Hepatitis B virus wild-type and rtN236T populations show similar early HBV DNA decline in adefovir refractory patients on a tenofovir-based regimen

Hepatitis B virus mutation pattern rtA181S+T184I+M204I may contribute to multidrug resistance in clinical practice: Analysis of a large cohort of Chinese patients

The study aimed to characterize the prevalence and virological features of the rtA181S + T184I + M204I mutant in a large cohort of patients with chronic HBV infection. In total, 22,009 nucleoside/nucleotide analog-treated patients who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital between 2007 and 2016 were enrolled. Serum samples were collected for HBV reverse-transcriptase gene sequencing. Phenotypic analysis of the viral replication capacity and drug susceptibility was performed. The rtA181S mutation was detected in 0.82% (180/22,009) of samples. rtA181S-positive patients had significantly higher lamivudine (LAM), adefovir (ADV), and entecavir (ETV) exposure than rtA181S-negative patients. Of 180 rtA181S-positive patients, 42 had no coexistent resistance mutations, 34 had coexisting LAM-resistance mutation (LAMr), 17 had coexisting ADV-resistance mutation (ADVr), and 86 had coexisting ETV-resistance mutation (ETVr), and one had ADVr + ETVr. rtA181S + T184I + M204I occurred in 79.1% (68/86) of patients with rtA181S + ETVr and 37.8% (68/180) of all rtA181S-positive patients. Longitudinal analysis of the clinical course of resistant mutant evolution for four representative cases showed that rtA181S + T184I + M204I developed in all patients who had received LAM/telbivudine ± ADV and was receiving ETV or ADV + ETV. Compared with wild-type, the rtA181S + T184I + M204I mutant had 53.7% lower replication capacity and >1000-, 3.9-, and 383.3-fold greater LAM, ADV, and ETV resistance, respectively, but remained sensitive to tenofovir. Artificial elimination of rtA181S from the rtA181S + T184I + M204I mutant restored viral susceptibility to ADV but decreased viral replication capacity. Our study presented the first evidence that HBV rtA181S + T184I + M204I mutation had features of multidrug-resistance that contributed to resistance to both nucleoside and nucleotide analogs.

Investigation of hepatitis B virus (HBV) rtS78T/sC69* mutation in a large cohort of chronic HBV-infected patients with nucleoside/nucleotide analogue treatment

This study aimed to investigate clinical occurrence and significance of the rtS78T/sC69* mutation of hepatitis B virus (HBV). A total of 22,009 consecutive chronic HBV-infected patients who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital (Original name Beijing 302 Hospital) from 2007 to 2016 were enrolled. Serum samples were collected for sequence analysis of HBV reverse-transcriptase (RT) and S regions. Phenotypic analysis was performed to evaluate the viral replication capacity and drug susceptibility. The rtS78T mutation was detected in 0.83% (182/22,009) of the patients' samples. All mutations simultaneously created a stop codon at sC69 (sC69*). The prevalence of rtS78T/sC69* did not differ significantly between the patients with and without entecavir/tenofovir treatment. Of the 182 mutation-positive samples, 41 (22.5%) were detected with signature drug-resistance mutations to adefovir (n = 26), lamivudine (n = 11), entecavir (n = 3), and lamivudine plus adefovir (n = 1). The HBV DNA and RNA levels of the rtS78T/sC69* mutant were significantly increased compared to the wild-type; while the mutant had undetectable secreted and intracellular HBsAg, and its half maximal effective concentration to lamivudine, adefovir, entecavir, and tenofovir were 3.73-, 1.61-, 4.76-, and 3.71-fold of the wild-type, respectively. Artificial elimination of the rtS78T mutation had a limited effect on the drug susceptibilities. The data obtained in the present study suggested that the emergence of the rtS78T/sC69* mutation was not closely related to entecavir/tenofovir treatment and itself appeared insufficient to confer drug resistance unless it coexisted with signature drug-resistance mutations.

