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

Recent Updates on Viral Oncogenesis: Available Preventive and Therapeutic Entities

Human viral oncogenesis is a complex phenomenon and a major contributor to the global cancer burden. Several recent findings revealed cellular and molecular pathways that promote the development and initiation of malignancy when viruses cause an infection. Even, antiviral treatment has become an approach to eliminate the viral infections and prevent the activation of oncogenesis. Therefore, for a better understanding, the molecular pathogenesis of various oncogenic viruses like, hepatitis virus, human immunodeficiency viral (HIV), human papillomavirus (HPV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV), could be explored, especially, to expand many potent antivirals that may escalate the apoptosis of infected malignant cells while sparing normal and healthy ones. Moreover, contemporary therapies, such as engineered antibodies antiviral agents targeting signaling pathways and cell biomarkers, could inhibit viral oncogenesis. This review elaborates the recent advancements in both natural and synthetic antivirals to control viral oncogenesis. The study also highlights the challenges and future perspectives of using antivirals in viral oncogenesis.

Antiviral and Antimicrobial Nucleoside Derivatives: Structural Features and Mechanisms of Action

The emergence of new viruses and resistant strains of pathogenic microorganisms has become a powerful stimulus in the search for new drugs. Nucleosides are a promising class of natural compounds, and more than a hundred drugs have already been created based on them, including antiviral, antibacterial and antitumor agents. The review considers the structural and functional features and mechanisms of action of known nucleoside analogs with antiviral, antibacterial or antiprotozoal activity. Particular attention is paid to the mechanisms that determine the antiviral effect of nucleoside analogs containing hydrophobic fragments. Depending on the structure and position of the hydrophobic substituent, such nucleosides can either block the process of penetration of viruses into cells or inhibit the stage of genome replication. The mechanisms of inhibition of viral enzymes by compounds of nucleoside and non-nucleoside nature have been compared. The stages of creation of antiparasitic drugs, which are based on the peculiarities of metabolic transformations of nucleosides in humans body and parasites, have been considered. A new approach to the creation of drugs is described, based on the use of prodrugs of modified nucleosides, which, as a result of metabolic processes, are converted into an effective drug directly in the target organ or tissue. This strategy makes it possible to reduce the general toxicity of the drug to humans and to increase the effectiveness of its action on cells infected by the virus.

Advances in Nucleoside and Nucleotide Analogues in Tackling Human Immunodeficiency Virus and Hepatitis Virus Infections

Nucleoside and nucleotide analogues are structurally similar antimetabolites and are promising small-molecule chemotherapeutic agents against various infectious DNA and RNA viruses. To date, these analogues have not been documented in-depth as anti-human immunodeficiency virus (HIV) and anti-hepatitis virus agents, these are at various stages of testing ranging from pre-clinical, to those withdrawn from trials, or those that are approved as drugs. Hence, in this review, the importance of these analogues in tackling HIV and hepatitis virus infections is discussed with a focus on the viral genome and the mechanism of action of these analogues, both in a mutually exclusive manner and their role in HIV/hepatitis coinfection. This review encompasses nucleoside and nucleotide analogues from 1987 onwards, starting with the first nucleoside analogue, zidovudine, and going on to those in current clinical trials and even the drugs that have been withdrawn. This review also sheds light on the prospects of these nucleoside analogues in clinical trials as a treatment option for the COVID-19 pandemic.

Drug Delivery Strategies for Antivirals against Hepatitis B Virus

Chronic hepatitis B virus (HBV) infection poses a significant health challenge due to associated morbidity and mortality from cirrhosis and hepatocellular cancer that eventually results in the breakdown of liver functionality. Nanotechnology has the potential to play a pivotal role in reducing viral load levels and drug-resistant HBV through drug targeting, thus reducing the rate of evolution of the disease. Apart from tissue targeting, intracellular delivery of a wide range of drugs is necessary to exert a therapeutic action in the affected organelles. This review encompasses the strategies and techniques that have been utilized to target the HBV-infected nuclei in liver hepatocytes, with a significant look at the new insights and most recent advances in drug carriers and their role in anti-HBV therapy.

