A-H HBV clinical isolates. All lamivudine- and entecavir-resistant isolates and 4/5 adefovir-resistant isolates were found to be sensitive to inhibition by TAF in vitro as compared to the wild-type isolate. The adefovir-resistant isolate rtA181V + rtN236T exhibited low-level reduced susceptibility to TAF. TAF is similarly active in vitro against wild-type genotype A-H HBV clinical isolates. The TAF sensitivity results for all drug-resistant isolates are consistent with what has been observed with the parent drug TFV. The in vitro cell-based HBV phenotyping assay results support the use of TAF in treatment of HBV infected subjects with diverse HBV genotypes, in both treatment-naive and treatment-experienced HBV infected patients.

Profile of HBV polymerase gene mutations during entecavir treatment in patients with chronic hepatitis B

BACKGROUND/AIMS

We investigated the efficacy of entecavir (ETV) monotherapy in 54 naïve patients and 27 lamivudine (LMV) and/or adefovir (ADV) experienced patients.

METHODS

Eighty-one chronic hepatitis B patients with a viral load above 4 log 10 copies/ml and high levels of serum alanine aminotransferase were treated with ETV 0.5mg daily. The viruses of patients were sequenced before ETV therapy and after every three months of ETV therapy.

RESULTS

Eight LAM-experienced and ADV-experienced patients emerged mutations in the ETV treatment. In one of these experienced patients, the ETV-resistant mutations were detected during ETV treatment, with the virological and the biochemical breakthrough. Two LAM-experienced and ADV-naïve patients were detected mutation during 1-2 years ETV therapy. All three LAM-naïve and ADV-experienced patients were detected mutations in the ETV treatment. Five in fifty for LAM-naïve and ADV-naïve patients showed mutations in the ETV monotherapy.

CONCLUSIONS

ETV has a high genetic barrier to resistance and the efficacy in LAM-experienced and/or ADV-experienced patients were much lower than in naïve patients.

Entecavir plus tenofovir combination therapy in patients with multidrug-resistant chronic hepatitis B: results of a multicentre, prospective study

BACKGROUND & AIMS

Sequential therapy posed a high risk of emergence of multidrug resistance and presented a management issue in chronic hepatitis B (CHB) treatment. We evaluated the antiviral efficacy and safety of entecavir (ETV) plus tenofovir (TDF) combination therapy in multidrug-resistant (MDR) CHB patients.

METHODS

In this prospective, multicentre study, MDR CHB patients, defined as measurable serum HBV DNA (≥60 IU/ml) while on any rescue treatment regimen for at least 24 weeks and the presence of documented prior genotypic resistance to both nucleoside analogue(s) and nucleotide analogue, were treated with ETV 1.0 mg and TDF 300 mg combination therapy for 48 weeks.

RESULTS

A total of 64 eligible patients who had previously failed to a median three lines of antiviral therapy (range, 2-6) were included. At baseline, median age was 47.0 years, 89.1% were HBeAg(+), and median HBV DNA was 4.24 (range, 2.11-6.73) log10 IU/ml. By week 4, 12, 24 and 48, 15/64 (23.4%), 36/64 (56.3%), 43/64 (67.2%) and 55/64 (85.9%) patients achieved a HBV DNA <60 IU/ml respectively. The mean reduction of HBV DNA from baseline to 4 and 48 weeks was 1.23 log10 IU/ml and 2.38 log10 IU/ml respectively. Although five patients experienced virological breakthrough, all were transient and no resistant mutation to TDF or novel mutation was detected in any patients.

CONCLUSIONS

In difficult-to-treat MDR CHB patients with a high exposure to multiple antiviral drugs, ETV plus TDF combination therapy can provide a very high rate of viral suppression through 48 weeks of treatment.

Tenofovir monotherapy versus tenofovir and entecavir combination therapy in adefovir-resistant chronic hepatitis B patients with multiple drug failure: results of a randomised trial

OBJECTIVE

Little clinical data are available regarding the optimal treatment of patients who harbour adefovir-resistant HBV.

DESIGN

In this multicentre trial, patients who had adefovir-resistant HBV with serum HBV DNA levels >60 IU/mL were randomised to receive tenofovir disoproxil fumarate (TDF, 300 mg/day) monotherapy (n=50) or TDF and entecavir (ETV, 1 mg/day) combination therapy (TDF/ETV, n=52) for 48 weeks. All who completed 48 weeks in either group received TDF monotherapy for 48 additional weeks.

