Entecavir for the treatment of chronic hepatitis B virus infection

Drug Nanocrystals: A Delivery Channel for Antiviral Therapies

Viral infections represent a significant threat to global health due to their highly communicable and potentially lethal nature. Conventional antiviral interventions encounter challenges such as drug resistance, tolerability issues, specificity concerns, high costs, side effects, and the constant mutation of viral proteins. Consequently, the exploration of alternative approaches is imperative. Therefore, nanotechnology-embedded drugs excelled as a novel approach purporting severe life-threatening viral disease. Integrating nanomaterials and nanoparticles enables ensuring precise drug targeting, improved drug delivery, and fostered pharmacokinetic properties. Notably, nanocrystals (NCs) stand out as one of the most promising nanoformulations, offering remarkable characteristics in terms of physicochemical properties (higher drug loading, improved solubility, and drug retention), pharmacokinetics (enhanced bioavailability, dose reduction), and optical properties (light absorptivity, photoluminescence). These attributes make NCs effective in diagnosing and ameliorating viral infections. This review comprises the prevalence, pathophysiology, and resistance of viral infections along with emphasizing on failure of current antivirals in the management of the diseases. Moreover, the review also highlights the role of NCs in various viral infections in mitigating, diagnosing, and other NC-based strategies combating viral infections. In vitro, in vivo, and clinical studies evident for the effectiveness of NCs against viral pathogens are also discussed.

Structural and Synthetic Aspects of Small Ring Oxa- and Aza-Heterocyclic Ring Systems as Antiviral Activities

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the structure-activity relationship (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists. The synergistic conclusions are extremely important for the introduction of a newer tool for the future drug discovery program.

OAT3 Participates in Drug-Drug Interaction between Bentysrepinine and Entecavir through Interactions with M8-A Metabolite of Bentysrepinine-In Rats and Humans In Vitro

Bentysrepinine (Y101) is a novel phenylalanine dipeptide for the treatment of hepatitis B virus. Renal excretion played an important role in the elimination of Y101 and its metabolites, M8 and M9, in healthy Chinese subjects, although the molecular mechanisms of renal excretion and potential drug-drug interactions (DDIs) remain unclear. The present study aimed to determine the organic anion transporters (OATs) involved in the renal disposition of Y101 and to predict the potential DDI between Y101 and entecavir, the first-line agent against HBV and a substrate of OAT1/3. Pharmacokinetic studies and uptake assays using rat kidney slices, as well as hOAT1/3-HEK293 cells, were performed to evaluate potential DDI. The co-administration of probenecid (an inhibitor of OATs) significantly increased the plasma concentrations and area under the plasma concentration-time curves of M8 and M9 but not Y101, while reduced renal clearance and the cumulative urinary excretion of M8 were observed in rats. The time course of Y101 and M8 uptake via rat kidney slices was temperature-dependent. Moreover, the uptake of M8 was inhibited significantly by probenecid and benzylpenicillin, but not by p-aminohippurate or tetraethyl ammonium. M8 was found to be a substrate of hOAT3, but Y101 is not a substrate of either hOAT1 or hOAT3. Additionally, the entecavir inhibited the uptake of M8 in the hOAT3-transfected cells and rat kidney slices in vitro. Interestingly, no significant changes were observed in the pharmacokinetic parameters of Y101, M8 or entecavir, regardless of intravenous or oral co-administration of Y101 and entecavir in rats. In conclusion, M8 is a substrate of OAT3 in rats and humans. Furthermore, M8 also mediates the DDI between Y101 and entecavir in vitro, mediated by OAT3. We speculate that it would be safe to use Y101 with entecavir in clinical practice. Our results provide useful information with which to predict the DDIs between Y101 and other drugs that act as substrates of OAT3.

A Pharmacokinetic Drug-Drug Interactions Study between Entecavir and Hydronidone, a Potential Novel Antifibrotic Small Molecule, in Healthy Male Volunteers

INTRODUCTION

Hepatic fibrosis is an inevitable process of hepatic sclerosis, malignancy, and insufficiency, and hydronidone is an innovative antifibrosis drug. This study focus on the pharmacokinetic interaction of hydronidone and entecavir in healthy Chinese male subjects.

METHODS

An open-label, three-period, multiple-dosage, self-controlled clinical trial was executed in 12 healthy male subjects. In period 1, the subjects took hydronidone 60 mg, q8h, for 7 days. In period 2, they were given entecavir 0.5 mg once daily for 9 days. Then, hydronidone and entecavir were given in combination for 6 days (days 20-26). Blood samples were taken up to 24 h post-dosing, while pre-dose blood samples were drawn on days 7, 19, and 26.

RESULTS

The area under the curve (AUC)_{0-t_ss} of entecavir slightly increased from 15.56 ± 2.67 to 16.17 ± 2.77 ng h/ml with coadministration with hydronidone, while the other pharmacokinetic parameters of hydronidone and entecavir were comparable between monotherapy and combination therapy. The geometric mean ratios (GMRs) [90% confidence intervals (CIs)] of C_{max_ss}, AUC_{0-t_ss}, and AUC_{0-∞_ss} of entecavir after coadministration compared with entecavir alone were 107.21% (97.04-118.45%), 103.85% (100.94-106.83%), and 110.81% (97.19-126.33%), respectively. And the GMRs and 90% CIs of C_max,ss, AUC_{0-t_ss}, and AUC_{0-∞_ss} for combination therapy compared with the hydronidone monotherapy group were 102.72% (84.21-125.29%), 106.52% (97.06-116.90%), and 108.86% (96.42-122.89%), respectively.

CONCLUSIONS

There was no drug-drug interaction between hydronidone and entecavir in healthy male volunteers. However, multiple doses of hydronidone have a risk with increasing exposure to entecavir in vivo, which needs to be further clarified.

REGISTRATION NUMBER

ChiCTR2200059683 (retrospectively registered).

Hepatocellular carcinoma in patients with renal dysfunction: Pathophysiology, prognosis, and treatment challenges

The population of patients with hepatocellular carcinoma (HCC) overlaps to a high degree with those for chronic kidney disease (CKD) and end-stage renal disease (ESRD). The degrees of renal dysfunction vary, from the various stages of CKD to dialysis-dependent ESRD, which often affects the prognosis and treatment choice of patients with HCC. In addition, renal dysfunction makes treatment more difficult and may negatively affect treatment outcomes. This study summarized the possible causes of the high comorbidity of HCC and renal dysfunction. The possible mechanisms of CKD causing HCC involve uremia itself, long-term dialysis status, immunosuppressive agents for postrenal transplant status, and miscellaneous factors such as hormone alterations and dysbiosis. The possible mechanisms of HCC affecting renal function include direct tumor invasion and hepatorenal syndrome. Finally, we categorized the risk factors that could lead to both HCC and CKD into four categories: Environmental toxins, viral hepatitis, metabolic syndrome, and vasoactive factors. Both CKD and ESRD have been reported to negatively affect HCC prognosis, but more research is warranted to confirm this. Furthermore, ESRD status itself ought not to prevent patients receiving aggressive treatments. This study then adopted the well-known Barcelona Clinic Liver Cancer guidelines as a framework to discuss the indicators for each stage of HCC treatment, treatment-related adverse renal effects, and concerns that are specific to patients with pre-existing renal dysfunction when undergoing aggressive treatments against CKD and ESRD. Such aggressive treatments include liver resection, simultaneous liver kidney transplantation, radiofrequency ablation, and transarterial chemoembolization. Finally, focusing on patients unable to receive active treatment, this study compiled information on the latest systemic pharmacological therapies, including targeted and immunotherapeutic drugs. Based on available clinical studies and Food and Drug Administration labels, this study details the drug indications, side effects, and dose adjustments for patients with renal dysfunction. It also provides a comprehensive review of information on HCC patients with renal dysfunction from disease onset to treatment.