Telbivudine treatment started in early and middle pregnancy completely blocks HBV vertical transmission

Background

To evaluate the efficacy and safety of treating HBV-positive mothers with telbivudine in early and middle pregnancy to prevent mother-to-infant HBV transmission.

Methods

The subject population comprised pregnant women with chronic hepatitis B (CHB; n = 188) from January 2013 to June 2015, with HBV DNA ≥1.0 × 10⁷copies/mL and increased alanine aminotransferase levels. Groups A (n = 62) and B (n = 61) were treated with telbivudine starting at 12 weeks or 20–28 weeks after gestation, respectively. Telbivudine was discontinued at postpartum 12 weeks. Group C (n = 65) received no antiviral. All infants were vaccinated with hepatitis B immunoglobulin (200 IU) and HBV vaccine (20 with hepatitis B The maternal HBV DNA levels of the groups were compared. Mother-to-infant transmission of HBV was indicated by the presence of HBsAg in infants 7 months after birth.

Results

Before treatment, the HBV DNA levels of the 3 groups were similar. Before delivery and 12 weeks after delivery, the HBV DNA levels of groups A and B were similar, but both were significantly lower than that of group C (P < 0.01, all). No infants in groups A and B were HBsAg-positive, but the infection rate of group C was 18.4% (P < 0.01). The HBV infection rate of infants was positively associated with the HBV DNA levels of the pregnant mothers.

Conclusion

Administration of telbivudine to HBV-infected mothers, started during early and middle pregnancy, completely blocked mother-to-infant HBV transmission.

Trial registration

The study was registered retrospectively on Janurary 25 in 2016 at Chinese Clinical Trial Registry (ChiCTR-OPC-16007899).

Telbivudine therapy for chronic hepatitis B: A journey to identify super-responders and to optimize treatment using the roadmap model

Hepatitis B virus (HBV) infection is one of the most serious health problems worldwide with a high risk for cirrhosis and liver cancer. Several antiviral agents have been approved for the treatment of chronic hepatitis B, leading to a rapid reduction in HBV DNA and normalization of serum alanine aminotransferase levels. Telbivudine, a potent inhibitor of HBV replication, has been shown to be well tolerated. Because of the emergence of drug resistance, optimization strategies for telbivudine therapy have been shown to improve patient responses. Optimal baseline characteristics in so-called super-responders have been used to predict the virological response. Baseline HBV DNA levels < 9 log₁₀ copies/mL (2 × 10⁸  IU/mL) or alanine aminotransferase levels of more than or equal to twofold the upper limit of normal in HBeAg-positive patients and HBV DNA < 7 log₁₀ copies/mL (2 × 10⁶  IU/mL) in HBeAg-negative patients were strong predictors for virological response. In addition, the roadmap model, based on early virological response at week 24 of therapy, is considered as a powerful tool to identify patients at risk of treatment failure (HBV DNA ≥ 300 copies/mL, i.e. 60 IU/mL) and to reduce the risk of antiviral resistance. When considering pre-treatment characteristics and on-treatment responses, telbivudine may provide physicians with a wide choice of options to effectively treat patients with chronic hepatitis B, especially those with or at risk of renal impairment, or women of childbearing age.

