Rescue therapy for drug resistant hepatitis B: another argument for combination chemotherapy?

Pharmacotherapy options for managing hepatitis B in children

INTRODUCTION

To eliminate viral hepatitis by 2030, the World Health Organization (WHO) launched the first global health sector strategy on viral hepatitis, with particular focus given to hepatitis B and C in 2016. To achieve the reduction of mortality in children, it is indispensable to know which children should be treated and how to treat them.

AREA COVERED

In this article, the authors review the antiviral treatment of children with chronic hepatitis B virus (HBV) infection including antivirals available for children with chronic HBV infection.

EXPERT OPINION

The approvals of nucleos(t)ide analogues (NAs) and pegylated interferon (PEG-IFN) for children have lowered a hurdle to the initiation of antiviral treatment in children. The international guidelines use nearly the same criteria of antiviral treatment for children with chronic HBV infection, but the WHO guidelines provide a cautious stance on the antiviral treatment of children. Not only PEG-IFN but also NAs with a high genetic barrier to drug resistance should be the first-line treatment for children. In settings with limited medical resources, NAs can be the first-line treatment for children. Although the concept of an 'immune-tolerant phase' is challenged, evidence is not sufficient to recommend the treatment of HBeAg-positive immune-tolerant children.

Adefovir dipivoxil in the treatment of chronic hepatitis B virus infection

Adefovir dipivoxil (Hepsera, Gilead Sciences) is a prodrug of adefovir, with potent antiviral activity against hepatitis B virus. Adefovir dipivoxil therapy, 10 mg daily for 48 weeks, is effective in hepatitis B e antigen-positive and -negative chronic hepatitis B. In hepatitis B e antigen-negative chronic hepatitis B, adefovir dipivoxil was recently found to maintain its efficacy even after 3 years of therapy. Adefovir dipivoxil is effective in patients with compensated or decompensated chronic viral B liver disease, and in pre- and post-transplant hepatitis B virus patients who develop resistance to lamivudine (Epivir, GlaxoSmithKline). It is well-tolerated and safe even after the third year of long-term therapy, and is associated with low rates of viral resistance. All these characteristics make adefovir dipivoxil an important drug for the treatment of hepatitis B virus infection and an excellent candidate for long-term maintenance therapy in chronic viral B liver disease.

Adefovir and lamivudine in combination compared with adefovir monotherapy in HBeAg-negative adults with chronic hepatitis B virus infection and clinical or virologic resistance to lamivudine: a retrospective, multicenter, nonrandomized, open-label study

OBJECTIVES

The aim of this study was to assess the therapeutic effectiveness of adefovir dipivoxil (ADV), administered in combination with lamivudine (LAM) or as monotherapy, and the rate of resistance to ADV, in hepatitis B e antigen (HBeAg)-negative adult patients with chronic hepatitis B virus (HBV) infection and clinical or virologic resistance to LAM. Furthermore, we evaluated in these selected patients the clinical co-variates associated with a sustained virologic response.

METHODS

Data from adult outpatients aged >18 years with chronic HBV infection and clinical or virologic resistance to LAM were used in this retrospective, multicenter, nonrandomized, open-label study. Patients were selected if they received ADV 10 mg PO QD + LAM 100 mg QD PO or ADV 10 mg PO QD as monotherapy for 24 to 32 months between June 2003 and July 2006. End points were the proportions of patients who achieved virologic response (undetectable HBV-DNA [<3.3 log(10) copies/mL]) and biochemical response (normalization [<40 IU/L] of alanine aminotransferase [ALT]), and the proportions in whom resistance to ADV (rebound serum HBV-DNA >1 log(10) copies/mL compared with on-treatment nadir, as confirmed on molecular analysis) was found. HBV-DNA and ALT levels were checked every month during the first 3 months of treatment and every 3 months thereafter until 28 months. Data from each center were stored in a centralized database and analyzed by a blinded independent investigator.