RESULTS

Baseline characteristics were comparable between groups, including HBV DNA levels (median, 3.38 log10 IU/mL). All patients had adefovir-resistant HBV mutations; rtA181V/T and/or rtN236T. The proportion of patients with HBV DNA <15 IU/mL was not significantly different between the TDF-TDF and TDF/ETV-TDF groups at weeks 48 (62% vs 63.5%; p=0.88) and 96 (64% vs 63.5%; p=0.96). The mean change in HBV DNA levels from baseline was not significantly different between groups at week 48 (-3.03 log10 IU/mL vs -3.31 log10 IU/mL; p=0.38). Virological breakthrough occurred in one patient on TDF-TDF and two patients on TDF/ETV-TDF over 96 weeks; all were attributed to poor drug adherence. At week 96, five and two patients in the TDF-TDF and TDF/ETV-TDF groups, respectively, retained some of their baseline resistance mutations (p=0.44). None developed additional resistance mutations. Safety profiles were comparable in the two groups.

CONCLUSIONS

In patients with adefovir-resistant HBV and multiple-drug failure, TDF monotherapy provided a virological response comparable to that of TDF and ETV combination therapy, and was safe up to 96 weeks.

TRIAL REGISTRATION NUMBER

NCT01639066.

Outcome of adefovir add-on lamivudine rescue therapy of up to 5 years in patients with lamivudine-resistant chronic hepatitis B

BACKGROUND AND AIM

We investigated the long-term efficacy of adefovir add-on lamivudine rescue therapy in lamivudine-resistant chronic hepatitis B and the optimal cutoff hepatitis B virus (HBV) DNA level that predicts complete virological response (CVR) among patients without CVR after 1 year of treatment.

METHODS

We reviewed 167 lamivudine-resistant chronic hepatitis B patients who received adefovir add-on rescue therapy for up to 5 years. Multivariate analysis, area under the receiver operating characteristic curves, and Youden index were used.

RESULTS

Median age was 47.0 years; 112 patients were male. Median baseline HBV DNA level was 6.6 log10 IU/mL; hepatitis B e antigen was positive in 130 (77.4%) patients. Five-year CVR, alanine aminotransferase normalization, hepatitis B e antigen seroconversion, and adefovir resistance rates were 86.9%, 92.5%, 16.7%, and 6.0%, respectively. One-year HBV DNA level independently associated with CVR. Optimal cutoff HBV DNA level to predict CVR among patients who failed to achieve CVR at 1 year was 800 IU/mL (area under receiver operating characteristic curve 0.752; sensitivity 49.3%, specificity 93.5%). During the 5-year treatment, 92.1% of patients with favorable response (HBV DNA < 800 IU/mL at 1 year) achieved CVR; 45.6% achieved CVR among suboptimal responders (HBV DNA ≥ 800 IU/mL at 1 year) (P < 0.001).

CONCLUSION

Complete virological response or HBV DNA level < 800 IU/mL after 1 year adefovir add-on lamivudine rescue therapy can favorably predict CVR.

A novel method for nucleos(t)ide analogues susceptibility assay of hepatitis B virus by viral polymerase transcomplementation

Nucleos(t)ide analogues (NUCs) susceptibility assay is important for the study of hepatitis B virus (HBV) drug resistance. The purpose of susceptibility assay is to test the sensitivity of a specific HBV variant to NUCs in vitro, by which assesses if and to what extent the mutant virus is resistant to a specific NUC. Among the existing susceptibility assay methods, stable cell line expressing the specific variant is one of the commonly used assessment systems based on its high repeatability. However, establishment of stable cell lines expressing individual variant is laborious and time-consuming. In the present study, we developed a novel strategy for rapidly establishing HBV replicating stable cell lines. We first established an acceptor cell line stably transfected with a polymerase-null HBV 1.1mer genome DNA, then lentiviruses expressing different mutant HBV polymerases were transduced into the acceptor cell line respectively. Stable cell lines replicating HBV DNA with the trans-complemented HBV polymerases were established by antibiotics selection. Lamivudine and entecavir susceptibility data from these polymerase-complementing cell lines were validated by comparing with other assays. Taken together, this transcomplementation strategy for establishment of stable cell lines replicating HBV DNA with clinically isolated HBV polymerase provides a new tool for NUC susceptibility assay of HBV.

Stable Human Hepatoma Cell Lines for Efficient Regulated Expression of Nucleoside/Nucleotide Analog Resistant and Vaccine Escape Hepatitis B Virus Variants and Woolly Monkey Hepatitis B Virus

Hepatitis B virus (HBV) causes acute and chronic hepatitis B (CHB). Due to its error-prone replication via reverse transcription, HBV can rapidly evolve variants that escape vaccination and/or become resistant to CHB treatment with nucleoside/nucleotide analogs (NAs). This is particularly problematic for the first generation NAs lamivudine and adefovir. Though now superseded by more potent NAs, both are still widely used. Furthermore, resistance against the older NAs can contribute to cross-resistance against more advanced NAs. For lack of feasible HBV infection systems, the biology of such variants is not well understood. From the recent discovery of Na⁺-taurocholate cotransporting polypeptide (NTCP) as an HBV receptor new in vitro infection systems are emerging, yet access to the required large amounts of virions, in particular variants, remains a limiting factor. Stably HBV producing cell lines address both issues by allowing to study intracellular viral replication and as a permanent source of defined virions. Accordingly, we generated a panel of new tetracycline regulated TetOFF HepG2 hepatoma cell lines which produce six lamivudine and adefovir resistance-associated and two vaccine escape variants of HBV as well as the model virus woolly monkey HBV (WMHBV). The cell line-borne viruses reproduced the expected NA resistance profiles and all were equally sensitive against a non-NA drug. The new cell lines should be valuable to investigate under standardized conditions HBV resistance and cross-resistance. With titers of secreted virions reaching >3x10⁷ viral genome equivalents per ml they should also facilitate exploitation of the new in vitro infection systems.