Hepatitis B virus mutation pattern rtL180M+A181C+M204V may contribute to entecavir resistance in clinical practice

Background and Aims: Entecavir (ETV) resistance of hepatitis B virus (HBV) conventionally requires rt184, 202, or 250 mutations plus lamivudine-resistance mutation (rtM204V/I ± L180M). This study aimed to clarify whether rtL180M+A181C+M204V mutations may contribute to HBV ETV resistance.

Methods: Serum samples were collected from 22,009 patients who underwent resistance testing in Beijing 302 Hospital from 2007 to 2016. HBV reverse transcriptase (RT) gene was screened by direct sequencing and verified by clonal sequencing. Phenotypic analysis was performed for evaluating replication capacity and drug susceptibility.

Results: Classical ETV-resistance mutations of HBV were detected in 1252 patients who were receiving ETV therapy. The rtA181C mutation was detected with rtL180M+M204V mutations in 18 lamivudine-experienced ETV-treated patients, and the emergence of the mutations was associated with virological breakthrough or inadequate virological response to ETV. Patient-derived representative rtA181C-containing mutants, rtL180M+A181C+M204V, rtL180M+A181C+M204V+M250V, and rtL180M+A181C+S202G+M204V, exhibited 45.7%, 25.9%, and 25.0% replication capacity and 85.6-, 356.1-, and 307.1-fold decreased susceptibility to ETV respectively compared to the wild-type strain, while the three mutants remained sensitive to tenofovir (TDF). Artificial elimination of rtA181C largely restored the rtL180M+A181C+M204V mutant’s sensitivity to ETV. Molecular modelling of viral RT binding to ETV showed that the rtL180M+A181C+M204V mutant had a less stable conformation compared to rtL180M+M204V mutant. In clinical practice, undetectable serum HBV DNA was achieved in two of five longitudinally followed rtA181C-positive patients who received switching-to TDF therapy, but not in the other three who received add-on adefovir therapy during observation.

Conclusions: Both clinical and experimental data support rtL180M+A181C+M204V as a novel non-classical ETV-resistance mutation pattern.

Prevalence of the entecavir-resistance-inducing mutation rtA186T in a large cohort of Chinese hepatitis B virus patients

This study aimed to clarify whether rtA186T and rtI163V substitutions of hepatitis B virus (HBV) contributed to entecavir (ETV) resistance. A total of 22,009 Chinese patients with chronic HBV infection who received resistance testing at Beijing 302 Hospital from 2007 to 2016 were enrolled. Among them, 6170 patients had been treated with ETV. The HBV reverse transcriptase gene was screened by direct sequencing and verified by clonal sequencing. Phenotypic analysis was performed for evaluating replication capacity and drug susceptibility. Classical ETV-resistance mutations rtT184/S202/M250substitution+rtM204V/I±L180M (LAM-r), rtA186T, and rtI163V were detected in 1252 (5.69%), 14 (0.06%), and 230 (1.05%) of the 22,009 patients, respectively. The rtA186T mutation always coexisted with LAM-r, but not with rtI163V. The 14 rtA186T-positive patients were all treated with LAM and ETV, and the emergence of the rtA186T+LAM-r was closely associated with virological breakthrough or inadequate virological response to ETV. By contrast, the emergence of rtI163V was not related to ETV treatment. Six rtA186T-positive patients were followed up longitudinally, showing that these patients all had received sequential adefovir and LAM monotherapies prior to ETV treatment. Compared to wild-type strain, two patient-derived mutants' rtL180M+A186T+M204V and rtL180M+T184S+A186T+M204V had 86.7% and 89.2% decreased replication capacity, 210- and 555-fold increased ETV resistance, respectively; and artificial elimination of rtA186T largely restored their ETV sensitivity. The rtA186T mutants remained sensitive to tenofovir. In conclusion, our study confirmed that rtA186T plus LAM-r is a novel ETV-resistance mutation pattern which conferred ETV resistance in multiple Chinese patients.