RESULTS

Data from 70 patients were included (48 men, 22 women; median age, 51 years; ADV + LAM, 36 patients; ADV monotherapy, 34). The median duration of the pharmacologic treatment in the 2 groups of patients was 28 months (range, 24-32 months). By month 3, virologic response was achieved in 30 patients (83%) in the ADV + LAM group and in 26 patients (76%) in the ADV monotherapy group. At 12 months, virologic response was achieved in 5 additional patients in the ADV + LAM group and 2 additional patients in the ADV monotherapy group. Biochemical response was found to be time dependent: in the 2 groups, the rates of biochemical response were, respectively, 56% and 54% at month 3, 80% and 71% at month 6, and 96% and 79% at month 12, persisting up to the end of the study period. The rates of clinical resistance to ADV were 3% with ADV + LAM and 18% with ADV monotherapy (with a 6% rate of resistance due to rtA181 mutation in the monotherapy group). Logistic regression analysis found that pre-treatment levels of HBV-DNA <5 log(10) copies/mL, ALT levels >150 IU/L, an inflammation score >7, and a fibrosis score <2 were the strongest covariates independently associated with a sustained virologic response in both groups of patients. No adverse events were reported in any of the patients.

CONCLUSION

ADV, administered in combination with LAM or as monotherapy, appeared to be effective in this small, selected group of HBeAg-negative patients with clinical or virologic resistance to LAM, especially in those with low pretreatment HBV-DNA levels, high ALT levels, and low fibrosis scores.

Clinical outcome of lamivudine-resistant chronic hepatitis B patients with compensated cirrhosis under adefovir salvage treatment. Importance of HCC surveillance

BACKGROUND

Data concerning the outcome of lamivudine-resistant (LAM-R) chronic hepatitis B (CHB) patients with compensated cirrhosis under adefovir (ADV) treatment are limited. The aim of our study was to evaluate the medium term outcome of these, high-risk for fatal events, patients.

METHODS

31 LAM-R patients with compensated cirrhosis who had been treated with ADV monotherapy (n=8) or ADV plus LAM (n=23) for a mean of 27.6 months, were evaluated. Virological response (VR) was defined as HBV-DNA levels <10(4) copies/ml within the first year of treatment.

RESULTS

Twenty-three patients (74.19%) achieved VR. Six patients (19.35%) developed ADV-related mutations (annual incidence 11%). Liver-related death, liver decompensation and hepatocellular carcinoma (HCC) were observed in 12.9%, 16.12% and 16.12% of patients, respectively. HCC (annual incidence 9.1%) was the main cause of liver decompensation (4/5, 80%) and of liver-related deaths (3/4, 75%). HCC development was not related to patients' age (p=0.440), HBeAg status (p=0.245), HBV genotype (p=0.598), baseline ALT levels (p=0.981), baseline viral load (p= 0.464), VR (p=0.504) as well as emergence of ADV resistance (p=0.871).

CONCLUSIONS

ADV suppresses viral replication in more than 70% of LAM-R cirrhotic patients during the first year of treatment. Despite that, HCC is frequently observed in these high-risk patients, irrespective of virological response or emergence of ADV resistance.

[Antiviral efficacy of lamivudine/adefovir combination therapy in chronic hepatitis b patients with resistance to lamivudine and adefovir consecutively]

BACKGROUND/AIMS

The aim of this study was to elucidate the antiviral efficacy of lamivudine (LMV)-adefovir (ADV) combination therapy in chronic hepatitis B patients who showed resistance to LMV and ADV consecutively.

METHODS

A retrospective review was performed in eighteen patients with chronic hepatitis B who developed virologic breakthroughs during LMV-ADV sequential mono-therapy and treated with LMV-ADV combination therapy.

