Selection of an entecavir-resistant mutant despite prolonged hepatitis B virus DNA suppression, in a chronic hepatitis B patient with preexistent lamivudine resistance: successful rescue therapy with tenofovir

Asociación Mexicana de Hepatología A.C. Clinical guideline on hepatitis B

Hepatitis B virus (HBV) infection continues to be a worldwide public health problem. In Mexico, at least three million adults are estimated to have acquired hepatitis B (total hepatitis B core antibody [anti-HBc]-positive), and of those, 300,000 active carriers (hepatitis B surface antigen [HBsAg]-positive) could require treatment. Because HBV is preventable through vaccination, its universal application should be emphasized. HBV infection is a major risk factor for developing hepatocellular carcinoma. Semi-annual liver ultrasound and serum alpha-fetoprotein testing favor early detection of that cancer and should be carried out in all patients with chronic HBV infection, regardless of the presence of advanced fibrosis or cirrhosis. Currently, nucleoside/nucleotide analogues that have a high barrier to resistance are the first-line therapies.

Asociación Mexicana de Hepatología A.C. Clinical guideline on hepatitis B

Hepatitis B virus (HBV) infection continues to be a worldwide public health problem. In Mexico, at least three million adults are estimated to have acquired hepatitis B (total hepatitis B core antibody [anti-HBc]-positive), and of those, 300,000 active carriers (hepatitis B surface antigen [HBsAg]-positive) could require treatment. Because HBV is preventable through vaccination, its universal application should be emphasized. HBV infection is a major risk factor for developing hepatocellular carcinoma. Semi-annual liver ultrasound and serum alpha-fetoprotein testing favor early detection of that cancer and should be carried out in all patients with chronic HBV infection, regardless of the presence of advanced fibrosis or cirrhosis. Currently, nucleoside/nucleotide analogues that have a high barrier to resistance are the first-line therapies.

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

OBJECTIVE

Little clinical data are available regarding the optimal treatment of patients who harbour entecavir (ETV)-resistant HBV.

DESIGN

In this multicentre randomised trial, patients who had HBV with ETV resistance-associated mutations and serum HBV DNA concentrations >60 IU/mL were randomised to receive tenofovir disoproxil fumarate (TDF, 300 mg/day) monotherapy (n=45) or TDF and ETV (1 mg/day) combination therapy (n=45) for 48 weeks.

RESULTS

Baseline characteristics were comparable between groups, including HBV DNA levels (median, 4.02 log10 IU/mL) and hepatitis B e antigen-positivity (89%). All patients had at least one ETV-resistance mutation: rtT184A/C/F/G/I/L/S (n=49), rtS202G (n=43) and rtM250L/V (n=7), in addition to rtM204V/I (n=90). All except one patient in the TDF group completed 48 weeks of treatment. At week 48, the proportion of patients with HBV DNA <15 IU/mL, the primary efficacy endpoint, was not significantly different between the TDF and TDF+ETV groups (71% vs. 73%; p>0.99). The mean change in HBV DNA levels from baseline was not significantly different between groups (-3.66 vs. -3.74 log10 IU/mL; p=0.81). Virological breakthrough occurred in one patient on TDF, which was attributed to poor drug adherence. At week 48, six and three patients in the TDF and TDF+ETV groups, respectively, retained their baseline resistance mutations (p>0.99). None developed additional resistance mutations. Safety profiles were comparable in the two groups.

CONCLUSIONS

TDF monotherapy for 48 weeks provided a virological response comparable to that of TDF and ETV combination therapy in patients infected with ETV-resistant HBV.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID NCT01639092.

Clinical course of partial virological responders under prolonged entecavir monotherapy in patients with chronic hepatitis B

Studies about long-term entecavir (ETV) therapy for partial virological response (PVR) are lacking. This study aimed to assess the clinical course of PVR patients receiving ETV therapy and analyze the efficacy of tenofovir (TDF). We retrospectively evaluated 130 patients who showed a PVR to ETV. Among these patients, 102 were nucleot(s)ide analogue (NUC)-naïve and 28 were lamivudine (LAM)-experienced. The cumulative rates of VR were 54.1%, 70.8%, and 83.7% for the NUC-naïve group and 37.0%, 42.8%, and 42.8% for the LAM-experienced group after 24, 36, and 48 months of ETV therapy, respectively (P  = 0.008). Low HBV DNA level at 12 months (P < 0.001) and absence of a LAM treatment history (P  = 0.031) were significant associated factors for VR. In VR prediction at 36 months of ETV therapy in NUC-naïve patients, HBV DNA level <95 IU/ml at 12 months showed a 92.9% sensitivity and a 78.3% specificity (AUROC, 0.909; P < 0.001). ETV resistance did not develop in NUC-naïve patients with HBV DNA levels <95 IU/ml at 12 months. The cumulative probability of VR in patients who switched to or additionally received TDF was 91.3% at 15 months. Prolonged ETV therapy induced a VR without the risk of ETV resistance in NUC-naïve patients with HBV DNA levels <95 IU/ml at 12 months. All patients with LAM-experienced or NUC-naïve with HBV DNA levels ≥95 IU/ml at 12 months should be switched to TDF rescue therapy.

