Cross-study analysis of the relative efficacies of oral antiviral therapies for chronic hepatitis B infection in nucleoside-naive patients

Management of Hepatitis B Virus Infection: 2018 Guidelines from the Canadian Association for the Study of Liver Disease and Association of Medical Microbiology and Infectious Disease Canada

Hepatitis B virus (HBV) infection is an important public health problem in Canada. In keeping with evolving evidence and understanding of HBV pathogenesis, the Canadian Association for the Study of Liver Disease periodically publishes HBV management guidelines. The goals of the 2018 guidelines are to (1) highlight the public health impact of HBV infection in Canada and the need to improve diagnosis and linkage to care, (2) recommend current best-practice guidelines for treatment of HBV, (3) summarize the key HBV laboratory diagnostic tests, and (4) review evidence on HBV management in special patient populations and include more detail on management of HBV in pediatric populations. An overview of novel HBV tests and therapies for HBV in development is provided to highlight the recent advances in HBV clinical research. The aim and scope of these guidelines are to serve as an up-to-date, comprehensive resource for Canadian health care providers in the management of HBV infection.

Adefovir dipivoxil is less expensive than lamivudine and associated with similar prognosis in patients with hepatitis B virus-related hepatocellular carcinoma after radical resection

Aim

Lamivudine (LAM) and adefovir dipivoxil (ADV) are widely used in patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), but few studies have directly compared their therapeutic efficacy and treatment cost. This study aims to compare LAM with ADV head-to-head in these patients.

Methods

We retrospectively analyzed 201 patients with HBV-related HCC who underwent radical resection and subsequently received LAM (n=155) or ADV (n=46). The two groups were compared in terms of HBV-DNA levels, liver function, antiviral resistance, recurrence-free, and overall survival, as well as antiviral medication costs.

Results

Despite significant improvement in HBV-DNA and alanine aminotransferase level in the LAM group after 1 year of antiviral therapy, these parameters did not differ significantly between the two groups over the following 2 years. Incidence of antiviral resistance after 1, 2, and 3 years of antiviral treatment was significantly higher in the LAM group (19.5%, 45.7%, and 56.4%) than in the ADV group (0%, 3.3%, and 14.5%; P<0.001). Overall survival at 1, 2, and 3 years after resection was similar for the LAM group (84.5%, 69.3%, and 64.6%) and the ADV group (84.1%, 77.8%, and 63.4%; P=0.905). Recurrence-free survival at the three follow-up points was also similar for the LAM group (71.7%, 58.3%, and 43.9%) and the ADV group (81.1%, 66.1%, and 53.0%; P=0.452). Cox regression analysis confirmed that both nucleos(t)ide analogues were associated with similar overall and recurrence-free survival. However, the average medication costs after 1, 2, and 3 years of antiviral treatment were significantly higher in the LAM group (€3.0, €4.8, and €5.6 per person per day) than in the ADV group (€2.2, €2.4, and €3.1 per person per day; all P<0.05).

Conclusion

ADV and LAM are associated with similar survival benefit in patients with HBV-related HCC after radical resection, but ADV is more cost-effective.

Response to potent anti-HBV agents in chronic hepatitis B and combined effect of HBV reverse transcriptase mutations

BACKGROUND AND AIM

Response to nucleos(t)ide analogue therapy against HBV infection depends on a number of factors. One of them is appearance of drug resistance mutations. The present study aimed to investigate the efficacy of ETV and TDF as anti-HBV agents and to analyze the role of HBV-RT mutations in reducing the efficacy of mentioned drugs.

MATERIAL AND METHODS

Sixty nine treatment naïve CHB patients (mean age 33.8 ± 11.9 years) were enrolled and treated with ETV or TDF for one year. Complete virological response (CVR) was defined as undetectable serum HBV DNA after 12 months of therapy. Amino acid and nucleotide sequence analyses of HBV-RT region were performed using Geno2pheno HBV drug resistance tool. The 3D model of HBV-RT protein was built by I-TASSER server and RMSD was calculated between wild type and mutated HBV-RT protein.

