Entecavir versus lamivudine for patients with HBeAg-negative chronic hepatitis B

Telbivudine: a new option for the treatment of chronic hepatitis B

Chronic hepatitis B virus (HBV) infection affects > 350 million individuals worldwide. Chronic hepatitis B is associated with complications of end-stage liver disease, including cirrhosis and hepatocellular carcinoma. HBV replication is the best predictor of liver disease progression to cancer, and antiviral therapy may diminish or halt this unfavorable outcome. Six drugs have been approved for the treatment of chronic hepatitis B: interferon-alpha(2b), pegylated interferon-alpha(2a), lamivudine, adefovir, entecavir and telbivudine. Most agents designed to target hepatitis B are hindered by the development of resistance, poor tolerability or limited efficacy; therefore, new agents and treatment strategies are needed. Telbivudine is the latest approved anti-HBV agent; it is an orally administered nucleoside analog that selectively inhibits HBV replication. It has demonstrated potent activity against HBV in Phase III clinical studies, with good tolerance, lack of mitochondrial toxicity and no dose-limiting side effects.

Drug resistance in antiviral treatment for infections with hepatitis B and C viruses

Treatments for infections with hepatitis B and C viruses have recently developed markedly, and range from nonspecific interferon-based treatments to specific antiviral treatments, such as those that inhibit hepatitis virus-coded protein production or activity. These developments have contributed to the achievement of excellent enhancement of the antiviral effect. On the other hand, the development of specific antiviral therapies has created unprecedented problems. Antiviral drug-resistant strains of viruses have emerged, leading to a poor prognosis for infected patients. Clarification of the mechanisms underlying the emergence of such resistance to drugs will be useful for the treatment of such patients. In this review, we outline pathological conditions associated with hepatitis B and C viruses and their treatments, and discuss the current situation and mechanisms underlying the emergence of antiviral drug-resistant strains.

Update on viral hepatitis: 2006

PURPOSE OF REVIEW

This is a concise review of recent developments in the field of viral hepatitis, based on publications between December 2005 and November 2006.

RECENT FINDINGS

Elevated hepatitis B virus DNA levels in patients in their 40s with perinatally acquired hepatitis B virus infection increases the risk for cirrhosis and hepatocellular carcinoma. Six approved therapies are available for chronic hepatitis B. Entecavir is a potent antiviral for nucleoside-naïve patients. For lamivudine resistant hepatitis B virus infection, adefovir should be added to lamivudine to reduce the risk of adefovir-resistant mutations; however, tenofovir may be a more promising alternative to adefovir. A shorter duration of treatment wth pegylated interferon and ribavirin is sufficient for genotype 2 hepatitis C infection but the benefits of extending treatment to 72 weeks for genotype 1 needs to be confirmed. Pegylated interferon monotherapy was shown to be effective in patients with hepatitis D and ribavirin provides no additional benefit.

SUMMARY

New developments in the past year will help us fine tune the treatment of viral hepatitis. Even as new treatments are approved, the potential benefits of treatment should be weighed against the risk of drug-resistant mutations with long-term therapy.

Experiences on antiviral treatment for chronic viral B and C hepatitis patients in Hungary. 1998–2004

Az utolsó évtizedben számos multicentrikus, randomizált vizsgálat bizonyította az előrehaladást a krónikus vírushepatitisek kezelésében. Ugyanakkor csak korlátozott számú és ellentmondásos adatokat közöltek az antivirális terápia reális értékéről a mindennapos rutin klinikai gyakorlatában. Cél: Retrospektív felmérést végeztünk a terápia hatékonyságának megállapítására krónikus B- és C-hepatitisben, egy 7 éves periódus alatt kezelt országos populációban. Emellett bemutatjuk még egy hazai prospektív vizsgálat néhány adatát is. Módszerek: 220 krónikus B-hepatitises beteget kezeltünk, közülük 112 standard interferon-, 23 pegilált interferon-, 85 lamivudin-terápiában részesült, akikben a HbeAg-szerokonverzió és/vagy HBV-DNS-negatívvá válás arányát vizsgáltuk. A retrospektív elemzésben szereplő 2442 krónikus C-hepatitises közül 333 standard interferon-monoterápiát, 1122 standard interferon + ribavirin kombinációt és 987 pegilált interferon + ribavirin-kezelést kapott. A prospektív vizsgálatban 69 HCV1-beteg pegilált interferon α-2a + ribavirin terápiában részesült 6–12 hónapon át. A tartós virológiai válasz mellett vizsgáltuk a kedvező kimenetel prediktorait és a mellékhatások előfordulását. Eredmények: Krónikus B-hepatitisben a standard interferon 31%-os, a pegilált interferon 30%-os, a lamivudin 31–33%-os tartós vírusnegativitáshoz vezetett. Krónikus C-hepatitisben a tartós virológiai válasz aránya az interferon-monoterápiával észlelt 13%-ról a pegilált interferon + ribavirin mellett 31%-ra nőtt, a prospektív vizsgálatban ez 48% volt. A jó prognózis prediktora a rapid (4 hetes) és a korai (12 hetes) virológiai válasz, a női nem, az életkor, BMI és az adherencia volt. A betegek 9%-ában fordult elő mellékhatás, leggyakrabban cytopenia, haemolysis és depresszió. Következtetés: A krónikus B-hepatitisszel ellentétben, a hepatitis C-vírusinfekció kezelésének effektivitása hazánkban is fokozatosan javult. A mindennapi gyakorlat országos adatai azonban elmaradnak a prospektív vizsgálat sikerességétől. A jövőben hatékonyabb terápiás stratégiák szükségesek, beleértve az individualizált dozírozást és az új antivirális szerek alkalmazását.