Tenofovir disoproxil fumarate has a substantial efficacy against multidrug-resistant strains of hepatitis B virus

BACKGROUND & AIMS

To evaluate the efficacy of tenofovir in chronic hepatitis B (CHB) patients with adefovir resistance (ADF-R) and suboptimal response to adefovir (ADF-S).

METHODS

Nucleos(t)ide analogue (NA)-naïve patients and patients with previous adefovir failure receiving tenofovir therapy for at least 6 months were included in the study. Biochemical and virological tests were obtained at baseline and 3-month intervals in the first year and every 6 months thereafter. The primary outcome measure was complete virological response (CVR) (HBVDNA < 20 IU/ml). CVR rates were calculated by Kaplan-Meier analysis, and a multivariate Cox proportional hazard model was generated to find out factors independently associated with CVR.

RESULTS

A total of 165 patients (118 men, mean age 42 ± 12, 64 HBeAg(+) ) were included in the study. There were 105 patients in NA-naïve, 32 patients in ADF-S and 28 patients in ADF-R groups. All patients in the ADF-R group had multidrug resistance patterns. Mean duration of tenofovir treatment was 29 ± 14 months. CVR rates in NA-naïve, ADF-S and ADF-R groups were 65% vs. 75% vs. 58% at 12th month, 77% vs. 87% vs. 79% at 24th month and 83% vs. 94% vs. 79% at 36th month respectively. According to multivariate Cox regression model, HBeAg positivity (HR = 0.56, 95%CI 0.36-0.86, P = 0.008), high baseline HBVDNA level (HR = 0.64, 95%CI 0.55-0.74, P < 0.001) and ADF-R (HR = 0.47, 95%CI 0.28-0.81, P = 0.006) were independent predictors for CVR. Seven patients encountered mild renal dysfunction and were managed by dose adjustments.

CONCLUSION

CVR rates during the follow-up show that tenofovir has a decreased, yet still potent in vivo efficacy against multidrug-resistant strains of HBV.

Monotherapy for hepatitis B infection: a review of treatment options

Chronic hepatitis B (CHB) is a global health problem, causing liver failure, cirrhosis and hepatocellular carcinoma. CHB treatment aims to prevent liver-related complication. The treatment of CHB infection includes monotherapy with either interferons (IFNs) or nucleos(t)ide (NUC) analogs. IFNs have moderate antiviral effects, and their use is limited by side effects. With the availability of NUCs, IFN-intolerant and decompensated cirrhotic patients began to be treated. Lamivudine and telbivudine, nucleoside analogs, have low genetic barrier to resistance. Adefovir, a nucleotide analog, has moderate potency and potential nephrotoxicity. Entecavir and tenofovir, with their high potency, high genetic barrier to resistance and favorable safety profile are the standard of care in CHB treatment. Long-term use of NUCs with maintained viral suppression results in a decrease in liver-related complications.

Prevalence and types of drug-resistant variants in Chinese patients with acute hepatitis B

The presence of therapy-associated hepatitis B virus (HBV) variants is the main drawback of antiviral therapy for HBV infection. Moreover, drug-resistant variants are more insensitive to a second agent and more therapy-associated mutations will be present. To apply better nucleos(t)ide analogues (NA) and reduce the occurrence of resistance, the prevalence and types of drug-resistant mutations in acute hepatitis B patients were investigated in this study. One hundred three HBV DNA-positive patients with symptomatic acute hepatitis B that were observed from 2011 to 2013 were enrolled. Direct polymerase chain reaction sequencing was used firstly to screen HBV reverse-transcriptase domain to detect HBV mutants. Five lamivudine-resistant variants were identified. Clonal sequencing was performed for 5 resistance-positive samples and 10 other random samples. Interestingly, all detected samples harbored drug-resistant mutations, although with different percentage. Thirteen harbored lamivudine-related alone (five) or together with other NA related mutations (five with adefovir, one with entecavir, and one with telbivudine), and two of them harbored adefovir-related mutations. Also, mutations associated with four currently used NA were all detected, and the frequency is in accordance with the popularity of NA used in clinical practice. These data suggest that drug-resistant variants are present in patients with acute hepatitis B and NA should be applied more carefully for chronic hepatitis B patients developed from acute hepatitis B.