Antiviral efficacy of combination therapy with entecavir and adefovir for entecavir/lamivudine-resistant hepatitis B virus with or without adefovir resistance

There is little clinical information on the management of hepatitis B virus (HBV) that is resistant to multiple drugs including entecavir (ETV). The present retrospective cohort study assessed the antiviral efficacy of ETV/adefovir dipivoxil (ADV) combination therapy for ETV-resistant HBV with prior lamivudine (LAM) resistance, and either with or without previous ADV resistance. The cumulative probability of achieving a virological response (undetectable serum HBV DNA) was compared by Kaplan-Meier analysis and the Breslow method. Seventeen patients with ETV-resistant HBV who were treated with ETV/ADV combination therapy for at least 6 months at a tertiary care center, were included; seven had dual resistance to ETV and LAM [ADV-r(-) group] and 10 had triple resistance to ETV, LAM, and ADV [ADV-r(+) group]. The median follow-up period was 9 months (range, 6-23). A virological response was noted in seven patients after a median of 3 months (range, 3-12) of treatment; five in the ADV-r(-) group and two in the ADV-r(+) group. The cumulative probability of a virological response was significantly higher in the ADV-r(-) group than in the ADV-r(+) group (6 months cumulative probability, 57.1% vs. 11.1%). In conclusion, ETV/ADV combination therapy led to virological responses in five of seven patients with resistance to ETV and LAM, but a significantly poorer response in patients with prior ADV resistance than in those without prior ADV resistance. Therefore, ETV/ADV combination therapy could be a useful therapeutic option for ETV- and LAM-resistant HBV without prior ADV resistance.

Efficacy of entecavir and adefovir combination therapy for patients with lamivudine- and entecavir-resistant chronic hepatitis B

BACKGROUND

The optimal treatment of patients with chronic hepatitis B (CHB) who develop resistance to both lamivudine (LMV) and entecavir (ETV) after sequential monotherapy of LMV and ETV remains little known.

METHODS

We evaluated the efficacy of entecavir (ETV) plus adefovir dipivoxil (ADV) combination therapy for patients with resistance to LMV and ETV. We reviewed the medical records of 12 patients, and treated all 12 patients with ETV plus ADV combination therapy for at least 18 months. Quantitative hepatitis B virus (HBV) DNA levels, serologic markers, and hepatic panel values were monitored at baseline and 3-month intervals thereafter for 18 months.

RESULTS

The baseline mean serum HBV DNA level was 7.26 ± 1.11 log(10) copies/ml. The mean reductions in serum HBV DNA levels from baseline to 3, 6, 9, 12, 15, and 18 months were -1.98 ± 1.03, -2.87 ± 1.02, -3.32 ± 1.10, -3.92 ± 1.30, -4.36 ± 1.22, and -4.57 ± 1.18 log(10) copies/ml, respectively. Complete virological response (HBV DNA of <2 log(10) copies/ml) at 6, 12, and 18 months was observed in 1 (8.3%), 4 (33.3%), and 6 (50.0%) patients, respectively. The 2 patients with baseline HBV DNA of <6 log(10) copies/ml achieved complete virological response at 18 months, while 4 of 10 patients with baseline HBV DNA of ≥6 log(10) copies/ml achieved complete virological response at 18 months. None of the 12 patients experienced virological breakthrough during follow-up.

CONCLUSIONS

ETV plus ADV combination therapy effectively reduced serum HBV DNA levels in patients with CHB who developed resistance to both LMV and ETV. Additional long-term studies are needed to assess the effect of long-term treatment with these drugs.