Serological prevalence of hepatitis B virus (HBV) in Mardan district, Khyber Pakhtunkhwa, Pakistan

Hepatitis B virus infection is perilous among the five types of Hepatitis, as it remains clinically asymptomatic. The present study draws up-to-date prevalence of Hepatitis B virus (HBV) in the general population of Mardan, Khyber Pakhtunkhwa Pakistan. The blood samples from 4803 individuals including 2399 male and 2404 females were investigated. All the suspected samples were analyzed for hepatitis B surface antigen using Immuno-chromatographic test (ICT), Enzyme-linked immunosorbent assay (ELISA), and followed by Reverse transcription-polymerase chain reaction (RT-PCR). Results showed that 312 (13.00%) out of 2399 individuals contained antibodies in their blood against HBV, while among the different age groups, the highest incidences of HBV antibodies were found in the age of 21-30 groups (10.73%). Furthermore, the ICT positive samples were screened by nested polymerase chain reaction to detect the existence of active HBV-DNA. It was observed that 169 (7.04%) out of (2399) male of the total population (4803) tested was positive. On the other hand, the female 463 (19.25%) possessed antibodies in their blood against HBV. Accumulatively, our results showed a higher percentage of HBV prevalence in males than females in the age group 21-30 years. The total HCV infected in Mardan general population was recorded at 5.7% comprising both male and female.

Complexities in the treatment of coinfection with HIV, hepatitis B, hepatitis C, and tuberculosis

HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) are commonly encountered blood-borne infectious microorganisms. Infection with these viruses typically requires long-lasting drug therapy. Coinfections, especially with tuberculosis, pose a challenge to the creation of a regimen with adequate efficacy and minimal drug-drug interactions and adverse effects. We present the case of a young man with a history of intravenous drug misuse who was diagnosed with disseminated tuberculosis and with a triple infection with HBV, HCV, and HIV. The treatment for tuberculosis was initiated first, followed 2 months later by antiretrovirals that were effective against both HIV and HBV. After 9 months of antitubercular therapy, HCV was successfully treated with 12 weeks of oral direct-acting antivirals. We describe the challenges faced in formulating a therapeutic plan for such patients and discuss the various drug interactions that can arise between antitubercular drugs, antiretrovirals, anti-HBV drugs, and direct-acting antivirals against HCV.

Voltammetric Methods Used in the Determination of Nucleoside Reverse Transcriptase Inhibitors

Background:

The Human Immunodeficiency Virus (HIV) has now been established as the causative agent of the Acquired Immunodeficiency Syndrome (AIDS) and exactly 25 antiretroviral drugs have been formally approved for clinical use in the treatment of AIDS. The life quality and duration of HIV-positive patients have increased with the usage of antiretroviral drugs in the treatment of AIDS. Nucleoside Reverse Transcriptase Inhibitors (NRTIs) are one of the subgroups of antiretroviral.

Objective:

The quantification of drugs is important, as they make positive contributions to dose adjustments in practice. Voltammetric methods are very powerful analytical methods used in the pharmaceutical industry because of the determination of therapeutic agents and/or their metabolites in clinical samples at extremely low concentrations (10-50 ng/ml).

Methods:

This review mainly includes the pharmacological properties and recent determination studies by voltammetric methods from pharmaceutical dosage forms and biological samples of eight NRTIs group antiretroviral drugs (zidovudine, abacavir, adefovir, entecavir, zalcitabine, didanosine, emtricitabine, lamivudine) that are used in the clinic and show electroactive properties, were performed.

Conclusion:

Due to the variety of working electrodes in voltammetric methods, it is possible to choose the electrode that best responds. In this way, the analysis of NRTIs was possible at lower concentrations in pharmaceuticals and biological samples with voltammetric methods in these studies without the necessity for the sample pre-treatment or time-consuming extraction steps. The voltammetric methods provide good stability, repeatability, reproducibility and high recovery for the analysis of the analyte. They could be used for the pharmacokinetic studies as well as for quality control laboratory studies.

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.

Effects of Fuzheng Huayu recipe on entecavir pharmacokinetics in normal and dimethylnitrosamine-induced hepatic fibrosis rats

Context: Fuzheng Huayu recipe (FZHY) combined with entecavir (ETV) is used to treat the cirrhosis caused by chronic hepatitis B (CHB) infection.Objective: To investigate the effect of FZHY on ETV pharmacokinetics under different conditions.Materials and methods: A model of liver fibrosis was created by intraperitoneal injection of dimethylnitrosamine (DMN; 10 μg/kg) for 4 weeks in Wistar rats. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used to determine the blood concentration of ETV. Pharmacokinetic characteristics of ETV (0.9 mg/kg) were investigated after co-administration with FZHY (0.55 g/kg) at certain time intervals in normal and model rats.Results: The analytical method for ETV was validated at 0.5-50 μg/L with a correlation coefficient = 0.9996, lower limit of quantitation of 0.5 μg/L and mean accuracy of 104.18 ± 9.46%. Compared with the ETV-N group, the pharmacokinetic parameters of the EF-2 group did not change significantly, but that of the EF-0 group decreased in C_max to 27.38 μg/L, in AUC_0-t from 323.84 to 236.67 μg/h/L, and a delay in T_max from 0.75 to 6.00 h; that of the EF-0 group presented a decrease in C_max of 61.92%, delay in t_1/2 of 2.45 h and delay in T_max of 2.92 h. The t_1/2e and V_d/F of ETV were increased significantly to 8.01 h and 24.38 L/kg in the ETV-M group.Conclusions: The effects of FZHY on ETV pharmacokinetics were diminished with an increase of interval time. The best time to administer both drugs is >2 h apart.