Efficacy of Tenofovir-based Rescue Therapy in Lamivudine-resistant Chronic Hepatitis B Patients With Failure of Lamivudine and Adefovir Combination

PURPOSE

In chronic hepatitis B patients, lamivudine (LAM) and adefovir (ADV) combination therapy is commonly used as a rescue therapy for LAM resistance, but it often results in incomplete viral suppression. We investigated the antiviral efficacy of tenofovir (TDF)/LAM combination therapy versus TDF monotherapy in LAM-resistant chronic hepatitis B (CHB) patients who failed to respond to LAM plus ADV rescue therapy.

METHODS

Among 108 patients with LAM-resistant CHB who had a partial virologic response (VR) to LAM and ADV combination therapy, Eighty one patients were finally included in this study.

FINDINGS

Resistance to ADV (ADV-R) was present in 32 patients (39.5%), and the remaining 49 patients (60.5%) had a partial virologic response to LAM/ADV combination (ADV-P). The study subjects were treated with TDF alone (n=15) or TDF/LAM combination (n=66). VR was achieved in 61 patients (75.3%). The rates of VR at 6 and 12 months were not significantly different between TDF monotherapy and TDF/LAM combination therapy groups (46.7 vs. 68.2% at 6 months, and 66.7 vs. 75.9% at 12 months, log-rank P=0.357). Treatment efficacy of TDF alone or TDF/LAM combination was not statistically different according to pre-existing ADV or LAM resistant strains. In multivariate analysis, absolute HBV DNA levels at the start of TDF rescue treatment (P<0.001; OR, 0.556; 95% CI, 0.422-0.731) were the only significantly associated with VR.

IMPLICATIONS

TDF monotherapy was as effective as TDF/LAM combination therapy in maintaining viral suppression in patients with LAM-resistant patients who failed to respond to LAM/ADV combination therapy.

Tenofovir-based rescue therapy in chronic hepatitis B patients with suboptimal responses to adefovir with prior lamivudine resistance

We evaluated the efficacy of tenofovir (TDF)-based rescue therapy and compared the outcomes of TDF monotherapy and TDF-based nucleoside analog (NA) combination therapy in patients with suboptimal response (SOR) to adefovir (ADV) with or without NAs in lamivudine (LAM)-resistant chronic hepatitis B. All study subjects received ADV with or without NAs due to prior LAM resistance, and were then switched to TDF-based rescue therapy due to SOR (hepatitis B virus DNA >20 IU/ml after at least 6 months of therapy). A total of 125 patients were eligible. The overall cumulative proportion of complete virologic response (CVR) was 64 of 74 patients (86.5%) at 48 weeks of treatment. During the follow-up period of 48 weeks, there was no significant difference in CVR rate (P = 0.750) between the TDF monotherapy (n = 18) and the TDF with NA groups (n = 107). Patients with ADV genotypic mutations showed inferior antiviral responses to TDF compared with the patients without ADV genotypic mutations, but this was not statistically significant (P = 0.069). Partial virological response to prior ADV therapy showed higher CVR rates compared to patients with non-response at 12 weeks (P = 0.013), but there was no significant difference after 24 (P = 0.076) and 48 weeks (P = 0.198) of treatment. TDF monotherapy is as effective as TDF plus NA combination therapy in patients with SOR to ADV-based rescue therapy and LAM resistance. TDF, with or without NAs, was effective even in cases of ADV resistance.

Tenofovir rescue regimen following prior suboptimal response to entecavir and adefovir combination therapy in chronic hepatitis B patients exposed to multiple treatment failures

In clinical practice, establishing a subsequent optimum treatment for chronic hepatitis B patients with a history of multiple NAs treatment failures, including a suboptimal response to a final therapy with combined ETV and ADV, is a complicated but crucial challenge. This study investigated the efficacy and safety of a tenofovir rescue regimen in these patients. A total of six eligible patients were enrolled and were switched to a tenofovir rescue regimen. At baseline, the genotypes and genotypic mutations of the reverse transcriptase and surface gene were determined by ultra-deep pyrosequencing, and further clonal analyses of the reverse transcriptase domain were performed to identify multidrug-resistant HBV strains. In addition, HBV DNA levels, serology, and biochemistry parameters were monitored at baseline and every 3 months, and abdominal ultrasonography was performed at baseline and every 6 months. All patients were confirmed to harbor LAM-related resistant HBV strains. After switching to the tenofovir rescue treatment, all patients had an undetectable level of HBV DNA within 6 months and achieved normalization of the ALT level within 9 months. These virological and biochemical responses persisted until the end of the observation period. None of the patients developed clinical deterioration or any adverse events related to the tenofovir therapy during the median 16.5-month follow-up. In conclusion, the tenofovir rescue regimen can be employed confidently as a highly effective and safe treatment choice following a suboptimal response to ETV plus ADV therapy for a subset of chronic hepatitis B patients with a history of multiple unsuccessful antiviral treatments.