Long-term monitoring drug resistance by ultra-deep pyrosequencing in a chronic hepatitis B virus (HBV)-infected patient exposed to several unsuccessful therapy schemes

The aim of this study was to analyze the spectrum and dynamics of low-prevalent HBV mutations in the reverse transcriptase (rt) and S antigen by ultra-deep pyrosequencing (UDPS). Samples were obtained from a chronically infected patient who was followed throughout a thirteen-year period. This technology enabled simultaneous analysis of 4084 clonally amplified fragments from the patient allowing detecting low prevalent (<1%) mutations during the follow-up. At baseline, HBV sequences were predominately wild-type. Under sequential HBV monotherapies including lamivudine, adefovir and entecavir, a high frequency of rtM204I mutation was detected initially as unique and then coexisting with rtM204V. Both mutations were statistically associated with rtA200V and rtV207I, respectively. Once the entecavir and tenofovir combined therapy was started, polymerase and consequently envelope gene mutations appeared at several positions at a higher frequency than before, including the entecavir resistance-associated mutation rtT184L.

Response to tenofovir monotherapy in chronic hepatitis B patients with prior suboptimal response to entecavir

Both entecavir (ETV) and tenofovir (TDF) are potent antiviral agents for hepatitis B virus (HBV). Suboptimal response (SOR) following antiviral therapy is associated with an increased risk of subsequent treatment failure and viral resistance. It remains unclear whether switching to TDF is a reasonable approach in patients with SOR to ETV treatment. This study was aimed to determine how HBV patients with SOR to ETV respond to TDF monotherapy. Data of patients with SOR to ETV (failure to achieve >1 log(10) HBV-DNA reduction during the last 24 weeks of ETV treatment) who were switched to TDF monotherapy during 2005 and 2010 were reviewed. Treatment adherence was assessed by pill-count. Fourteen patients (2.9%) were identified from a total cohort of 482 ETV-treated patients. All 14 patients were Chinese and were infected with HBV genotype C (71%) or B (29%). Nine patients were men, and the median age was 41.5 years (19-64). Twelve were treatment naïve (one lamivudine- and one peginterferon-experienced patient); 85.7% were HBeAg positive. The median baseline HBV-DNA was 7.55 (5.30-9.40) log(10) copies/mL, and 57% had abnormal serum alanine aminotransferase (ALT) levels. Precore and/or basal core promoter mutations were detected in four patients, whereas no genotypic resistance was detected at baseline and before switching to TDF. The median duration of ETV treatment was 64.5 (26-126) weeks. The median HBV-DNA at the time of switching to TDF was 3.69 (3.00-4.90) log(10) copies/mL. The median HBV-DNA reduction from baseline and during the last 6-month observation period prior to switching to TDF was 4.04 (0.51-6.06) log(10) and 0.43 (-0.09-1.13) log(10) copies/mL, respectively. After the switching to TDF, all 14 patients (100%) achieved undetectable HBV-DNA and ALT normalization within a median duration of 30 weeks. In 12 patients who were HBeAg positive, HBeAg seroconversion was observed in two patients after TDF treatment of 75- and 84-weeks duration. There was no virological breakthrough observed after switching to TDF with a median follow-up period of 50 (24-160) weeks. TDF treatment was safe and well tolerated. In conclusion, suboptimal response to ETV is rare (approximately 3%). TDF monotherapy is safe and very effective in the management of HBV patients with SOR to ETV.

Unsuccessful therapy with adefovir and entecavir-tenofovir in a patient with chronic hepatitis B infection with previous resistance to lamivudine: a fourteen-year evolution of hepatitis B virus mutations

Background

Complex mutants can be selected under sequential selective pressure by HBV therapy. To determine hepatitis B virus genomic evolution during antiviral therapy we characterized the HBV quasi-species in a patient who did no respond to therapy following lamivudine breakthrough for a period of 14 years.

Case Presentation

The polymerase and precore/core genes were amplified and sequenced at determined intervals in a period of 14 years. HBV viral load and HBeAg/Anti-HBe serological profiles as well as amino transferase levels were also measured. A mixture of lamivudine-resistant genotype A2 HBV strains harboring the rtM204V mutation coexisted in the patient following viral breakthrough to lamivudine. The L180M+M204V dominant mutant displayed strong lamivudine-resistance. As therapy was changed to adefovir, then to entecavir, and finally to entecavir-tenofovir the viral load showed fluctuations but lamivudine-resistant strains continued to be selected, with minor contributions to the HBV quasi-species composition of additional resistance-associated mutations. At the end of the 14-year follow up period, high viral loads were predominant, with viral strains harboring the lamivudine-resistance signature rtL180M+M204V. The precore/core frame A1762T and G1764A double mutation was detected before treatment and remaining in this condition during the entire follow-up. Specific entecavir and tenofovir primary resistance-associated mutations were not detected at any time. Plasma concentrations of tenofovir indicated adequate metabolism of the drug.