Lamivudine treatment in patients with chronic hepatitis B and cirrhosis

Chronic hepatitis B is a common disease and approximately 20% of infected patients with compensated cirrhosis will decompensate over 5 years. If untreated, the survival of decompensated cirrhosis is poor (15% at 5 years). The extent of hepatitis B virus (HBV) replication, as assessed by serum HBV-DNA level, is a strong predictor of the risk of disease progression and hepatocellular carcinoma. This provides a rationale for antiviral therapy to arrest progression of liver disease. Lamivudine is a pyrimidine analogue that inhibits HBV-DNA reverse transcriptase. It decreases HBV replication, normalises alanine aminotransferase levels and reduces hepatic inflammation and fibrosis in patients with chronic hepatitis B. This article will focus on the use of lamivudine in patients with HBV-cirrhosis. In patients with compensated HBV-cirrhosis, a randomised, placebo-controlled trial has shown that lamivudine significantly reduced the rate of disease progression and hepatocellular carcinoma development over a 3-year period. In patients with decompensated cirrhosis, treatment with lamivudine can produce spectacular improvements of liver function, but the improvement is slow and a clinical benefit is usually not observed until after at least 3-6 months of treatment. A major drawback of lamivudine treatment is the development of resistance, observed in 15-20% of patients after 1 year and up to 70% after 5 years of continued treatment. Thus, patients with HBV-cirrhosis treated with lamivudine should have regular monitoring of serum HBV-DNA levels and prompt institution of additional antiviral therapy if viral breakthrough is observed. Adefovir, tenofovir and entecavir have demonstrated efficacy in patients with lamivudine resistance. In patients with decompensated cirrhosis, in whom the development of resistance can be fatal, combination therapy (such as lamivudine plus adefovir) may prove more effective than monotherapy and this issue needs further study.

Infections in Patients With End-stage Liver Disease

Infections in patients with end-stage liver disease (ESLD) are an important cause of morbidity and mortality in these patients. Abnormalities in their natural defense mechanisms, alterations in the enteric flora and the growing utilization of invasive procedures increase the risk of infections in these patients. Common bacterial infections in ESLD patients include spontaneous bacterial peritonitis, urinary tract infections, community-acquired pneumonia, dermatologic infections, and bacteremia. Viral infections such as influenza can have a devastating course in ESLD patients. Hepatitis B and C are now among the most common causes of ESLD. They also present an important therapeutic challenge. As patients with human immunodeficiency virus are surviving longer, ESLD due to hepatitis C is now emerging as a leading cause of morbidity in these patients. Prompt detection of infections, use of appropriate antibiotics for treatment and prophylactic measures such as vaccinations can help improve survival in these patients.

Management of hepatitis B: summary of a clinical research workshop

Chronic hepatitis B is caused by persistent infection with the hepatitis B virus (HBV), a unique DNA virus that replicates through an RNA intermediate produced from a stable covalently closed circular DNA molecule. Viral persistence appears to be due to inadequate innate and adaptive immune responses. Chronic infection has a variable course after several decades resulting in cirrhosis in up to one-third of patients and liver cancer in a proportion of those with cirrhosis. Sensitive assays for HBV DNA levels in serum have been developed that provide important insights into pathogenesis and natural history. Therapy of hepatitis B is evolving. Peginterferon induces long-term remissions in disease in one-third of patients with typical hepatitis B e antigen (HBeAg) positive chronic hepatitis B, but a lesser proportion of those without HBeAg. Several oral nucleoside analogues with activity against HBV have been shown to be effective in suppressing viral levels and improving biochemical and histological features of disease in a high proportion of patients with and without HBeAg, at least in the short term. What is uncertain is which agent or combination of agents is most effective, how long therapy should last, and which criteria should be used to start, continue, switch or stop therapy. Long-term therapy with nucleoside analogues may be the most appropriate approach to treatment, but the expense and lack of data on long-term safety and efficacy make recommendations difficult. Clearly, many basic and clinical research challenges remain in defining optimal means of management of chronic hepatitis B.

Targets of emerging therapies for viral hepatitis B and C

Viral hepatitis B and C, structurally two completely different viruses, commonly infect human hepatocytes and cause similar clinical manifestations. Since their discovery, IFN has been a pillar in the treatment. However, because of the different natures of the viruses, therapeutic approaches diverge and new treatment targets are tailored specifically for each virus. Herein, the authors analyse therapeutic approaches for hepatitis B virus (HBV) and hepatitis C virus (HCV) and focus on emerging concepts that are under clinical evaluation. In particular, promising viral inhibitors for HBV and HCV are reviewed and the current status of research for gene therapy for HCV is described. Immune therapy is a fast-moving field with fascinating results which include therapeutic vaccines and toll-like receptor agonists that could improve tomorrow's treatment approaches.

