Chronic hepatitis B: early viral suppression and long-term outcomes of therapy with oral nucleos(t)ides

Efficacy of Real-world Entecavir Therapy in Treatment-naïve Chronic Hepatitis B Patients

Background:

Entecavir (ETV) has been shown to be effective in randomized controlled trials in highly selected patients with hepatitis B virus (HBV) infection. This study aimed to evaluate the efficacy of ETV in chronic hepatitis B (CHB) patients in the real-world setting.

Methods:

A total of 233 treatment-naïve, CHB patients who received at least 12 months of ETV treatment were included in this retrospective study. Rates of virological response (VR), hepatitis B s antigen (HBsAg) loss, hepatitis B e antigen (HBeAg) clearance/seroconversion, virological breakthrough, cirrhosis, and hepatocellular carcinoma were evaluated.

Results:

Of 233 patients, 175 patients were male, with mean age of 43 years old, and 135 patients were HBeAg positive. The mean baseline levels of serum alanine aminotransferase and HBV DNA in all patients were 230 U/L and 6.6 log 10 IU/ml, respectively. The mean follow-up period was 28 months. The cumulative rates of achieving VR increased from 3.4% at 3 months to 94.4% at 60 months. Primary nonresponse occurred in 3 (1.3%) patients. Partial VR (PVR) occurred in 61 (26.2%) patients at 12 months. The baseline serum HBV DNA level (hazard ratio [HR], 2.054; P < 0.001) was an independent risk factor for PVR. HBsAg loss did not occur. The cumulative rates of HBeAg clearance increased from 2.2% at 3 months to 28.2% at 60 months. PVR was the significant determinant of HBeAg clearance (HR, 0.341; P = 0.026). Age (HR, 1.072; P = 0.013) and PVR (HR, 5.131; P = 0.017) were the significant determinants of cirrhosis.

Conclusions:

ETV treatment was effective for HBV DNA suppression in this study, but HBsAg loss and HBeAg clearance/seroconversion rates were lower compared with previous clinical trials. PVR was associated with HBeAg clearance and cirrhosis.

Relationship between pre-existing resistance mutations and HBV genotype in patients with HBV related liver cirrhosis

AIM

To investigate the relationship between hepatitis B virus (HBV)-related drug resistance mutations and HBV genotype in patients with HBV-related liver cirrhosis (LC).

METHODS

Serum samples were collected from 112 patients with HBV-related LC who did not receive prior anti-viral treatment. HBV reverse transcriptase regions were amplified by PCR, and PCR products were directly sequenced.

RESULTS

Among 112 HBV-related LC patients, 13 (11.61%, 13/112) had lamivudine resistance associated mutations, 15 (13.39%, 15/112) had adefovir resistance associated mutations, and 1 had mutations associated with both lamivudine and adefovir resistance. All of these resistance mutations occurred in patients infected with HBV genotype C, and there was no mutation in patients infected with HBV genotype B.

CONCLUSION

Adefovir/lamivudine resistance associated mutations exist in patients with HBV-related LC, and the mutations are related to HBV genotype. Compared with patients infected with HBV genotype B, those infected with HBV genotype C are prone to resistance mutations.

Manipulation of Regulatory Cells' Responses to Treatments for Chronic Hepatitis B Virus Infection

BACKGROUND

Identification of effective treatments in hepatitis B virus (HBV) infection remains a controversial topic. Although the currently approved drugs for HBV control the disease's progression and also limit associated outcomes, these drugs may not fully eradicate HBV infection. In addition to better managing patients with chronic hepatitis B (CHB) infection, the induction of seroclearance by these drugs has been a commonly discussed topic in recent years.

OBJECTIVES

In this study, we focused on treating CHB infection via the manipulation of T cells' responses to identify possible approaches to cure CHB.

MATERIALS AND METHODS

All studies relevant to the role of cellular and humoral responses in HBV infection (especially regulatory cells) were investigated via a systematic search of different databases, including PubMed, Scopus, and Google Scholar. Considering extracted data and also our unpublished data regarding the association between regulatory cytokines and CHB, we introduced a novel approach for the induction of seroclearance.

RESULTS

Considering the increased levels of regulatory cytokines and also regulatory T cells (Tregs) during CHB, it seems that these cells are deeply involved in CHB infection. The inhibition of regulatory T cells may reverse the dysfunction of effector T cells in patients with CHB infection. In order to inhibit Tregs' responses, different types of approaches could be employed to restore the impaired function of effector T cells. The blockade of IL-10, IL-35, CTLA-4, PD-1, and TIM-3 were discussed throughout this study. Regardless of the efficacy of these methods, CHB patients may experience serious liver injuries due to the cytotoxic action of CD8+ T cells. Antiviral therapy and a decrease in HBV DNA to undetectable levels could also significantly reduce the risk of the hepatitis B flare.

CONCLUSIONS

The inhibition of Tregs is a novel therapeutic approach to cure chronically HBV infected patients. However, further studies are needed to investigate the safety and efficacy of this approach.

Treatment Outcomes With First-line Therapies With Entecavir and Tenofovir in Treatment-Naive Chronic Hepatitis B Patients in a Routine Clinical Practice

BACKGROUND

Given their high efficacy, entecavir (ETV) and tenofovir (TDF), are the recommended first-line therapies for chronic hepatitis B, but it is not clear whether the efficacy reported from pivotal trials is similar to the outcomes seen in routine practice.

GOALS

Our goal was to examine the treatment outcomes of antiviral therapy in such setting.

PATIENTS AND METHODS

We conducted a retrospective study of 557 consecutive treatment-naive patients who started either ETV (n=443) or TDF (n=114) at 3 US liver clinics between January 2005 and 2012. Primary study endpoint was complete viral suppression (CVS) rate (hepatitis B virus DNA<40 IU/mL).

RESULTS

The majority of patients in both ETV and TDF groups were Asians, hepatitis B e antigen (HBeAg) negative, male, and with similar pretreatment alanine aminotransferase and hepatitis B virus DNA levels. Similar proportions of patients in the ETV and TDF groups achieved CVS at 24 months: 87.7% versus 87.0%, respectively. Cumulative rates of virological breakthrough in the ETV and TDF groups were 1.0% versus 4.8% (P=0.26) and 3.7% versus 9.8% (P=0.04) at month 12 and 24, respectively; and all were associated with medication nonadherence. Cumulative rate of medication nonadherence was lower in the ETV than TDF group: 4.6% versus 7.8% at month 12 and 8.9% versus 16.9% at month 24, respectively.