Efficacy of tenofovir disoproxil fumarate switch therapy in chronic hepatitis B patients with suboptimal response to adefovir-based combination therapy

In the present study, the efficacy and safety of tenofovir disoproxil fumarate (TDF) switch therapy were assessed in patients with chronic hepatitis B exhibiting a suboptimal response to adefovir (ADV)-based combination therapy. First, the efficacy of the TDF switch therapy was retrospectively evaluated in 50 patients with chronic hepatitis B who failed to respond to ADV-based combination treatment. Among those, 48 patients with a median age of 35 years were hepatitis B e antigen (HBeAg)-positive and 17, 14 and 19 patients were previously treated with lamivudine (LAM) plus ADV, telbivudine plus ADV and entecavir (ETV) plus ADV, respectively. A total of 41 patients were treated with TDF alone and 9 with TDF plus ETV. The median time of follow-up was 102 weeks. The primary end-point was the cumulative probability of achieving a complete virologic response (CVR). The secondary end-points were the rate of alanine aminotransferase (ALT) normalization, HBeAg seroconversion in HBeAg-positive patients, and the plasma levels of creatinine and creatine kinase. The mean serum hepatitis B virus DNA levels prior to initiation of the TDF switch therapy were 4.8±1.6 log₁₀IU/ml. The cumulative probability of achieving a VR at 24, 48, 96 and 108 weeks was 52.0, 76.0, 89.8 and 94.9%, respectively. The cumulative probability of normalization of ALT at 12, 24, 36, 48, 60,72, 84, 96, 108, 120 and 132 weeks was 34, 44, 50, 58, 66, 70, 74, 80, 90, 92 and 94%, respectively. HBeAg seroconversion was achieved in 5 patients. During the follow-up, 6 patients suffered from a virologic breakthrough, 3 patients failed to respond to the TDF treatment and the remaining patients were able to obtain VR following the continuation of TDF treatment. Slightly elevated serum levels of creatinine were observed in one patient, whereas creatine kinase activity did not increase in any of the subjects. In conclusion, TDF switch therapy is efficient and safe for patients with chronic hepatitis B with a suboptimal response to ADV-based combination therapy.

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.

Prevalence of hepatitis B antiviral drug resistance variants in North American patients with chronic hepatitis B not receiving antiviral treatment

Antiviral drug resistance hepatitis B virus (HBV) variants (HBV-DR) occur spontaneously in chronic hepatitis B (CHB) patients and after exposure to nucleos(t)ide analogues (NUCs). We determined the prevalence of HBV-DR variants among participants of the Hepatitis B Research Network (HBRN) Cohort Study conducted at 21 sites in the United States (US) and Canada. Samples obtained from 1342 CHB participants aged ≥18 years, and who were currently not receiving NUCs, were tested for HBV-DR variants by Sanger sequencing. In addition, next generation sequencing (NGS) was used to characterize HBV-DR variants from 66 participants with and 66 participants with no prior NUC exposure matched for HBV genotype and HBV DNA level. Half the participants were men, 75% Asian, 26% HBeAg positive. Primary HBV-DR variants were detected by Sanger sequencing in 16 (1.2%) participants: 2/142 (1.4%) with and 14/1200 (1.2%) without prior NUC exposure; only 1 of these 16 had a secondary variant. In total, 23 (1.7%) participants had secondary variants, including 1 with prior NUC experience. In the subset of 132 participants, NGS detected HBV-DR variants in a higher proportion of participants: primary variants in 18 (13.6%) (8 [12.1%] with, and 10 [15.2%] without prior NUC therapy) and secondary variants in 10 (7.6%) participants. Based on Sanger sequencing, prevalence of primary HBV-DR variants is low (1.2%) among adults with CHB in US/Canada. The similar low prevalence of HBV-DR variants in participants with and without NUC treatment suggests transmission of these variants is uncommon.

Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update

Worldwide, some 240 million people have chronic hepatitis B virus (HBV), with the highest rates of infection in Africa and Asia. Our understanding of the natural history of HBV infection and the potential for therapy of the resultant disease is continuously improving. New data have become available since the previous APASL guidelines for management of HBV infection were published in 2012. The objective of this manuscript is to update the recommendations for the optimal management of chronic HBV infection. The 2015 guidelines were developed by a panel of Asian experts chosen by the APASL. The clinical practice guidelines are based on evidence from existing publications or, if evidence was unavailable, on the experts' personal experience and opinion after deliberations. Manuscripts and abstracts of important meetings published through January 2015 have been evaluated. This guideline covers the full spectrum of care of patients infected with hepatitis B, including new terminology, natural history, screening, vaccination, counseling, diagnosis, assessment of the stage of liver disease, the indications, timing, choice and duration of single or combination of antiviral drugs, screening for HCC, management in special situations like childhood, pregnancy, coinfections, renal impairment and pre- and post-liver transplant, and policy guidelines. However, areas of uncertainty still exist, and clinicians, patients, and public health authorities must therefore continue to make choices on the basis of the evolving evidence. The final clinical practice guidelines and recommendations are presented here, along with the relevant background information.

Evaluation of antiviral resistant hepatitis B virus subpopulations in patients with chronic hepatitis B by using terminal restriction fragment length polymorphism

Antiviral therapies with nucleotide analogues (NA) is crucial in the treatment of chronic hepatitis B as it substantially protects patients from the complications of the disease . However in most of the available NA therapies, resistance emerges in the patients' HBV populations. Therefore, detection of antiviral resistance as early as possible by means of genotypically monitoring the patients' HBV pool during NA therapy is critical to manage treatment regime. In this research study we have investigated the sensitivity and specificity of the terminal restriction fragment length polymorphism (T-RFLP) method in detecting HBV subpopulations carrying antiviral resistance mutations. For this aim, differentiation of mutant strains from wild type strains was demonstrated by PCR-RFLP method. With using recombinant plasmids containing mutant and wild type HBV genomes, we constructed artificial HBV genome populations in order to determine the sensitivity of PCR-T-RFLP method in detecting antiviral resistant minor HBV populations. Finally by comparing with the DNA sequencing method, we demonstrated the specificity of T-RFLP method in genotyping HBV populations. As a result we showed that T-RFLP is able to detect HBV subpopulations representing as low as 1 % of the whole viral population. Additionally T-RFLP showed 100 % concordance with the DNA sequencing method in genotyping HBV populations. As a conclusion, considering the other genotyping methods used in evaluating HBV populations, T-RFLP showed high sensitivity and specificity profiles in detecting antiviral resistant HBV subpopulations. Therefore T-RFLP method can be easily employed in genotypic evaluation of patients' HBV populations during the course of antiviral treatment.

Efficacy of tenofovir disoproxil fumarate therapy in Chinese chronic hepatitis B patients after multiple antiviral failures

AIM

In this prospective study, we aimed to evaluate the efficacy and safety of tenofovir disoproxil fumarate (TDF) in Chinese chronic hepatitis B (CHB) patients after multiple nucleoside/nucleotide analog (NA) treatment failures.

METHODS

A total of 115 Chinese CHB patients with suboptimal response to two or more NA treatments were included in this study. All patients were changed to TDF (300 mg/day, oral administration) antiviral treatment for at least 72 weeks. Hepatitis B virus (HBV) polymerase (P) gene mutation screening for each patient was performed. In addition, virological, biochemical responses and estimated glomerular filtration rate (eGFR) of each patient at weeks 12, 24, 48 and 72 of TDF treatment were evaluated.

RESULTS

Seventy-six out of 115 patients had drug-resistance mutations (R(+) ), including 27 with adefovir (ADV)-associated mutations (35.5%) and 49 with lamivudine (LMV)-associated mutations (64.5%). For all included patients, complete viral response (CVR) of HBV DNA (<100 IU/mL) was 57.4%, 69.6%, 74.8% and 86.1% at weeks 12, 24, 48 and 72 of TDF treatment, respectively. Alanine aminotransferase normalization and hepatitis B e-antigen seroclearance occurred in 77.3% and 23.2%, respectively, after 72-week TDF treatment. CVR at weeks 12, 24 and 48 was observed more commonly in patients with baseline HBV DNA of less than 10(6)  IU/mL. There was no significant reduction of eGFR induced by the TDF treatment.