Screening, prevention and treatment of viral hepatitis B reactivation in patients with haematological malignancies

The prevalence of hepatitis B virus (HBV) infection in patients with haematological malignancies is increased compared with the general population worldwide. HBV reactivation is common following chemotherapy and is associated with a high mortality despite prompt anti-viral treatment. HBV reactivation may necessitate interruption of chemotherapy with adverse prognostic consequences for the haematological disease. Chemotherapy-induced immune suppression may lead to increased HBV replication. Immune reconstitution within the weeks and months following recovery from chemotherapy may be associated with a flare of hepatitis B manifested by hepatocellular injury. Risk factors associated with HBV reactivation include detectable hepatitis B surface antigen (HBsAg), HBV DNA, Hepatitis B e (HBeAg) antigen, antibodies to hepatitis B core antigen (anti-HBc), treatment with corticosteroids, young age and male gender. Lamivudine is effective during HBV reactivation due to immune suppression. Clinical trials have demonstrated that pre-emptive antiviral treatment with lamivudine is superior to deferred treatment. Current recommendations emphasise screening for HBV infection in all haematology patients, particularly prior to chemotherapy. Patients who are HBsAg positive or HBV DNA positive should receive pre-emptive treatment with lamivudine before chemotherapy. The duration of lamivudine treatment may be prolonged commensurate with the degree of immunosuppression. HBV naïve patients should be immunised against hepatitis B, as should haematopoietic stem cell donors. In summary, overt and occult HBV pose a serious, but preventable, threat. Pre-treatment screening of patients at risk should be practiced diligently by all clinicians that treat patients with malignancies.

New and emerging treatment of chronic hepatitis B

Conventional treatment of chronic hepatitis B with interferon alfa-2b, lamivudine, and adefovir is limited by low rates of sustained hepatitis B virus DNA suppression and hepatitis B e antigen (HBeAg) seroconversion, increasing rates of drug resistance to the oral agents, and poor tolerability of interferon. Recently several promising new antiviral agents have emerged that possess potent antiviral effects, less toxicity, and have little or no risk of drug resistance. Two new agents, entecavir and peginterferon alfa-2a, have received recent approval by regulatory authorities in the United States and several other countries for the treatment of adults with chronic hepatitis B. In large phase III clinical trials, these agents have demonstrated superior efficacy over lamivudine in both HBeAg-positive and HBeAg-negative patients. Drug resistance occurs at a low rate in lamivudine-refractory patients treated with entecavir or is, to date, nonexistent in nucleoside-naïve patients treated with entecavir and all patients receiving peginterferon. In addition, several novel agents in clinical development, such as emtricitabine, clevudine, telbivudine, valtorcitabine, and tenofovir, have shown promising clinical profiles in patients with chronic hepatitis B. This review summarizes the recent clinical studies of these new agents and discusses the implications of these data for the management of chronic hepatitis B.

Lamivudine and IFN-beta sequential therapy in HBe antigen-positive patients with chronic hepatitis B virus genotype C infection

Sequential treatment with lamivudine and interferon (IFN) has induced sustained biochemical and virologic responses in the majority of patients with chronic hepatitis B in France. However, the efficacy of sequential treatment in patients with chronic hepatitis B virus (HBV) genotype C infection has not been evaluated. Twenty-four HBe antigen-positive patients were treated with 100 mg lamivudine alone for 16-32 weeks, then with both 6 MU IFN-beta and lamivudine for 4 weeks, and lastly with IFN-beta alone for 20 weeks. Sustained response was achieved in 7 (29%) patients 24 weeks after the end of therapy. No lamivudine-resistant variants emerged in any patient. Hepatitis flare occurred in 3 patients after the withdrawal of lamivudine, but none had decompensation. The patients with sustained response were significantly younger at baseline (p = 0.033) and had a significantly lower HBV DNA level at the start of IFN (p = 0.020) than those without sustained response. In conclusion, the rate of response to sequential therapy with lamivudine and IFN in HBe antigen-positive patients with HBV genotype C infection was lower than the rate reported previously. Patients who were young or who had a favorable virologic response to lamivudine were more likely to have a sustained response.

Fatal liver failure caused by reactivation of lamivudine-resistant hepatitis B virus: A case report

We present a case of fetal liver failure caused by the activation of lamivudine-resistant hepatitis B virus (HBV) nine months after lamivudine treatment. A 57-year old man visited our hospital for the treatment of decompensated chronic hepatitis B. Lamivudine was started in December 2001. Subsequently, serum HBV was negative for HBV DNA with seroconversion from HBeAg to anti-HBe and improvement of liver function. However, HBV DNA and HBeAg were again detected in September 2002. He was complicated by breakthrough hepatitis and admitted to our hospital in November for severely impaired liver function. Vidarabine treatment was started and serum HBV DNA and alanine aminotransferase (ALT) decreased transiently. However, after the start of α-interferon treatment, HBV DNA level increased and liver function deteriorated. He died 1 mo after admission. An analysis of amino acid sequences in the polymerase region revealed that rtM204I/V with rtL80I/V occurred at the time of viral breakthrough. After the start of antiviral treatment, rtL180M was detected in addition to rtM204I/V and rtL80I/V, and became predominant in the terminal stage of the disease. HBV clone with a high replication capacity may be produced by antiviral treatment leading to the worsening of liver function. Antiviral therapy for patients with breakthrough hepatitis in advanced liver disease should be carefully performed.

Entecavir pharmacokinetics, safety, and tolerability after multiple ascending doses in healthy subjects

A double-blind, placebo-controlled, multiple oral dose escalation study was conducted to investigate the pharmacokinetics, safety, and tolerability of entecavir in healthy subjects. Eight subjects were assigned to each of the 3 dose panels (0.1 mg, 0.5 mg, and 1 mg or matched placebo once daily for 14 days). Blood and urine samples were collected for pharmacokinetic analyses. Entecavir was rapidly absorbed, with peak plasma concentration occurring within 1 hour of dosing. Steady-state plasma concentrations of entecavir were achieved by 10 days following the initial dose. At steady state, the mean area under the plasma concentration-time curve over 1 dosing interval, increased approximately proportional to dose. Entecavir had a mean terminal half-life ranging from 128 to 149 hours and an effective half-life of approximately 24 hours. Elimination was predominantly through renal excretion, with mean urinary recovery ranging from 62% to 73%. Entecavir was safe and well tolerated when administered at doses ranging from 0.1 mg to 1 mg/d for 14 days.