CONCLUSIONS

Patients treated with either ETV or TDF achieve a similar rate of CVS at 24 months. The primary contributor to suboptimal response was medication nonadherence. Attention to medication adherence is needed in a routine clinical setting.

Dynamics of Genotypic Mutations of the Hepatitis B Virus Associated With Long-Term Entecavir Treatment Determined With Ultradeep Pyrosequencing: A Retrospective Observational Study

The aim of the study is to explore the evolution of genotypic mutations within the reverse transcriptase region in partial virological responders (PVRs) receiving long-term entecavir (ETV) treatment. A total of 32 patients were classified as completely virological responders (CVRs) (n = 12) or PVRs (n = 20). Five partial responders were hepatitis B virus (HBV)-DNA positive after long-term therapy, which lasted for >3 years. A total of 71 serum samples from these 32 patients were assayed by ultra-deep pyrosequencing (UDPS): 32 samples were from all patients at baseline, and 39 were from PVRs with sequential inter-treatment. Approximately 84,708 sequences were generated per sample. At baseline, the quasispecies heterogeneity did not significantly differ between the 2 groups. The frequencies of substitutions indicating pre-existence of nucleos(t)ide analog resistant (NAr) mutants ranged from 0.10% to 6.70%, which did not statistically differ between groups either. However, the substitutions associated with the NAr mutants were significantly different from those associated with the non-NAr mutants in 13 patients; 6 of these patients were PVRs and the others were CVRs. Five patients were HBV DNA positive after regular ETV monotherapy for >3 years, and 4 of these patients underwent mild NAr substitution fluctuations (<20%). One patient developed virological breakthrough while bearing single, double, and triple (rtL180 M, rtM204 V, rtS202G) substitutions. In addition to the common substitutions, unknown amino acid substitutions, such as rtL145 M/S, rtF151Y/L, rtR153Q, rtI224 V, rtN248H, rtS223A, rtS256C, need to be further verified. NAr substitutions are observed at frequencies of 0.10% to 6.7% before therapy. Long-term ETV therapy generally results in virological responses, as long as the proportion of resistance mutations remains at a relatively low level. Genotypic resistance to ETV is detected in all PVRs receiving long-term ETV therapy.

Partial virological response to entecavir treatment in nucleos(t)ide-naïve patients with HBeAg-positive chronic hepatitis B is not caused by reduced sensitivity

Some patients with chronic hepatitis B (CHB) receiving entecavir (ETV) exhibit partial virological response (PVR) to ETV and the mechanism is not clear. In this study, we aim to investigate the in vitro susceptibility of residual clinical strains isolated from the sera of nucleos(t)ide-naïve hepatitis B virus e antigen (HBeAg)-positive patients with CHB and PVR to ETV, and to evaluate the clinical and virological responses to prolonged ETV monotherapy in these patients. We followed 69 nucleos(t)ide-naïve HBeAg-positive CHB patients receiving ETV treatment, with 13 partial responders to ETV. And we found that no genotypic resistance mutants were detected among the 13 PVR patients. Phenotypic analysis revealed that the residual HBV strains had normal replication capacity, and were as susceptible to ETV as wild-type HBV. All PVR patients continued to receive ETV monotherapy, and serum HBV DNA of the majority became undetectable after prolonged treatment. However, none of these patients achieved HBeAg loss. In contrast, 25.6% and 23.2% of the patients with virological response achieved HBeAg loss (P < 0.001) and HBeAg seroconversion (P < 0.001) at week 144, respectively. Thus, we conclude suboptimal response to ETV might not be due to reduced HBV susceptibility to ETV, and prolonging ETV monotherapy in patients with PVR is recommended.

Mutation analysis of hepatitis B virus reverse transcriptase region among untreated chronically infected patients in Ahvaz city (South-West of Iran)

BACKGROUND

It has been revealed that mutations can occur spontaneously and naturally in HBV reverse transcriptase (RT) region among untreated patients. These HBV mutants pre-exist as minor viral population in naive patients and can emerge as major viral population, conferring drug resistance and treatment failure.

OBJECTIVES

The aim of this study was to investigate and identify prevalent mutations of RT region of hepatitis B virus genome in patients with chronic hepatitis B (CHB) untreated with antiviral drugs in South-West of Iran.

MATERIALS AND METHODS

A total of 45 cases with CHB who did not receive the treatment of lamivudine and any other antivirus drugs within the last one year were randomly chosen. After sample collection and HBV DNA extraction, RT region was amplified by polymerase chain reaction (PCR). Then PCR products were sequenced and HBV RT region mutations and amino acid changes were analyzed either manually or using web-based programs, on the basis of comparison of the obtained sequences with a set of HBV reference sequences.

RESULTS

A total of 23 (51.1%) mutations and amino acid changes were detected in studied 45 untreated patients. Of these, 3 (6.6%) patients had primary resistance mutation (rtM204I, rtA181T and rtA181S) and 20 (44.4%) patients had secondary resistance mutations.

CONCLUSION

High prevalence of mutations was found in HBV RT region of untreated patients. Most of these mutations were associated with resistance to adefovir and one patient had primary resistance mutation to lamivudine. Awareness of these resistance patterns might help in the antiviral therapy and for predicting clinical outcomes.

Intracellular levels of hepatitis B virus DNA and mutational patterns of the polymerase gene of hepatitis B virus in peripheral blood mononuclear cells of patients with lamivudine or telbivudine resistance

Studies are limited regarding the association between the quantity of hepatitis virus B (HBV) DNA loads in serum and peripheral blood mononuclear cells (PBMCs) in patients with drug resistance and few studies focus on the mutational pattern of the polymerase gene of HBV in PBMCs of patients with drug resistance. The aim of the present study was to investigate the association between the quantity of HBV DNA loads in serum and PBMCs in patients with lamivudine (LAM) or telbivudine (LdT) resistance and to explore the mutational pattern of the polymerase gene of HBV in PBMCs of these patients. A total of 51 patients underwent antiviral therapy with LAM or LdT for at least half a year. The present study applied quantitative polymerase chain reaction for the quantification of total HBV DNA, and direct sequencing was used to detect the mutation. In total, 31 patients (60.78%) were detected to have drug resistance. The mean serum HBV DNA levels were significantly higher than the HBV DNA levels of PBMCs, whether in patients with LAM or LdT resistance. The PBMCs HBV DNA loads were correlated with the serum HBV DNA loads in the two groups. Three and two mutational patterns were found in the serum of patients with LAM and LdT resistant, respectively. In total, 85.71% of patients with LAM resistance and 75.00% of patients with LdT resistance presented the same mutational pattern in paired PBMCs and serum. The HBV DNA levels in the PBMCs of patients with LAM or LdT resistance were significantly lower than those in serum and there were positive correlations between them. The majority of the mutational patterns of the polymerase gene of HBV DNA in PBMCs were the same as those in the paired serum. These findings may help to increase knowledge regarding HBV drug resistance.

