Future prospectives for the management of chronic hepatitis B

Chronic hepatitis B virus infection affects about 400 million people around the globe and causes approximately a million deaths a year. Since the discovery of interferon-α as a therapeutic option the treatment of hepatitis B has evolved fast and management has become increasingly complicated. The amount of viral replication reflected in the viral load （HBV-DNA） plays an important role in the development of cirrhosis and hepatocellular carcinoma. The current treatment modalities for chronic hepatitis B are immunomodulatory （interferons） and antiviral suppressants （nucleoside and nucleotide analogues） all with their own advantages and limitations. An overview of the treatment efficacy for both immunomodulatory as antiviral compounds is provided in order to provide the clinician insight into the factors influencing treatment outcome. With nucleoside or nucleotide analogues suppression of viral replication by 5-7 log10 is feasible, but not all patients respond to therapy. Known factors influencing treatment outcome are viral load, ALT levels and compliance. Many other factors which might influence treatment are scarcely investigated. Identifying the factors associated with response might result in stopping rules, so treatment could be adapted in an early stage to provide adequate treatment and avoid the development of resistance. The efficacy of compounds for the treatment of mutant virus and the cross-resistance is largely unknown. However, genotypic and phenotypic testing as well as small clinical trials provided some data on efficacy in this population. Discontinuation of nucleoside or nucleotide analogues frequently results in viral relapse; however, some patients have a sustained response. Data on the risk factors for relapse are necessary in order to determine when treatment can be discontinued safely. In conclusion： chronic hepatitis B has become a treatable disease; however, much research is needed to tailor therapy to an individual patient, to predict the sustainability of response and determine the best treatment for those failing treatment.

Adverse effects of oral antiviral therapy in chronic hepatitis B

Oral nucleoside/nucleotide analogues(NAs) are currently the backbone of chronic hepatitis B(CHB) infection treatment. They are generally well-tolerated by patients and safe to use. To date, a significant number of patients have been treated with NAs. Safety data has accumulated over the years. The aim of this article is to review and update the adverse effects of oral NAs. NAs can cause class adverse effects(i.e., myopathy, neuropathy, lactic acidosis) and dissimilar adverse effects. All NAs carry a "Black Box" warning because of the potential risk for mitochondrial dysfunction. However, these adverse effects are rarely reported. The majority of cases are associated with lamivudine and telbivudine. Adefovir can lead to dose- and time-dependent nephrotoxicity, even at low doses. Tenofovir has significant renal and bone toxicity in patients with human immunodeficiency virus(HIV) infection. However, bone and renal toxicity in patients with CHB are not as prominent as in HIV infection. Entecavir and lamivudine are not generally associated with renal adverse events. Entecavir has been claimed to increase the risk of lactic acidosis in decompensated liver disease and high Model for End-Stage Liver Disease scores. However, current studies reported that entecavir could be safely used in decompensated cirrhosis. An increase in fetal adverse events has not been reported with lamivudine, telbivudine and tenofovir use in pregnant women, while there is no adequate data regarding entecavir and adefovir. Further long-term experience is required to highlight the adverse effects of NAs, especially in special patient populations, including pregnant women, elderly and patients with renal impairment.

Potent antiviral therapy improves survival in acute on chronic liver failure due to hepatitis B virus reactivation

Acute on chronic liver failure(ACLF)is a disease entity with a high mortality rate.The acute event arises from drugs and toxins,viral infections,bacterial sepsis,interventions(both surgical and non-surgical)and vascular events on top of a known or occult chronic liver disease.ACLF secondary to reactivation of chronic hepatitis B virus is a distinct condition;the high mortality of which can be managed in the wake of new potent antiviral therapy.For example,lamivudine and entecavir use has shown definite short-term survival benefits,even though drug resistance is a concern in the former.The renoprotective effects of telbivudine have been shown in a few studies to be useful in the presence of renal dysfunction.Monotherapy with newer agents such as tenofovir and a combination of nucleos(t)ides is promising for improving survival in this special group of liver disease patients.This review describes the current status of potent antiviral therapy in patient with acute on chronic liver failure due to reactivation of chronic hepatitis B,thereby providing an algorithm in management of such patients.