RESULTS

The median duration of follow up was 17 months (range, 6-27) after the start of LMV-ADV combination therapy. Mean HBV DNA level in log10 IU/mL was 6.08+/-0.95, 4.05+/-1.66, 3.17+/-1.58, 3.18+/-2.16, and 2.35+/-1.52 at 0, 3, 6, 12, and 24 months, respectively. Sixteen patients (88.9%) showed HBV DNA reduction below detection limit (<20,000 IU/mL). HBeAg seroconversion was observed in one patient (7.1%) after 8 months of combination therapy. Virologic breakthrough occurred in only one patient after 21 months of combination therapy. Viral rebound occurred in two patients at 12 months and 14 months of combination therapy. Normalization of serum ALT was achieved in twelve patients (66.7%). Primary non-response was observed in two cases (11.1%).

CONCLUSIONS

LMV-ADV combination treatment was effective in 88.9% of patients with resistance to LMV and ADV in a short-term follow up. It may be applied as a bridge therapy until another effective antiviral regimen becomes available.

Association of lamivudine-resistant mutational patterns with the antiviral effect of adefovir in patients with chronic hepatitis B

Adefovir has a potent antiviral activity as a rescue treatment against lamivudine-resistant strains. The aim of this study was to assess the patterns of lamivudine-resistant mutations and their influence on the virologic response to adefovir rescue therapy in patients with lamivudine-resistant chronic hepatitis B. Sixty-seven patients with lamivudine-resistant chronic hepatitis B were treated with adefovir monotherapy. Baseline blood samples were analyzed for lamivudine-resistant mutations via restriction fragment mass polymorphism. Virologic responses, ALT normalization and loss of HBeAg were assessed. Serum HBV DNA levels were measured using real-time PCR at baseline and 24 weeks of adefovir therapy. Of the 67 patients with chronic hepatitis B, 65 patients (97%) had lamivudine-resistant mutations in the YMDD motif [27 (41%) rtM204I, 22 (34%) rtM204V, and 16 (25%) rtM204I/V]. In addition to the YMDD mutations, the rtL180M, rtL80I, and rtV173L mutations were also present in 78%, 43%, and 11% of patients, respectively. The rtM204V mutation always accompanied rtL180M, and rtL80I was always observed in conjunction with rtM204I. Decrease in mean serum HBV did not differ between patients carrying the rtM204I versus rtM204V mutant at week 24 (-3.3 vs. -3.3 log(10) copies/ml, respectively; P = 0.303). The presence of the rtL180M, rtL80I, and rtV173L did not significantly affect viral load reduction during adefovir administration. These results demonstrate that the rtL80I mutant is co-selected with rtM204I as a compensatory mutation in the same manner as rtL180M with rtM204V, and that adefovir shows similar antiviral efficacy against all of the evaluated patterns of lamivudine-resistant HBV mutations.

Current treatment indications and strategies in chronic hepatitis B virus infection

The optimal approach to the management of several marginal cases with chronic hepatitis B virus (HBV) infection is controversial. Serum HBV DNA and aminotransferase levels, and the degree of necroinflammation and fibrosis determine the therapeutic decisions. All patients with elevated aminotransferase (> twice the upper limit of normal) and serum HBV DNA above 20 000 IU/mL should be treated. Liver biopsy is important for therapeutic decisions in cases with mild aminotransferase elevations and serum HBV DNA below 20 000 IU/mL. Chronic HBV patients who do not receive treatment should be followed for life. There are seven agents licensed for chronic hepatitis B: standard and pegylated interferon-alpha, lamivudine, adefovir, entecavir, telbivudine and tenofovir. One-year courses with pegylated interferon-alpha induce sustained off-therapy remission in 30%-32% of patients with HBeAg-positive chronic hepatitis B and in a smaller proportion of patients with HBeAg-negative chronic hepatitis B. Oral antivirals achieve initial on-therapy responses in the majority of patients, but are intended as long-term therapies. Viral suppression has favourable effects on patients’ outcome and modifies the natural course of the disease. Viral resistance, however, is the major drawback of long-term oral antiviral therapy. Lamivudine monotherapy is associated with the highest and entecavir monotherapy with the lowest resistance rate so far. There has been no resistance to tenofovir, but after only 18 mo of treatment to date. The optimal first-line anti-HBV therapy with the best long-term cost/benefit ratio remains unclear. If oral antiviral agents are used, compliance should always be ascertained and HBV DNA levels should be regularly tested.

