Combination therapy with interferon-alpha and ribavirin for hepatitis C: practical treatment issues

Synthesis of β-Enantiomers of N4-Hydroxy-3′-Deoxy-Pyrimidine Nucleosides and Their Evaluation against Bovine Viral Diarrhoea Virus and Hepatitis C Virus in Cell Culture

N4-Hydroxycytidine (NHC) was recently reported to have anti-pestivirus and anti-hepacivirus activity. It is thought that this nucleoside acts as a weak alternative substrate for the hepatitis C virus (HCV) polymerase. In addition to NHC, 3′-deoxyuridine (3′-dU) was found to inhibit bovine diarrhoea virus (BVDV) production by 1 log10 at 37.2 μM. These initial findings prompted the synthesis of β-D and β-L analogues of (i) base-modified 3′-deoxy-NHC; (ii) 3′-deoxyuridine; and 3′-deoxycytidine. The antiviral activity of these 42 nucleosides was evaluated against BVDV and HCV bicistronic replicon in cell culture. Among the NHC analogues, the antiviral activity observed for the β-L-3′-deoxy-5-fluoro-derivative 1-(3-deoxy-β-L- erythro-pentofuranosyl)-5-fluoro-4-hydrox-yaminopyrimidin-2( 1H)-one and the β-D-3′-deoxy-5-iodo-derivative 1-(3-deoxy-β-D-erythro-pentofuranosyl)-5-iodocytosine in the replicon system (1 log10 reduction at 100 μM) was due to the concomitant toxicity towards intracellular ribosomal RNA levels (CC90 equal or lower than the EC90). In conclusion, none of the newly synthesized derivatives exhibited enhanced antiviral activity compared to the parent nucleoside NHC.

What can post-mortem studies tell us about the pathoetiology of suicide?

Suicide is a major public health concern; however, its neurobiology is unclear. Post-mortem brain tissue obtained from suicide victims and normal controls offers a useful method for studying the neurobiology of suicide. Despite several limitations, these studies have offered important leads in the neurobiology of suicide. In this article, we discuss some important findings resulting from these studies, focusing on serotonergic mechanisms, signal transduction systems, neuroendocrine studies and immune function abnormalities in suicide. These studies suggest that abnormalities of certain receptor subtypes, components of signaling systems such as protein kinase C and protein kinase A, transcription factors such as cyclic AMP response element-binding protein and neurotrophins may play an important role in the pathophysiology of suicide. These studies also suggest abnormalities of hypothalamic-pituitary-adrenal axis system components, feedback mechanisms and cytokines, which are chemical mediators of the immune functions. Post-mortem brain tissue offers an opportunity for future studies, such as genetic and epigenetic studies.

Gene-gene and gene-environment interactions in interferon therapy for chronic hepatitis C

INTRODUCTION

In studies of pharmacogenomics, it is essential to address gene-gene and gene-environment interactions to describe complex traits involving pharmacokinetic and pharmacodynamic mechanisms. In this work, our goal is to detect gene-gene and gene-environment interactions resulting from an analysis of chronic hepatitis C patients' clinical factors including SNPs, viral genotype, viral load, age and gender.

MATERIALS & METHODS

We collected blood samples from 523 chronic hepatitis C patients who had received interferon and ribavirin combination therapy. Based on the treatment strategy for chronic hepatitis C patients, we focused our search for candidate genes involved in pathways related to interferon signaling and immunomodulation. To investigate gene-gene and gene-environment interactions, we implemented an artificial neural network-based method for identifying significant interactions between clinical factors with the fivefold crossvalidation method and permutation tests. The artificial neural network model was trained by an algorithm with an adaptive momentum and learning rate.