Tenofovir disoproxil fumarate vs adefovir dipivoxil in Chinese patients with chronic hepatitis B after 48 weeks: a randomized controlled trial

Tenofovir disoproxil fumarate (TDF) has demonstrated long-term efficacy and a high barrier to resistance in multiple chronic hepatitis B (CHB) populations outside of China. This study aimed to evaluate the efficacy and safety of TDF compared with adefovir dipivoxil (ADV) in Chinese patients with CHB during 48 weeks of treatment (ClinicalTrial.gov number, NCT01300234). A Phase 3, multicentred, randomized, double-blind, controlled trial compared the efficacy and safety of TDF with ADV in Chinese patients with CHB. The primary endpoint was the proportion of patients with HBV DNA <400 copies/mL in each treatment group at Week 48, using an unpooled Z-test for superiority. Secondary endpoints included viral suppression, serologic response, histological improvement, normalization of alanine aminotransferase (ALT) levels and the emergence of resistance mutations. A total of 509 patients, 202 hepatitis B e antigen (HBeAg)-positive and 307 HBeAg-negative, with HBV DNA ≥10(5) copies/mL received either TDF 300 mg od or ADV 10 mg od. At Week 48, TDF demonstrated superior viral suppression compared with ADV in both HBeAg-positive (76.7% vs 18.2%, P < 0.0001) and HBeAg-negative (96.8% vs 71.2%, P < 0.0001) patients. The majority of patients in both treatment arms achieved ALT normalization (>85%). No resistance to TDF was observed. The frequency of adverse events was comparable between treatment arms (TDF 3.9% vs ADV 4.8%). In this double-blind, randomized, clinical trial, TDF demonstrated superiority over ADV with respect to viral suppression in Chinese patients with CHB at 48 weeks of treatment and without the development of resistance.

Long-term efficacy of tenofovir disoproxil fumarate therapy after multiple nucleos(t)ide analogue failure in chronic hepatitis B patients

BACKGROUND/AIMS

The efficacy of tenofovir disoproxil fumarate (TDF) for the treatment of chronic hepatitis B (CHB) patients following prior treatment failure with multiple nucleos(t)ide analogues (NAs) is not well defined, especially in Asian populations. In this study we investigated the efficacy and safety of TDF rescue therapy in CHB patients after multiple NA treatment failure.

METHODS

The study retrospectively analyzed 52 CHB patients who experienced failure with two or more NAs and who were switched to regimens containing TDF. The efficacy and safety assessments included hepatitis B virus (HBV) DNA undetectability, hepatitis B envelop antigen (HBeAg) seroclearance, alanine transaminase (ALT) normalization and changes in serum creatinine and phosphorus levels.

RESULTS

The mean HBV DNA level at baseline was 5.4 ± 1.76 log10 IU/mL. At a median duration of 34.5 months of TDF treatment, the cumulative probabilities of achieving complete virological response (CVR) were 25.0%, 51.8%, 74.2%, and 96.7% at 6, 12, 24, and 48 months, respectively. HBeAg seroclearance occurred in seven of 48 patients (14.6%). ALT levels were normalized in 27 of 31 patients (87.1%) with elevated ALT at baseline. Lower levels of HBV DNA at baseline were significantly associated with increased CVR rates (p < 0.001). However, CVR rates did not differ between TDF monotherapy or combination therapy with other NAs, and were not affected by mutations associated with resistance to NAs. No significant adverse events were observed.

CONCLUSIONS

TDF is an efficient and safe rescue therapy for CHB patients after treatment failure with multiple NAs.

Safety and efficacy of entecavir in adefovir-experienced patients

BACKGROUND AND AIM

Suboptimal viral suppression with adefovir (ADV) poses a challenge in managing chronic hepatitis B. Few studies have evaluated the efficacy of entecavir (ETV) in ADV-experienced patients. Our aim is to assess treatment effectiveness of ETV in ADV-experienced patients.

METHODS

ADV-experienced patients switched to ETV were enrolled from six US clinics. Patients completed a median of 24 months of ETV after switch. Patients were categorized into partial responders (detectable HBV-DNA at switch) or complete responders (undetectable HBV-DNA at switch) to ADV. Primary and secondary outcome measurements were complete viral suppression (CVS, HBV-DNA < 60 IU/mL) and biochemical response (BR, alanine aminotransferase [ALT] < 40 U/L), respectively.

RESULTS

A total of 120 patients were included in the analysis (80 ADV partial responders; 40 ADV complete responders). In partial responders, CVS rate was 84% after 24 months of ETV. BR rate was 58% at switch to ETV and increased to 90% after 24 months. All complete responders continued to experience CVS after switch. On multivariate analysis inclusive of age, male gender, ALT level at switch, and history of lamivudine (LAM) exposure, we identified positive, hepatitis B e antigen status before ADV and higher HBV-DNA level at time of switch as significant independent negative predictors of CVS. In eight patients with ADV resistance, seven achieved CVS after 24 months of ETV, and all achieved BR.