A library of nucleotide analogues terminate RNA synthesis catalyzed by polymerases of coronaviruses that cause SARS and COVID-19

SARS-CoV-2, a member of the coronavirus family, is responsible for the current COVID-19 worldwide pandemic. We previously demonstrated that five nucleotide analogues inhibit the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp), including the active triphosphate forms of Sofosbuvir, Alovudine, Zidovudine, Tenofovir alafenamide and Emtricitabine. We report here the evaluation of a library of nucleoside triphosphate analogues with a variety of structural and chemical features as inhibitors of the RdRps of SARS-CoV and SARS-CoV-2. These features include modifications on the sugar (2' or 3' modifications, carbocyclic, acyclic, or dideoxynucleotides) or on the base. The goal is to identify nucleotide analogues that not only terminate RNA synthesis catalyzed by these coronavirus RdRps, but also have the potential to resist the viruses' exonuclease activity. We examined these nucleotide analogues for their ability to be incorporated by the RdRps in the polymerase reaction and to prevent further incorporation. While all 11 molecules tested displayed incorporation, 6 exhibited immediate termination of the polymerase reaction (triphosphates of Carbovir, Ganciclovir, Stavudine and Entecavir; 3'-OMe-UTP and Biotin-16-dUTP), 2 showed delayed termination (Cidofovir diphosphate and 2'-OMe-UTP), and 3 did not terminate the polymerase reaction (2'-F-dUTP, 2'-NH2-dUTP and Desthiobiotin-16-UTP). The coronaviruses possess an exonuclease that apparently requires a 2'-OH at the 3'-terminus of the growing RNA strand for proofreading. In this study, all nucleoside triphosphate analogues evaluated form Watson-Crick-like base pairs. The nucleotide analogues demonstrating termination either lack a 2'-OH, have a blocked 2'-OH, or show delayed termination. Thus, these nucleotide analogues are of interest for further investigation to evaluate whether they can evade the viral exonuclease activity. Prodrugs of five of these nucleotide analogues (Cidofovir, Abacavir, Valganciclovir/Ganciclovir, Stavudine and Entecavir) are FDA-approved medications for treatment of other viral infections, and their safety profiles are well established. After demonstrating potency in inhibiting viral replication in cell culture, candidate molecules can be rapidly evaluated as potential therapies for COVID-19.

Optimal drug administration manner would rescue partial virological response in chronic hepatitis B patients with entecavir or tenofovir treatment

Not all treatment-naïve patients receiving entecavir (ETV) or tenofovir disoproxil fumarate (TDF) therapy can achieve complete virological response, and many factors may be related with the outcome of partial virological response. This study aimed to determine whether the manner of drug administration affects the antiviral efficacy of ETV/TDF monotherapy. All eligible patients were divided into complete or partial response cohorts based on their virological response following 24-week therapy. Factors related with partial response were evaluated. Patients with partial response were further grouped depending on whether they later adjusted the manner of drug administration, and the antiviral efficacy was compared between the two groups during prolonged treatment. A total of 518 patients were enrolled. Suboptimal drug administration (OR 77.511, P = .000), positive-HBeAg (OR 3.191, P = .000) and ETV treatment (OR 2.537, P = .001) were identified as independent risk factors for partial response. Among patients with partial response, 213 were in the adjusted group and 76 were in the unadjusted group. The percentages of patients with undetectable serum HBV DNA (78.9% vs 31.6%, P < .001) and with normal alanine aminotransferase (ALT) (88.7% vs 68.4%, P < .001) were both higher in the adjusted group than that in unadjusted group following a further 6-month therapy. In conclusion, the manner of drug administration is an important factor influencing the efficacy of ETV/TDF therapy, and optimal drug administration manner can help to increase antiviral efficacy and rescue patients with partial response.

Nucleoside Reverse Transcriptase Inhibitor Interaction with Human Equilibrative Nucleoside Transporters 1 and 2

Equilibrative nucleoside transporters (ENTs) transport nucleosides across the blood-testis barrier (BTB). ENTs are of interest to study the disposition of nucleoside reverse-transcriptase inhibitors (NRTIs) in the human male genital tract because of their similarity in structure to nucleosides. HeLa S3 cells express ENT1 and ENT2 and were used to compare relative interactions of these transporters with selected NRTIs. Inhibition of [³H]uridine uptake by NBMPR was biphasic, with IC₅₀ values of 11.3 nM for ENT1 and 9.6 μM for ENT2. Uptake measured with 100 nM NBMPR represented ENT2-mediated transport; subtracting that from total uptake represented ENT1-mediated transport. The kinetics of ENT1- and ENT2-mediated [³H]uridine uptake revealed no difference in J_max (16.53 and 30.40 pmol cm^-2 min^-1) and an eightfold difference in K_t (13.6 and 108.9 μM). The resulting fivefold difference in intrinsic clearance (J_max/K_t) for ENT1- and ENT2 transport accounted for observed inhibition of [³H]uridine uptake by 100 nM NBMPR. Millimolar concentrations of the NRTIs emtricitabine, didanosine, lamivudine, stavudine, tenofovir disoproxil, and zalcitabine had no effect on ENT transport activity, whereas abacavir, entecavir, and zidovudine inhibited both transporters with IC₅₀ values of ∼200 µM, 2.5 mM, and 2 mM, respectively. Using liquid chromatography-tandem mass spectrometry and [³H] compounds, the data suggest that entecavir is an ENT substrate, abacavir is an ENT inhibitor, and zidovudine uptake is carrier-mediated, although not an ENT substrate. These data show that HeLa S3 cells can be used to explore complex transporter selectivity and are an adequate model for studying ENTs present at the BTB. SIGNIFICANCE STATEMENT: This study characterizes an in vitro model using S-[(4-nitrophenyl)methyl]-6-thioinosine to differentiate between equilibrative nucleoside transporter (ENT) 1- and ENT2-mediated uridine transport in HeLa cells. This provides a method to assess the influence of nucleoside reverse-transcriptase inhibitors on natively expressed transporter function. Determining substrate selectivity of the ENTs in HeLa cells can be effectively translated into the activity of these transporters in Sertoli cells that comprise the blood-testis barrier, thereby assisting targeted drug development of compounds capable of circumventing the blood-testis barrier.

Tenofovir monotherapy versus tenofovir plus entecavir combination therapy in HBeAg-positive chronic hepatitis patients with partial virological response to entecavir

AIMS

The aim of this retrospective study was to compare the efficacy and safety of tenofovir disoproxil fumarate (TDF) monotherapy and TDF + entecavir (ETV) combination therapy for chronic hepatitis B (CHB) patients with the partial virological response (PVR) to ETV.

METHODS

CHB patients with PVR to ETV were switched to TDF monotherapy or TDF + ETV combination therapy. The primary efficacy outcome was a virological response (VR), and the secondary efficacy outcomes were hepatitis B e antigen (HBeAg) seroconversion and alanine aminotransferase (ALT) normalization. The primary safety outcomes were changes in serum creatinine and serum phosphorus levels.