RESULTS

A total of 20 SNPs were selected from six candidate genes including adenosine deaminase-RNA-specific (ADAR), caspase 5 (CASP5), interferon consensus sequence binding protein 1 (ICSBP1), interferon-induced protein 44 (IFI44), phosphoinositide-3-kinase catalytic gamma polypeptide (PIK3CG), and transporter 2 ATP-binding cassette subfamily B (TAP2) genes. By applying our artificial neural network-based approach, IFI44 was found in the significant two-locus, three-locus and four-locus gene-gene effect models, as well as in the significant two-factor and three-factor gene-environment effect models. Furthermore, viral genotype remained in the best two-factor, three-factor and four-factor gene-environment models. These results support the hypothesis that IFI44 and viral genotype may play a role in the pharmacogenomics of interferon treatment. In addition, our approach identified a panel of ten clinical factors that may be more significant than the others for further study.

CONCLUSION

We demonstrated that our artificial neural network-based approach is a promising method to assess the gene-gene and gene-environment interactions for interferon and ribavirin combination treatment in chronic hepatitis C patients by using clinical factors such as SNPs, viral genotype, viral load, age and gender.

The mechanism of action of beta-D-2'-deoxy-2'-fluoro-2'-C-methylcytidine involves a second metabolic pathway leading to beta-D-2'-deoxy-2'-fluoro-2'-C-methyluridine 5'-triphosphate, a potent inhibitor of the hepatitis C virus RNA-dependent RNA polymerase

beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a potent inhibitor of hepatitis C virus (HCV) RNA replication in an HCV replicon assay. The 5'-triphosphate of PSI-6130 is a competitive inhibitor of the HCV RNA-dependent RNA polymerase (RdRp) and acts as a nonobligate chain terminator. Recently, it has been shown that the metabolism of PSI-6130 also results in the formation of the 5'-triphosphate of the uridine congener, beta-D-2'-deoxy-2'-fluoro-2'-C-methyluridine (PSI-6206; RO2433). Here we show that the formation of the 5'-triphosphate of RO2433 (RO2433-TP) requires the deamination of PSI-6130 monophosphate and that RO2433 monophosphate is subsequently phosphorylated to the corresponding di- and triphosphates by cellular UMP-CMP kinase and nucleoside diphosphate kinase, respectively. RO2433-TP is a potent inhibitor of the HCV RdRp; however, both enzymatic and cell-based assays show that PSI-6130 triphosphate is a more potent inhibitor of the HCV RdRp than RO2433-TP.

Therapeutic mechanism of interferon's anti-hepatic fibrosis action

Hepatic fibrosis is a common pathological change occurring in chronic liver disease which is induced by a variety of etiological factors. Hepatic fibrosis is a dynamic process, and a reversible pathological change. However, when it has progressed to hepatic cirrhosis, it is irreversible. Therefore, to block or reverse the course of hepatic fibrosis is a very significant target for the treatment of chronic liver disease. Interferon (IFN) has extensive functions, including anti-viral, anti-tumor and immunological roles. Recent research has reported that IFN possesses an anti-hepatic fibrosis function, with potential clinical application. However, the exact mechanism underlying its anti-hepatic fibrosis action remains unknown. Some scholars believe that this mechanism involves interferon's anti-viral effects, the inhibition of hepatic stellate cell (HSC) activation, the promotion of HSC apoptosis, the inhibition of extracellular matrix (ECM) synthesis and the promotion of ECM degradation.

Synthesis and biological activity of 5',9-anhydro-3-purine-isonucleosides as potential anti-hepatitis C virus agents

In order to study structure-activity relationships among the derivatives and congeners of 5',9-anhydro-3-(beta-D-ribofuranosyl)xanthine for anti-hepatitis C virus activity, a series of 5',9-anhydro-purine-isonucleosides with a substituent (s) at 6- or/and 8-position of the purine moiety were synthesized, and their anti-hepatitis C virus activity and cytotoxicity were evaluated and discussed.