Telbivudine treatment of hepatitis B virus-infected pregnant women at different gestational stages for the prevention of mother-to-child transmission: Outcomes of telbivudine treatment during pregnancy

This prospective study evaluated the viability of telbivudine for blocking mother-to-child transmission (MTCT) of hepatitis B virus (HBV) infection.Pregnant women positive for the hepatitis B surface antigen began telbivudine treatment before 14 weeks of gestation (i.e., early), between 14 and 28 weeks of gestation (late), or not at all (control). In the late-treatment group, 55 women terminated telbivudine therapy within puerperium. All neonates underwent routine hepatitis B immunoglobulin plus vaccination. Mothers and infants were followed for 7 months after birth.Pregnancy outcomes were similar among the 3 groups. HBV MTCT rates in the early and late treatment and control groups were 0, 0, and 4.69%, respectively. The rates of infant vaccination success among the 3 groups were similar, as were neonatal outcomes including birth weights, asphyxia, hyperbilirubinemia, Apgar score, birth defects, and weight and height at 7 months. Puerperal discontinuation of telbivudine did not increase the alanine transaminase value at 7 months after birth, but increased serum HBV DNA levels, and rates of positive hepatitis Be-antigen.Telbivudine treatment in HBV-infected pregnant women was associated with lower serum HBV DNA levels and reduced rates of HBV MTCT; there were no associated changes in pregnancy or neonatal outcomes at birth or 7 months after birth, or in the rate of infant vaccination success. Puerperal drug withdrawal after short-term antiviral therapy will not influence hepatic function, but may increase virus replication.

Efficacy and safety of telbivudine treatment: an open-label, prospective study in pregnant women for the prevention of perinatal transmission of hepatitis B virus infection

We evaluated the efficacy and safety of telbivudine (LdT, 600 mg/day) vs control patients (no treatment) in decreasing vertical transmission of HBV, in HBeAg-positive mothers (HBVDNA >6log(10) copies/mL). HBeAg-positive pregnant women either in the second or third trimester were recruited in a prospective, case-control, open-label study, at the Second Affiliated Hospital of the Southeast University, China (February 2008-December 2010). Efficacy (month 7: HBVDNA (+), HBsAg (+) infants) in either the overall group or the treated group and control group was analysed using student's t-test. Infants were followed for at least 1 year. 362 women received LdT (second trimester n = 257; third trimester n = 105) and 92 were untreated. Before delivery, the mean maternal HBVDNA was 2.73, 2.47, 3.34 and 7.94 log10 copies/mL in the overall, second and third trimester treated and control groups, respectively (P < 0.001). At birth, 11.8% of babies overall (43/365), 13.5% (35/259) of those treated in the second trimester, 7.5% of those treated in the third trimester (8/106) and 20.7% (19/92) of untreated infants were HBsAg positive. At month 7, none of the LdT-treated infant had detectable HBVDNA, while eight infants from control mothers were HBsAg positive. Vertical transmission was 0% in LdT treated and 9.3% (8/86) in the control groups (P < 0.001). No difference in the vertical transmission rate was found in mothers treated in the second or third trimester. LdT treatment was safe for mothers and infants, and no congenital deformities were reported.

Efficient syntheses of [¹¹C]zidovudine and its analogs by convenient one-pot palladium(0)-copper(I) co-mediated rapid C-[¹¹C]methylation

The nucleosides zidovudine (AZT), stavudine (d4T), and telbivudine (LdT) are approved for use in the treatment of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections. To promote positron emission tomography (PET) imaging studies on their pharmacokinetics, pharmacodynamics, and applications in cancer diagnosis, a convenient one-pot method for Pd(0)-Cu(I) co-mediated rapid C-C coupling of [(11)C]methyl iodide with stannyl precursor was successfully established and applied to synthesize the PET tracers [(11)C]zidovudine, [(11)C]stavudine, and [(11)C]telbivudine. After HPLC purification and radiopharmaceutical formulation, the desired PET tracers were obtained with high radioactivity (6.4-7.0 GBq) and specific radioactivity (74-147 GBq/µmol) and with high chemical (>99%) and radiochemical (>99.5%) purities. This one-pot Pd(0)-Cu(I) co-mediated rapid C-[(11)C]methylation also worked well for syntheses of [methyl-(11)C]thymidine and [methyl-(11)C]4'-thiothymidine, resulting twice the radioactivity of those prepared by a previous two-pot method. The mechanism of one-pot Pd(0)-Cu(I) co-mediated rapid C-[(11)C]methylation was also discussed.