CONCLUSION

Seventy-two-week treatment with TDF in Chinese CHB patients with previously multiple NA treatment failures exhibited effective and safe outcomes, which were independent of baseline mutations conferring ADV or LMV resistance.

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.

The rtA181S mutation of hepatitis B virus primarily confers resistance to adefovir dipivoxil

The study aimed to clarify clinical significance of hepatitis B virus (HBV) rtA181S mutation in Chinese HBV-infected patients. A total of 18 419 patients with chronic HBV infection from Beijing 302 Hospital were investigated. HBV complete reverse transcriptase region of polymerase was screened by direct sequencing, and the results were verified by clonal sequencing. Replication-competent mutant and wild-type HBV genomic amplicons were constructed and transfected into the HepG2 cells and cultured in the presence or absence of serially diluted nucleos(t)ide analogues. Intracellular HBV replicative intermediates were quantitated for calculating the 50% effective concentration of the drug (EC(50)). The rtA181S was detected in 98 patients with 12 kinds of mutational patterns. Genotype C and genotype B HBV infection occupied 91.8% and 8.2% in rtA181S-positive patients, in contrast to 84.6% and 15.4% in rtA181S-negative patients (P < 0.01). All rtA181S-positive patients had received nucleos(t)ide analogues. rtA181S was detected in multiple patients with virologic breakthrough. Phenotypic analysis of patient-derived viral strains showed that rtA181S, rtA181S+N236T, rtN236T and rtA181V strains had 68.5%, 49.9%, 71.4% and 66.2% of natural replication capacity of wild-type strain, and 3.7-fold, 9.8-fold, 7.9-fold and 5.6-fold increased EC(50) to adefovir dipivoxil (ADV). The rtA181S strain remained susceptible to lamivudine, entecavir and tenofovir, and ADV susceptibility was restored after the mutation was eliminated through site-directed mutagenesis. Rescue therapy with entecavir or combination therapy was effective in rtA181S-related ADV-refractory patients. The rtA181S mutation confers moderate resistance to ADV. It could be induced by either lamivudine or ADV and contribute ADV treatment failure.

Investigation into drug-resistant mutations of HBV from 845 nucleoside/nucleotide analogue-naive Chinese patients with chronic HBV infection

BACKGROUND

This study aimed to clarify the clinical significance of drug-resistant HBV in nucleoside/nucleotide analogue (NA)-naive Chinese patients with chronic HBV infection in real clinical practice.

METHODS

A total of 845 NA-naive patients who were admitted to Beijing 302 Hospital between July 2007 and March 2012 were included in the study. HBV drug-resistant mutations were examined by direct sequencing of the viral reverse transcriptase gene and verified by clonal sequencing. Phenotypic analysis of viral replication capacity and drug susceptibility were performed by measuring viral replicative intermediate level in 1.1-mer mutant or wild-type HBV amplicon-transfected HepG2 cells in absence or presence of serially diluted drugs.

RESULTS

Drug-resistant mutations were detected in 2.01% (17/845) of the patients by direct sequencing, including 15 with lamivudine-resistant mutations (rtM204V, rtM204I), one with adefovir-resistant mutation (rtA181V), and one with both lamivudine- and adefovir-resistant mutations (rtA181V, rtM204I). Clonal sequencing identified 13 drug-resistant HBV strains: rtL80I+M204I, rtL80I+M204V, rtL180M+M204I, rtL180M+M204V, rtM204I, rtM204V, rtL80I+L180M+M204I, rtL80I+L180M+M204V, rtA181V, rtA181V+M204I, rtA181T+N236T, rtA181V+N236T and rtN236T. Phenotypic analysis showed that two pre-existing lamivudine-resistant strains (rtL80I+M204I, rtL180M+M204V) had >1,000-fold resistance to lamivudine, and one pre-existing adefovir-resistant strain (rtA181V+N236T) had 15.4-fold resistance to adefovir compared with the wild-type strain. A follow-up study showed that the presence of pre-existing rtM204I strain in one patient increased from 20% at baseline to 85% after 13 months of entecavir treatment with corresponding recession of wild-type strain in the viral pool.