RESULTS

After 12 months of treatment, four CHB patients did not achieve CVR and all of them were with HBV genotype D. HBeAg seroconversion was achieved in 56% HBeAg positive patients after 12 months of antiviral therapy. The HBV-RT amino acid sequences from these four patients were used for in-silico analysis. It was found that the presence of many mutations in HBV-RT region of HBV isolated from these patients led to a high degree of variation in configuration of atoms of HBV-RT protein and also caused displacement of active site of this protein.

CONCLUSION

The efficacy of antiviral drugs in inhibiting HBV replication may be reduced by combined effect of many HBV-RT mutations; however, an in vitro study is needed to validate the findings.

The Molecular and Structural Basis of HBV-resistance to Nucleos(t)ide Analogs

Infection with hepatitis B virus (HBV) is a worldwide health problem. Chronic hepatitis B can lead to fibrosis, liver cirrhosis, and hepatocellular carcinoma (HCC). Management of the latter two conditions often requires liver transplantation. Treatment with conventional interferon or pegylated interferon alpha can clear the virus, but the rates are very low. The likelihood, however, of viral resistance to interferon is minimal. The main problems with this therapy are the frequency and severity of side effects. In contrast, nucleos(t)ide analogs (NAs) have significantly lower side effects, but require long term treatment as sustained virological response rates are extremely low. However, long term treatment with NAs increases the risk for the development of anti-viral drug resistance. Only by understanding the molecular basis of resistance and using agents with multiple sites of action can drugs be designed to optimally prevent the occurrence of HBV antiviral resistance.

Nucleoside analogs prevent disease progression in HBV-related acute-on-chronic liver failure: validation of the TPPM model

PURPOSE

This study aimed to evaluate the efficacy and safety of entecavir, lamivudine and telbivudine for treating patients with HBV-ACLF and to validate the Tongji prognostic predictor model (TPPM) in these patients.

METHODS

In this retrospective study, we enrolled 283 patients with HBV-ACLF (100 treated with entecavir, 98 treated with lamivudine and 85 treated with telbivudine). There were no significant differences in baseline clinical and virological characteristics among patients treated with entecavir, telbivudine or lamivudine.

RESULTS

There were no significant differences in the 4- and 12-week survival rates of entecavir-, telbivudine- and lamivudine-treated patients (79.00, 81.18 and 86.73 %, respectively, at 4 weeks; 67.00, 65.88 and 73.47 %, respectively, at 12 weeks). Patients in all three groups achieved an improvement in the model for end-stage liver disease (MELD) score. Using the Hosmer-Lemeshow test, the validation of the TPPM score for HBV-ACLF demonstrated a good degree of fit with disease prognosis. Based on this unique group of patients, the TPPM score with an AUC of 0.787 was superior to the MELD score, which had an AUC of 0.736 in the prediction of 12-week mortality. The TPPM had an AUC of 0.733, and the MELD score had an AUC of 0.672 in the prediction of 4-week mortality. Using a cutoff value of 0.22 for 12-week mortality prediction by the TPPM, the positive predictive value was 49.66 %, with a negative predictive value of 89.55 %.

CONCLUSION

Treatment with nucleoside analogs including entecavir, lamivudine and telbivudine prevented disease progression and increased the survival of patients with HBV-ACLF. Validation of the established TPPM scoring system in this study confirmed its superior predictive value for HBV-ACLF patients when compared with the MELD system.