An artificial neural network approach to the drug efficacy of interferon treatments

INTRODUCTION

Interferon taken alone or in combination with ribavirin can be used for the treatment of persons with chronic hepatitis C. It is highly desirable, both clinically and economically, to establish tools to distinguish responders from nonresponders and to predict possible outcomes of the treatments. In this work, our goal is to develop a prediction model resulting from the analysis of chronic hepatitis C patients' single nucleotide polymorphisms, viral genotype, viral load, age and gender, to predict the responsiveness of interferon combination treatment.

MATERIALS AND METHODS

We collected blood samples from 523 chronic hepatitis C patients that had received interferon and ribavirin combination therapy. Based on the current treatment strategy for chronic hepatitis C patients, we focused our search for candidate genes involved in pathways related to interferon signaling and immunomodulation. With artificial neural network algorithms, we then developed pattern recognition methodologies to achieve predictions among the patients. The artificial neural network model was trained by an algorithm with an adaptive momentum and learning rate.

RESULTS

There were seven single nucleotide polymorphisms selected from six candidate genes including adenosine deaminase-RNA-specific, caspase 5, interferon consensus sequence binding protein 1, interferon-induced protein 44, phosphoinositide-3-kinase catalytic gamma polypeptide and transporter 2 ATP-binding cassette subfamily B genes. We further applied the artificial neural network algorithms with these seven single nucleotide polymorphisms, viral genotype, viral load, age and gender information to build tools for predicting the responsiveness of interferon. Based on the fivefold cross-validation method to evaluate the performance, the model achieved a high success rate of prediction.

CONCLUSION

We demonstrated that a trained artificial neural network model is a promising method for providing the inference from factors such as single nucleotide polymorphisms, viral genotype, viral load, age and gender to the responsiveness of interferon.

Inhibition of hepatitis C replicon RNA synthesis by beta-D-2'-deoxy-2'-fluoro-2'-C-methylcytidine: a specific inhibitor of hepatitis C virus replication

beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a cytidine analogue with potent and selective anti-hepatitis C virus (HCV) activity in the subgenomic HCV replicon assay, 90% effective concentration (EC90)=4.6 +/- 2.0 microM. The spectrum of activity and cytotoxicity profile of PSI-6130 was evaluated against a diverse panel of viruses and cell types, and against two additional HCV-1b replicons. The S282T mutation, which confers resistance to 2'-C-methyl adenosine and other 2'-methylated nucleosides, showed only a 6.5-fold increase in EC90. When assayed for activity against bovine diarrhoea virus (BVDV), which is typically used as a surrogate assay to identify compounds active against HCV, PSI-6130 showed no anti-BVDV activity. Weak antiviral activity was noted against other flaviviruses, including West Nile virus, Dengue type 2, and yellow fever virus. These results indicate that PSI-6130 is a specific inhibitor of HCV. PSI-6130 showed little or no cytotoxicity against various cell types, including human peripheral blood mononuclear and human bone marrow progenitor cells. No mitochondrial toxicity was observed with PSI-6130. The reduced activity against the RdRp S282T mutant suggests that PSI-6130 is an inhibitor of replicon RNA synthesis. Finally, the no-effect dose for mice treated intraperitoneally with PSI-6130 for six consecutive days was > or =100 mg/kg per day.

Investigating the hedonic effects of interferon-alpha on female rats using brain-stimulation reward

Interferon-alpha (IFN-alpha) is used as a front-line treatment for cancer and other diseases. Reports of depression as a consequence of IFN-alpha therapy scatter the literature, generating interest in the CNS disruptions elicited by this cytokine. In the present work, we investigated the short- and long-term effects of a single systemic injection of vehicle, 10, or 1000 units of IFN-alpha on temperature, body weight, food intake, sickness behaviours, locomotor activity, and brain stimulation reward (BSR) thresholds elicited from the ventral tegmental area in female Long-Evans rats. Pioneered for studying motivational processes, BSR has been exploited as a tool for tracking hedonic status in animal models of depression. In this study, the main findings were that IFN-alpha did not induce anhedonia as defined by no increase in frequency thresholds. However, the analyses of sickness behaviours unveiled a significant increase in piloerection in all sham control animals that received an IFN-alpha injection while the BSR animal scores remained relatively unchanged between pre- and post-injection days. This pattern was also evident in the overall total sickness behaviour scores. Our data suggest that a single exposure to IFN-alpha treatment in female rats elicits long-term somatic effects, without altering hedonic status.