RESULTS

A total of 143 patients were investigated, including 63 patients in the TDF monotherapy group and 80 patients in the TDF + ETV combination therapy group. Baseline demographics and clinical characteristics were comparable between groups. The median age of patients was 44.5 years, and 76.2% of them were male. The VR rate in TDF + ETV group was higher than that of the TDF group at 48 weeks (88.8% vs 71.4%; P = .009). At 48 weeks, the HBeAg seroconversion rate of TDF + ETV group was higher than that of the TDF group (30% vs 15.9%; P = .049). There was no significant difference in the proportion of patients with elevated ALT in the TDF group and TDF + ETV group at 48 weeks (9.5% vs 7.5%; P = .665). After adjusting the treatment regimen, serum creatinine levels increased slightly and serum phosphorus level decreased slightly in both groups.

CONCLUSIONS

TDF + ETV combination therapy for 48 weeks had a higher VR rate than TDF monotherapy in CHB patients with PVR to ETV.

Design and in vivo evaluation of entecavir-3-palmitate microcrystals for subcutaneous sustained delivery

The objectives of this study were to formulate microcrystals of entecavir-3-palmiate (EV-P), a palmitic acid ester of entecavir (EV), and evaluate the influence of particle size on its pharmacokinetic behavior following subcutaneous (SC) injection. Systemic toxicity and local tolerability of the hepatitis B anti-viral suspension were further evaluated in normal rats. EV-P microcrystals possessing median diameters of 2.1, 6.3, and 12.7 µm were fabricated using anti-solvent crystallization technique with polysorbate 20 and polyethylene glycol 4000 as steric stabilizer. Dissolution rate of EV-P microcrystals was controlled by adjusting the particle size, under sink condition. Pharmacokinetic profiles of 2.1 µm-sized and 6.3 µm-sized EV-P microcrystals were quite comparable (1.44 mg/kg as EV), over 46 days in rats. The absorption rate and extent of EV after SC injection of 12.7 µm-sized microcrystals were significantly retarded, due to its slower dissolution rate in aqueous media. No single-dose systemic toxicity was observed after SC injection of high dose of EV-P microcrystal suspension (30-300 mg/kg as EV). The microcrystals were tolerable in the injected site, showing mild inflammatory responses at a dose of 30 mg/kg. Therefore, the novel microcrystal system with median particle size of below 6.3 µm is expected to be a unique long-acting system of the anti-viral agent, improving patient's compliance with chronic disease.

Perfused human hepatocyte microtissues identify reactive metabolite-forming and mitochondria-perturbing hepatotoxins

Hepatotoxins cause liver damage via many mechanisms but the formation of reactive metabolites and/or damage to liver mitochondria are commonly implicated. We assess 3D human primary hepatocyte microtissues as a platform for hepatotoxicity studies with reactive metabolite-forming and mitochondria-perturbing compounds. We show that microtissues formed from cryopreserved human hepatocytes had bile canaliculi, transcribed mRNA from genes associated with xenobiotic metabolism and expressed functional cytochrome P450 enzymes. Hierarchical clustering was used to distinguish dose-dependent hepatotoxicity elicited by clozapine, fialuridine and acetaminophen (APAP) from control cultures and less liver-damaging compounds, olanzapine and entecavir. The regio-isomer of acetaminophen, N-acetyl-meta-aminophenol (AMAP) clustered with the hepatotoxic compounds. The principal metabolites of APAP were formed and dose-dependent changes in metabolite profile similar to those seen in patient overdose was observed. The toxicological profile of APAP was indistinguishable from that of AMAP, confirming AMAP as a human hepatotoxin. Tissue oxygen consumption rate was significantly decreased within 2h of exposure to APAP or AMAP, concomitant with glutathione depletion. These data highlight the potential utility of perfused metabolically functional human liver microtissues in drug development and mechanistic toxicology.

Current antiviral drugs and their analysis in biological materials - Part II: Antivirals against hepatitis and HIV viruses

This review is a Part II of the series aiming to provide comprehensive overview of currently used antiviral drugs and to show modern approaches to their analysis. While in the Part I antivirals against herpes viruses and antivirals against respiratory viruses were addressed, this part concerns antivirals against hepatitis viruses (B and C) and human immunodeficiency virus (HIV). Many novel antivirals against hepatitis C virus (HCV) and HIV have been introduced into the clinical practice over the last decade. The recent broadening portfolio of these groups of antivirals is reflected in increasing number of developed analytical methods required to meet the needs of clinical terrain. Part II summarizes the mechanisms of action of antivirals against hepatitis B virus (HBV), HCV, and HIV, their use in clinical practice, and analytical methods for individual classes. It also provides expert opinion on state of art in the field of bioanalysis of these drugs. Analytical methods reflect novelty of these chemical structures and use by far the most current approaches, such as simple and high-throughput sample preparation and fast separation, often by means of UHPLC-MS/MS. Proper method validation based on requirements of bioanalytical guidelines is an inherent part of the developed methods.

Entecavir Interacts with Influx Transporters hOAT1, hCNT2, hCNT3, but Not with hOCT2: The Potential for Renal Transporter-Mediated Cytotoxicity and Drug-Drug Interactions

Entecavir (ETV) is one of the most potent agents for the treatment of the hepatitis B viral infection. The drug is principally eliminated by the kidney. The goal of this study was to investigate the potential of ETV to interact in vitro with the renal SLC transporters hOAT1, hOCT2, hCNT2 and hCNT3. Potential drug–drug interactions of ETV at the renal transporters with antiviral drugs known to be excreted by the kidney (adefovir, tenofovir, cidofovir) as well as transporter-dependent cytotoxicity were also examined. Interactions with the selected transporters along with cytotoxicity were studied in several transiently transfected cellular models using specific substrates and inhibitors. ETV was found to be both a substrate and inhibitor of hOAT1 (IC₅₀ = 175.3 μM), hCNT2 (IC₅₀ = 241.9 μM) and hCNT3 (IC₅₀ = 278.4 μM) transporters, although it interacted with the transporters with relatively low affinities. ETV inhibited the cellular uptake of adefovir, tenofovir, and cidofovir by hOAT1; however, effective inhibition was shown at ETV concentrations exceeding therapeutic levels. In comparison with adefovir, tenofovir, and cidofovir, ETV displayed no transporter-mediated cytotoxicity in cells transfected with hOAT1, hCNT2, and hCNT3. No significant interaction of ETV with hOCT2 was detected. The study demonstrates interactions of ETV with several human renal transporters. For the first time, an interaction of ETV with the hCNTs was proved. We show that the potency of ETV to cause nephrotoxicity and/or clinically significant drug-drug interactions related to the tested transporters is considerably lower than that of adefovir, tenofovir, and cidofovir.