Conclusions

We report the selection of HBV mutants carrying well-defined primary resistance mutations that escaped lamivudine in a fourteen-year follow-up period. With the exception of tenofovir resistance mutations, subsequent unselected primary resistance mutations were detected as minor populations into the HBV quasispecies composition during adefovir or entecavir monotherapies. Although tenofovir is considered an appropriate therapeutic alternative for the treatment of entecavir-unresponsive patients, its use was not effective in the case reported here.

Recent advances in the treatment of chronic hepatitis B

INTRODUCTION

At present, two strategies exist for the treatment of chronic hepatitis B (CHB): i) standard or pegylated interferon alpha (IFN) with mainly immune modulatory effects; and ii) nucleos(t)ide analogues (NA) with direct antiviral effects. The optimal treatment for an individual patient remains controversial.

AREAS COVERED

The treatment efficacy and prediction of response to antiviral agents for chronic hepatitis B are reviewed and discussed.

EXPERT OPINION

The rates of hepatitis B e antigen (HBeAg) and hepatitis B surface antigen (HBsAg) loss or seroconversion are continuously increasing in CHB patients after stopping a finite course of IFN, whereas long-term NA therapy is usually required to improve the adverse outcomes of CHB. Lower baseline HBV DNA level is a strong predictor for both sustained viral suppression and HBeAg seroconversion in patients receiving IFN-based as well as NAs therapy. In addition, HBeAg-positive patients with genotype A or B infection have better responses to IFN-based therapy than those with genotypes C or D infection. Furthermore, on-treatment predictors such as declines of serum HBV DNA, HBsAg and HBeAg levels may be helpful in making decisions of subsequent therapy. Regarding the association of host genetic factors with responses to antiviral therapy, current evidence is limited.

Tenofovir disoproxil fumarate in the treatment of chronic hepatitis B

Tenofovir is a nucleotide analog reverse transcriptase inhibitor approved recently by the US FDA for the treatment of chronic hepatitis B (CHB) in adult patients based on the results of two double-blind randomized trials demonstrating superiority of tenofovir compared with adefovir. Tenofovir is available orally as tenofovir disoproxil fumarate (ester pro-drug of tenofovir) and inhibits replication of both hepatitis B virus and HIV-1. Owing to its potent antiviral activity, favorable safety profile, and higher barrier to the development of resistance, tenofovir has replaced adefovir as a first-line oral monotherapy option in the treatment of CHB in the 2009 update of the American Association for the Study of Liver Diseases (AASLD) Practice Guidelines. Additionally, tenofovir monotherapy or in combination with nucleoside analogs are options for patients who have developed resistance to other CHB therapies including lamivudine and adefovir.

Antiviral resistance and hepatitis B therapy

The management of chronic hepatitis B currently rests with long-term therapy using oral nucleoside analogs. The major limitation of long-term therapy is antiviral resistance. Antiviral resistance is due to the high rate of mutations that can occur during hepatitis B virus (HBV) replication and the selection of these mutants due to a replication advantage in the presence of the antiviral agent. Indeed, high rates of antiviral resistance have been found with long-term use of lamivudine, in up to 76% of patients treated for 5 years or more. Rates of antiviral resistance are lower with adefovir therapy, approximately 30% at 5 years. Newer more potent nucleoside analogs (tenofovir and entecavir) have proven to have much lower rates of antiviral resistance (<1% after 2 years in treatment-naïve subjects), but the long-term rates of resistance have yet to be fully defined. The appearance of these viral mutations (genotypic resistance) is usually followed by rises in HBV DNA levels (virological breakthrough) and then by rises in serum aminotransferase levels (biochemical breakthrough). The appearance of antiviral resistance can be accompanied by a transient but occasionally severe exacerbation of the underlying liver disease which in some instances has led to acute liver failure. Combinations of nucleoside analogs may offer an approach to preventing antiviral resistance, but the efficacy and safety of this approach have yet to be shown. A future research priority is to identify new agents active against HBV that target different steps in the viral life-cycle and might provide effective means to circumvent the antiviral resistance of nucleoside analogs.