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.

Pharmacokinetics of anti-HBV polyoxometalate in rats

Polyoxometalates are non-nucleoside analogs that have been proven to exhibit broad-spectrum antiviral activity. In particular, Cs₂K₄Na[SiW₉Nb₃O₄₀].H₂O 1 shows low toxicity and high activity against HBV. The preclinical pharmacokinetics of Compound 1 in rats were characterized by establishing and applying inductively coupled plasma-mass spectrometry method to determine the concentration of W in plasma, urine, feces, bile and organ samples. The quantitative ICP-MS method demonstrated good sensitivity and application in the pharmacokinetics study of polyoxometalates. The pharmacokinetic behavior of Compound 1 after intravenous or oral administration fit a two-compartment model. T_max ranges from 0.1 h to 3 h and the T_1/2 of Compound 1 is between 20 h and 30 h. The absolute bioavailability of Compound 1 at 45, 180 and 720 mg/kg groups were 23.68%, 14.67% and 11.93%, respectively. The rates of plasma protein binding of Compound 1 at 9, 18 and 36 mg/ml of Compound 1 are 62.13±9.41%, 71.20±24.98% and 49.00±25.59%, respectively. Compound 1 was widely distributed throughout the body, and high levels of compound 1 were found in the kidney and liver. The level of Compound 1 in excretion was lower: 30% for urine, 0.28% for feces and 0.42% for bile, respectively. For elaborate pharmacokinetic characteristics to be fully understood, the metabolism of Compound 1 needs to be studied further.

Assessment of current criteria for primary nonresponse in chronic hepatitis B patients receiving entecavir therapy

A primary nonresponse to oral drugs against hepatitis B virus (HBV) is a generally accepted criterion for interrupting treatment. We investigated whether the concept of primary nonresponse suggested by current American (AASLD) and European (EASL) guidelines is appropriate for treatment with entecavir (ETV). The study included 1,254 treatment-naïve patients who had pretreatment HBV DNA levels of >2,000 IU/mL and received ETV 0.5 mg/day for over 6 months. "Primary nonresponse" was defined as a <2 log drop in HBV DNA after 6 months of therapy by AASLD and as a <1 log drop after 3 months by EASL. The cumulative probability of virological response (VR; HBV DNA of <15 IU/mL) was compared in patients with and without primary nonresponse. Median time to achieve VR was significantly shorter in primary responders by AASLD than nonresponders (12 versus 24 months; P = 0.004), but the cumulative probability of achieving a VR at 54 months was similar in the two groups (95.8% versus 100%). Time to achieve a VR and cumulative probability of VR over time did not differ between primary responders and nonresponders by EASL. On-treatment virological breakthrough occurred in 18 patients with a cumulative rate of 5.6% at 72 months. ETV resistance was detected in 13 of these 18 patients (72.2%), who were all classified as primary responder according to both guidelines.

CONCLUSION

Long-term ETV therapy generally leads to a VR in treatment-naïve patients, although the time to achieve it is delayed in primary nonresponders. The current recommendation to change therapy in primary nonresponders needs to be modified to reflect drug differences in antiviral potency and resistance risk.

Baseline prognostic factors and statistic model to predict early virological response in telbivudine-treated patients with chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) infection is still a worldwide disease, which may cause liver cirrhosis or even hepatocellular carcinoma. Telbivudine is a potent nucleoside analogue used in the treatment of chronic hepatitis B (CHB); however, drug resistance has remained a challenge. As early virological response can predict long-term efficacy of nucleotide analogue treatment, numerous studies have been conducted in this area.

OBJECTIVES

The aim of this study was to establish baseline prognostic factors and a statistical model to predict early virological response in telbivudine-treated CHB patients.

PATIENTS AND METHODS

One hundred and eight CHB patients without any experience of nucleotide analogue therapy were assigned to receive telbivudine (600 mg, once daily) for at least 24 weeks, and then were followed up every two weeks. Cox proportional hazard regression model analyses were employed to evaluate baseline variables, and further developing a statistical model to predict early virological response.

RESULTS

Negative family history of HBV infection (P = 0.000235), baseline higher serum TBIL (P = 0.038714) and AST (P = 0.020684) concentrations, and lower level of HBV-DNA (P = 0.0034784) were identified to be associated with higher possibility of early virological response. A model was established based on these variables to calculate the risk scores (R) for CHB patients. R > -0.38 suggested early virological response to telbivudine. The model was validated among an independent set of 20 patients.

CONCLUSIONS

Family history as well as baseline bilirubin, AST and HBV DNA levels can predict early virological response. The model provides a better tool for response prediction based on the four prognostic factors.

Prolonged Combination Therapy is More Effective than Monotherapy in Management of Chronic Hepatitis B Patients With Sustained Virological Response: An Experience From a 'Real-World' Clinical Setting

BACKGROUND

Little is known about the duration of combination therapy for patients with chronic hepatitis B (CHB) and suboptimal response to nucleos(t)ide analogues(NAs) monotherapy.

OBJECTIVES

This study aimed to assess whether monotherapy could be used for treatment of CHB patients, who poorly responded to Adefovir Dipivoxil (ADV) but obtained good responses after at least 12-month lamivudine (LAM) or telbivudine (LdT) add-on therapy.

PATIENTS AND METHODS

Forty-five patients were enrolled, and the baseline time-point was determined according to enrollment data. Twenty-six patients chose to continue combination therapy (LAM+ADV or LdT+ADV, Group A) and 19 patients switched to single-drug maintenance therapy (LAM or LdT or ADV, Group B).