Telbivudine prevents vertical transmission from HBeAg-positive women with chronic hepatitis B

BACKGROUND & AIMS

Telbivudine reduces hepatitis B virus (HBV) DNA and normalizes levels of alanine aminotransferase (ALT) in patients with chronic hepatitis B (CHB). We investigated its use in preventing vertical transmission.

METHODS

We performed an open-label, prospective study of 88 hepatitis B (HB) e antigen (HBeAg)-positive pregnant women with CHB, levels of HBV DNA >6 log(10) copies/mL, and increased levels of ALT. Women were given telbivudine (n = 53) starting in the 2nd or 3rd trimester, or no treatment (controls, n = 35) and followed until postpartum week (PPW) 28. All infants received standard immunoprophylaxis after birth.

RESULTS

At 28 weeks, none of the infants whose mothers received telbivudine had immunoprophylaxis failure, whereas 8.6% of the infants of control mothers did (P = .029). There were no differences between groups in mothers' adverse events or infants' congenital deformities, gestational age, height, and weight, or Apgar scores. At postpartum week 28, significantly more telbivudine-treated mothers had levels of HBV DNA <500 copies/mL, normalized levels of ALT, and hepatitis B e antigen seroconversion compared with controls (58% vs none, P < .001; 92% vs 71%; P = .008; and 15% vs none; P < .001, respectively) but none had loss of hepatitis B surface antigen. Telbivudine-treated mothers had no virologic breakthrough (HBV DNA >1 log(10) increase from <500 copies/mL) or discontinuations from adverse events. After delivery, 13/52 patients discontinued telbivudine due to preference. There were no episodes of severe hepatitis (levels of ALT >10 times the upper limit of normal) in either group during 28 weeks of postpartum observation.

CONCLUSIONS

Women with CHB given telbivudine during the second or third trimester of pregnancy have reduced rates of perinatal transmission. Telbivudine produced no adverse events in mothers or infants by 28 weeks.

A prospective and open-label study for the efficacy and safety of telbivudine in pregnancy for the prevention of perinatal transmission of hepatitis B virus infection

BACKGROUND & AIMS

In the Asia-Pacific region, perinatal transmission of the hepatitis B virus (HBV) is the primary cause of chronic hepatitis B infection. Despite the use of HBIG and HBV vaccination, HBV perinatal transmission (PT) occurs in 10-30% of infants born to highly viremic mothers. We evaluated the efficacy and safety of LTD use during late pregnancy in reducing HBV transmission in highly viremic HBeAg+mothers.

METHODS

Two hundred and twenty-nine HBeAg+HBV DNA levels>1.0×10(7) copies/ml mothers received telbivudine 600 mg/day from week 20 to 32 of gestation (n=135) or served as untreated controls (n=94). All infants in both arms received 200 IU of HBIg within 12 h postpartum and recombinant HBV vaccine of 20 μg at 0, 1, and 6 months. HBsAg and HBV DNA results of infants at week 28 were used to determine perinatal transmission rate. All telbivudine treated subjects were registered in the Antiretroviral Pregnancy Registry.

RESULTS

Telbivudine treatment was associated with a marked reduction in serum HBV DNA and hepatitis B e antigen (HBeAg) levels and normalization of elevated ALT levels before delivery. A striking decline of HBV DNA levels started from treatment onset to week 4, and sustained in a low level since week 12. Forty-four (33%) of the 135 telbivudine-treated mothers and none (0%) of the untreated controls had polymerase chain reaction-undetectable viremia (DNA<500 copies/ml) at delivery. Seven months after delivery, the incidence of perinatal transmission was lower in the infants that completed follow-up born to the telbivudine-treated mothers than to the controls (0% vs. 8%; p=0.002). HBV DNA levels were only detectable in HBsAg+infants. No significant differences in anti-HBs levels were observed during postnatal follow-up. No serious adverse events were noted in the telbivudine-treated mothers or their infants.

