Adefovir dipivoxil is effective for the treatment of cirrhotic patients with lamivudine failure

Effects of antiviral therapy in patients with chronic hepatitis B and cirrhosis

Hepatitis B virus (HBV) infection is the major cause of cirrhosis worldwide. The ultimate goal of current antiviral treatments for chronic hepatitis B (nucleos(t)ide analogs and interferon-α) is to prevent the development of end-stage liver diseases. Areas covered: We present a review of the current literature on antiviral therapy in patients with chronic hepatitis B and cirrhosis. Medline search was performed to identify relevant literature from 1993 through January of 2017. Expert commentary: One randomized controlled trial and a number of observational studies have shown that nucleos(t)ide analogs can decrease the incidence of hepatocellular carcinoma (HCC) in chronic hepatitis B patients with advanced fibrosis. Data from clinical trials of entecavir and tenofovir have shown that histological improvement and regression of fibrosis can be achieved in the majority of patients with chronic hepatitis B by successful viral suppression. Entecavir and tenofovir are the preferred antiviral agents for treatment of chronic hepatitis B in patients with cirrhosis due to their high antiviral potency and high genetic barrier to resistance. Pegylated interferon-α is another therapeutic option for chronic hepatitis B patients with well-compensated cirrhosis. However, interferon therapy is contraindicated in patients with decompensated cirrhosis, and evidence for reduced HCC is currently insufficient.

Evidence-based clinical practice guidelines for liver cirrhosis 2015

The Japanese Society of Gastroenterology revised the evidence-based clinical practice guidelines for liver cirrhosis in 2015. Eighty-three clinical questions were selected, and a literature search was performed for the clinical questions with use of the MEDLINE, Cochrane, and Igaku Chuo Zasshi databases for the period between 1983 and June 2012. Manual searching of the latest important literature was added until August 2015. The guidelines were developed with use of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. This digest version in English introduces selected clinical questions and statements related to the management of liver cirrhosis and its complications. Branched-chain amino acids relieve hypoalbuminemia and hepatic encephalopathy and improve quality of life. Nucleoside analogues and peginterferon plus ribavirin combination therapy improve the prognosis of patients with hepatitis B virus related liver cirrhosis and hepatitis C related compensated liver cirrhosis, respectively, although the latter therapy may be replaced by direct-acting antivirals. For liver cirrhosis caused by primary biliary cirrhosis and active autoimmune hepatitis, urosodeoxycholic acid and steroid are recommended, respectively. The most adequate modalities for the management of variceal bleeding are the endoscopic injection sclerotherapy for esophageal varices and the balloon-occluded retrograde transvenous obliteration following endoscopic obturation with cyanoacrylate for gastric varices. Beta-blockers are useful for primary prophylaxis of esophageal variceal bleeding. The V2 receptor antagonist tolvaptan is a useful add-on therapy in careful diuretic therapy for ascites. Albumin infusion is useful for the prevention of paracentesis-induced circulatory disturbance and renal failure. In addition to disaccharides, the nonabsorbable antibiotic rifaximin is useful for the management of encephalopathy. Anticoagulation therapy is proposed for patients with acute-onset or progressive portal vein thrombosis.

Antiviral Agents☆

Antiviral agents are drugs approved in the USA by the Food and Drug Administration (FDA) for the treatment or control of viral infections. Available antiviral agents mainly target stages in the viral life cycle. The target stages in the viral life cycle are; viral attachment to host cell, uncoating, synthesis of viral mRNA, translation of mRNA, replication of viral RNA and DNA, maturation of new viral proteins, budding, release of newly synthesized virus, and free virus in body fluids.

Two important factors that can limit the utility of antiviral drugs are toxicity and the development of resistance to the antiviral agent by the virus. In addition, host phenotypic behaviors toward antiviral drugs because of either genomic or epigenetic factors could limit the efficacy of an antiviral agent in an individual. This article summarizes the most relevant pharmacologic and clinical properties of current antiviral agents, and targets for novel antiviral agents.

Binding sensitivity of adefovir to the polymerase from different genotypes of HBV: molecular modeling, docking and dynamics simulation studies

AIM

To investigate the molecular mechanisms underlying the influence of DNA polymerase from different genotypes of hepatitis B virus (HBV) on the binding affinity of adefovir (ADV).