RESULTS

There were no significant differences between two groups in baseline characteristics (P > 0.05). At 12th month, sustained virological response rate was greater in group A compared to group B (96.2% vs. 47.4%, P < 0.001), and the rates of NAs-associated resistance were 0% in group A and 15.8% in group B. Alanine aminotransferase normalization rate was also significantly higher in group A compared with group B (92.3% vs. 36.8%, P < 0.001). Among hepatitis positive patients with Be antigen (HBeAg)-, 40% (4/10) in group A and 9.1% (1/11) in group B achieved HBeAg seroconversion at the 12th month. Of patients in group B with positive-HBeAg before the previous combination therapy and detectable HBV DNA at 6 months of previous combination therapy were associated with high risks of viral relapse after switching to single-drug maintenance therapy.

CONCLUSIONS

Prematurely switching to single-drug maintenance therapy would be resulted in viral relapse, and prolonged combination therapy was effective to maintain sustained responses for patients with initial suboptimal response to ADV.

Economic evaluation of treatments for chronic hepatitis B

The aim of this study was to conduct a cost-utility study of adefovir, entecavir, interferon alpha, pegylated interferon alpha, lamivudine and tenofovir for chronic hepatitis B in the context of Brazilian Public Health Care System. A systematic review was carried out for efficacy and safety. Another review was performed to collect utility data and transition probabilities between health states. A Markov model was developed in a time horizon of 40 years with annual cycles for three groups of: HBeAg positive, HBeAg negative, and all patients. These strategies were compared to a fourth group that received no treatment. Discount rates of 5% were applied and sensitivity analyses were performed. Tenofovir offered the best cost-utility ratio for the three evaluated models: U$397, U$385 and U$384 (per QALY, respectively, for HBeAg positive, negative, and all patients). All other strategies were completely dominated because they showed higher costs and lower effectiveness than tenofovir. The sequence of cost-utility in the three models was: tenofovir, entecavir, lamivudine, adefovir, telbivudine, pegylated interferon alpha, and interferon alpha. In the sensitivity analysis, adefovir showed lower cost-utility than telbivudine in some situations. The study has some limitations, primarily related to the creation of scenarios and modeling. In this study, tenofovir presented the best cost-utility ratio. The results obtained in this study will be valuable in decision-making and in the review of the clinical protocol, mainly involving the allocation of available resources for health care.

Response to higher dose of entecavir 1.0 mg daily in patients with partial response to entecavir 0.5 mg daily

BACKGROUND

Despite its high potency against hepatitis B virus (HBV), entecavir (ETV) 0.5 mg daily may not be sufficient to induce complete viral suppression in some patients with very high pretreatment viremia. It is not clear whether ETV 1.0 mg daily would have additive effect in such patients.

GOALS

Our goal was to examine virologic outcome of ETV 1.0 mg daily in patients with partial response to ETV 0.5 mg daily.

METHODS

We retrospectively studied 31 consecutive treatment-naive patients who were switched to ETV 1.0 mg daily after partial response [reduction of HBV DNA ≥2 log10 IU/mL but with detectable HBV DNA levels (>100 IU/mL) after 24 weeks of therapy or longer] with ETV 0.5 mg daily from January 2005 to January 2010 at 2 clinics.

RESULTS

All patients were Asians and 90% had positive hepatitis B e antigen. Mean HBV DNA was 8.04±0.65 log10 IU/mL before therapy and 3.64±0.91 log10 IU/mL at the time of switch. Overall rate of complete viral suppression were 29% (n=9/31) after 24 weeks of ETV 1.0 mg daily and 22% (n=5/23) after 48 weeks. Complete viral suppression after 24 weeks with ETV 1.0 mg daily was significantly higher in patients with lower HBV DNA (<3 log10 IU/mL) at time of switch: 75% versus 5%, P<0.0001.

CONCLUSIONS

The majority of patients with partial response to ETV 0.5 mg daily did not achieve complete viral suppression with the higher dose of ETV 1.0 mg daily except those with minimal residual viremia (HBV DNA <3 log10 IU/mL).

Treatment eligibility of patients with chronic hepatitis B initially ineligible for therapy

BACKGROUND & AIMS

Chronic hepatitis B (CHB) is a dynamic disease, therefore patients initially ineligible for treatment, based on current guidelines, often become eligible at some point during their follow-up evaluation. We investigated the reasons for this change and developed a timeline for treatment eligibility for this population.

METHODS

We performed a retrospective cohort study of 245 consecutive treatment-naive, community-based patients with CHB who were not eligible for treatment when they first presented, from March 2007 through June 2010 (mean age, 44 y, almost all Asian). The patients were followed up for a median period of 26 months, receiving standard laboratory tests. They were treated according to US panel 2008 and American Association for Liver Disease (AASLD) 2009 guidelines.

RESULTS

Fifty-four patients (22%) became eligible for treatment during the follow-up period; most of these (n = 47; 87%) were based on only the US Panel algorithm and the rest were based on AASLD guidelines (n = 7; 13%). Six percent of patients met the treatment criteria at 1 year, 18% at 2 years, and 29% at 3 years. Among hepatitis B e antigen-positive patients with levels of hepatitis B virus (HBV) DNA greater than 3 log IU/mL at baseline, 11% met treatment criteria at 1 year, 52% at 2 years, and 80% at 3 years. Based on Cox multivariate analysis, which included age; sex; and levels of hepatitis B e antigen, alanine aminotransferase, and HBV DNA, an increase in HBV DNA level was the only factor from the US panel associated with treatment eligibility (hazard ratio, 1.43; P < .001), and an increase in alanine aminotransferase was the only factor associated with treatment eligibility from the AASLD guidelines (hazard ratio, 1.03; P = .001).

CONCLUSIONS

Although most patients with CHB who initially are not eligible for treatment remain ineligible, almost 30% become eligible within 3 years. These findings indicate the importance of carefully following disease status in patients with CHB.

Influence of age and HBeAg status on the correlation between HBV DNA and hepatic inflammation and fibrosis in chronic hepatitis B patients

AIMS

The purpose of this study was to examine the correlation between serum HBV DNA level and the severity of hepatic inflammation and fibrosis in patients with chronic hepatitis B.