Therapeutic strategies in the management of patients with chronic hepatitis B virus infection

Currently available options for the treatment of chronic hepatitis B virus (HBV) infection include standard and pegylated interferon alfa and four oral antiviral agents (lamivudine, adefovir, entecavir, and telbivudine). These treatment strategies are either therapies of finite duration that aim to achieve sustained off-therapy responses, or long-term treatments that aim to maintain on-therapy remission. Pegylated interferon alfa may offer higher sustained off-therapy responses after 1 year, but most patients do not respond. Oral antivirals are the only candidates for long-term treatment of patients with chronic HBV infection. Viral suppression has favourable effects on patients' outcome and modifies the natural history of the disease. Viral resistance is the main drawback of long-term antiviral therapy. Lamivudine monotherapy is associated with higher resistance (year 1, 10-27%; year 2, 37-48%; year 4, 60-65%) than adefovir (year 1, 0%; year 2, 3%; year 5, 29%) or telbivudine (year 1, 3-4%; year 2, 9-22%). Entecavir resistance is rare in naive individuals (year 4, <1%), but increases over time in lamivudine-resistant patients (year 4, 43%). The best strategy for long-term therapy in chronic HBV infection has yet to be established.

Viral genotype and baseline load predict the response to adefovir treatment in lamivudine-resistant chronic hepatitis B patients

BACKGROUND/AIMS

To determine the factors associated with virological response (VR), HBeAg loss or the emergence of adefovir (ADV)-related mutations in ADV-treated chronic hepatitis B (CHB) patients with lamivudine (LAM) resistance.

METHODS

Fifty-four LAM-resistant CHB patients (46% HBeAg-positive) were treated with ADV monotherapy (n=28) or ADV plus LAM (n=26) for a mean of 30.4 months.

RESULTS

Thirty-eight patients (70.4%) achieved VR defined as HBV-DNA levels <10(4)copies/ml within the first 12 months of treatment. Six (24%) of 25 HBeAg-positive patients exhibited HBeAg loss and 20% seroconverted to anti-HBe. Eight patients (14.8%) developed ADV-related mutations. In the multivariate analysis, female gender (HR=0.20, 95% CI: 0.05-0.76, p=0.018), HBeAg-negative (HR=0.37, 95% CI: 0.14-0.96, p=0.040) and low baseline HBV-DNA levels (HR=0.65, 95% CI: 0.45-0.95, p=0.027) were independent predictors of VR, whereas low HBV-DNA levels (HR=0.36, 95% CI: 0.11-1.20, p=0.095) and HBV-genotype D (HR=0.06, 95% CI: 0.004-0.84, p=0.037) independently predicted HBeAg loss.

CONCLUSIONS

ADV therapy suppresses viral replication in more than 70% of LAM-R patients. Factors associated with virologic response are female gender, HBeAg-negative status and low baseline serum HBV-DNA levels. Genotype D HBV infection and low baseline HBV-DNA levels independently predict HBeAg loss.