Inhibition of hepatitis B virus polymerase by entecavir

Entecavir (ETV; Baraclude) is a novel deoxyguanosine analog with activity against hepatitis B virus (HBV). ETV differs from the other nucleoside/tide reverse transcriptase inhibitors approved for HBV therapy, lamivudine (LVD) and adefovir (ADV), in several ways: ETV is >100-fold more potent against HBV in culture and, at concentrations below 1 microM, displays no significant activity against human immunodeficiency virus (HIV). Additionally, while LVD and ADV are obligate DNA chain terminators, ETV halts HBV DNA elongation after incorporating a few additional bases. Three-dimensional homology models of the catalytic center of the HBV reverse transcriptase (RT)-DNA-deoxynucleoside triphosphate (dNTP) complex, based on the HIV RT-DNA structure, were used with in vitro enzyme kinetic studies to examine the mechanism of action of ETV against HBV RT. A novel hydrophobic pocket in the rear of the RT dNTP binding site that accommodates the exocyclic alkene moiety of ETV was predicted, establishing a basis for the superior potency observed experimentally. HBV DNA chain termination by ETV was accomplished through disfavored energy requirements as well as steric constraints during subsequent nucleotide addition. Validation of the model was accomplished through modeling of LVD resistance substitutions, which caused an eightfold decrease in ETV susceptibility and were predicted to reduce, but not eliminate, the ETV-binding pocket, in agreement with experimental observations. ADV resistance changes did not affect the ETV docking model, also agreeing with experimental results. Overall, these studies explain the potency, mechanism, and cross-resistance profile of ETV against HBV and account for the successful treatment of naive and LVD- or ADV-experienced chronic HBV patients.

Sequential algorithms combining non-invasive markers and biopsy for the assessment of liver fibrosis in chronic hepatitis B

AIM: To assess the performance of several non-invasive markers and of our recently proposed stepwise combination algorithms to diagnose significant fibrosis (F ≥ 2 by METAVIR) and cirrhosis (F4 by METAVIR) in chronic hepatitis B (CHB).

METHODS: One hundred and ten consecutive patients (80 males, 30 females, mean age: 42.6 ± 11.3) with CHB undergoing diagnostic liver biopsy were included. AST-to-Platelet ratio (APRI), Forns’ index, AST-to-ALT Ratio, Goteborg University Cirrhosis Index (GUCI), Hui’s model and Fibrotest were measured on the day of liver biopsy. The performance of these methods and of sequential algorithms combining Fibrotest, APRI and biopsy was defined by positive (PPV) and negative (NPV) predictive values, accuracy and area under the curve (AUC).

RESULTS: PPV for significant fibrosis was excellent (100%) with Forns and high (> 92%) with APRI, GUCI, Fibrotest and Hui. However, significant fibrosis could not be excluded by any marker (NPV < 65%). Fibrotest had the best PPV and NPV for cirrhosis (87% and 90%, respectively). Fibrotest showed the best AUC for both significant fibrosis and cirrhosis (0.85 and 0.76, respectively). Stepwise combination algorithms of APRI, Fibrotest and biopsy showed excellent performance (0.96 AUC, 100% NPV) for significant fibrosis and 0.95 AUC, 98% NPV for cirrhosis, with 50%-80% reduced need for liver biopsy.

CONCLUSION: In CHB sequential combination of APRI, Fibrotest and liver biopsy greatly improves the diagnostic performance of the single non-invasive markers. Need for liver biopsy is reduced by 50%-80% but cannot be completely avoided. Non-invasive markers and biopsy should be considered as agonists and not antagonists towards the common goal of estimating liver fibrosis.

Entecavir: a new nucleoside analog for the treatment of chronic hepatitis B infection

BACKGROUND

Chronic hepatitis B infection carries considerable risk for the development of cirrhosis and hepatocellular carcinoma. Treatment options are increasing but are limited to interferon alfa-2b, pegylated interferon alfa-2a, lamivudine, adefovir dipivoxil, and entecavir. Entecavir, a nucleoside analog, is the newest oral antiviral approved in the United States for treatment of chronic hepatitis B.

OBJECTIVE

To review the available data for entecavir regarding its pharmacology, pharmacokinetics, safety, efficacy, and clinical use.

METHODS

A MEDLINE, EMBASE, and Cochrane search of the English-language literature from January 1997-May 2006 was performed. Preapproval studies provided by the manufacturer and abstracts from recent scientific meetings on infectious disease and hepatology were also reviewed.

RESULTS

Three phase III clinical trials representing more than 1600 subjects established the superior efficacy and equivalent safety of entecavir compared with lamivudine for treating patients who are hepatitis B early antigen (HBeAg) positive, HBeAg negative, or refractory to lamivudine. Entecavir resistance has not occurred in nucleoside-naïve patients but may develop in those who already possess lamivudine resistance mutations.

CONCLUSION

Trial results, along with previously published response rates for adefovir dipivoxil and interferon monotherapy, make entecavir the preferred first-line treatment option for patients with chronic hepatitis B who are nucleoside naïve, HBeAg positive or negative, and have compensated liver disease. Both entecavir and adefovir dipivoxil maintain activity against hepatitis B virus in patients with chronic hepatitis B who are refractory to lamivudine, and both agents are reasonable first-line treatment options. Longer trials involving nucleoside-naïve, lamivudine-refractory patients are needed to determine entecavir's optimal treatment duration, long-term safety, and durability of response, including rate of resistance.