METHODS

Liver function, serological markers of HBV and serum HBV DNA quantification were assayed in 215 CHB patients who also underwent liver biopsy. Liver pathology was regarded as the evaluation criteria to evaluate the correlation between serum HBV DNA level and the severity of liver inflammation and fibrosis.

RESULTS

Of the 215 patients, 136 were HBeAg-positive and 79 were HBeAg-negative; 134 patients had mild hepatic inflammation and fibrosis and 81 had significant hepatic inflammation and fibrosis in pathological diagnosis. We found that positive correlation between the severity of hepatic inflammation and fibrosis and serum HBV DNA level was only present in HBeAg-negative patients but not HBeAg-positive patients (P < 0.001). Patients' age was a key factor influencing the correlation between serum HBV DNA level and the severity of hepatic inflammation and fibrosis. the cutoff values to predict the severity of hepatic inflammation and fibrosis were 33.5 and 36 years, respectively. Using 35 years as the cutoff value, positive correlation between serum HBV DNA level and hepatic inflammation and fibrosis was observed in both HBeAg-positive and HBeAg-negative patients aged ≥ 35 years (P < 0.05), however no correlation was observed in HBeAg-positive patients aged <35 years.

CONCLUSIONS

There was positive correlation between serum HBV DNA level and hepatic inflammation and fibrosis in both HBeAg-positive and HBeAg-negative patients' aged ≥ 35 years, but in patients aged <35 years, positive correlation was only observed in HBeAg-negative patients.

Hepatitis B viral factors and treatment responses in chronic hepatitis B

Baseline and on-treatment hepatitis B viral factors are reported to affect treatment responses. A lower baseline hepatitis B virus (HBV) DNA level is a strong predictor of the response to antiviral therapy. HBV genotype A/B patients have better responses to interferon-based therapy than those with genotypes C/D. Regarding the association of HBV mutants with responses to antiviral therapy, current evidence is limited. On-treatment viral suppression is the most important predictor of response to nucleoside analogs. On-treatment hepatitis B surface antigen decline is significantly associated with response to pegylated interferon. In the future, individualized therapy should be based on treatment efficacy, adverse effects, baseline and on-treatment predictors of antiviral therapy.

Effect of nucleos(t)ide analogue therapy on hepatocarcinogenesis in chronic hepatitis B patients: a propensity score analysis

BACKGROUND & AIMS

Some patients with chronic hepatitis B virus (HBV) infection progress to hepatocellular carcinoma (HCC). However, the long-term effect of nucleos(t)ide analogue (NA) therapy on progression to HCC is unclear.

METHODS

Therefore, we compared chronic hepatitis B patients who received NA therapy to those who did not, using a propensity analysis.

RESULTS

Of 785 consecutive HBV carriers between 1998 and 2008, 117 patients who received NA therapy and 117 patients who did not, were selected by eligibility criteria and propensity score matching. Factors associated with the development of HCC were analyzed. In the follow-up period, HCC developed in 57 of 234 patients (24.4%). Factors significantly associated with the incidence of HCC, as determined by Cox proportional hazards models, include higher age (hazard ratio, 4.36 [95% confidence interval, 1.33-14.29], p=0.015), NA treatment (0.28 [0.13-0.62], p=0.002), basal core promoter (BCP) mutations (12.74 [1.74-93.11], p=0.012), high HBV core-related antigen (HBcrAg) (2.77 [1.07-7.17], p=0.036), and high gamma glutamyl transpeptidase levels (2.76 [1.49-5.12], p=0.001).

CONCLUSIONS

NA therapy reduced the risk of HCC compared with untreated controls. Higher serum levels of HBcrAg and BCP mutations are associated with progression to HCC, independent of NA therapy.

Comparative efficacy of oral nucleoside or nucleotide analog monotherapy used in chronic hepatitis B: a mixed-treatment comparison meta-analysis

STUDY OBJECTIVE

To compare the efficacy of nucleoside or nucleotide analog monotherapy for the treatment of chronic hepatitis virus B (HBV) with adefovir dipivoxil, entecavir, lamivudine, telbivudine, and tenofovir disoproxil fumarate.

DESIGN

Mixed-treatment comparison meta-analysis of nine randomized controlled clinical trials.

PATIENTS

A total of 3972 adults with a diagnosis of chronic hepatitis B.

MEASUREMENTS AND MAIN RESULTS

A systematic review was conducted to search for randomized clinical trials that evaluated the efficacy of nucleoside or nucleotide analogs used as monotherapy. The evaluated outcomes were reduction of HBV DNA levels, normalization of alanine aminotransferase levels, and seroconversion of hepatitis B e antigen (HBeAg). A mixed-treatment comparison was conducted to compare the odds ratios among the treatments and to rank the therapies to determine the optimal treatment option. Tenofovir had the best results among the nucleoside or nucleotide analogs for the three evaluated efficacy outcomes in both HBeAg-positive and -negative patients.

CONCLUSION

Tenofovir has the highest probability of reducing HBV DNA, normalizing alanine aminotransferase levels and inducing HBeAg seroconversion after 1 year of treatment. An efficacy comparison of therapies is an important tool to guide clinicians in selecting the optimal treatment option.

Prevalence and significance of Hepatitis B reverse transcriptase mutants in different disease stages of untreated patients

AIMS

Hepatitis B virus (HBV) reverse transcriptase (RT) mutants, which have not been well characterized according to different disease stages. This study aimed to characterize the profiles of naturally occurring mutations in the HBV RT region and their associated clinical outcomes.

METHODS

HBV RT region mutations and genotypes were determined by PCR-direct sequencing and compared with p-distance model.

RESULTS

Among 467 consecutive eligible patients (262 chronic hepatitis B patients, 105 cirrhotic patients and 100 hepatocellular carcinoma patients), the nucleos(t)ide analogues-related mutations (rtI169T, rtV173L, rtL180M, rtA181T, rtS202C, rtM204I/V, rtN236T) were found. The p-distance value reached a peak in the age of 20-30 years in the CHB patients and in the age of 40-45 years in the cirrhotic patients and hepatocellular carcinoma patients. The naturally occurring mutation, rtS106C mutation was higher in chronic hepatitis B patients (14/100, 14.0%) and cirrhotic patients (14/100, 14.0%) than that in hepatocellular carcinoma patients (4/100, 4.0%, P = 0.013). And the rtD134E/G/N/S mutations were also higher in chronic hepatitis B patients (22/100, 22.0%) and cirrhotic patients (21/100, 21.0%) than that in hepatocellular carcinoma patients (10/100, 10.0%, P = 0.021 and P = 0.032 respectively). The mutation frequencies in A-B interdomain were higher in cirrhotic patients (101/1900, 5.3%) than that in hepatocellular carcinoma patients (68/1900, 3.6%) (P = 0.009).