New developments in the treatment of chronic hepatitis B

Significant progress has been made during the last 2 years in the treatment of chronic hepatitis B (CHB). Treatment decisions differ significantly depending on whether patients are HBeAg+ or HBeAg-, treatment-naive or nucleoside/nucleotide-resistant, and in early or advanced stages of liver disease. Courses of finite duration, aiming to achieve sustained off-therapy responses, are practically restricted to HBeAg+ patients with compensated chronic liver disease, whereas long-term therapy aiming to achieve maintained on-therapy remission is mostly applicable to HBeAg- individuals either with early or advanced liver disease. A course of finite duration with pegylated (PEG)-IFN-alpha-2a offers the highest probability of sustained off-therapy response in HBeAg+ individuals, as well as in some HBeAg- individuals. Long-term therapy with nucleoside/nucleotide analogues, both in HBeAg+ and HBeAg- CHB, has most favourable effects on patient outcome, provided that virological and biochemical remission is maintained without development of viral resistance. The best results are achievable with potent analogues suppressing serum hepatitis B virus (HBV) DNA to non-detectability by most sensitive techniques. The best 2-year resistance profile has hitherto been reported with entecavir monotherapy, and the best long-term resistance profile was seen with adefovir of 5-year duration. Adefovir is effective in most lamivudine (LAM)-resistant patients, but should be administered as an add-on rather than as a substitute for LAM. Combination therapies have entered the treatment arena of CHB by the side doors of LAM-resistance and of end-stage liver disease, and the most recent results suggest that treatment with combinations of two strong nucleosides/nucleotides with different resistance profiles may turn out to be the optimal first-line/first choice option in CHB.

Detection of rtN236T and rtA181V/T mutations associated with resistance to adefovir dipivoxil in samples from patients with chronic hepatitis B virus infection by the INNO-LiPA HBV DR line probe assay (version 2)

The nucleotide analog adefovir dipivoxil (ADV) is an effective antiviral treatment for chronic hepatitis B virus (HBV) infection, with resistance to ADV estimated to occur less frequently than resistance to lamivudine treatment. The detection of ADV resistance mutations is necessary during therapy to monitor and anticipate possible treatment failure. The INNO-LiPA HBV DR v2 (LiPA; Innogenetics, Ghent, Belgium) is a DNA hybridization line probe assay for the detection of HBV polymerase mutations associated with resistance to lamivudine and ADV. Evaluation of this assay to detect ADV resistance mutations was performed by analyzing 38 patients treated with ADV. Serial samples taken at 6-month intervals during treatment were available for most patients. A total of 124 samples were analyzed by both LiPA and sequencing. By LiPA analysis, 12 patients (31.5%) were found to have mutations associated with resistance to ADV (rtA181V/T and/or rtN236T). This contrasted with sequence analysis, which found nine patients (24%) with either or both mutations. Twice as many samples were rtN236T positive by LiPA (18 of 124) compared to sequence analysis (9 of 124). LiPA detected the rtN236T mutation at least 6 months earlier than its detection by sequencing in patients for whom consecutive serum samples were available. Although less sensitive, sequencing has the advantage of providing information on other polymerase mutations not represented on LiPA strips. The INNO-LiPA HBV DR v2 assay is a very sensitive and specific assay for the detection of the rtN236T mutation associated with resistance to ADV.

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Switching to adefovir monotherapy after emergence of lamivudine-resistant mutations in patients with liver cirrhosis

Switching to adefovir (ADV) monotherapy is effective in patients with lamivudine (LAM)-resistant hepatitis B virus (HBV) mutations (rtM204 I/V). However, it was recommended to continue LAM therapy for months after starting ADV therapy for safety concern. The safety and efficacy of switching to ADV monotherapy was examined in compensated and decompensated patients with liver cirrhosis. The clinical, biochemical and virological responses were compared between ADV monotherapy in 18 cirrhotic patients and ADV add-on LAM therapy in 10 comparable cirrhotic patients with LAM-resistant rtM204 I/V. After switching to ADV monotherapy, Child-Pugh's score, serum alanine aminotransferase (ALT), bilirubin, albumin and HBV DNA levels improved significantly (P < 0.01). Serum HBV DNA response, defined as HBV DNA decreased to below 10(5) copies/mL or > or =2 log(10) reduction form baseline, was achieved in all patients. A transient ALT flare without concurrent changes in serum bilirubin or prothrombin time was observed in only two patients (11%). The efficacy and safety profile was similar to those with ADV add-on LAM therapy. In conclusion, switching to ADV monotherapy after emergence of LAM-resistant rtM204 I/V is effective and safe in cirrhotic patients, even in those with hepatic decompensation. To stop LAM and switch to ADV in patients with breakthrough is a reasonably safe and cost-effective approach.