CONCLUSIONS

The incidence of drug-resistant HBV mutations was low in NA-naive Chinese HBV-infected patients. Pre-existing mutants had similar resistance characteristics to those from NA refractory patients.

Evaluation of HBV DNA decay kinetics in patients containing both rtM204V/I mutant and wild-type HBV subpopulations during tenofovir DF (TDF) monotherapy or combination therapy with emtricitabine (FTC)/TDF

Tenofovir disoproxil fumarate (TDF) is recommended as treatment for chronic hepatitis B patients harboring lamivudine-associated resistance mutations (LAM-R, rtM204V/I ± rtL180M). This study evaluated the clinical response of rtM204V and rtM204I subpopulations to TDF by comparing their early viral load decay kinetics to wild-type (WT) subpopulations in chronic hepatitis B patients harboring rtM204V/I prior to initiating TDF or emtricitabine (FTC)/TDF therapy. Allele-specific PCR assays capable of detecting rtM204V or rtM204I subpopulations as low as 0.5% were developed and used to assess patient samples from a Phase 3b study evaluating TDF and FTC/TDF treatment in LAM-R patients. Baseline samples (n = 280) were quantified for rtM204V/I subpopulations and rtM204V or rtM204I subpopulations were detected in 269/273 (98.5%) baseline samples with a range of 0.7% to >95%. On-treatment analyses were conducted for seventeen patients (TDF, n = 8; FTC/TDF, n = 9) that harbored baseline WT and either rtM204V or rtM204I (no rtM204V/I mixtures) and HBV DNA ≥1,000 copies/ml at/after week 4. The median change in HBV DNA through week 12 for WT and rtM204V/I subpopulations was similar, -2.64 and -3.30 log10  copies/ml, respectively, with no significant difference between TDF and FTC/TDF treatment. In conclusion, rtM204V/I subpopulations demonstrate similar early HBV DNA decline kinetics to WT subpopulations during treatment with either TDF or FTC/TDF. These results demonstrate that TDF is similarly active against both WT and rtM204V/I subpopulations in vivo.

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.

Long-term efficacy and safety of emtricitabine plus tenofovir DF vs. tenofovir DF monotherapy in adefovir-experienced chronic hepatitis B patients

BACKGROUND & AIMS

Suboptimal virologic response to nucleos(t)ide analogs may represent a significant risk factor for resistance development in patients with chronic hepatitis B virus infection; treatment options have not been well studied. We evaluated long-term efficacy and safety of tenofovir alone and in combination with emtricitabine in a prospective, placebo-controlled trial in patients who remained viremic on adefovir therapy.

METHODS

Hepatitis B e antigen-positive and -negative patients with hepatitis B virus DNA ⩾ 1000 copies/ml despite up to 96 weeks of adefovir were randomized to double-blind tenofovir or emtricitabine/tenofovir for 168 weeks. Patients with hepatitis B virus DNA ⩾ 400 copies/ml (⩾ 69IU/ml) at or after week 24 could switch to open-label emtricitabine/tenofovir.

RESULTS

Overall, 90/105 (86%) patients (46/53 tenofovir and 44/52 emtricitabine/tenofovir) completed the 168-week study period, including 74/105 (70%) patients (35/53 tenofovir and 39/52 emtricitabine/tenofovir) who completed the study on their initial randomized treatment. Long-term viral suppression (hepatitis B virus DNA <400 copies/ml) was maintained at week 168 in 84% and 82% of patients receiving either emtricitabine/tenofovir combination or tenofovir monotherapy, respectively (non-completer equal to failure analysis). Baseline viral load as well as the presence of lamivudine and/or adefovir resistance-associated mutations at baseline had no impact on long-term treatment response. No resistance to tenofovir was observed through 168 weeks. Both treatments had a favorable safety profile.