Management of chronic hepatitis B: Canadian Association for the Study of the Liver consensus guidelines

Chronic hepatitis B (CHB) is a dynamic disease that is influenced by host and virological factors. The management of CHB has become more complex with the increasing use of long-term oral nucleos⁄tide analogue antiviral therapies and the availability of novel diagnostic assays. Furthermore, there is often a lack of robust data to guide optimal management such as the selection of therapy, duration of treatment, potential antiviral side effects and the treatment of special populations. In November 2011, the Canadian Liver Foundation and the Canadian Association for the Study of the Liver convened a consensus conference to review the literature and analyze published data, including other international expert guidelines on CHB management. The proceedings of the consensus conference are summarized and provide updated clinical practice guidelines to assist Canadian health care providers in the prevention, diagnosis, assessment and treatment of CHB.

Mixed treatment comparison meta-analysis evaluating the relative efficacy of nucleos(t)ides for treatment of nucleos(t)ide-naive patients with chronic hepatitis B

BACKGROUND/AIMS

Five nucleoside/nucleotide treatments are now available for chronic hepatitis B (CHB). This meta-analysis aimed to assess the relative efficacy of adefovir, entecavir, lamivudine, telbivudine, tenofovir disoproxil fumarate (TDF), and nucleos(t)ide combinations in the treatment of CHB.

METHODS

A systematic review of MEDLINE and the Cochrane library was conducted to identify all studies evaluating these nucleos(t)ides in adults with CHB. Randomized controlled trials were included in the meta-analysis if they reported the proportion of patients with undetectable hepatitis B virus (HBV) DNA or hepatitis B e antigen (HBeAg) loss/seroconversion at 1 year. Bayesian mixed treatment comparison meta-analyses were conducted in WinBUGS to assess relative efficacy.

RESULTS

A random-effects meta-analysis of trials on treatment-naive patients with HBeAg-positive CHB demonstrated that 94% of patients will achieve HBV DNA < 300 copies/ml after 1 year with TDF, compared with 73% for entecavir, 50% for adefovir, and 38% for lamivudine. There was a 97.7% probability that TDF enabled a greater proportion of patients to achieve HBV DNA < 300 copies/ml at 1 year than all other treatments considered in the analysis. TDF was significantly superior to all nucleos(t)ides for this outcome at the 0.05 level. There were no statistically significant differences between nucleos(t)ides in HBeAg seroconversion at 1 year, based on a fixed-effects meta-analysis in the same population. More trials on HBeAg-negative and drug-resistant patients are required to facilitate meta-analyses for these subgroups.

CONCLUSIONS

In nucleos(t)ide-naive patients with HBeAg-positive CHB, TDF is associated with the highest probability of achieving undetectable HBV DNA at 1 year of all nucleos(t)ides considered.

Entecavir: a review of its use in chronic hepatitis B

Entecavir (Baraclude), a nucleoside analogue, is rapidly phosphorylated to the active intracellular 5'-triphosphate form that inhibits replication of hepatitis B virus (HBV). Oral entecavir is approved in the US, EU and several countries worldwide for the treatment of chronic HBV infection in adults (> or =16 years of age) with evidence of active viral replication and persistently elevated serum ALT and/or AST levels, and/or histological evidence of active disease. In several randomized, double-blind, multicentre trials, oral entecavir was an effective and generally well tolerated treatment in nucleoside-naive and lamivudine-refractory adult patients with chronic HBV infection, irrespective of whether patients were hepatitis B e antigen (HBeAg)-positive or -negative. Furthermore, it was more efficacious, associated with a lower risk of resistance, and more cost effective than lamivudine in these patient populations, with both drugs having a similar tolerability profile. In the EARLY trial, entecavir was significantly more effective than and as well tolerated as adefovir dipivoxil therapy in nucleoside-naive patients. In addition, in a double-blind, multicentre trial, entecavir plus lamivudine-based highly active antiretroviral therapy (HAART) was more effective than placebo plus lamivudine-based HAART in patients co-infected with HBV and HIV. Although the exact position of entecavir relative to other agents, such as tenofovir disoproxil fumarate and adefovir dipivoxil, for the treatment of chronic HBV infection remains to be fully determined, an important aspect in this positioning is the emergence of drug resistance. Hence, entecavir therapy provides a valuable first-line option in nucleoside-naive patients with chronic HBV infection and is a useful alternative in lamivudine-refractory patients.