Adefovir rapidly suppresses hepatitis B in HBeAg-negative patients developing genotypic resistance to lamivudine

Progression of hepatitis B in patients with lamivudine-resistant strains is slowed down by adefovir dipivoxil (ADV). Whether the time point of ADV administration (genotypic vs. phenotypic resistance) influences the outcome of therapy is unknown. We compared the outcome of ADV therapy in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B patients with genotypic and phenotypic resistance to lamivudine. Ten milligrams of ADV was administered daily for 2 years to 46 HBeAg-negative patients at the time of phenotypic resistance (group A, >6 log(10) copies/mL of hepatitis B virus [HBV] DNA and high alanine aminotransferase [ALT] levels) and 28 patients at the time of genotypic resistance (group B, 3-6 log(10) copies/mL of HBV-DNA and normal ALT). HBV DNA was assessed every 2 months using Versant 3.0 assay, and lamivudine resistance was confirmed via INNO-LiPA assay in all patients. By month 3, HBV DNA tested negative in all patients from group B compared with only 20 (46%) in group A (P < .0001). The 2-year rates of virological response were 100% in the former patients and 78% in the latter ones (P < .0001). ALT levels remained persistently normal in all group B patients, whereas in group A patients they normalized at rates of 50% at month 6 (P < .0001), 72% at month 12 (P < .01), and 93% at month 24. None of the patients developed ADV resistance or ADV-related side effects. In conclusion, to optimize antiviral treatment in HBeAg-negative patients selecting resistant strains to lamivudine, ADV should be added to lamivudine as soon as genotypic resistance is detected.

Entecavir for the treatment of chronic hepatitis B

Chronic infection with the hepatitis B virus remains a serious and life-threatening disease for approximately 5% of the world's population, despite the availability of effective vaccines. Although prognoses can be improved by chemotherapy, treatment options are limited and none has been consistently successful. Interferon-alpha, the longest established therapy, has limited efficacy, is slow-acting and frequently causes adverse effects. Newer drugs comprise of mainly nucleoside and nucleotide analogs. The two that are currently approved, lamivudine and adefovir dipivoxil, are well tolerated; both produce rapid and dramatic responses, but their effects may not be sustainable in the long-term due to the emergence of resistant virus. Development of resistance to lamivudine is approximately ten-times more frequent than development of resistance to adefovir dipivoxil (approximately 60 and 6%, respectively) during the first 3 years of therapy. Entecavir, a carbocyclic deoxyguanosine analog that is active against both lamivudine- and adefovir dipivoxil-resistant HBV, is in the vanguard of new antihepatitis B virus drugs that have progressed to Phase III clinical trials. It is the most potent antihepatitis B virus agent discovered to date.

Emerging treatments in chronic hepatitis B

Although the management of chronic hepatitis B has improved over the last decade, none of the available therapeutic agents, IFN-alpha, lamivudine and adefovir dipivoxil, can achieve sustained off-therapy responses in most cases. Therefore, several newer, mainly antiviral and immunomodulatory agents, are being evaluated. Pegylated IFN-alpha(2a) has been shown to be more effective than lamivudine or standard IFN-alpha monotherapy in achieving post-therapy biochemical and virological responses, and is expected to be licensed soon for the treatment of chronic hepatitis B. Newer antiviral agents, such as entecavir and telbivudine, appear to be quite effective initially, but their sustained off-therapy response rates remain unknown. The preliminary data of monotherapies with immunomodulatory agents, or of combination therapies, have been rather disappointing. Long-term maintenance treatment with antiviral agent(s) with good safety and tolerability profiles and low resistance rates appears to be the most realistic future therapeutic option for most chronic hepatitis B patients.