Antinociceptive and behavioral effects of ribavirin in mice

The antinociceptive effect of ribavirin, an antiviral drug, was studied after systemic injection using several pain tests in mice. In the hot-plate test of thermal pain, capsaicin-induced chemogenic pain, formalin test and abdominal stretching assay induced by the i.p. injection of 0.6% acetic acid, ribavirin produced a dose-related reduction in nociceptive responses. The visceral antinociceptive effect of ribavirin was unaffected by co-treatment with yohimbine, atropine or theophylline, but partially reversed by naloxone. Antinociception by ribavirin was augmented by treatment with prazosin, doxazosin, propranolol, guanethidine, glibenclamide, baclofen, indomethacin or cysteamine. Further, the ribavirin induced antinociception was enhanced by D2 receptor antagonists haloperidol, sulpiride, clozapine or domperidone and by the dopamine D2 receptor agonist bromocryptine. Ribavirin did not exhibit depression-like effect, nor it influenced the effect of amitriptyline in the forced swimming test. It did not impair cognitive performance in the Morris water Maze test. The present data demonstrate that ribavirin administered via systemic route possesses visceral and thermal anti-nociceptive properties. The ribavirin analgesic effect was partially reversed by naloxone, an opioid antagonist.

Drug interactions between psychoactive substances and antiretroviral therapy in individuals infected with human immunodeficiency and hepatitis viruses

The liver disease characteristic of alcohol dependence encompasses three main related entities: steatosis, alcoholic hepatitis, and cirrhosis. Alcoholic cirrhosis is a leading cause of global morbidity and mortality. Alcohol intake among injecting drug users is a major contributor to transmission of viral infections, such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C viruses (HCV). HIV and HCV coinfected patients develop liver diseases earlier and more severely than the monoinfected individuals, including hepatocellular carcinoma. Interactions exist between the therapeutic drugs used to minimize and control the drug and alcohol dependence. Furthermore, drug-drug interactions occur between the highly active antiretroviral therapy (HAART) and alcohol, different HAART components and methadone, or each one of the therapies with the other, thus contributing to a higher toxicity level. With the evolution of effective antiretroviral therapy, survival of persons with HIV, and the syndrome it causes, acquired immunodeficiency syndrome (AIDS) has increased dramatically. Drug-drug interactions may appear between alcohol and anti-HBV or anti-HCV, therapy in the presence or absence of anti-HIV therapy. Several other medical-, social-, and drug-related factors of this population have to be considered when providing HAART. Because many coinfected patients also have problems with substance use, dealing with their drug dependence is an important first step in an attempt to improve adherence to and tolerance of antiviral therapy. It is necessary to minimize the risk of liver disease acceleration and/or reinfection with hepatitis viruses. Knowledge of potential drug interactions between methadone, antiretroviral therapy, psychoactive drugs, and antipsychotics and the role of coinfection with HBV or HCV and the drugs used in eradicating viral hepatitis permits suitable antiretroviral combinations.

Synthesis of N3,5'-cyclo-4-(beta-D-ribofuranosyl)-vic-triazolo[4,5-b]pyridin-5-one and its 3'-deoxysugar analogue as potential anti-hepatitis C virus agents

We recently discovered a novel compound, identified as N3, 5-cyclo-4-(beta-D-ribofuranosyl)-vic-triazolo[4,5-b]pyridinin-5-one, with anti-hepatitis C virus (HCV) activity in vitro. The structure was confirmed by chemical synthesis from 2-hydroxy-5-nitropyridine. It showed anti-HCV activity with EC50= 19.7 microM in replicon cells. Its 3'-deoxy sugar analogue was also synthesized, but was inactive against HCV in vitro.