CONCLUSION

In ADV-experienced patients, high rates of CVS and BR can be achieved/sustained after switching to ETV, including those with ADV resistance or with prior exposure to LAM.

Different mechanism of selection of adefovir-resistant mutant viruses during adefovir monotherapy in patients with lamivudine-resistant chronic hepatitis B

BACKGROUND

Adefovir (ADV) resistance is more frequent in lamivudine (LMV)-resistant chronic hepatitis B (CHB) patients than in nucleos(t)ide analogue-naïve patients. The majority of LMV-resistant mutants harbor the rtM204V/I mutation, while a minor fraction harbor the rtA181V/T mutation. We aimed to elucidate the mechanism of the high rate of ADV resistance in LMV-resistant patients during ADV therapy.

METHODS

We performed a clonal analysis of HBV reverse transcriptase in treatment-naïve (n = 3) and LMV-resistant patients before ADV therapy (n = 14). Dynamic changes in the viral population (n = 9) during ADV therapy were also analyzed.

RESULTS

Before ADV therapy, rtA181V/T was observed in 30 of 680 clones (4.4%) from 7 patients with LMV resistance under dominant rt204V/I mutation and in one of 150 clones in treatment-naïve patients. The rtA181V/T mutation was more frequently found in clones from LMV-resistant patients than in treatment-naïve patients (p = 0.029). The rtN236T mutation was not observed in any clone. During ADV therapy, most rtM204V/I mutants were replaced by wild type in all 3 patients without the rtA181V/T mutation and in one patient with the rtA181V/T mutation. Subsequently, wild type was replaced by the rtN236T and/or rtA181V/T mutant. In patients with the rtA181V/T mutation (n = 6), the rtA181V/T mutant overtook the rtM204V/I mutant in 3 of 4 patients with ADV resistance. In 2 patients without ADV resistance, most of the viral population was replaced by wild type by the last follow-up.

CONCLUSION

The high rate of ADV resistance in patients with LMV-resistance might be attributable to preexisting rtA181V/T mutant virus.

Screening and identification of a novel adefovir dipivoxil resistance associated mutation, rtN236V, of HBV from a large cohort of HBV-infected patients

BACKGROUND

The study aimed to clarify whether rtN236V mutation of HBV derived from adefovir dipivoxil (ADV)-refractory patients was associated with drug resistance.

METHODS

A total of 18,419 patients from Beijing 302 Hospital were investigated. HBV complete reverse transcriptase region of polymerase was screened by direct sequencing and verified by clonal sequencing if necessary. Replication-competent wild-type and mutant HBV genomic amplicons were constructed, transfected into HepG2 cells and cultured in the presence or absence of serially diluted nucleoside/nucleotide analogues. Intracellular HBV replicative intermediates were quantitated for calculating the 50% effective concentration of drug.

RESULTS

rtN236V was detected in six ADV-refractory patients; signature ADV-resistant mutations rtA181V and rtN236T were detected in 1,311 patients. rtN236V mutants emerged predominantly with virological breakthrough in the clinical course of the six patients. Phenotypic analysis of the mutants from two patients was performed. rtN236V mutants from patient 1 and patient 2 exhibited 3.90-fold and 3.10-fold decreased susceptibility to ADV, respectively, compared to the wild-type virus; by contrast, rtN236T mutants from the patients had 4.50-fold and 4.75-fold decreased susceptibility, respectively. Both mutants had a relatively lower viral replication capacity compared to wild-type virus in the absence of antivirals and remained susceptible to lamivudine, entecavir and tenofovir disoproxil fumarate. In clinical practice, switching to entecavir rescue therapy suppressed HBV DNA to an undetectable level and normalized alanine aminotransferase level for both patients.

CONCLUSIONS

rtN236V was a novel infrequently occurring ADV-resistance-associated mutation. It conferred a moderate resistance to ADV with relatively lower natural replication capacity.

Efficacy of tenofovir in adefovir-experienced patients compared with treatment-naive patients with chronic hepatitis B

BACKGROUND

Tenofovir (TDF) has similar antiviral efficacy in both treatment-naive and lamivudine-resistant chronic hepatitis B (CHB) patients. Data on TDF use in patients with adefovir (ADV) resistance is inconsistent. The aim of our study was to assess antiviral efficacy of TDF against nucleoside analogue-naive (NN) and ADV-resistant (ADV-R) CHB and suboptimal responders to ADV (ADV-S).

METHODS

A database of 135 CHB patients treated with TDF was analysed. A total of 37 patients with incomplete data were excluded and analysis was performed in 98 (44 NN, 30 ADV-R and 24 ADV-S). Patients with primary ADV-R mutations had either A181T/V or N236T mutations or both. HBV DNA was measured at 3-month intervals until month 24. Primary outcome measures were comparison of the decline of HBV DNA between the three treatment groups.