Early hepatitis B virus DNA reduction in hepatitis B e antigen-positive patients with chronic hepatitis B: A randomized international study of entecavir versus adefovir

This study was undertaken to compare the early antiviral activity and viral kinetic profiles of entecavir (ETV) versus adefovir (ADV) in hepatitis B e antigen positive nucleoside-naïve adults with chronic hepatitis B (CHB). Sixty-nine nucleoside-naïve CHB patients with baseline HBV DNA of 10(8) copies/mL or more were randomized 1:1 to open-label treatment with entecavir 0.5 mg/day or adefovir 10 mg/day for a minimum of 52 weeks. The primary efficacy analysis compared mean reduction in HBV DNA at week 12 adjusted for baseline levels using linear regression. Entecavir was superior to adefovir for mean change from baseline in HBV DNA at week 12 (-6.23 log(10) copies/mL versus -4.42 log(10) copies/mL, respectively; mean difference -1.58 log(10) copies/mL; P < 0.0001). Both drugs demonstrated biphasic viral kinetics, with a first phase of rapid decline lasting 10 days. A significant difference favoring ETV was reached at day 10 (day 10 ETV-ADV difference estimate: -0.66 log(10) copies/mL; 95% CI [-0.30, -0.01]). Early virological response was found to be predictive of subsequent virological response, with those having lower HBV DNA levels at day 10 being more likely to achieve HBV DNA of less than 300 copies/mL at week 48. In addition, there was considerably less variability in the extent of HBV DNA reductions in patients treated with entecavir versus adefovir. Both the mean decrease in serum HBV DNA and the proportion of patients achieving HBV DNA less than 300 copies/mL were greater in entecavir-treated than adefovir-treated patients at weeks 2, 4, 8, 12, 24, and 48. At week 48, one (3%) ETV-treated versus 15 (47%) ADV-treated patients had HBV DNA of 10(5) copies/mL or more. Both antivirals were well tolerated.

CONCLUSION

Entecavir therapy resulted in earlier and superior reduction in HBV DNA compared with adefovir in nucleoside-naïve HBeAg-positive patients with CHB.

Impact of viral replication inhibition by entecavir on peripheral T lymphocyte subpopulations in chronic hepatitis B patients

BACKGROUND

To investigate dynamic fluctuations of serum viral load and peripheral T-lymphocyte subpopulations of chronic hepatitis B patients and their correlation during entecavir therapy.

METHODS

Fifty-five patients received entecavir 0.5 mg/d therapy. Serum HBV DNA load was measured by Real-Time-PCR, and the levels of peripheral T-lymphocyte subpopulations by flow cytometry biweekly, every four weeks and every eight weeks during weeks 1-12, 13-24 and 24-48, respectively. Multilevel modelling was used to analyse the relationship between these variables.

RESULTS

Of the 55 patients, all HBeAg positive and with detectable HBV DNA, the majority (81.8%) had serum levels of HBV DNA over 10(7) copies per milliliter. HBV viral load dropped sharply during the first two weeks. In 28 and 43 patients, the level became undetectable from week 24 and 48, respectively. Using pre-therapy level as the reference, a significant decrease in CD8+ T cells and increase in CD4+ T cells were found from week 12. Both parameters and CD4+/CD8+ ratio steadily improved throughout the 48 weeks. Multilevel analyses showed that the level of decrement of HBV DNA was associated with the increment of T-lymphocyte activities only in the later period (4-48 week). After 4 weeks of therapy, for each log10 scale decrement of HBV DNA, the percentage of CD4+ lymphocyte was increased by 0.49 and that of CD8+ decreased by 0.51.