Then and now: The progress in hepatitis B treatment over the past 20 years

The ultimate goals of treating chronic hepatitis B(CHB)is prevention of hepatocellular carcinoma(HCC)and hepatic decompensation.Since the advent of effective antiviral drugs that appeared during the past two decades,considerable advances have been made not only in controlling hepatitis B virus(HBV)infection,but also in preventing and reducing the incidence of liver cirrhosis and HCC.Furthermore,several recent studies have suggested the possibility of reducing the incidence of recurrent or new HCC in patients even after they have developed HCC.Currently,six medications are available for HBV treatment including,interferon and five nucleoside/nucleotide analogues.In this review,we will examine the antiviral drugs and the progresses that have been made with antiviral treatments in the field of CHB.

Low-dose tenofovir is more potent than adefovir and is effective in controlling HBV viremia in chronic HBeAg-negative hepatitis B

AIM: To study the efficacy of tenofovir disoproxil fumarate (TDF) at low dose in a small open trial of chronic hepatitis B patients with advanced stage disease. METHODS: Eleven patients were treated with TDF 75 mg for a median period of 80 (range, 24-576) wk and then 7 cases were shifted to an adefovir 10 mg treatment group. All patients had been pre-treated with lamivudine: 5 had YMDD resistant mutants and 6 wild- type virus. When TDF was started, 4 patients had low- level viremia and 6 were PCR-negative. RESULTS: During TDF treatment, PCR remained negative in 10 patients, transaminase levels were normal and no significant viral breakthrough was observed. The drug was well tolerated in all cases. When TDF 75 mg was substituted with adefovir 10 mg, 3 out of 7 patients had a persistent viral rebound (2700-130 000 copies/mL), in whom lamivudine had to be reintroduced. CONCLUSION: Low-dose TDF monotherapy can control HBV viremia for an extended period of time without the emergence of resistance and is more potent than adefovir at the standard dosage. The use of a reduced dose of TDF could diminish the cost of therapy in low-income countries, but further studies in a larger population and in HBeAg-positive subjects are needed.

Emerging antivirals for the treatment of hepatitis B

Chronic infection with hepatitis B virus(HBV)constitutes a major global public health threat,causing substantial disease burdens such as liver cirrhosis and hepatocellular carcinoma,thus representing high unmet medical needs.Currently available therapies are safe,well tolerated,and highly effective in decreasing viremia and improving measured clinical outcomes with low rates of antiviral resistance.However,long-term management remains a clinical challenge,mainly due to the slow kinetics of HBV surface antigen clearance.In this article,we review emerging antivirals directed at novel targets derived from mechanisms of viral cellular entry,viral replication,viral assembly,and the host immune response,leading to preclinical and clinical trials for possible future therapeutic intervention.The recent therapeutic advances in the development of all categories of HBV inhibitors may pave the way for regimens of finite duration that result in long-lasting control of chronic hepatitis B infection.

Impact of modern antiviral therapy of chronic hepatitis B and C on clinical outcomes of liver disease

Chronic infections with the hepatitis B and C viruses have significant worldwide health and economic impacts.Previous treatments for hepatitis C such as interferon and ribavirin therapy were ineffective and poorly tolerated by patients.The introduction of directly acting curative antiviral therapy for hepatitis C and the wider use of nucleos(t)ide analogues for suppression of chronic Hepatitis B infection have resulted in many positive developments.Decreasing the prevalence of hepatitis B and C have concurrently reduced transmission rates and hence,the number of new infections.Antiviral treatments have decreased the rates of liver decompensation and as a result,lowered hospitalisation and mortality rates for both chronic hepatitis B and C infection.The quality of life of chronically infected patients has also been improved significantly by modern treatment.Antiviral therapy has stopped the progression of liver disease to cirrhosis in certain patient cohorts and prevented ongoing hepatocellular damage in patients with existing cirrhosis.Longer term benefits of antiviral therapy include a reduced risk of developing hepatocellular carcinoma and decreased number of patients requiring liver transplantation.This review article assesses the literature and summarises the impact of modern antiviral therapy of chronic hepatitis B and C on clinical outcomes from liver disease.

Synthesis of photolabile dUTP analogues and their enzymatic incorporation for DNA labeling

Two new photolabile nucleotide analogues with furan-fused deoxyuridine were synthesized through Sonogashira coupling.Their enzymatic incorporation into DNA was evaluated with two DNA polymerases(Taq and Deep vent exo-)by polymerase chain reaction(PCR).Deep vent exo-recognized both nucleotides as substrates for primer extension,while Taq was much less proficient.Light irradiation of PCR products released the amino and carboxyl moieties of DNA.Further labeling with fluorescein isothiocyanate for a long DNA construct with F-dUnTP incorporation was successfully achieved.