Antiviral therapy and resistance with hepatitis B virus infection

Hepatitis B virus (HBV) infection is still the most common cause of hepatocellular carcinoma and liver cirrhosis world wide. Recently, however, there has been quite dramatic improvement in the understanding of HBV associated liver disease and its treatment. It has become clear that high viral replication is a major risk factor for the development of both cirrhosis and hepatocellular carcinoma. Early studies have shown lamivudine lowers the risk of HBV associated complications. There are currently three nucleos(t)ides licensed, in addition to interferon, and there are more drugs coming to the market soon. Interferon or its pegylated counterpart are still the only options for treatment with defined end points, while nucleos(t)ides therapy is used mostly for long term treatment. Combination therapies have not been shown to be superior to monotherapy in naïve patients, however, the outcome depends on how the end point is defined. Interferon plus lamivudine achieves a higher viral suppression than either treatment alone, even though Hbe-seroconversion was not different after a one year treatment. HBV-genotypes emerge as relevant factors, with genotypes "A" and "B" responding relatively well to interferon, achieving up to 20% HBsAg clearance in the case of genotype "A". In addition to having a defined treatment duration, interferon has the advantage of lacking resistance selection, which is a major drawback for lamivudine and the other nucleos(t)ides. The emergence of resistance against adefovir and entecavir is somewhat slower in naïve compared to lamivudine resistant patients. Adefovir has a low resistance profile with 3%, 9%, 18%, and 28% after 2, 3, 4, and 5 years, respectively, while entecavir has rarely produced resistance in naïve patients for up to 3 years.

Future therapy for hepatitis B

Therapy for hepatitis B virus (HBV) infection, the most common worldwide cause of viremia and chronic liver disease, is currently limited to interferon preparations and nucleoside or nucleotide analogs. Although these treatments result in suppression of HBV replication, virologic rebounds are common when treatment is ended or when viral resistance emerges. This review considers novel approaches targeting viral or host factors involved in the HBV lifecycle, as well as immunomodulatory strategies that are likely to be used concomitantly with antiviral drugs in future research.

Hepatitis B awareness, knowledge, and screening among Asian Americans

BACKGROUND

Due to the high prevalence of hepatitis B, Asian Americans have high rates of liver cancer. Screening for hepatitis B leads to monitoring and treatment and prevent further infection through vaccination of contacts.

METHODS

We reviewed the published literature up to 2006 on hepatitis B awareness, knowledge, and screening among Asian Americans.

RESULTS

Many Asian Americans lack knowledge about hepatitis B and have not been screened. Sociodemographics, knowledge, beliefs, and health care variables are associated with screening.

CONCLUSIONS

Further research and health policy changes are needed to address the problem of hepatitis B and liver cancer among Asian Americans.

Special considerations and treatment of patients with HBV-HIV coinfection

Coinfection with HIV and hepatitis B virus (HBV) substantially alters the natural course of HBV infection as well as its management. Therapy for HBV infection in HIV-coinfected patients requires several factors to be taken into consideration, such as whether the antiviral activity of a particular agent is specific for HBV (that is, adefovir, entecavir, telbivudine and pegylated interferon) or for both viruses (that is, lamivudine, emtricitabine and tenofovir), whether the chosen drug has the potential for inducing drug resistance and cross-resistance, and whether use of the agent is associated with hepatotoxicity. For coinfected patients who do not require therapy for their HIV infection, clinicians should avoid prescribing monotherapy with agents that have activity against HIV (that is, tenofovir, entecavir, emtricitabine or lamivudine) so as not to compromise future HIV care. This review discusses the current status of treatment of hepatitis B in the setting of HIV infection. It describes emerging therapeutic strategies and addresses challenges in the treatment of coinfection.

Status Presens of Antiviral Drugs And Strategies: Part I: DNA Viruses and Retroviruses

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of HIV infections. The others have been approved for the therapy of herpesvirus (HSV, VZV, CMV), hepadnavirus (HBV), hepacivirus (HCV) and myxovirus (influenza, RSV) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these are targeting HIV infections. Yet, quite a number of important viral pathogens (i.e. HPV, HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Treatment of chronic hepatitis B

Hepatitis B virus (HBV) infection is the leading cause of chronic liver disease and hepatocellular carcinoma worldwide. Approximately 350 million individuals are infected with HBV and >500,000 deaths per year can be attributed to HBV. Although universal vaccination has reduced HBV incidence in many countries, it still remains a major public health problem, especially in parts of Asia and Africa. Improved understanding of HBV virology and virus-host interactions has revolutionized chronic hepatitis B therapy in the past two decades. Development of oral nucleoside/nucleotide analogues heralds a new era of safe and effective treatment of this disease. On the basis of these advances, new guidelines for the treatment of chronic hepatitis B have been issued. Successful long-term treatment of chronic hepatitis B may rest on combination therapy that is based on molecular approaches targeting various stages of the HBV life-cycle. In this review, we summarize the current modalities and highlight important issues in the treatment of chronic hepatitis B monoinfection.