RESULTS

NN patients had higher baseline HBV DNA compared with ADV-R and ADV-S patients (6.08 log10 IU/ml versus 5.53 and 4.88, respectively; P=0.002). By exponential regression analysis, HBV DNA decline kinetics differed between the three groups. HBV DNA decline was faster in NN patients compared to ADV-R and ADV-S CHB patients (P=0.002 and P=0.004, respectively). Undetectable HBV DNA was achieved in 77.2%, 60% and 75% of NN, ADV-R and ADV-S CHB patients, respectively, at month 12 (P= not significant).

CONCLUSIONS

HBV DNA decline is slower in ADV-experienced patients compared with treatment-naive patients. The clinical significance of this slow response may be important in patients with critical liver reserve and high viral load. Optimal combination treatment (TDF+ entecavir) could be considered in these patients.

Entecavir plus adefovir combination treatment for chronic hepatitis B patients after failure of nucleoside/nucleotide analogues

BACKGROUND

The combination of entecavir, a nucleoside analogue, and adefovir, a nucleotide analogue, would be a promising salvage treatment for chronic hepatitis B (CHB) patients who fail nucleoside/nucleotide analogue (NA) regimens.

METHODS

A total of 89 CHB patients who had failed NA regimens and were treated with entecavir plus adefovir combination for at least 12 months were included.

RESULTS

Mean baseline HBV DNA of patients was 6.16 ±1.44 log(10) IU/ml. Patients were classed by the number of previously failed NAs; 1 NA (lamivudine; n=15; Group 1), 2 NAs (lamivudine and either adefovir or entecavir; n=39; Group 2) and 3 NAs (lamivudine, adefovir and entecavir; n=35; Group 3). After 12 months of treatment, the mean reduction in HBV DNA was greater in Group 1 than in Group 2 or 3 (-5.81 ±1.71, -3.20 ±1.36 and -2.93 ±1.56 log(10) IU/ml, respectively; P<0.01). The rates of virological response (HBV DNA<2,000 IU/ml) were 100%, 79.5% and 34.3% (P<0.01), and the rates of complete virological response (HBV DNA<60 IU/ml) were 53.3%, 25.6% and 14.3% in Group 1, 2 and 3, respectively (P<0.01) at 12 months. Higher baseline HBV DNA (odds ratio =0.59; P=0.02) and increasing number of previously failed NAs (P<0.01) were independently associated with a lower rate of complete virological response at 12 months.

CONCLUSIONS

Entecavir plus adefovir combination treatment was effective in achieving virological response in CHB patients after failure of NAs. However, its effect progressively decreased as the number of previously failed NAs increased.

Evolution of adefovir-resistant HBV polymerase gene variants after switching to tenofovir disoproxil fumarate monotherapy

BACKGROUND

Tenofovir disoproxil fumarate (TDF), an acyclic nucleotide analogue was shown to be effective in many HBV-infected patients with resistance to adefovir dipivoxil (ADV). This observation is intriguing because in vitro studies show that HBV mutations selected by ADV confer cross-resistance to TDF. To assess the clinical relevance of this cross-resistance, we studied the evolution of HBV polymerase gene variants in patients with genotypic resistance against ADV (rtN236T and/or rtA181V/T) during TDF treatment.

METHODS

In 10 HBV-monoinfected patients (9 male, mean age 47 ±11 [range 27-67] years, 6 hepatitis B e antigen-positive) with virological breakthrough during ADV treatment associated with the mutations rtN236T and/or rtA181T/V, HBV polymerase gene variants were studied during up to 24 months of consecutive monotherapy with TDF by population sequencing, line probe assay and clonal analysis.

RESULTS

In all patients, switching to TDF resulted in a continuous reduction of HBV DNA from a median of 7.6 (4.6-9.4) log(10) copies/ml to 3.3 (2-5) log(10) copies/ml, remaining in 7 patients >400 copies/ml at 12 months. ADV-resistance mutations remained detectable throughout the whole observation period in most patients. Apart from an M204Q mutation in one sample, no new HBV polymerase gene mutations were found. In two patients with low level viraemia after 72 weeks of TDF, adding lamivudine led to a complete response within a few weeks.

CONCLUSIONS

ADV-resistant HBV variants may further become selected during TDF treatment, however they cause only a mild decrease in TDF susceptibility.

Treatment response and evolution of HBV resistance during lamivudine plus adefovir or entecavir therapy in patients with adefovir-resistant mutants

BACKGROUND

Here, we investigated the treatment response and evolution of HBV resistance during lamivudine (LAM) plus adefovir (ADV) and entecavir (ETV) monotherapy in patients with ADV-resistant mutants.

METHODS

Of the 53 patients with ADV-resistant mutants, 25 received combined LAM plus ADV therapy (LAM+ADV group) and 28 received ETV monotherapy (ETV group) for at least 12 months (median 24 months and range 12-67 months).