Structure of the HIV-1 reverse transcriptase Q151M mutant: insights into the inhibitor resistance of HIV-1 reverse transcriptase and the structure of the nucleotide-binding pocket of Hepatitis B virus polymerase

Hepatitis B virus polymerase (HBV Pol) is an important target for anti-HBV drug development; however, its low solubility and stability in vitro has hindered detailed structural studies. Certain nucleotide reverse transcriptase (RT) inhibitors (NRTIs) such as tenofovir and lamivudine can inhibit both HBV Pol and Human immunodeficiency virus 1 (HIV-1) RT, leading to speculation on structural and mechanistic analogies between the deoxynucleotide triphosphate (dNTP)-binding sites of these enzymes. The Q151M mutation in HIV-1 RT, located at the dNTP-binding site, confers resistance to various NRTIs, while maintaining sensitivity to tenofovir and lamivudine. The residue corresponding to Gln151 is strictly conserved as a methionine in HBV Pol. Therefore, the structure of the dNTP-binding pocket of the HIV-1 RT Q151M mutant may reflect that of HBV Pol. Here, the crystal structure of HIV-1 RT Q151M, determined at 2.6 Å resolution, in a new crystal form with space group P321 is presented. Although the structure of HIV-1 RT Q151M superimposes well onto that of HIV-1 RT in a closed conformation, a slight movement of the β-strands (β2-β3) that partially create the dNTP-binding pocket was observed. This movement might be caused by the introduction of the bulky thioether group of Met151. The structure also highlighted the possibility that the hydrogen-bonding network among amino acids and NRTIs is rearranged by the Q151M mutation, leading to a difference in the affinity of NRTIs for HIV-1 RT and HBV Pol.

Telaprevir and ribavirin interaction: higher ribavirin levels are not only due to renal dysfunction during triple therapy

A higher incidence of anemia has been observed during the treatment of hepatitis C virus genotype 1 (HCV-1) infection with pegylated alpha interferon (pegIFN-α), ribavirin, and telaprevir. We assessed the impacts that concomitant administration of telaprevir and changes in the glomerular filtration rate have on ribavirin plasma levels. The minimum concentrations of ribavirin in plasma (ribavirin Cmin) determined during triple therapy including telaprevir were compared with those observed after telaprevir withdrawal and those observed in the same subjects and in a large cohort during a previous course of pegIFN-α plus ribavirin. Intensive pharmacokinetic sampling for ribavirin was performed at steady state during the triple-therapy phase. Ribavirin levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Twenty-seven HCV-1/HIV-coinfected patients were enrolled. The median ribavirin Cmin for triple therapy (4.08 μg/ml; range, 2.14 to 5.56 μg/ml) was higher than that observed after telaprevir withdrawal (1.96 μg/ml; range, 0.41 to 3.45 μg/ml) (P < 0.001) and that observed for 125 HCV-1/HIV-coinfected patients treated only with pegIFN-α plus ribavirin (1.65 μg/ml; range, 0.41 to 5.56 μg/ml) (P < 0.001). The estimated glomerular filtration rate (eGFR) decreased >20% from the baseline value in 11 of 27 patients and became normal after telaprevir removal in almost all cases. There was a negative correlation between eGFR and ribavirin clearance (r(2) = 0.257; P = 0.064) but not the ribavirin area under the concentration-time curve from 0 to 12 h (AUC0-12) (r(2) = 0.001; P = 0.455). Thus, there is a significant pharmacokinetic interaction between telaprevir and ribavirin that results in very high ribavirin levels, which explains the excess of toxicity observed with this drug combination. A blockade of the proximal tubular transporters might be implicated in both the increase in plasma creatinine and the high ribavirin levels. (This study has been registered at ClinicalTrials.gov under registration no. NCT01818856.).

Hepatitis B virus infection in children

For two decades, hepatitis B vaccine has been integrated into national routine childhood vaccination programs in almost all countries. The prevalence of HBsAg has decreased in children worldwide. However, there are children who miss the benefit of hepatitis B vaccine in some regions and countries. Long-term follow-up studies have revealed the clinical outcomes of chronic hepatitis B virus infection in children. A small percentage of chronically infected children develop liver cirrhosis and hepatocellular carcinoma. However, it is controversial who should be treated and when antiviral treatment should be initiated in children. Compared with adult studies, the data are insufficient to evaluate the pathogenesis of hepatitis B infection and the efficacy of antiviral treatment in childhood. New antiviral drugs have been approved for children and adults. Also, oral antiviral drugs are administered to pregnant women to reduce the hepatitis B virus mother-to-child transmission rate.

Telbivudine protects renal function in patients with chronic hepatitis B infection in conjunction with adefovir-based combination therapy

Previous studies have demonstrated that the treatment of chronic hepatitis B (CHB) infection with adefovir (ADV) can impair renal function. In contrast, treatment with telbivudine (LdT) improves renal function in CHB patients. The aim of this study was to evaluate the renoprotective effect of LdT in CHB patients receiving ADV-based combination therapy. The effects of treatment with ADV + LdT on renal function were compared to those resulting from treatment with ADV + entecavir (ETV), ADV + lamivudine (LAM), ADV alone and ETV alone. The consecutive cohort analysis included 831 CHB patients who received ADV + LdT, ADV + LAM, ADV + ETV, ADV alone or ETV alone for 96 weeks. Alterations in estimated glomerular filtration rate (eGFR) were compared between the five groups using a linear mixed-effects model. HBV DNA levels were also compared between the five groups during the 96-week period. Among the five treatment groups, significant improvements in eGFR were observed in the ADV + LdT and ADV + LAM groups over time (P < 0.001 for each group compared with baseline eGFR). In patients with a baseline eGFR between 50 and 90 mL/min, the change in eGFR was the most significant in the ADV + LdT group (+0.641 mL/min; P < 0.001). Age, gender, baseline eGFR and treatment option were significant predictive factors for eGFR changes. In conclusion, our results suggest that the combination therapy of LdT and ADV is significantly associated with renoprotective effects in CHB patients when compared with other ADV-based combination or single therapies.

Entecavir treatment in kidney transplant recipients infected with hepatitis B

Although nucleotide/side analogs improve the clinical outcome of hepatitis B surface antigen-positive (HBsAg+) kidney transplant recipients (KTR), a significant proportion of subjects have developed resistance to lamivudine (LAM). We retrospectively analyzed the efficacy and tolerability of entecavir (ETV) in HBsAg+ KTR at Queen Mary Hospital during 2005-2013. Twenty-one patients (10 treatment-naïve, 11 with LAM resistance) were included (duration of ETV treatment 34.7 ± 22.9 months, range 6-75 months). ETV treatment led to a decline of hepatitis B virus (HBV) DNA titer compared to baseline and is more significant in the treatment-naïve group (treatment-naïve: p = 0.028, <0.001 and <0.001; LAM-resistant p = 0.273, 0.180, and 0.109 after 12, 24, and 36 months). The cumulative rate of HBV DNA undetectability at 12, 24, and 36 months was 60%, 100%, and 100% for treatment-naïve group, and 27%, 45%, and 45% for LAM-resistant group, respectively. Time-to-HBV DNA undetectability and time-to-alanine transaminase (ALT) normalization were 15.7 ± 4.6 and 12.6 ± 3.7 months for treatment-naïve patients, and 24.5 ± 4.2 and 28.2 ± 3.5 months for those with LAM resistance. Genotypic resistance to ETV emerged after 20.0 ± 3.5 months with increase in ALT and HBV DNA in two patients with LAM resistance, but was not observed in the treatment-naïve group. Allograft dysfunction, de novo cirrhosis, or hepatocellular carcinoma did not occur during follow-up.