Synthesis and anti-hepatitis C virus activity of nucleoside derivatives of N3, 5'-anhydro-4-(beta-D-ribofuranosyl)-8-aza-purin-2-ones

A series of N3, 5-Anhydro-4-(beta-D-ribofuranosyl)-8-azapurin-2-ones were prepared in multistep reactions from uridine as potential anti-hepatitis C virus (HCV) agents. The synthetic details as well as biological evaluations are discussed.

Synthesis and Structure−Activity Relationships of Novel Anti-hepatitis C Agents: N3,5‘-Cyclo-4-(β-d-ribofuranosyl)-vic-triazolo[4,5-b]pyridin-5-one Derivatives

Several 6- and 7-monosubstituted N3,5'-cyclo-4-(beta-d-ribofuranosyl)-vic-triazolo[4,5-b]pyridin-5-one derivatives as well as the 5-thiono analogue were synthesized, providing structure-anti-hepatitis C virus (HCV) activity relationships for the series. Among the compounds synthesized, the 6-bromo, 7-methylamino, and 5-thiono analogues exhibited more potent anti-HCV activity in an HCV subgenomic replicon cell based assay (EC90 = 1.9, 7.4, and 10.0 microM, respectively) than the lead compound N3,5'-cyclo-4-(beta-D-ribofuranosyl)-vic-triazolo[4,5-b]pyridin-5-one (EC90 = 79.8 microM).

Development of a cell-based high-throughput specificity screen using a hepatitis C virus-bovine viral diarrhea virus dual replicon assay

The hepatitis C virus (HCV) replicon is a unique system for the development of a high-throughput screen (HTS), since the analysis of inhibitors requires the quantification of a decrease in a steady-state level of HCV RNA. HCV replicon replication is dependent on host cell factors, and any toxic effects may have a significant impact on HCV replicon replication. Therefore, determining the antiviral specificity of compounds presents a challenge for the identification of specific HCV inhibitors. Here we report the development of an HCV/bovine viral diarrhea virus (BVDV) dual replicon assay suitable for HTS to address these issues. The HCV reporter enzyme is the endogenous NS3 protease contained within the HCV genome, while the BVDV reporter enzyme is a luciferase enzyme engineered into the BVDV genome. The HTS uses a mixture of HCV and BVDV replicon cell lines placed in the same well of a 96-well plate and isolated in the same cell backgrounds (Huh-7). The format consists of three separate but compatible assays: the first quantitates the amount of cytotoxicity based upon the conversion of Alamar blue dye via cellular enzymes, while the second indirectly quantitates HCV replicon replication through measurement of the amount of NS3 protease activity present. The final assay measures the amount of luciferase activity present from the BVDV replicon cells, as an indicator of the specificity of the test compounds. This HCV/BVDV dual replicon assay provides a reliable format to determine the potency and specificity of HCV replicon inhibitors.

Synthesis of N3,5‘-Cyclo-4-(β-d-ribofuranosyl)-vic-triazolo[4,5-b]pyridin-5-one, a Novel Compound with Anti-Hepatitis C Virus Activity

A novel anti-hepatitis C virus (HCV) agent, N(3),5'-cyclo-4-(beta-D-ribofuranosyl)-vic-triazolo[4,5-b]pyridinin-5-one, was identified, and the structure was confirmed by chemical synthesis from 2-hydroxy-5-nitropyridine.