RESULTS

During 24 months therapy, no significant difference was noted in HBV DNA reduction from baseline, HBV DNA<200 copies/ml, hepatitis B e antigen loss and ALT normalization between the two groups. In the LAM+ADV group, patients with single rtN236T resistant mutation had higher rates of undetectable HBV DNA than those with the double mutant rtA181T/V+rtN236T at months 3-18 of therapy. No virological breakthrough occurred except for one patient with rtN236T resistant mutation who experienced virological and biochemical breakthrough after the emergence of an additional rtA181T mutant under LAM+ADV therapy. Of the 28 patients receiving ETV monotherapy, ETV-resistant mutants developed in 8. The cumulative rates of ETV-resistant mutations and virological breakthrough at months 12, 24 and 36 were 3.6%, 25.7% and 46.8%, respectively. ADV-resistant mutations were rapidly replaced by LAM-resistant mutations (median 12 months) followed by ETV-resistant mutations.

CONCLUSIONS

There was no significant difference in virological response between the LAM+ADV and ETV groups in patients with ADV-resistant mutants. LAM+ADV were less effective in patients with the double mutant rtA181T/V+rtN236T than the single rtN236T mutation. The incidence of ETV-resistant mutation was high in patients with LAM/ADV-resistant mutants treated with ETV monotherapy.

Evolution of hepatitis B virus mutation during entecavir rescue therapy in patients with antiviral resistance to lamivudine and adefovir

BACKGROUND

The efficacy of entecavir (ETV) monotherapy in treatment-experienced patients with chronic hepatitis B (CHB) is debatable.

METHODS

A total of 22 hepatitis B e antigen (HBeAg)-positive CHB patients who had shown viral breakthrough or suboptimal response with lamivudine (3TC) and adefovir disoproxil (ADV) therapy were treated with 1.0 mg of ETV. Clinical and virological parameters were monitored every 3 months. Restriction fragment mass polymorphism assays were used to detect antiviral resistance.

RESULTS

During 3TC and ADV therapy, 11 patients had rtM204V/I mutations, 2 had rtA181V/T or rtN236T, 7 had both and 2 had no 3TC- or ADV-related mutations. After switching to ETV monotherapy, the median change in serum hepatitis B virus (HBV) DNA level was -2.1 log(10) copies/ml. Virological response (HBV DNA<300 copies/ml) was achieved in 1 of 18 patients with pre-existing rt204 mutations, whereas it was achieved in all 4 patients without pre-existing rt204 mutations regardless of the presence of rt181 or rt236 mutations. Changes in mutational patterns during ETV therapy showed that rt204 mutations persisted or re-emerged. Relative abundances of rtM204V/I mutations in total viral populations gradually increased under ETV rescue, whereas those with rtA181V/T and rtN236T mutations decreased. ETV resistance mutations (rtL180M+rtT184I/L[rtS202G]+rtM204V) were detected in five patients with pre-existing rt204 mutations.

CONCLUSIONS

ETV monotherapy resulted in a limited virological response in patients who had previously failed 3TC and ADV rescue therapy. The limited efficacy might be associated with residual or reselected rtM204V/I mutations leading to ETV resistance. Combination treatment including potent antiviral agents should be recommended for patients with pre-existing rtM204V/I mutations.

Anti-hepatitis B virus activity in vitro of combinations of tenofovir with nucleoside/nucleotide analogues

BACKGROUND

Long-term management of some chronic hepatitis B patients might require combination therapy using drugs with distinct resistance profiles to sustain viral suppression and to reduce the resistance-associated failure. Tenofovir disoproxil fumarate (TDF), approved for hepatitis B virus (HBV) and HIV-1 treatment, is active against wildtype HBV and HBV containing YMDD mutations, which confer resistance to emtricitabine (FTC), lamivudine (3TC) and telbivudine (LdT) and contribute to entecavir (ETV) resistance. We therefore evaluated the in vitro anti-HBV activity of tenofovir (TFV), the active parent drug of TDF, combined with FTC, 3TC, ETV, LdT and adefovir (AFV).

METHODS

The anti-HBV activities of the compounds were tested using the AD38 cell line that expresses wild-type HBV from a tetracycline-controllable promoter. Intracellular HBV DNA levels were quantified using real-time PCR assay and cytotoxicities were assessed with XTT assays. The antiviral data of the drug combinations were evaluated using MacSynergy analyses on the basis of the Bliss independence model as well as isobologram analyses on the basis of the Loewe additivity theory.

RESULTS

All drug combinations tested, FTC+TFV, 3TC+TFV, ETV+TFV, LdT+TFV and AFV+TFV, showed additive antiviral interactions as analysed by MacSynergy. Isobologram analyses revealed that these combination pairs were additive, with the exception of FTC+TFV, which demonstrated slight synergistic activity. No cytotoxic or antagonistic effects were observed with any of the combinations tested.

CONCLUSIONS

The combination of TFV with FTC, 3TC, ETV, LdT or AFV had additive to slightly synergistic anti-HBV effects in vitro. These results support the use of TDF as a component in combination regimens with currently available anti-HBV nucleoside analogues.