New approaches in the management of chronic hepatitis B: role of tenofovir

In the field of HIV management, tenofovir disoproxil fumarate (TDF) plays a pivotal role and has been demonstrated to be a safe and well-tolerated antiviral agent. Recent data showed the efficacy of TDF in the treatment of chronically hepatitis B virus (HBV)-infected patients. TDF was superior to adefovir dipivoxil (ADV) in both nucleos(t)ide-naïve HBeAg-positive and HBeAg-negative HBV patients, and appeared to be one of the most potent antiviral agents so far. In addition, several reports showed that TDF was also effective in the nucleos(t)ide-experienced population, although conflicting results have been presented concerning patients with genotypic resistance to ADV. TDF seems to have a good resistance profile as well. The rtA194T mutation in association with lamivudine resistance may confer resistance to TDF, although both in vivo and in vitro studies regarding this mutation demonstrate conflicting results. As treatment with TDF may be associated with nephrotoxicity, all TDF-treated patients should be monitored for renal function at baseline and periodically thereafter. While the relative roles of interferon vs nucleos(t)ide analogues (NA) as initial anti-HBV therapy remains unclear, TDF will probably become one of the key factors in HBV management both as first-choice NA for nucleos(t)ide-naïve patients and as rescue therapy for nucleos(t)ide-experienced patients.

The rtA194T polymerase mutation impacts viral replication and susceptibility to tenofovir in hepatitis B e antigen-positive and hepatitis B e antigen-negative hepatitis B virus strains

Tenofovir is a new effective treatment option for patients with chronic hepatitis B, but could be potentially hampered by mutations in the hepatitis B virus (HBV) polymerase conferring drug resistance. Drug resistance may occur preferentially if long-term administration is required, for example, in patients with hepatitis B e antigen (HBeAg)-negative HBV infection bearing precore (PC) and basal core promoter (BCP) mutations. The rtA194T polymerase mutation has been found in HBV/HIV coinfected patients during tenofovir treatment and may be associated with tenofovir resistance. We generated replication-competent HBV constructs harboring rtA194T alone or in addition to lamivudine (LAM) resistance (rt180M + rtM204V), PC mutations, and BCP mutations and assessed their replicative capacity after transient transfection in human hepatoma cells. The rtA194T polymerase mutation alone or in conjunction with LAM resistance reduced the replication efficiency as compared with wild-type (WT) HBV. In contrast, combination of rtA194T (+/- LAM resistance) with HBeAg-negative PC or BCP mutants increased the replication capacity of the drug-resistant polymerase mutants, thereby restoring the viral replication to similar levels as WT clones. Clones harboring rtA194T showed partial resistance to tenofovir in vitro and also to LAM but remained susceptible to telbivudine and entecavir.

CONCLUSION

The rtA194T polymerase mutation is associated with partial tenofovir drug resistance and negatively impacts replication competence of HBV constructs. Viral replication, however, can be restored to WT levels, if these polymerase mutations occur together with precore or basic core promoter substitutions as found in HBeAg-negative hepatitis B. Patients with HBeAg-negative chronic HBV infection may therefore be at particular risk when developing drug resistance to tenofovir. Telbivudine or entecavir should be considered as effective alternative treatment options for these patients.

Tenofovir and its potential in the treatment of hepatitis B virus

Recent literature is reviewed about treatment of chronic hepatitis B virus (CHB), focusing on tenofovir disoproxil fumarate (TDF; Viread((R))), among the nucleotide and nucleoside analogs. TDF pharmacokinetics and pharmacodynamics, activity in respect of hepatitis B virus (HBV) multi-drug-resistant mutations, efficacy in treatment-naïve and treatment-experienced patients, and side effects are described. The most predictive response factors to TDF therapy are discussed and all available combination therapies to optimize clinical outcome in the various patient profiles are analyzed, such as compensated and/or decompensated cirrhotic patients. The use of TDF in pregnancy, and prophylaxis after exposure to HBV and post-liver transplantation are also evaluated.

Tenofovir Disoproxil Fumarate Tablets

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Role of combination therapy in chronic hepatitis B

Combination therapy includes the use of two or more antivirals for the treatment of chronic hepatitis B. No study has shown that combination therapy is superior to monotherapy in naive patients for achieving treatment end points, but combination appears to result in a lower incidence of resistance. Moreover, the higher-potency compounds have not yet been studied. Consideration should be given to treating lamivudine-resistant patients with combination therapy, preferably with a nucleotide analogue in conjunction with a nucleoside analogue. Combination therapy should be considered in patients with decompensated cirrhosis who are unable to achieve an undetectable viral level on monotherapy and in naive patients who still have a detectable viral level 6 to 12 months after starting therapy.