Peginterferon-alpha-2a (40kD) plus ribavirin: a review of its use in the management of chronic hepatitis C

Pegylation of interferon-alpha-2a is associated with improved sustained virological response rates in patients with chronic hepatitis C. Subsequently, combination therapy with peginterferon-alpha-2a (40kD) [Pegasys] and ribavirin (Copegus trade mark, Rebetol) was investigated to establish if the efficacy of peginterferon-alpha-2a (40kD) monotherapy could be further enhanced. Subcutaneous peginterferon-alpha-2a (40kD) was administered at a dosage of 180 micro g once weekly and oral ribavirin was usually administered at a dosage of 1000 or 1200 mg/day. In treatment-naive patients with chronic hepatitis C, the sustained virological response rate (assessed 24 weeks after the end of a 48-week treatment period) was significantly higher in peginterferon-alpha-2a (40kD) plus ribavirin recipients than in peginterferon-alpha-2a (40kD) plus placebo recipients or interferon-alpha-2b plus ribavirin recipients (56% vs 29% and 44%). Retrospective analysis revealed that peginterferon-alpha-2a (40kD) plus ribavirin recipients who did not achieve an early virological response were unlikely to achieve a sustained response. Treatment with peginterferon-alpha-2a (40kD) plus another antiviral agent (ribavirin, mycophenolate mofetil, amantadine, or ribavirin and amantadine) was beneficial in patients with chronic hepatitis C who had relapsed during or after, or had not responded to, treatment with interferon-alpha-2b plus ribavirin. In the relapse study, sustained virological response rates in recipients of peginterferon-alpha-2a (40kD) plus ribavirin were 45% with and 38% without amantadine. Peginterferon-alpha-2a (40kD) plus ribavirin appears beneficial in patients with chronic hepatitis C considered difficult to treat (e.g. patients infected with hepatitis C virus genotype 4, African-American patients, patients with advanced fibrosis or cirrhosis and patients co-infected with HIV). Flu-like symptoms and depression occurred significantly less frequently with peginterferon-alpha-2a (40kD) plus ribavirin than with interferon-alpha-2b plus ribavirin. Similar proportions of patients receiving peginterferon-alpha-2a (40kD) plus ribavirin, peginterferon-alpha-2a (40kD) plus placebo and interferon-alpha-2b plus ribavirin withdrew from treatment because of laboratory abnormalities or other adverse events. In conclusion, combination therapy comprising subcutaneous peginterferon-alpha-2a (40kD) and oral ribavirin is an important new treatment option for chronic hepatitis C. Peginterferon-alpha-2a (40kD) plus oral ribavirin is significantly more effective than peginterferon-alpha-2a (40kD) monotherapy or interferon-alpha-2b plus ribavirin at inducing a sustained virological response in treatment-naive patients with chronic hepatitis C. Preliminary data suggest that peginterferon-alpha-2a (40kD) plus ribavirin is also beneficial in treatment-experienced patients and in patients who have traditionally been considered difficult to treat. Combination therapy with peginterferon-alpha-2a (40kD) and oral ribavirin is poised to become a valuable first-line treatment option in chronic hepatitis C.

Ribonucleoside analogue that blocks replication of bovine viral diarrhea and hepatitis C viruses in culture

A base-modified nucleoside analogue, beta-D-N(4)-hydroxycytidine (NHC), was found to have antipestivirus and antihepacivirus activities. This compound inhibited the production of cytopathic bovine viral diarrhea virus (BVDV) RNA in a dose-dependant manner with a 90% effective concentration (EC(90)) of 5.4 microM, an observation that was confirmed by virus yield assays (EC(90) = 2 microM). When tested for hepatitis C virus (HCV) replicon RNA reduction in Huh7 cells, NHC had an EC(90) of 5 microM on day 4. The HCV RNA reduction was incubation time and nucleoside concentration dependent. The in vitro antiviral effect of NHC was additive with recombinant alpha interferon-2a and could be prevented by the addition of exogenous cytidine and uridine but not of other natural ribo- or 2'-deoxynucleosides. When HCV RNA replicon cells were cultured in the presence of increasing concentrations of NHC (up to 40 micro M) for up to 45 cell passages, no resistant replicon was selected. Similarly, resistant BVDV could not be selected after 20 passages. NHC was phosphorylated to the triphosphate form in Huh7 cells, but in cell-free HCV NS5B assays, synthetic NHC-triphosphate (NHC-TP) did not inhibit the polymerization reaction. Instead, NHC-TP appeared to serve as a weak alternative substrate for the viral polymerase, thereby changing the mobility of the product in polyacrylamide electrophoresis gels. We speculate that incorporated nucleoside analogues with the capacity of changing the thermodynamics of regulatory secondary structures (with or without introducing mutations) may represent an important class of new antiviral agents for the treatment of RNA virus infections, especially HCV.