Comprehensive treatment of acute-on-chronic liver failure in a patient with hepatitis B: a case report

The clinical data of a patient with acute-on-chronic liver failure were analyzed retrospectively. The patient has suffered from hepatitis B for 30 years. His liver function deteriorated, yielding Child-Pugh grade C and reaching a model for end-stage liver disease score of 33 points within a short period; this condition was complicated with highly active variceal bleeding and coagulation system failure (PT > 100 s). The patient also presented hepatocellular carcinoma. Comprehensive treatments included effective inhibition of hepatitis B virus replication and intensive care support. Piggyback orthotopic liver transplantation was performed as the final treatment. The patient recovered uneventfully and was discharged after surgery.

Telbivudine versus entecavir for nucleos(t)ide-naive HBeAg-positive chronic hepatitis B: a meta-analysis

BACKGROUND

We performed a meta-analysis to compare the efficacies of entecavir and telbivudine in treatment-naive hepatitis B e-antigen (HBeAg)-positive Asian patients with chronic hepatitis B (CHB).

METHODS

Randomized controlled trials (January 1, 2000 to March 30, 2012) directly comparing entecavir 0.5 mg/d and telbivudine 600 mg/d, used for a minimum of 12 weeks in nucleos(t)ide-naive Asian patients with HBeAg-positive CHB, were searched in the PubMed, Embase, OVID, Cochrane Library, CNKI, VIP and WanFang databases. Publication quality was assessed using the Jadad quality scale. The rates of viral response, biochemical response, HBeAg loss and HBeAg seroconversion were analyzed using forest plots.

RESULTS

Seven eligible articles (867 patients in total) were included in this meta-analysis. With regard to the rates of hepatitis B virus DNA suppression, there were no significant differences between patients treated with entecavir or telbivudine at 12 and 48 weeks, but telbivudine was superior at 24 weeks. Twelve, 24 and 48 weeks after the start of therapy, the rates of alanine aminotransferase normalization were similar between the 2 drugs, and patients treated with telbivudine had higher HBeAg loss and seroconversion rates than patients treated with entecavir.

CONCLUSIONS

In nucleos(t)ide-naive Asian patients with HBeAg-positive CHB, assessed 12, 24, and 48 weeks after beginning treatment, telbivudine was as potent as entecavir in viral suppression, but superior with regard to HBeAg loss and seroconversion. Telbivudine seems to be more effective and suitable for these patients.

Large-scale production and structural and biophysical characterizations of the human hepatitis B virus polymerase

Hepatitis B virus (HBV) is a major human pathogen that causes serious liver disease and 600,000 deaths annually. Approved therapies for treating chronic HBV infections usually target the multifunctional viral polymerase (hPOL). Unfortunately, these therapies--broad-spectrum antivirals--are not general cures, have side effects, and cause viral resistance. While hPOL remains an attractive therapeutic target, it is notoriously difficult to express and purify in a soluble form at yields appropriate for structural studies. Thus, no empirical structural data exist for hPOL, and this impedes medicinal chemistry and rational lead discovery efforts targeting HBV. Here, we present an efficient strategy to overexpress recombinant hPOL domains in Escherichia coli, purifying them at high yield and solving their known aggregation tendencies. This allowed us to perform the first structural and biophysical characterizations of hPOL domains. Apo-hPOL domains adopt mainly α-helical structures with small amounts of β-sheet structures. Our recombinant material exhibited metal-dependent, reverse transcriptase activity in vitro, with metal binding modulating the hPOL structure. Calcomine orange 2RS, a small molecule that inhibits duck HBV POL activity, also inhibited the in vitro priming activity of recombinant hPOL. Our work paves the way for structural and biophysical characterizations of hPOL and should facilitate high-throughput lead discovery for HBV.

IMPORTANCE

The viral polymerase from human hepatitis B virus (hPOL) is a well-validated therapeutic target. However, recombinant hPOL has a well-deserved reputation for being extremely difficult to express in a soluble, active form in yields appropriate to the structural studies that usually play an important role in drug discovery programs. This has hindered the development of much-needed new antivirals for HBV. However, we have solved this problem and report here procedures for expressing recombinant hPOL domains in Escherichia coli and also methods for purifying them in soluble forms that have activity in vitro. We also present the first structural and biophysical characterizations of hPOL. Our work paves the way for new insights into hPOL structure and function, which should assist the discovery of novel antivirals for HBV.

LC-MS/MS method for the characterization of the forced degradation products of Entecavir

A rapid, specific, and reliable isocratic LC-MS/MS method has been developed and validated for the identification and characterization of the stressed degradation products of Entecavir (ETV). ETV, an antiviral drug, was subjected to hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis and thermal stress, as per the international conference on harmonization specified conditions. The drug showed extensive degradation under oxidative and acid hydrolysis stress conditions. However, it was stable to thermal, acidic, neutral, and photolysis stress conditions. A total of five degradation products were observed and the chromatographic separation of the drug and its degradation products were achieved on a Waters Symmetry C18 (250 mm × 4.6 mm, id, 5 μm) column using 20 mM ammonium acetate (pH 3)/acetonitrile (50:50, v/v) as a mobile phase. The degradation products were characterized by LC-MS/MS and its fragmentation pathways were proposed. The LC-MS method was validated with respect to specificity, linearity, accuracy, and precision. No previous reports were found in the literature regarding the degradation behavior of ETV.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Efficacy and Safety of Telbivudine Compared to Entecavir Among HBeAg+ Chronic Hepatitis B Patients: a Meta-Analysis Study

BACKGROUND

Hepatitis B virus (HBV) infection is a serious global health problem that is associated with huge social and economic costs. Early antiviral drugs, such as interferon-α2b, peginterferon-α2a, lamivudine, and adefovir, all have their limitations (such as low responses or safety concerns) in clinical application. Telbivudine and entecavir are two of the latest nucleotide drugs and both have been shown to have potent viral suppression. However, in patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB), inconsistent results have been generated for efficacy between telbivudine and entecavir. Therefore, evidence-based medical data are required to compare the efficacies, in terms of virological and biochemical responses, and safety between telbivudine and entecavir.

OBJECTIVES

We aimed to compare the early antiviral efficacy and safety of telbivudine and entecavir in the treatment of patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB).

PATIENTS AND METHODS

A search for relevant randomized controlled trials (RCTs) on HBeAg-positive CHB patients treated with telbivudine and entecavir for 24 or 52 weeks, published before December 2011, was performed. Primary efficacy endpoint was the cumulative rate of undetectable HBV DNA, and secondary efficacy endpoints included rates of alanine aminotransferase (ALT) normalization, HBeAg disappearance, HBeAg seroconversion and adverse events. Meta-analysis was performed using the Review Manager v5.1.4 software package. We assessed the pooled risk ratios (RRs) and 95% confidence intervals (CIs) using the fixed-or random-effects model.