Two-year assessment of entecavir resistance in Lamivudine-refractory hepatitis B virus patients reveals different clinical outcomes depending on the resistance substitutions present

Entecavir (ETV) is a deoxyguanosine analog approved for use for the treatment of chronic infection with wild-type and lamivudine-resistant (LVDr) hepatitis B virus (HBV). In LVD-refractory patients, 1.0 mg ETV suppressed HBV DNA levels to below the level of detection by PCR (<300 copies/ml) in 21% and 34% of patients by Weeks 48 and 96, respectively. Prior studies showed that virologic rebound due to ETV resistance (ETVr) required preexisting LVDr HBV reverse transcriptase substitutions M204V and L180M plus additional changes at T184, S202, or M250. To monitor for resistance, available isolates from 192 ETV-treated patients were sequenced, with phenotyping performed for all isolates with all emerging substitutions, in addition to isolates from all patients experiencing virologic rebounds. The T184, S202, or M250 substitution was found in LVDr HBV at baseline in 6% of patients and emerged in isolates from another 11/187 (6%) and 12/151 (8%) ETV-treated patients by Weeks 48 and 96, respectively. However, use of a more sensitive PCR assay detected many of the emerging changes at baseline, suggesting that they originated during LVD therapy. Only a subset of the changes in ETVr isolates altered their susceptibilities, and virtually all isolates were significantly replication impaired in vitro. Consequently, only 2/187 (1%) patients experienced ETVr rebounds in year 1, with an additional 14/151 (9%) patients experiencing ETVr rebounds in year 2. Isolates from all 16 patients with rebounds were LVDr and harbored the T184 and/or S202 change. Seventeen other novel substitutions emerged during ETV therapy, but none reduced the susceptibility to ETV or resulted in a rebound. In summary, ETV was effective in LVD-refractory patients, with resistant sequences arising from a subset of patients harboring preexisting LVDr/ETVr variants and with approximately half of the patients experiencing a virologic rebound.

Entecavir: a review of its use in chronic hepatitis B

Entecavir (Baraclude) is a novel nucleoside analogue of 2'-deoxyguanosine whose intracellular triphosphate form inhibits replication of the hepatitis B virus (HBV). In large, randomised, double-blind, phase III clinical trials in patients with chronic HBV infection, oral entecavir 0.5 or 1.0mg once daily for up to 96 weeks was superior to lamivudine 100 mg/day in improving hepatic histology, normalising aminotransferase levels and suppressing viraemia to levels undetectable by polymerase chain reaction (PCR) assay in nucleoside-naive hepatitis B e antigen (HBeAg)-negative (precore or core promoter mutants) and/or HBeAg-positive patients, and in lamivudine-refractory (persistent viraemia during lamivudine therapy) HBeAg-positive patients. In addition, the tolerability profile of entecavir was generally similar to that of lamivudine. Thus, entecavir is a primary option in the treatment of chronic HBV infection in both nucleoside-naive and lamivudine-refractory patients.

Long-term therapy with adefovir dipivoxil for HBeAg-negative chronic hepatitis B for up to 5 years

BACKGROUND & AIMS

Treatment with adefovir dipivoxil for 48 weeks resulted in clinical improvement in patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B that was lost when treatment was discontinued. We investigated the efficacy, safety, and resistance profile of adefovir dipivoxil treatment for up to 240 weeks.

METHODS

HBeAg-negative patients were treated double blind with placebo or adefovir dipivoxil 10 mg once daily for 48 weeks, followed by adefovir dipivoxil from week 49 to 96. At week 97, 125 patients enrolled in a 144-week, open-label phase. Patients received adefovir dipivoxil for up to 192 or 240 weeks.

RESULTS

Serum hepatitis B virus (HBV) DNA levels were less than 1000 copies per milliliter in 67% of patients, and alanine aminotransferase (ALT) levels normalized in 69% after 240 weeks. After 192 or 240 weeks of treatment, over 83% of patients had improvement in necroinflammation, and over 73% had improvement in fibrosis. Ishak fibrosis scores improved compared with baseline in 35%, 55%, and 71% of patients after 48, 192, and 240 weeks of adefovir dipivoxil, respectively. After 240 weeks, the cumulative probability of HBV polymerase mutations was 29%, but the cumulative probability of mutations with virologic resistance was 20% and of mutations, virologic resistance, and ALT elevations was 11%. Slight elevations in creatinine were confirmed in 4 (3%) patients.

CONCLUSIONS

Treatment with adefovir dipivoxil for up to 240 weeks was well tolerated and produced significant, increasing improvement in hepatic fibrosis, durable suppression of HBV replication, normalization of liver enzymes, and delayed development of resistance.

Entecavir resistance is rare in nucleoside naïve patients with hepatitis B

Comprehensive monitoring of genotypic and phenotypic antiviral resistance was performed on 673 entecavir (ETV)-treated nucleoside naïve hepatitis B virus (HBV) patients. ETV reduced HBV DNA levels to undetectable by PCR (<300 copies/mL, <57 IU/mL) in 91% of hepatitis B e antigen (HBeAg)-positive and -negative patients by Week 96. Thirteen percent (n = 88) of the comparator lamivudine (LVD)-treated patients experienced a virologic rebound (> or =1 log increase from nadir by PCR) in the first year, with 74% of these having LVD resistance (LVDr) substitutions evident. In contrast, only 3% (n = 22) of ETV-treated patients exhibited virologic rebound by Week 96. Three ETV rebounds were attributable to LVDr virus present at baseline, with one having a S202G ETV resistance (ETVr) substitution emerge at Week 48. None of the other rebounding patients had emerging genotypic resistance or loss of ETV susceptibility. Genotyping all additional ETV patients with PCR-detectable HBV DNA at Weeks 48, 96, or end of dosing identified seven additional patients with LVDr substitutions, including one with simultaneous emergence of LVDr/ETVr. Generally, ETV patients with LVDr were detectable at baseline (8/10) and most subsequently achieved undetectable HBV DNA levels on ETV therapy (7/10). No other emerging substitutions identified decreased ETV susceptibility. In conclusion, ETVr emergence in ETV-treated nucleoside naïve patients over a 2-year period is rare, occurring in two patients with LVDr variants. These findings suggest that the rapid, sustained suppression of HBV replication, combined with a requirement for multiple substitutions, creates a high genetic barrier to ETVr in nucleoside naïve patients.