CONCLUSIONS

Tenofovir monotherapy is as effective as emtricitabine/tenofovir combination therapy in maintaining long-term viral suppression in patients with a suboptimal response to adefovir, and is well tolerated in this population.

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.

No detectable resistance to tenofovir disoproxil fumarate after 6 years of therapy in patients with chronic hepatitis B

One major challenge in the treatment of chronic hepatitis B is to maintain long-term viral suppression without promoting the selection of drug-resistant mutations. We analyzed data from 347 hepatitis B e antigen-negative and 238 hepatitis B e antigen positive patients receiving tenofovir disoproxil fumarate (TDF) in an open-label, longterm extension of two phase 3 studies. To date, resistance analyses have been completed for patients receiving up to 288 weeks (6 years) of TDF. Population sequencing of hepatitis B virus (HBV) polymerase/reverse transcriptase (pol/RT) was attempted for all patients at baseline, and any patient who remained viremic (HBV DNA 400 copies/mL [69 IU/mL]) at week 288 or at the end of treatment with TDF (n552) or emtricitabine(FTC)/TDF (n57). Phenotypic analyses were performed in HepG2 cells using recombinant HBV containing patient pol/RT sequences. Approximately half of the patients on open-label treatment who qualified for genotyping had pol/RT sequence changes compared to baseline (23/52 [44%] on TDF, 4/7 [57%] on FTC/TDF). Most changes were at polymorphic sites and none were associated with TDF resistance. Virologic breakthrough occurred infrequently and was associated with nonadherence to study medication in the majority of cases (12/16, 75%). Per protocol, 57 patients (10%)were eligible to switch to FTC/TDF; the majority had HBV DNA <400 copies/mL at their last study visit regardless of whether they switched to FTC/TDF (n534) or maintained TDF monotherapy (n517). No patient exhibited persistent viremia (HBV DNA never <400 copies/mL) after week 240.

CONCLUSION

TDF monotherapy maintains effective suppression of HBV DNA through 288 weeks of treatment with no evidence of TDF resistance.

Similar evolution of hepatitis B virus quasispecies in patients with incomplete adefovir response receiving tenofovir/emtricitabine combination or tenofovir monotherapy

BACKGROUND & AIMS

Adefovir (ADV) resistance mutations induce low-level cross-resistance to tenofovir in vitro. Our aim was to compare viral kinetics, nucleos(t)ide analog resistance mutations, and quasispecies (QS) evolution during therapy with tenofovir disoproxil fumarate (TDF) or emtricitabine + TDF (FTC/TDF) in selected patients with incomplete ADV responses.

METHODS

Patients with chronic hepatitis B and incomplete response to ADV were randomized in a double-blind trial of TDF vs. FTC/TDF. Extensive analysis of QS evolution was performed in 17 patients through 48 weeks of treatment.

RESULTS

At week 24, 48% of patients (9/17) achieved HBV DNA undetectability (<69 IU/ml) with no difference between treatment groups. ADV and/or LAM resistance mutations were detected in all 17 patients at baseline and in 5/6 analyzable patients at week 48. A total of 1224 reverse transcriptase clones were analyzed. Clonal analysis revealed no significant difference at baseline in QS complexity or diversity between treatment groups. There was a trend in both treatment groups for an increase in QS complexity at week 12, followed by a decrease in complexity and diversity by week 48. Analysis of individual patients showed no consistent selection/accumulation of specific viral resistance patterns during treatment, but at week 48, mutations at rtA181 persisted in 4 patients.

CONCLUSIONS

TDF or FTC/TDF demonstrated strong viral suppression in patients with an incomplete response to ADV and no significant selective pressure on pre-existing ADV or LAM resistant strains. TDF monotherapy and FTC/TDF combination therapy had a comparable impact on QS evolution.