CONCLUSIONS

Telbivudine used during pregnancy in CHB HBeAg+highly viremic mothers can safely reduce perinatal HBV transmission. Telbivudine was well-tolerated with no safety concerns in the telbivudine-treated mothers or their infants on short term follow up. These data support the use of telbivudine in this special population.

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.

Extending thymidine kinase activity to the catalytic repertoire of human deoxycytidine kinase

Salvage of nucleosides in the cytosol of human cells is carried out by deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1). Whereas TK1 is only responsible for thymidine phosphorylation, dCK is capable of converting dC, dA, and dG into their monophosphate forms. Using structural data on dCK, we predicted that select mutations at the active site would, in addition to making the enzyme faster, expand the catalytic repertoire of dCK to include thymidine. Specifically, we hypothesized that steric repulsion between the methyl group of the thymine base and Arg104 is the main factor preventing the phosphorylation of thymidine by wild-type dCK. Here we present kinetic data on several dCK variants where Arg104 has been replaced by select residues, all performed in combination with the mutation of Asp133 to an alanine. We show that several hydrophobic residues at position 104 endow dCK with thymidine kinase activity. Depending on the exact nature of the mutations, the enzyme's substrate preference is modified. The R104M-D133A double mutant is a pyrimidine-specific enzyme due to large K(m) values with purines. The crystal structure of the double mutant R104M-D133A in complex with the L-form of thymidine supplies a structural explanation for the ability of this variant to phosphorylate thymidine and thymidine analogs. The replacement of Arg104 by a smaller residue allows L-dT to bind deeper into the active site, making space for the C5-methyl group of the thymine base. The unique catalytic properties of several of the mutants make them good candidates for suicide-gene/protein-therapy applications.

Antiviral agents acting as DNA or RNA chain terminators

Nucleoside or nucleotide analogue inhibitors of viral replication almost act as chain terminators during DNA (DNA- and retroviruses) or RNA (RNA viruses) synthesis. Following intracellular phosphorylation, by viral and/or cellular kinases, the 5'-triphosphate metabolites (or 2'-diphosphate metabolites in the case of acyclic nucleoside phosphonate analogues) compete with the natural substrate in the DNA or RNA polymerization reaction. Obligatory chain terminators (e.g., acyclovir) do not offer the 3'-hydroxyl function at the riboside moiety of the molecule. Nucleoside analogues that possess a hydroxyl function at a position equivalent of the 3'-hydroxyl position may act as chain terminators if this hydroxyl group is conformationally constrained (e.g., ganciclovir) or sterically hindered to enter into a phosphodiester linkage with the incoming nucleotide. In case that the 3'-hydroxylgroup is correctly positioned, chain elongation may be hampered through steric hindrance from neighboring substituents (e.g., 2'-C-methyl or 4'-azido nucleoside inhibitors of HCV replication). Here, we review the molecular mechanism of action and the clinical applications of the nucleosides and nucleotides acting as chain terminators. A further discussion of clinical applications in combination therapy can be found in Chap. 12.

Diagnosis of hepatitis B virus infection through serological and virological markers

Hepatitis B virus (HBV) infection is an important health problem and the major cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) worldwide. The natural history of chronic HBV infection can be divided into four dynamic phases in HBV carriers who acquire the virus early in life. Diagnosis of HBV infection is usually through serological and virological markers. Hepatitis B surface antigen (HBsAg) is the hallmark of HBV infection and is the first serological marker to appear in acute hepatitis B, and persistence of HBsAg for more than 6 months suggests chronic HBV infection. Hepatitis B e antigen (HBeAg) usually indicates active HBV replication and risk of transmission of infection. Recently, occult HBV infection is recognized as the absence of circulating HBsAg in individuals positive for serum or tissue HBV DNA, irrespective of other HBV serological markers. Meanwhile, monitoring the serum HBV DNA level is valuable for assessing liver disease activity, differentiating other etiologies of hepatitis activity in HBV carriers, predicting risk of HCC development or liver-related mortality, deciding to administer antiviral therapy, determination of the response to antiviral treatment, predicting the risk of developing drug resistance, and detecting the emergence of drug-resistant mutants. On the other hand, HBV genotype C, basal core promoter mutant and pre-S deletion mutant are reported to be associated with increased risk of HCC development. The roles of quantitative HBV serology and intrahepatic HBV covalently closed circular (ccc)DNA deserve further studies. In conclusion, it is particularly important for physicians to screen for HBV infection in HBV-endemic areas and to monitor liver disease progression in HBV carriers by using both serological and virological markers, so that effective treatment can be initiated early before the development of advanced liver disease.