Hepatitis B treatment: Lessons for the nephrologist

Hepatitis B affects approximately 350 million people worldwide, and an estimated 1.25 million people in the United States. Although most people infected with the virus do not develop significant hepatic disease from hepatitis B, 15-40% will develop serious complications. These complications include cirrhosis, the development of hepatocellular carcinoma , and hepatic decompensation. Patients with renal failure have increased risk of acquiring the virus through blood transfusions and contact with bodily fluids at hemodialysis centers, and of developing complications from hepatitis B virus infection. Renal transplant patients are at increased risk for exacerbations of hepatitis B with immunosuppression. Thus, it is crucial for the nephrologist to have a clear understanding of the natural history and treatment of hepatitis B, both pre- and post-renal transplant.

The "return" of hepatitis B

There has been a significant advance in the treatment of chronic Hepatitis B virus (HBV) infection and the following drugs were approved for therapy: Conventional interferon (IFN), pegylated interferon alfa-2a (PEG IFN alpha2a), lamivudine, adefovir and entecavir. Compared to nucleoside analogues IFN induces higher rates of sustained remission and HBsAg loss. Conventional IFN in lower doses (1, 5-3 MIU) tiw for 4-6 mo has similar efficacy in comparison to "standard IFN therapy". Longer IFN treatment is a significant factor for long-term remission in HBeAg-negative CHB, but the higher actual IFN dose is not such a factor. PEG IFN is superior to conventional IFN. There is no significant difference between PEG IFN alpha2a at doses 90 mcg/wk and 180 mcg/wk in HBeAg-positive patients. These results provide a rational for further clinical trials with lower doses PEG IFN alpha2a given in prolonged course as maintenance or intermittent treatment. Serious new problems arose after the introduction of nucleoside/nucleotide analogues in clinical practice. The most important ones are drug-resistance and the high rates of relapse after treatment discontinuation. Therapy should only be recommended if the expected benefit exceeds significantly the abstain from treatment. The choice of therapy should take into account the patient's age, co-morbidity, severity of liver disease and the risk of drug-resistance. New antivirals significantly suppress HBV-replication, but have no effect on cccDNA in hepatocytes, and after the treatment discontinuation viral relapses occurs. At the present level of knowledge it is impossible "to eradicate the virus" The realistic treatment goal is to achieve durable response by clearance of HBeAg, sustained decrease of serum HBV DNA levels, normalization of ALT, improvement of liver histology and stopping of liver fibrogenesis. The competition between IFN based therapy and nucleoside or nucleotide analogues still remains. IFN can cure the liver disease while nucleotide analogues only suppress the viral replication during therapy and can reduce the liver fibrosis. Treatment should be prolonged for 24-mo or longer by using maintenance or intermittent treatment course with the lowest effective IFN and PEG IFN doses. Nucleoside/nucleotide analogues are a promising treatment option, but additional data for treatment duration and long-term post-treatment outcome are necessary.

Treatment of chronic hepatitis B

Treatment of chronic hepatitis B has improved substantially over the past five years. Pegylated interferon alpha2a and entecavir have been approved by the FDA and joined the armamentarium of therapies that includes inteferon alpha (IFN-alpha), lamivudine, and adefovir dipivoxil. Several key questions come to mind regarding treatment. Who should receive treatment? Which agent should they be given? How long should treatment last? Treatment is indicated for patients with a high pretreatment alanine aminotransferase level, detectable HBV DNA, and active inflammation on liver biopsy. When selecting an agent, the likelihood of achieving a sustained response should be weighed against long-term risks. IFN-alpha, lamivudine, and adefovir dipivoxil are equally efficacious; however, even though IFN-alpha and pegylated IFN-alpha have a durable response, both are associated with unpleasant side effects. Long-term lamivudine therapy has a high rate of drug resistance compared with adefovir dipivoxil, which has a low rate of drug resistance and a small risk of reversible nephrotoxicity. Entecavir reduces HBV load more effectively than the other therapies, but it is associated with increased drug resistance in patients with lamivudine-resistant HBV. The key to therapy seems to be some combination of therapies--both existing and those in development--that has yet to be determined.

[Treatment of viral hepatitis (I). Treatment of chronic hepatitis B]

In the past 25 years remarkable progress has been made in our understanding of the natural history of chronic HBV. The infection is now perceived as having three consecutive phases: immune tolerance, immune clearance, and inactive carrier status, with possible reactivation episodes. Accumulating evidence indicates that antiviral therapy can prevent progression of HBV-related liver disease, particularly among patients with sustained response. Five agents are now approved for therapy of chronic hepatitis B: interferon-alpha (standard and pegylated), lamivudine, adefovir and entecavir. All five drugs are effective in suppressing HBV DNA levels and improving serum alanineaminotransferase levels and hepatic histology, but it is still unclear who should be treated, with which agent (or combination of agents), for how long, and what endpoints measure the success or failure of treatment. Until a drug therapy results in lasting virological remission in most patients after a reasonably short period of treatment, individualized treatment decisions will remain key to maximizing efficacy, and chronic HBV infection will continue to be treated as a liver disease rather than as an infectious disease.