CONCLUSION

T-lymphocyte subpopulations could be restored partially by entecavir treatment in patients with chronic hepatitis B concurrently with reduction of viremia.

Understanding the molecular basis of HBV drug resistance by molecular modeling

Despite the significant successes in the area of anti-HBV agents, resistance and cross-resistance against available therapeutics are the major hurdles in drug discovery. The present investigation is to understand the molecular basis of drug resistance conferred by the B and C domain mutations of HBV-polymerase on the binding affinity of five anti-HBV agents [lamivudine (3TC, 1), adefovir (ADV, 2), entecavir (ETV, 3), telbivudine (LdT, 4) and clevudine (l-FMAU, 5)]. In this regard, homology modeled structure of HBV-polymerase was used for minimization, conformational search and induced fit docking followed by binding energy calculation on wild-type as well as on mutant HBV-polymerases (L180M, M204V, M204I, L180M+M204V, L180M-M204I). Our studies suggest a significant correlation between the fold resistances and the binding affinity of anti-HBV nucleosides. The binding mode studies reveals that the domain C residue M204 is closely associated with sugar/pseudosugar ring positioning in the active site. The positioning of oxathiolane ring of 3TC (1) is plausible due the induced fit orientation of the M204 residue in wild-type, and further mutation of M204 to V204 or I204 reduces the final binding affinity which leads to the drug resistance. The domain B residue L180 is not directly close ( approximately 6A) to the nucleoside/nucleoside analogs, but indirectly associated with other active-site hydrophobic residues such as A87, F88, P177 and M204. These five hydrophobic residues can directly affect on the incoming nucleoside analogs in terms of its association and interaction that can alter the final binding affinity. There was no sugar ring shifting observed in the case of adefovir (2) and entecavir (3), and the position of sugar ring of 2 and 3 is found similar to the sugar position of natural substrate dATP and dGTP, respectively. The exocyclic double bond of entecavir (3) occupied in the backside hydrophobic pocket (made by residues A87, F88, P177, L180 and M204), which enhances the overall binding affinity. The active site binding of LdT (4) and l-FMAU (5) showed backward shifting along with upward movement without enforcing M204 residue and this significant different binding mode makes these molecules as polymerase inhibitors, without being incorporated into the growing HBV-DNA chain. Structural results conferred by these l- and d-nucleosides, explored the molecular basis of drug resistance which can be utilized for future anti-HBV drug discovery.

New paradigms for the treatment of chronic hepatitis B

The main goals of chronic hepatitis B treatment should be the long-term suppression of viral replication to minimize disease progression and the risk for the development of hepatocellular carcinoma. Treatment end-points, depending on surrogate markers alone, in particular hepatitis B e-antigen seroconversion, may not be ideal for patients who acquire the disease early in life. Currently-available drugs include interferons and oral nucleoside/nucleotide analogs. Although interferon therapy provides a finite treatment period, a significant proportion of patients may not respond, and long-term outcome is inconclusive. Long-term efficacy has been demonstrated for both lamivudine and adefovir. However, prolonged nucleoside/nucleotide analog therapy is associated with the emergence of drug-resistant mutations. Therefore, nucleoside/nucleotide analogs with a high genetic barrier and potent antiviral activity, such as entecavir, should be used to reduce the chance of developing drug-resistant mutations. Drugs with a low genetic barrier, including lamivudine and telbivudine, should be used in conjunction with early testing for antiviral response. This can predict favorable outcomes in the long term. The early detection of drug-resistant mutations should prompt clinicians to either add or switch to another agent with a different drug-resistance profile. There are currently no treatment models in the use of combination or sequential therapy in treatment-naïve patients. To date, long-term treatment appears to be the most effective option. Despite recent advances made with better understanding on the natural history of chronic hepatitis B infection and with newer antiviral drugs available, challenges remain with respect to treatment criteria, treatment end-points, and duration of treatment.