Care of HIV patients with chronic hepatitis B: updated recommendations from the HIV-Hepatitis B Virus International Panel

Nearly 10% of the estimated 36 million people having HIV worldwide suffer from chronic hepatitis B virus (HBV) infection. The advent of new antiviral agents against HBV and the recent availability of improved molecular diagnostic tools have revolutioned the management of HIV/HBV coinfected patients. The present study represents an update of the current knowledge about HBV/HIV coinfection and an intent to provide practical advise about how to give the best care to HIV-infected persons with chronic hepatitis B.

Hepatitis infection in the treatment of opioid dependence and abuse

Many new and existing cases of viral hepatitis infections are related to injection drug use. Transmission of these infections can result directly from the use of injection equipment that is contaminated with blood containing the hepatitis B or C virus or through sexual contact with an infected individual. In the latter case, drug use can indirectly contribute to hepatitis transmission through the dis-inhibited at-risk behavior, that is, unprotected sex with an infected partner. Individuals who inject drugs are at-risk for infection from different hepatitis viruses, hepatitis A, B, or C. Those with chronic hepatitis B virus infection also face additional risk should they become co-infected with hepatitis D virus. Protection from the transmission of hepatitis viruses A and B is best achieved by vaccination. For those with a history of or who currently inject drugs, the medical management of viral hepatitis infection comprising screening, testing, counseling and providing care and treatment is evolving. Components of the medical management of hepatitis infection, for persons considering, initiating, or receiving pharmacologic therapy for opioid addiction include: testing for hepatitis B and C infections; education and counseling regarding at-risk behavior and hepatitis transmission, acute and chronic hepatitis infection, liver disease and its care and treatment; vaccination against hepatitis A and B infection; and integrative primary care as part of the comprehensive treatment approach for recovery from opioid abuse and dependence. In addition, participation in a peer support group as part of integrated medical care enhances treatment outcomes. Liver disease is highly prevalent in patient populations seeking recovery from opioid addiction or who are currently receiving pharmacotherapy for opioid addiction. Pharmacotherapy for opioid addiction is not a contraindication to evaluation, care, or treatment of liver disease due to hepatitis virus infection. Successful pharmacotherapy for opioid addiction stabilizes patients and improves patient compliance to care and treatment regimens as well as promotes good patient outcomes. Implementation and integration of effective hepatitis prevention programs, care programs, and treatment regimens in concert with the pharmacological therapy of opioid addiction can reduce the public health burdens of hepatitis and injection drug use.

Lamivudine-resistant chronic hepatitis B: an observational study on adefovir in monotherapy or in combination with lamivudine

BACKGROUND/AIMS

In lamivudine-resistant patients with chronic hepatitis B (CHB), we compared efficacy, predictive response factors and changes in viral mutants in two antiviral approaches with adefovir.

METHODS

A prospective cohort study on therapy with adefovir alone (29 patients) or combined with ongoing lamivudine (23 patients) was performed.

RESULTS

A virological response was achieved in 55% of patients treated with adefovir and in 83% of those treated with the combination (p>0.05). This response was directly related to the basal viral load (p<0.0001) and obtained in 10 patients with basal HBV-DNA<17,200 IU/ml using both strategies. In patients with a higher basal viral load, the virological response was more frequent when treated with the combination (p<0.05). Mutation at locus rt181 predicted HBV-DNA persistence during therapy. A virological rebound was observed in 18% of non-responders while on adefovir monotherapy.