CONCLUSIONS

The nucleos(t)ide analogues-related mutations do exist in treatment naive patients with different disease stages. rtS106C, rtD134E/G/N/S and A-B interdomain mutations may be associated with necro-inflammation, immune response and cirrhosis development at ages older than 40.

Pretreatment serum HBsAg-to-HBV DNA ratio predicts a virologic response to entecavir in chronic hepatitis B

Background/Aims

Decay of hepatitis B surface antigen (HBsAg) titers has previously been shown to be predictive of a virologic response (VR), especially during peginterferon-alpha therapy. However, the role of HBsAg levels in predicting a VR to nucleos(t)ide analog therapy has not yet been established. In this study we sought to determine whether the VR can be predicted from HBsAg titers in nucleos(t)ide-naïve chronic hepatitis B (CHB) patients treated with entecavir.

Methods

CHB patients who started entecavir as an initial antiviral therapy were enrolled in this study. Serum hepatitis B virus (HBV) DNA, HBsAg, and alanine aminotransferase levels were measured every 3 months during treatment. A VR was defined as undetectable serum HBV DNA titer by real-time PCR assay (<60 IU/mL).

Results

Fifty-two patients were enrolled, and the median duration of treatment was 26 months (range 7-35 months). Forty-five patients achieved a VR; the cumulative VR rates at 3, 6, 12, and 24 months were 40%, 71.2%, 81.5%, and 88%, respectively. Baseline HBV DNA levels were significantly lower in patients with VR, whereas the HBsAg levels did not differ significantly between patients with or without VR. In a univariate analysis the cumulative VR rate was significantly higher in HBeAg negative patients and patients with an HBsAg/HBV DNA ratio above 0.56. However, in a multivariate analysis only an HBsAg/HBV DNA ratio above 0.56 was an independent predictor of VR (P=0.003). The area under the receiver operating characteristic curve was larger for the HBsAg/HBV DNA ratio than for either HBV DNA or HBsAg.

Conclusions

Pretreatment HBsAg/HBV DNA ratio can predict a long-term VR to entecavir therapy in nucleos(t)ide-naïve CHB patients.

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.

The efficacy of entecavir therapy in chronic hepatitis B patients with suboptimal response to adevofir

BACKGROUND

An increasing number of patients with chronic hepatitis B (CHB) have experienced treatment failure to adefovir (ADV) and their management poses a growing challenge. Very limited data are available on the efficacy of entecavir (ETV) in patients previously treated with ADV.

AIM

To examine the effect of ETV monotherapy on HBV DNA and ALT levels in CHB patients previously treated with ADV, but switched to ETV due to suboptimal response.

METHODS

Study candidates were enrolled from five community gastroenterology clinics in the U.S. Each completed at least 12 months of ETV treatment after being previously treated with ADV and experiencing suboptimal response. Primary and secondary outcome measurements were complete viral suppression (CVS, HBV DNA <100 IU/mL) and biochemical response (BR, ALT < 40 U/L), respectively.

RESULTS

A total of 60 patients were included in this analysis. Twelve were lamivudine (LAM)-experienced and none were LAM-resistant. At time of switch to ETV, no patients had experienced CVS. The CVS rate was 68% after 12 months of ETV therapy. The BR rate was 67% at switch to ETV and 80% after 12 months. There was no significant difference in response rates between LAM-experienced and naïve patients. Among the eight patients with ADV resistance, each achieved CVS after 12 months of ETV therapy and seven achieved BR.

CONCLUSIONS

In patients with suboptimal response to adefovir, complete viral suppression and biochemical response can be achieved in the majority by 12 months after switching to entecavir, including patients with prior exposure to lamivudine and those with adefovir resistance.

Characterization of drug-resistance mutations in HBV D-genotype chronically infected patients, naïve to antiviral drugs

Presence of drug-resistance mutations in drug-naïve hepatitis B virus (HBV) infected patients can seriously compromise response to antiviral treatment. Therefore, our study was aimed at defining the prevalence of HBV drug-resistance in a population of 140 patients, all infected with HBV-D-genotype (the most common HBV-genotype in Eastern Europe, Mediterranean countries and Middle East) and naïve to antiviral therapy. HBV reverse-transcriptase (RT) region was sequenced and analyzed for 20 mutations, confirmed by in vitro studies as associated with resistance to nucleos(t)ide HBV-RT inhibitors (rtL80I/V-rtI169T-rtV173L-rtL180M-rtA181T/V/S-rtT184A/S/G/C-rtA194T-rtS202C/G/I-rtM204V/I-rtN236T-rtM250V). Amino acid changes at other six RT positions, potentially associated with resistance, were also analyzed (rtV84M-rtV191I-rtV207L-rtV214A-rtQ215S-rtI233V). Overall, only 2/140 (1.4%) patients carried primary drug-resistance mutations [rtA181V (0.7%), and rtA194T (0.7%)], while 3/140 (2.1%) patients harbored the secondary mutations rtV173L (1.4%) and rtL180M (0.7%). Additionally, five polymorphic mutations, with a suggested role in drug resistance, were detected [rtQ215S (12.8%), rtI233V (4.3%), rtV214A (3.6%), rtV191I (0.7%), rtV207L (0.7%)]. Notably, no YMDD mutations, namely rtM204V/I, were found. Taken together, the rate of important drug resistance mutations in naïve HBV D-genotype infected patients is today very low, and suggests the potential full efficacy of new-generation antiviral drugs used in first line therapy. Whether such low rate can be extrapolated to non HBV-D subtypes, requires a detailed investigation to be performed in a different cohort of patients.