RESULTS

Six randomized controlled trials (RCTs) involving 555 patients were included. Telbivudine was associated with significantly higher rates of HBeAg disappearance (RR = 1.46, 95% CI: 1.11 - 1.91) and HBeAg seroconversion (RR = 1.76, 95%CI: 1.25-2.48) than entecavir, but had higher adverse events (RR = 2.11, 95%CI: 1.23 - 3.60), compared with entecavir. There was no difference between telbivudine and entecavir in the rate of cumulative undetectable HBV DNA (RR = 0.99, 95% CI: 0.90 - 1.10) and ALT normalization (RR = 0.93, 95% CI: 0.85 - 1.00).

CONCLUSIONS

Telbivudine is associated with significantly higher rates of HBeAg disappearance and HBeAg seroconversion than entecavir, whereas entecavir is superior to telbivudine in safety. Both drugs have similar efficacy on rates of cumulative undetectable HBV DNA and ALT normalization.

Evaluation of single and combination therapies with tenofovir disoproxil fumarate and emtricitabine in vitro and in a robust mouse model supporting high levels of hepatitis B virus replication

Next-generation therapies for chronic hepatitis B virus (HBV) infection will involve combinations of established and/or experimental drugs. The current study investigated the in vitro and in vivo efficacy of tenofovir disoproxil fumarate (TDF) and/or emtricitabine [(-)-FTC] alone and in combination therapy for HBV infection utilizing the HepAD38 system (human hepatoblastoma cells transfected with HBV). Cellular pharmacology studies demonstrated increased levels of (-)-FTC triphosphate with coincubation of increasing concentrations of TDF, while (-)-FTC had no effect on intracellular tenofovir (TFV) diphosphate levels. Quantification of extracellular HBV by real-time PCR from hepatocytes demonstrated the anti-HBV activity with TDF, (-)-FTC, and their combination. Combination of (-)-FTC with TDF or TFV (ratio, 1:1) had a weighted average combination index of 0.7 for both combination sets, indicating synergistic antiviral effects. No cytotoxic effects were observed with any regimens. Using an in vivo murine model which develops robust HBV viremia in nude mice subcutaneously injected with HepAD38 cells, TDF (33 to 300 mg/kg of body weight/day) suppressed virus replication for up to 10 days posttreatment. At 300 mg/kg/day, (-)-FTC strongly suppressed virus titers to up to 14 days posttreatment. Combination therapy (33 mg/kg/day each drug) sustained suppression of virus titer/ml serum (<1 log(10) unit from pretreatment levels) at 14 days posttreatment, while single-drug treatments yielded virus titers 1.5 to 2 log units above the initial virus titers. There was no difference in mean alanine aminotransferase values or mean wet tumor weights for any of the groups, suggesting a lack of drug toxicity. TDF-(-)-FTC combination therapy provides more effective HBV suppression than therapy with each drug alone.

Antiviral drugs for viruses other than human immunodeficiency virus

Most viral diseases, with the exception of those caused by human immunodeficiency virus, are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 3 main groups of viruses: herpes, hepatitis, and influenza viruses. With the exception of the antisense molecule fomivirsen, all antiherpes drugs inhibit viral replication by serving as competitive substrates for viral DNA polymerase. Drugs for the treatment of influenza inhibit the ion channel M(2) protein or the enzyme neuraminidase. Combination therapy with Interferon-α and ribavirin remains the backbone treatment for chronic hepatitis C; the addition of serine protease inhibitors improves the treatment outcome of patients infected with hepatitis C virus genotype 1. Chronic hepatitis B can be treated with interferon or a combination of nucleos(t)ide analogues. Notably, almost all the nucleos(t) ide analogues for the treatment of chronic hepatitis B possess anti-human immunodeficiency virus properties, and they inhibit replication of hepatitis B virus by serving as competitive substrates for its DNA polymerase. Some antiviral drugs possess multiple potential clinical applications, such as ribavirin for the treatment of chronic hepatitis C and respiratory syncytial virus and cidofovir for the treatment of cytomegalovirus and other DNA viruses. Drug resistance is an emerging threat to the clinical utility of antiviral drugs. The major mechanisms for drug resistance are mutations in the viral DNA polymerase gene or in genes that encode for the viral kinases required for the activation of certain drugs such as acyclovir and ganciclovir. Widespread antiviral resistance has limited the clinical utility of M(2) inhibitors for the prevention and treatment of influenza infections. This article provides an overview of clinically available antiviral drugs for the primary care physician, with a special focus on pharmacology, clinical uses, and adverse effects.

Pooled model-based approach to compare the pharmacokinetics of entecavir between Japanese and non-Japanese chronic hepatitis B patients

This study evaluated the population pharmacokinetics (PK) of entecavir in Japanese patients with chronic hepatitis B infection enrolled in 2 Japanese phase IIb clinical trials and compared them to non-Japanese patients enrolled in global phase II trials. The objectives were to identify significant and clinically meaningful covariate effects on entecavir population pharmacokinetic parameters and assess whether differences exist between Japanese and non-Japanese patients. A total of 843 observations were obtained from 142 patients who received once daily administration of entecavir at 0.1, 0.5, and 1.0 mg doses in the 2 Japanese studies. Consistent with findings in non-Japanese patients, creatinine clearance estimated with ideal body weight (ICrCL) was found to be statistically significant for clearance in a 2-compartment model. Also, the entecavir dose was identified as a covariate on intercompartmental clearance. Age, gender, and hepatic function were not identified as covariate for clearance. The estimated population average of oral clearance in a typical patient with a reference ICrCL value of 100 mL/min was 26.4 L/h (interindividual variability: 19.4%). This model-based analysis indicates that the PK of entecavir are similar in Japanese and non-Japanese chronic hepatitis B patients.

Seroprevalence of markers for hepatitis B viral infection

OBJECTIVES

To provide a comprehensive review of the prevalence of selected hepatitis B virus (HBV) seromarkers and to identify variability in seroprevalence across the 14 World Health Organization (WHO) sub-regions and among special groups and populations.

METHODS

Analyses involved 568 papers and 736 population studies. The complete data set included 21, 838, 249 individuals and covered the 14 WHO sub-regions.

RESULTS

Of the 687 studies that assessed hepatitis B surface antigen (HBsAg) seroprevalence, 30% had low (<2% affected), 36% had intermediate (2-8% affected), and 34% had high (>8% affected) endemicity. Median HBsAg seroprevalence differed by selected populations and among geographic regions. Overall, median seroprevalence was highest for 'other' populations, followed by patients, then by pregnant women and children. Median seroprevalence of antibody to hepatitis B core antigen (anti-HBc) followed a similar endemicity pattern to that of HBsAg across the 14 WHO sub-regions. Median seroprevalence of hepatitis B e antigen (HBeAg) showed considerable variability within each population group, with the greatest potential for infectivity seen among children.