Acute effects of low-dose interferon-alpha on serum cortisol and plasma interleukin-6

Major depression is associated with both hypothalamic-pituitary-adrenal (HPA) axis overactivity and immune system activation. Depression is a common occurrence following interferon (IFN)-a treatment. While IFN-alpha is known to stimulate the HPA axis, little is known about the effects of exogenous IFN-a in humans on the proinflammatory cytokine interleukin (IL)-6, a marker of immune system activation. This study examined the acute effects of IFN-alpha on cortisol and IL-6 release, and the time course of any changes in these variables. Serum cortisol and plasma IL-6 were assessed in healthy volunteers over an 8-h period following 3 million units subcutaneous IFN-alpha or placebo using a double-blind, placebo-controlled crossover design. IFN-alpha resulted in a significant increase in both cortisol and IL-6. Regular sampling over 8 h did not delineate any sequential effect of the rise in these variables over time. We conclude that IFN-alpha acutely stimulates both the HPA axis and proinflammatory cytokine release. The hypothesis that the effect of IFN-alpha on the HPA axis is indirect and mediated by IL-6 was not supported by this study. Our findings are nonetheless of relevance to the aetiology of depression following IFN-alpha.

Interferon-alpha-2b plus ribavirin: a review of its use in the management of chronic hepatitis C

Relatively few patients (< or =20%) with chronic hepatitis C achieve a sustained virological response after interferon-alpha monotherapy. Hence, alternative treatment strategies such as the addition of the broad spectrum antiviral agent ribavirin to interferon-alpha-2b have been investigated. Combination therapy with subcutaneous interferon-alpha-2b [3 million units (MU) three times per week] plus oral ribavirin (1000 to 1200 mg/day) has proven effective in several well designed trials of 24 to 48 weeks' duration in adult patients with compensated chronic hepatitis C. Compared with interferon-alpha-2b (3 or 6 MU three times per week) with or without placebo, combination treatment with interferon-alpha-2b plus ribavirin significantly enhanced end-of-treatment and sustained virological and biochemical response rates in treatment-naive and treatment-experienced patients [sustained virological response rates in treatment-naive recipients (6 to 19% vs 31 to 43% of patients); sustained overall (virological plus biochemical) response rates in nonresponders to (1 vs 14%) or relapsers (4 to 5% vs 30 to 44%) after previous interferon-alpha monotherapy]. Forty-eight weeks of combination therapy was superior to 24 weeks in treatment-naive patients infected with hepatitis virus C (HCV) genotype 1, whereas response rates were similar at 24 and 48 weeks in those infected with other HCV genotypes. Furthermore, there were marked improvements in histological inflammatory scores in patients who responded to treatment with either interferon-alpha-2b plus ribavirin or interferon-alpha-2b alone. Although adverse events associated with either drug during combination therapy occurred frequently, these were generally mild to moderate in intensity and were consistent with those reported for each individual agent. Twenty-six percent of patients required dosage modifications of one or both drugs during combination therapy.

CONCLUSIONS

Interferon-alpha-2b plus ribavirin is an efficacious first- and second-line therapy in adult patients with compensated chronic hepatitis C, significantly improving sustained virological and biochemical responses versus interferon-alpha-2b monotherapy. The tolerability profile of interferon-alpha-2b plus ribavirin therapy is consistent with the individual profiles of these agents with no evidence of additive effects. The place of interferon-alpha-2b plus ribavirin combination therapy in relation to newer agents, including pegylated interferons-alpha and other multidrug regimens, remains to be determined in this rapidly evolving area of therapeutic management. Currently, combination therapy with interferon-alpha-2b plus ribavirin is recommended as first-line therapy for patients with chronic hepatitis C and compensated liver disease, and is an option for use as second-line therapy in those who have relapsed after, or failed to respond to, previous treatment with interferon-alpha.