Unawareness of HBV infection among inpatients in a Southern Italian hospital

Hepatitis B virus (HBV) infection may run undetected. Unawareness of an ongoing infection delays the diagnosis of HBV-related liver disease and favours the spread of the virus. We have evaluated among hepatitis B surface antigen-positive (HBsAg) inpatients admitted to a Southern Italian hospital the proportion of those aware of their carrier status and correlated the status to signs of liver disease. All patients admitted to the San Giovanni Rotondo Hospital from March 2008 to July 2009 were tested for HBV and hepatitis C virus (HCV) markers, and those positive for HBsAg were interviewed and underwent examinations for liver function and abdominal ultrasound. Overall, of 25,000 patients admitted during the observation period 311 (1.2%) were positive for HBsAg, most of them (98%) being anti-HBe positive. HCV and HDV co-infections were ascertained in 2.9% and 0.6% of cases, respectively. Two hundred and fifty-three subjects (81%) agreed to undergo further investigation, 132 of them (52%) were HBV-DNA positive. One hundred and two patients (40.3%) were unaware of their infection; this was encountered among 29% of HBV-DNA-positive and 52% of HBV-DNA-negative subjects (P < 0.01). Subjects already aware of their infection were more likely to present with abnormal alanine aminotransferase (ALT) levels (27%vs 15%), serological presence of HBV-DNA (63.6% vs. 36%) and liver cirrhosis (30%vs. 13%). A high proportion of HBsAg-positive patients (40.3%) were unaware of their infection, which had evolved to the stage of liver cirrhosis in a consistent percentage of them.

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.

Influence of mutagenesis and viral load on the sustained low-level replication of an RNA virus

Lethal mutagenesis is an antiviral strategy that aims to extinguish viruses as a consequence of enhanced mutation rates during virus replication. The molecular mechanisms that underlie virus extinction by mutagenic nucleoside analogues are not well understood. When mutagenic agents and antiviral inhibitors are administered sequentially or in combination, interconnected and often conflicting selective constraints can influence the fate of the virus either towards survival through selection of mutagen-escape or inhibitor-escape mutants or towards extinction. Here we report a study involving the mutagenesis of foot-and-mouth disease virus (FMDV) by the nucleoside analogue ribavirin (R) and the effect of R-mediated mutagenesis on the selection of FMDV mutants resistant to the inhibitor of RNA replication, guanidine hydrochloride (GU). The results show that under comparable (and low) viral load, an inhibitory activity by GU could not substitute for an equivalent inhibitory activity by R in driving FMDV to extinction. Both the prior history of R mutagenesis and the viral population size influenced the selection of GU-escape mutants. A sufficiently low viral load allowed continued viral replication without selection of inhibitor-escape mutants, irrespective of the history of mutagenesis. These observations imply that reductions of viral load as a result of a mutagenic treatment may provide an opportunity either for immune-mediated clearing of a virus or for an alternative antiviral intervention, even if extinction is not initially achieved.

Antiviral drug resistance: mechanisms and clinical implications

Antiviral drug resistance is an increasing concern in immunocompromised patient populations, where ongoing viral replication and prolonged drug exposure lead to the selection of resistant strains. Rapid diagnosis of resistance can be made by associating characteristic viral mutations with resistance to various drugs as determined by phenotypic assays. Management of drug resistance includes optimization of host factors and drug delivery, selection of alternative therapies based on knowledge of mechanisms of resistance, and the development of new antivirals. This article discusses drug resistance in herpesviruses and hepatitis B.

Antiviral drug resistance: mechanisms and clinical implications

Antiviral drug resistance is an increasing concern in immunocompromised patient populations, where ongoing viral replication and prolonged drug exposure lead to the selection of resistant strains. Rapid diagnosis of resistance can be made by associating characteristic viral mutations with resistance to various drugs as determined by phenotypic assays. Management of drug resistance includes optimization of host factors and drug delivery, selection of alternative therapies based on knowledge of mechanisms of resistance, and the development of new antivirals. This article discusses drug resistance in herpesviruses and hepatitis B.

Treatment outcomes of clevudine versus lamivudine at week 48 in naïve patients with HBeAg positive chronic hepatitis B

The authors assessed the efficacy and antiviral resistance of 48-week clevudine therapy versus lamivudine in treatment of naïve patients with HBeAg positive chronic hepatitis B. In this retrospective study, a total of 116 HBeAg positive patients, who received 30 mg of clevudine once daily (n=53) or 100 mg of lamivudine once daily (n=63) for 48 weeks, were included. At week 48, clevudine therapy produced a significantly greater mean reductions in serum HBV DNA levels from baseline than lamivudine therapy (-5.2 vs. -4.2 log(10)IU/mL; P=0.005). Furthermore, a significantly higher proportion of patients on clevudine achieved negative serum HBV DNA by PCR (<13 IU/mL) at week 48 (60.4% vs. 38.1%; P=0.025). The incidence of virologic breakthrough in the clevudine group was significantly lower than in the lamivudine group (9.4% vs. 25.4%; P=0.031). However, rates of alanine aminotransferase normalization and HBeAg loss or seroconversion were similar in the two groups (83.0% vs. 81.0%, 11.3% vs. 11.1%; P=0.813, 1.000, respectively). In conclusion, clevudine is more potent for viral suppression and lower for antiviral resistance at week 48 than lamivudine in treatment of naïve patients with HBeAg positive chronic hepatitis B.

On-treatment serum HBsAg level is predictive of sustained off-treatment virologic response to telbivudine in HBeAg-positive chronic hepatitis B patients

BACKGROUND

Effective management of chronic hepatitis B infection is still very challenging, despite decades of clinical research. Telbivudine is one of the most frequently used antiviral drug at the current stage, but its long-term effectiveness, particularly at off-treatment, is still unclear.

OBJECTIVES

To assess on-treatment HBsAg kinetics in patients treated with telbivudine for 2 years, and predicting sustained virologic response (SR) at 2 years off-treatment.

STUDY DESIGN

Serum HBV DNA/HBsAg levels were assessed from 17 HBeAg+ patients treated with telbivudine 600 mg/day for 104 weeks, at baseline, weeks 24, 52 and 104, as well as during off-treatment follow-up.

RESULTS

HBsAg levels <2 log(10)IU/ml at treatment week 104 were highly predictive of SR (i.e., HBV DNA <300 copies/ml, HBeAg seroconversion, ALT normalization) at 2 years off-treatment (positive predictive value [PPV], 93%; negative predictive value [NPV], 100%). HBsAg levels consistently declined from baseline only in patients achieving SR during 2 years off-treatment. At weeks 24 and 52, HBsAg decline rate was a better predictor of off-treatment response than HBV DNA decline rate. HBsAg decline rates of >0.8 and >1 log(10)IU/ml at treatment weeks 24 and 52 were predictive of SR (PPV, 75%; NPV, 86% at week 24; PPV, 75%; NPV, 86% at week 52).