CONCLUSIONS

This population-based review provides a comprehensive assessment of the burden of HBV throughout the world. Significant differences in seroprevalence exist between WHO regions, study populations, and seromarker testing methods. The results presented in this study will enable health professionals to track worldwide reported seroprevalence of hepatitis B markers.

Efficacy of initial treatment with clevudine in naive patients with chronic hepatitis B

BACKGROUND/AIMS

Clevudine, a pyrimidine nucleoside analogue, has potent antiviral effects in patients with chronic viral hepatitis B (CHB). We report the efficacy of initial treatment with clevudine in naïve patients with CHB living in Daejeon and Chungcheong Province, South Korea.

METHODS

One hundred five adults with CHB were administered 30 mg of clevudine per day for an average of 51 weeks. We evaluated viral markers and liver biochemistry retrospectively every 3 months.

RESULTS

Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and hepatitis B virus (HBV) DNA before the treatment were 184 ± 188 IU/L, 150 ± 138 IU/L, and 7.1 ± 1.2 log copies/mL, respectively. Undetectable rates (< 60 IU/mL) of DNA were 36.2%, 68.9%, 83.6%, 76.2%, and 75.8% at 12, 24, 36, 48, and 60 weeks, respectively. Seroconversion rates were 9.1%, 13.6%, 24.6%, 26.5%, and 26.1% and ALT normalization rates were 64.5%, 78.1%, 87.9%, 90.0% at 12, 24, 36, and 48 weeks, respectively. Six patients (5.7%) had a viral breakthrough.

CONCLUSIONS

Clevudine is a useful drug in the initial treatment of patients with CHB, with a potent antiviral effect and low incidence of viral breakthrough.

Comparison of clinical application of the Abbott HBV PCR kit and the VERSANT HBV DNA 3.0 test to measure serum hepatitis B virus DNA in Taiwanese patients

With an estimated 350-400 million people worldwide chronically infected with hepatitis B virus (HBV), and the subsequent serious complications caused by liver damage including cirrhosis, liver failure, and hepatocellular carcinoma, HBV infection remains a global health issue, particularly in Taiwan, an HBV-hyperendemic area. Sensitive and accurate quantification of HBV DNA is necessary to monitor patients with chronic hepatitis B who are receiving antiviral therapy to determine treatment response and adapt therapy. We evaluated and compared the clinical performance of two HBV DNA assays based on different technologies: the RealArt HBV PCR Kit (Abbott HBV DNA PCR kit, real-time polymerase chain reaction assay, detection limit: 27 IU/mL) and the VERSANT bDNA 3.0 assay (Bayer, branched DNA signal amplification assay, detection limit: 357 IU/mL). Serum levels of HBV DNA in 173 chronic HBV carriers were determined using both the RealArt HBV PCR Kit and the VERSANT bDNA 3.0 test. Of the 173 samples analyzed for baseline viral load detection, HBV DNA was quantifiable in 147 patients (82.1%) by the RealArt HBV PCR Kit, which was significantly higher than the 92 (53.2%) samples quantified by the VERSANT bDNA 3.0 assay. A total of 86 (49.7%) samples were quantifiable by both assays, whereas 25 (14.5%) were below the detection limit of both assays. The HBV DNA quantification values measured by the RealArt HBV PCR Kit and the VERSANT bDNA 3.0 assay were positively correlated (Spearman's rank correlation coefficient r = 0.932, p < 0.001). On average, the results derived from the RealArt HBV PCR Kit were 0.67 log lower than those of the VERSANT bDNA 3.0 assay. HBV DNA concentrations were significantly higher in 63 HBV e antigen (HBeAg)-seropositive patients than in 110 HBeAg-seronegative patients (5.42 +/- 2.34 logs vs. 3.21 +/- 2.27 logs, p < 0.001). The RealArt HBV PCR Kit is more sensitive and has a wider dynamic range than the VERSANT bDNA 3.0 assay in the clinical setting of chronic hepatitis B patients. The sensitivity and wide dynamic range of the PCR assay allow optimal monitoring and timely adaptation of antiviral therapy. Nevertheless, the HBV DNA values measured by the RealArt HBV PCR Kit and the VERSANT bDNA 3.0 assay were significantly correlated.

[Entecavir]

Chronic hepatitis B continues to be a serious problem worldwide. Because a high viral load is associated with greater progression to cirrhosis and hepatocarcinoma in these patients, new drugs that achieve rapid, potent and lasting suppression of viral replication must be sought. Entecavir is a new, highly potent antiviral agent; phase II and III studies have demonstrated this drug to be superior to placebo and lamivudine in patients with chronic hepatitis B virus in terms of histological improvement, efficacy in achieving suppression of viral replication and normalizing transaminase counts. The drug is well tolerated, since its adverse effects are usually mild or moderate and their incidence is similar to that found with placebo or lamivudine. Moreover, in treatment-naïve patients, no resistance has been observed after 3 years of therapy. However, in patients with prior resistance to lamivudine, the incidence of resistance is approximately 15% at 3 years. Further studies are required that compare this drug with other currently available therapeutic options, as well as longer term trials to evaluate its safety. It seems that entecavir will occupy a major place in the treatment of patients with chronic hepatitis B virus infection.

Characterization of a new sensitive PCR assay for quantification of viral DNA isolated from patients with hepatitis B virus infections

Sensitive and accurate quantification of hepatitis B virus (HBV) DNA is necessary for monitoring patients with chronic hepatitis receiving antiviral therapy in order to determine treatment response and to adapt therapy in case of inadequate virologic control. The development of quantitative PCR assays has been crucial in meeting these needs. The objective of this study was to compare the performance of a new real-time PCR assay (Abbott RealTime) for HBV DNA with that of three other commercial assays for the detection of HBV DNA. These were the Versant 3.0 branched-chain DNA assay, the Cobas Amplicor HBV Monitor test, and the Cobas AmpliPrep-Cobas TaqMan hepatitis B virus assay (CAP-CTM). HBV DNA was measured in blood samples taken from two cohorts of patients with chronic hepatitis. HBV DNA levels measured with the Abbott RealTime assay were highly correlated with those measured with the other three tests over their respective dynamic ranges (r, 0.88 to 0.96). The sensitivity (detection limit, 10 IU/ml) and dynamic range of the Abbott RealTime assay (10(1) to 10(9) IU/ml) was superior to that of the Versant assay. The RealTime assay recognized both HBV strains belonging to genotypes A to G and those bearing polymerase gene mutations equivalently. In conclusion, this study demonstrates the utility of the Abbott RealTime assay for monitoring HBV DNA levels in patients with chronic hepatitis B. Its sensitivity and wide dynamic range should allow optimal monitoring of antiviral therapy and timely treatment adaptation.

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.