Peginterferon-alpha-2a (40 kD): a review of its use in the management of chronic hepatitis C

Peginterferon-alpha-2a (40 kD) is a new 'pegylated' subcutaneous formulation of interferon-alpha-2a that has been developed to improve on the pharmacokinetic profile and therapeutic efficacy of interferon-alpha-2a. Peginterferon-alpha-2a (40 kD) is produced by the covalent attachment of recombinant interferon-alpha-2a to a branched mobile 40 kD polyethylene glycol moiety, which shields the interferon-alpha-2a molecule from enzymatic degradation, reduces systemic clearance and enables once-weekly administration. Peginterferon-alpha-2a (40 kD) was significantly more effective than interferon-alpha-2a in interferon-alpha therapy-naive adults with chronic hepatitis C in three nonblind, randomised, multicentre trials. Virological responses (intention-to-treat results) were achieved in 44 to 69% of patients with or without cirrhosis after 48 weeks of treatment with peginterferon-alpha-2a (40kD) 180 microg/week; sustained virological responses 24 weeks after the end of treatment occurred in 30 to 39% of patients. Virological responses at the end of treatment and at long-term follow-up were significantly higher than those achieved with interferon-alpha-2a. Peginterferon-alpha-2a (40 kD) was significantly more effective than interferon-alpha in patients with or without cirrhosis infected with HCV genotype 1. Sustained biochemical responses achieved with peginterferon-alpha-2a (40 kD) 180 microg/week ranged from 34 to 45% and were significantly higher than with interferon-alpha-2a. Recipients of peginterferon-alpha-2a (40 kD) also experienced histological improvements; 24 weeks after discontinuation of treatment with peginterferon-alpha-2a (40 kD) 180 microg/week, 54 to 63% of patients had a > or =2-point improvement in histological activity index score. Peginterferon-alpha-2a (40 kD) produced histological responses in patients (with or without cirrhosis) with or without a sustained virological response. Peginterferon-alpha-2a (40 kD) produced better results than interferon-alpha-2a alone or interferon-alpha-2b plus oral ribavirin on various measures of quality of life in patients with chronic hepatitis C. The tolerability profile of peginterferon-alpha-2a (40 kD) is broadly similar to that of interferon-alpha-2a in patients with chronic hepatitis C with or without cirrhosis. Headache, fatigue and myalgia are among the most common adverse events.

CONCLUSION

Peginterferon-alpha-2a (40 kD) administered once weekly produces significantly higher sustained responses, without compromising tolerability, than interferon-alpha-2a administered thrice weekly in noncirrhotic or cirrhotic patients with chronic hepatitis C, including those infected with HCV genotype 1 - a group in whom interferon-alpha treatment has usually been unsuccessful. Peginterferon-alpha-2a (40 kD) is a valuable new treatment option and appears poised to play an important role in the first-line treatment of patients with chronic hepatitis C, including difficult-to-treat patients such as those with compensated cirrhosis and/or those infected with HCV genotype 1.

Ribavirin--current status of a broad spectrum antiviral agent

Ribavirin is a very broad-spectrum virustatic antiviral agent, first synthesised in 1972. It is characterised by low toxicity apart from reversible anaemia, usually mild. Its multiple mechanisms of action mean that viral resistance rarely develops. It can be administered orally, intravenously, or via a nebuliser. It has shown varying degrees of clinical efficacy in a variety of human diseases including respiratory tract infections due to respiratory syncytial virus and influenza, measles, herpesvirus infections, HIV infection, Lassa fever, haemorrhagic fever with renal syndrome, and (in combination with IFN-alpha) chronic hepatitis C infection. It may well prove of value against other emerging exotic infections (e.g., West Nile virus, Nipah virus).