METHODS

Computational approaches, including homology modeling, docking, MD simulation and MM/PBSA free energy analyses were used.

RESULTS

Sequence analyses revealed that residue 238 near the binding pocket was not only a polymorphic site but also a genotype-specific site (His238 in genotype B; Asn238 in genotype C). The calculated binding free-energy supported the hypothesis that the polymerase from HBV genotype C was more sensitive to ADV than that from genotype B. By using MD simulation trajectory analysis, binding free energy decomposition and alanine scanning, some energy variation in the residues around the binding pocket was observed. Both the alanine mutations at residues 236 and 238 led to an increase of the energy difference between genotypes C and B (ΔΔG(C-B)), suggesting that these residues contributed to the genotype-associated antiviral variability with regard to the interaction with ADV.

CONCLUSION

The results support the hypothesis that the HBV genotype C polymerase is more sensitive to ADV than that from genotype B. Moreover, residue N236 and the polymorphic site 238 play important roles in contributing to the higher sensitivity of genotype C over B in the interaction with ADV.

Meta-analysis: oral anti-viral agents in adults with decompensated hepatitis B virus cirrhosis

BACKGROUND

The optimal oral anti-viral agent to use in patients with decompensated HBV cirrhosis remains unclear.

AIM

We performed a meta-analysis of the oral nucleos(t)ide analogues in patients with decompensated HBV cirrhosis.

METHODS

One year efficacy and safety outcomes in 22 studies published in English between '95 and 2010 were analysed.

RESULTS

Substantial heterogeneity was noted in the inclusion/exclusion criteria, controls, and sensitivity of the HBV DNA assay used. Pooled 1-year data showed benefit favouring lamivudine (LAM) vs. untreated controls for Child-Turcotte-Pugh (CTP) score improvement by ≥2 (OR: 117 (15 921), P ≤ 0.0001) and transplant-free survival (OR: 3.2 (1.2, 9), P = 0.022). Adefovir (ADV) led to undetectable HBV DNA at 1-year in 41% compared to 83% with LAM and 80% with entecavir (ETV). Overall, 1-year transplant-free survival rates varied from 78% with LAM to 95% and 94% with Tenofovir (TDF) and Telbivudine (TBV), respectively. The 1-year incidence of drug resistant HBV was 0% with ADV, ETV and TDF and 11% with LAM although TBV was associated with a 29% incidence at 2 years. Drug-related adverse events were infrequently reported.

CONCLUSIONS

All the oral anti-viral agents were associated with improved virological, biochemical and clinical parameters at 1-year. However, the efficacy of lamivudine and telbivudine is limited by drug resistance, and adefovir is limited by its potency and slower onset of action. Additional studies of tenofovir and entecavir are needed to determine the optimal agent(s) for treatment naïve patients and in those with drug-resistant decompensated HBV cirrhosis.

Drug safety evaluation of adefovir in HBV infection

INTRODUCTION

Several nucleos(t)ide analogs (NUC) are available for the management of patients with chronic hepatitis B (CHB). In most patients, NUC need to be administered on a long-term basis, thus increasing the risk of adverse effects. Adefovir dipivoxil (ADV), the first nucloeotide analog developed to treat CHB, may indeed cause nephrotoxicity.

AREAS COVERED

The pharmacokinetic mechanism of action, potential mechanism of renal damage and long-term safety profile of ADV in CHB patients have been reported. The current monitoring modalities, together with dosage adjustments, treatment of patients with ADV-related kidney impairment and the therapeutic algorithm in place at the authors' Liver Center are also summarized. Although, in short-term clinical trials, a daily dose of 10 mg of ADV was safe owing to a low rate of negligible nephrotoxic effects, the same dose may be associated with a usually reversible, proximal renal tubular toxicity as reflected by hypophosphatemia and elevated creatinine levels. Occasionally, Fanconi syndrome occurred in ADV-treated patients.

EXPERT OPINION

Renal function at baseline and during treatment should be carefully assessed in all patients receiving ADV to adjust the dose according to creatinine clearance, aimed to prevent or minimize nephrotoxicity.