Treatment of chronic hepatitis B: efficacy of current drugs and prospects for the future

Chronic hepatitis B is an important clinical problem often leading to severe complications. In this review, the results obtained in the last few years with the use of current drugs, such as interferon and nucleo(t)side analogues, are summarized and the problems of obtaining a sustained remission, which is only achieved in a small number of patients, are discussed. The new approaches, such as the use of combinations of drugs, to optimize long-term tolerable treatment are also considered.

Hepatitis B in liver transplant recipients

1. The use of low-dose immunosuppressive therapy along with pre- and posttransplantation nucleos(t)ide therapy and posttransplantation hepatitis B immunoglobulin (HBIG) has yielded marked improvements in survival. 2. Lamivudine (Epivir-HBV), adefovir (Hepsera), entecavir (Baraclude), tenofovir (Viread), emtricitabine (Emtriva), and the combination drugs tenofovir + emtricitabine (Truvada) and abacavir + lamivudine (Epzicom) are effective nucleos(t)ide antiviral agents that, in some cases, may help reverse liver disease sufficiently to avoid transplant. 3. In posttransplantation patients, virus suppression with some combination of HBIG and the nucleos(t)ide agents may prevent graft loss and death or the need for a second transplant. 4. In both the pre- and posttransplantation setting, the goal of hepatitis B virus management is complete virus suppression. 5. The use of low-dose intramuscular HBIG is evolving, with studies showing that dosing and cost can be reduced by 50-300% with a customized approach. 6. Elimination of HBIG from the treatment paradigm is currently under evaluation and may be possible with the use of newer medications that have no or low resistance rates. 7. Although there is growing evidence that some types of combination therapy may decrease the chance that drug resistance will develop and increase the likelihood of long-term success in preventing graft loss and death, additional research will be required to determine which combinations will work well in the long term, and which will not.

New developments in the treatment of chronic hepatitis B

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

Where does adefovir stand amongst newly developed antivirals: from pharmacology to virology

Adefovir, an acyclic nucleotide analog of adenosine monophosphate, has demonstrated potent activities against several viruses in vitro. Since 2002, the diester prodrug of this molecule, adefovir dipivoxil, has been approved as a well-tolerated and efficacious treatment for chronic hepatitis B. It is the first nucleotide analog to be approved for this indication and it is now challenged by several other molecules that also inhibit hepatitis B virus replication. In this article, we analyze the strengths and limitations of adefovir in the context of hepatitis B treatment and consider the other alternatives in the treatment of this difficult-to-treat chronic disease. Adefovir dipivoxil has offered a real opportunity for patients who developed lamivudine resistance and were facing a therapeutic deadlock; the next challenge for clinicians will be to offer the best therapeutic strategy to limit the inexorable selection of resistant strains.

Treatment alternatives for hepatitis B cirrhosis: a cost-effectiveness analysis

BACKGROUND

Hepatitis B virus (HBV) patients with cirrhosis are at risk for developing costly, morbid, or mortal events, and therefore need highly effective therapies. Lamivudine is effective but is limited by viral resistance. In contrast, adefovir and entecavir have lower viral resistance, but are more expensive. The most cost-effective approach is uncertain.

METHODS

We evaluated the cost-effectiveness of six strategies in HBV cirrhosis: (1) No HBV treatment ("do nothing"), (2) lamivudine monotherapy, (3) adefovir monotherapy, (4) lamivudine with crossover to adefovir on resistance ("adefovir salvage"), (5) entecavir monotherapy, or (6) lamivudine with crossover to entecavir on resistance ("entecavir salvage"). The primary outcome was the incremental cost per quality-adjusted life-year (QALY) gained.

RESULTS

The "do nothing" strategy was least effective yet least expensive. Compared with "do nothing," using adefovir cost an incremental US dollars 19,731. Entecavir was more effective yet more expensive than adefovir, and cost an incremental US dollars 25,626 per QALY gained versus adefovir. Selecting between entecavir versus adefovir was highly dependent on the third-party payer's "willingess-to-pay" (e.g., 45% and 60% of patients fall within budget if willing-to-pay US dollars 10K and US dollars 50K per QALY gained for entecavir, respectively). Both lamivudine monotherapy and the "salvage" strategies were not cost-effective. However, between the two salvage strategies, "adefovir salvage" was more effective and less expensive than "entecavir salvage."

CONCLUSION

Both entecavir and adefovir are cost-effective in patients with HBV cirrhosis. Choosing between adefovir and entecavir is highly dependent on available budgets. In patients with HBV cirrhosis with previous lamivudine resistance, "adefovir salvage" appears more effective and less expensive than "entecavir salvage."

Entecavir: a new treatment for chronic hepatitis B infection

Hepatitis B virus can cause both acute and chronic liver disease in humans. Entecavir, a new, potent, orally administered guanosine analog for the treatment of chronic hepatitis B, has recently approved in the USA and Europe. Monotherapy with entecavir in nucleoside-naive patients has been associated with statistically superior histological improvement, greater reduction in hepatitis B virus-DNA levels, and improved normalization of alanine aminotransferase levels when compared with lamivudine. After 2 years of treatment, viral resistance to entecavir has not developed in the antiviral-naive patient population. Similar findings in terms of efficacy have also been observed in patients with lamivudine-resistant hepatitis B virus. The use of entecavir in the lamivudine-resistant patient population could lead to the development of entecavir-resistant mutants at the rate of 9% by 2 years. Entecavir is well tolerated with a good safety profile and should be considered as primary therapy for chronic hepatitis B. Entecavir may also be considered for use in the lamivudine-resistant patient at twice the dose recommended for nucleoside-naive patients, with the recognition that virologic breakthrough could develop.