CONCLUSIONS

Serum HBsAg levels <2 log(10)IU/ml at treatment week 104 are highly predictive of SR to telbivudine at 2 years off-treatment. HBsAg decline rate at on-treatment weeks 24 and 52 from baseline were also more predictive of SR than HBV DNA decline rate.

Tenofovir for the treatment of hepatitis B virus

Tenofovir disoproxil fumarate is a nucleotide analog reverse transcriptase inhibitor recently approved by the United States Food and Drug Administration (FDA) for the treatment of chronic hepatitis B virus (HBV) infection in adults. Tenofovir has been available in the United States for the treatment of human immunodeficiency virus (HIV) since 2001. It blocks HBV replication in liver cells and is available as a once-daily oral formulation. The efficacy of tenofovir for the treatment of chronic HBV has been demonstrated to be superior to adefovir in randomized controlled trials, which led to its FDA approval for use in chronic HBV. Because of its potent antiviral activity, favorable safety profile, and higher barrier to the development of resistance, tenofovir should replace adefovir as a first-line monotherapy option in the treatment of HBV in monoinfected patients. In the HIV-HBV-coinfected population, tenofovir is already a preferred agent in combination with other anti-HBV agents (lamivudine or emtricitabine), which are cotreatments for HIV as well. In addition, tenofovir monotherapy or in combination with nucleoside analogs are options for patients who have developed resistance to other therapies for chronic HBV, including lamivudine and adefovir.

HBV and HCV therapy

One year of interferon therapy inhibits HBV replication in one third of the patients whereas long-term administration of oral nucleos(t)ide analogues is efficient in most of them, as long as early treatment adaptation in patients with partial virological response and resistance is provided. Following the demonstration of a more potent antiviral effect in terms of sustained virological response (SVR) rates, Pegylated-IFN coupled with Ribavirin has become the standard treatment for chronic hepatitis C, with nearly 65% of all treated patients achieving a SVR. Long-term suppression of HBV and eradication of HCV would halt the progression of chronic hepatitis to cirrhosis, hepatocellular carcinoma and liver decompensation.

On-treatment monitoring of HBV DNA levels: predicting response and resistance to oral antiviral therapy at week 24 versus week 48

The suppression of hepatitis B viral (HBV) load correlates with favorable histologic, biochemical, and serologic responses in clinical trials of patients with chronic hepatitis B (CHB). The ability to identify patients who will not experience durable viral suppression in response to a specific antiviral regimen affords the opportunity for early treatment modification to optimize outcomes and avoid the development of antiviral resistance. Substantial evidence demonstrates that on-treatment serum HBV DNA levels are predictive of virologic response and risk of resistance. Regional clinical practice guidelines for the management of CHB universally recommend monitoring serum HBV DNA levels at treatment week 24. However, the value of this time point as a predictor of long-term success may not be applicable to all types of antiviral therapy. Indeed, each oral nucleos(t)ide analog (NA) antiviral therapy has a unique profile of potency, genetic barriers to resistance, and viral kinetics that may affect the optimal time point for on-treatment monitoring. This review discusses available data for appropriate predictors for long-term response and antiviral resistance for patients receiving specific oral NA antiviral therapy. Guidelines for on-treatment monitoring are also discussed.

Potential benefits of sequential inhibitor-mutagen treatments of RNA virus infections

Lethal mutagenesis is an antiviral strategy consisting of virus extinction associated with enhanced mutagenesis. The use of non-mutagenic antiviral inhibitors has faced the problem of selection of inhibitor-resistant virus mutants. Quasispecies dynamics predicts, and clinical results have confirmed, that combination therapy has an advantage over monotherapy to delay or prevent selection of inhibitor-escape mutants. Using ribavirin-mediated mutagenesis of foot-and-mouth disease virus (FMDV), here we show that, contrary to expectations, sequential administration of the antiviral inhibitor guanidine (GU) first, followed by ribavirin, is more effective than combination therapy with the two drugs, or than either drug used individually. Coelectroporation experiments suggest that limited inhibition of replication of interfering mutants by GU may contribute to the benefits of the sequential treatment. In lethal mutagenesis, a sequential inhibitor-mutagen treatment can be more effective than the corresponding combination treatment to drive a virus towards extinction. Such an advantage is also supported by a theoretical model for the evolution of a viral population under the action of increased mutagenesis in the presence of an inhibitor of viral replication. The model suggests that benefits of the sequential treatment are due to the involvement of a mutagenic agent, and to competition for susceptible cells exerted by the mutant spectrum. The results may impact lethal mutagenesis-based protocols, as well as current antiviral therapies involving ribavirin.

RNA viruses are associated with many important human and animal diseases such as AIDS, influenza, hemorrhagic fevers and several forms of hepatitis. RNA viruses mutate at very high rates and, therefore, can adapt easily to environmental changes. Viral mutants resistant to antiviral inhibitors are readily selected, resulting in treatment failure. The simultaneous administration of three or more inhibitors is a means to prevent or delay selection of resistant mutants. A new antiviral strategy termed lethal mutagenesis is presently under investigation. It consists of the administration of mutagenic agents to elevate the mutation rate of the virus above the maximum level compatible with virus infectivity, without mutagenizing the host cells. Since low amounts of virus are extinguished more easily, the combination of a mutagen and inhibitor was more efficient than a mutagen alone in driving virus to extinction. Here we show that foot-and-mouth disease virus replicating in cell culture can be extinguished more easily when the inhibitor guanidine is administered first, followed by the mutagenic agent ribavirin, than when both drugs are administered simultaneously. Interfering mutants that contribute to extinction were active in the presence of ribavirin but not in the presence of guanidine. This observation provides a mechanism for the advantage of the sequential versus the combination treatment. This unexpected effectiveness of a sequential treatment is supported by a theoretical model of virus evolution in the presence of the inhibitor and the mutagen. The results can have an application for future lethal mutagenesis protocols and for current antiviral treatments that involve the antiviral agent ribavirin when it acts as a mutagen.