CONCLUSIONS

To achieve a complete virological response and reduce the risk of adefovir-resistant mutants in lamivudine-resistant patients, rescue therapy is preferable at early evidence of genotypic resistance. However, in subjects with a significant viral load, combination therapy is more effective. The presence of the rt181 mutation is associated with incomplete response.

The implications of antiviral drugs with activity against hepatitis B virus and HIV

PURPOSE OF REVIEW

Around 10% of individuals infected with HIV suffer from chronic hepatitis B virus infection. This represents at least 4 million people worldwide. HIV infection modifies the course of hepatitis B virus associated liver disease with faster progression to cirrhosis. The number of anti-hepatitis B virus drugs has increased within the last few years, and some of them also exert activity against HIV-1. The aim of this article is to update the current knowledge on antiviral therapy for chronic hepatitis B in HIV-infected patients.

RECENT FINDINGS

In the absence of successful anti-hepatitis B virus therapy, morbidity and mortality associated with liver disease are increased in hepatitis B virus/HIV coinfected individuals. Data derived from studies using new more potent anti-hepatitis B virus drugs are very promising, and strategies to use these antivirals sequentially and/or in combination are being developed. Hopefully, this success will help bring a halt to liver-related complications and death in the hepatitis B virus/HIV coinfected population.

SUMMARY

Appropriate diagnosis and monitoring of chronic hepatitis B, including the use of noninvasive tools for assessing liver fibrosis, measurement of serum hepatitis B virus-DNA, and drug resistance testing, along with wise use of antivirals may convert hepatitis B virus/HIV coinfection into a manageable disease.

Telbivudine in the treatment of chronic hepatitis B

Treatment of chronic hepatitis B with oral nucleos(t)ide analogs is evolving rapidly with newer compounds gaining approval. Recently, the US FDA and European Medicines Agency (EMEA) have approved telbivudine, a potent anti-hepatitis B virus (HBV)-specific agent with a hitherto excellent safety profile. This review focuses on the efficacy of this agent in chronic hepatitis B compared with lamivudine, evaluated clinically in Phase II and a large Phase III study. Monitoring of the virologic response under treatment with sensitive HBV-DNA assays has been applied, aiming at increasing efficacy and reducing HBV resistance. The results are critically presented and the evolving concept of effective long-term telbivudine and other nucleos(t)ide analog therapy, predicted by the extent of suppression of HBV replication at week 24, are analyzed and discussed.

Role of viral factors in the natural course and therapy of chronic hepatitis B

Hepatitis B virus (HBV) infection is a global health problem that causes a wide spectrum of liver disease, including acute or fulminant hepatitis, inactive carrier state, chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of hepatocyte damage associated with HBV is mainly through immune-mediated mechanisms. On the basis of the virus and host interactions, the natural history of HBV carriers who are infected in early life can be divided into four dynamic phases. The frequency, extent, and severity of hepatitis flares or acute exacerbation in the second immune clearance and/or fourth reactivation phase predict liver disease progression in HBV carriers. In the past decade, hepatitis B viral factors including serum HBV DNA level, genotype, and naturally occurring mutants predictive of clinical outcomes have been identified. The higher the serum HBV DNA level after the immune clearance phase, the higher the incidence of adverse outcomes over time. In addition, high viral load, genotype C, basal core promoter mutation, and pre-S deletion correlate with increased risk of cirrhosis and HCC development. As to the treatment of chronic hepatitis B, patients with high HBV DNA level and genotype C or D infection are shown to have a worse response to interferon therapy. In conclusion, serum HBV DNA level, genotype, and naturally occurring mutants are identified to influence liver disease progression and therapy of chronic hepatitis B. More investigations are needed to clarify the molecular mechanisms of the viral factors involved in the pathogenesis of each stage of liver disease and the response to antiviral treatments.