Managing patients with hepatitis‑B-related or hepatitis‑C-related decompensated cirrhosis

Treatment of patients with hepatitis-B-related or hepatitis-C-related decompensated cirrhosis should focus on controlling the complications of cirrhosis, surveillance for hepatocellular carcinoma and, if applicable, preparation for orthotopic liver transplant. Interferon-based regimens for the treatment of hepatitis C have been somewhat successful in patients with cirrhosis, although treatment of patients with decompensated cirrhosis should be approached with caution. Given the potential for exacerbation of decompensation and poor tolerance of adverse effects, treatment should be reserved for those patients awaiting liver transplantation. Eradication of HCV before liver transplantation reduces the chances of recurrent hepatitis C infection after transplant. HBV can be treated with few adverse effects in patients with decompensated cirrhosis. This treatment is associated with improvement in decompensation in some patients. Hepatocellular carcinoma remains a significant risk in all patients with cirrhosis, and control of or eradication of HBV or HCV does not remove this risk.

Antiviral treatment of chronic hepatitis B virus (HBV) infections

While 25 compounds have been formally licensed for the treatment of HIV infection (AIDS), only seven licensed products are currently available for the treatment of chronic hepatitis B virus (HBV) infection: interferon-α, pegylated interferon-α, lamivudine, adefovir (dipivoxil), entecavir, telbivudine and tenofovir (disoproxil fumarate). In contrast to the treatment of HIV infections where the individual drugs are routinely used in combination, for the treatment of chronic HBV infection the individual drugs are generally used in monotherapy. In principle, combination drug therapy should allow reducing the likelihood of drug-resistant development.

Combination of Lamivudine and adefovir therapy in HBeAg-positive chronic hepatitis B patients with poor response to adefovir monotherapy

At present, there is no consensus treatment for patients who have poor response to Adevofir dipivoxil (ADV) monotherapy and no ADV-associated mutation. The purpose of this study was to evaluate the effect of a new therapeutic strategy combining Lamivudine (LAM) and ADV in patients with HBeAg-positive chronic hepatitis B (CHB) and poor response to ADV monotherapy. Thirty-one patients with chronic hepatitis B with HBV DNA > or = 10(4) copies/mL after 48 weeks of ADV monotherapy were included and received ADV plus LAM for 24 weeks. Compared with ADV monotherapy, ADV + LAM had an improved response rate at weeks 12 and 24 - compared with baseline, the median decrease in HBV-DNA level at week 12 and 24 were 1.27 and 2.03 log respectively. The virological response (VR) rate (HBV-DNA level <10(3) copies/mL) was 6.5% and 35.5% at weeks 12 and 24, respectively; the biochemical response (BR) rate (normalization of alanine aminotransferase levels) was 67.8% and 100%, respectively; the HBeAg loss rate was 6.9% and 34.5%, respectively; and the seroconversion rate (from HBeAg to HBeAb) was 3.5% and 6.9% respectively. No ADV-associated mutation was detected at baseline. After combination therapy for 24 weeks, no LAM-resistant or ADV-resistant mutations were detected. Only one patient had a mild adverse reaction. In conclusion, optimization of therapy combining LAM and ADV may be a good choice for patients with hepatitis B who have a poor response to ADV monotherapy.

Meta-analysis: adefovir dipivoxil in combination with lamivudine in patients with lamivudine-resistant hepatitis B virus

Background

Currently, there are no conclusive results on the efficacy of adefovir dipivoxil (ADV) plus lamivudine (LAM) in LAM-resistant patients with chronic hepatitis B (CHB). The aim of study was to evaluate the efficacy of rescue therapy with ADV plus LAM compared to ADV monotherapy in LAM-resistant CHB patients.

Results

We searched PUBMED, EMBASE, Web of Science, CNKI (National Knowledge Infrastructure), VIP database, the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews. Six eligible trials (442 patients in total) were included and evaluated for methodologic quality and heterogeneity. Greater virological response and lower emergence rate of ADV-associated mutants was observed in ADV plus LAM compared to ADV monotherapy (both P < 0.05). On the contrary, the rate of ALT normalization, HBeAg clearance and seroconversion were all similar between ADV plus LAM and ADV (all P > 0.05). Additionally, adding-on or switch-to ADV was both well tolerated.

Conclusion

The combination of ADV with LAM was superior in inhibiting HBV replication and preventing drug resistance as compared to ADV alone for LAM-resistant CHB patients.