Evaluation of amantadine in chronic hepatitis C: a meta-analysis

Granulocyte colony-stimulating factor for alcoholic hepatitis: A systematic review and meta-analysis of randomised controlled trials

Background & Aims

Granulocyte colony-stimulating factor (G-CSF) treatment has been proposed as a therapeutic option for patients with severe alcoholic hepatitis (AH). The aim of this study was to synthesise available evidence on the efficacy of G-CSF in AH.

Methods

This is a meta-analysis of randomised controlled trials evaluating the risk of death at 90 days and the risk of infection.

Results

Seven studies were included. Of a total of 396 patients, 336 had AH, 197 patients were treated with G-CSF, and 199 received placebo or pentoxifylline. In overall meta-analysis, G-CSF therapy was associated with a reduced risk of death at 90 days (odds ratio [OR] 0.28; 95% CI 0.09–0.88; p = 0.03). There was high heterogeneity between studies (p <0.001; I² = 80%). Five studies were performed in Asia and 2 in Europe. In the subgroup analysis of studies performed in Asia, G-CSF was associated with a reduced risk of death (OR 0.15; 95% CI 0.08–0.28; p <0.001; heterogeneity: p = 0.5, I² = 0%). In European studies, G-CSF tended to increase mortality compared with controls, although the difference was not significant (OR 1.89; 95% CI 0.90–3.98; p = 0.09; heterogeneity: p = 0.8, I² = 0%). In Asian studies, occurrence of infection was less frequent in G-CSF patients than in controls (OR 0.12; 95% CI 0.06–0.23; p <0.001; heterogeneity: p = 0.7, I² = 0%), whilst in European studies, this occurrence was not statistically different (OR 0.92; 95% CI 0.50–1.68; p = 0.78; heterogeneity: p = 0.5, I² = 0%). In sensitivity analyses, excluding studies that included patients with acute-on-chronic liver failure (ACLF) other than AH, patients with less severe AH, or patients with non-response to corticosteroids, results were similar to those of overall analyses, both for mortality and occurrence of infection.

Conclusions

Granulocyte colony-stimulating factor therapy may improve the prognosis of patients with severe AH. However, owing to the high heterogeneity observed in the overall analysis caused by conflicting results between the Asian and European studies, G-CSF cannot currently be recommended for AH, particularly in Europe. Whether these differences can be explained by ethnic differences or disparities in patient selection and disease severity remains unclear.

Lay summary

The main finding of this meta-analysis is that the use of granulocyte colony-stimulating factor (G-CSF) is associated with a mortality reduction of more than 70% at 3 months amongst patients with alcoholic hepatitis (AH) compared with controls who did not receive this therapy. However, owing to the high heterogeneity observed in the overall analysis caused by conflicting results between the Asian and European studies, G-CSF cannot currently be recommended for patients with AH, particularly in Europe. Whether these differences can be explained by ethnic differences or disparities in patient selection and disease severity remains unclear.

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This meta-analysis reports pooled data from 7 studies on the use of G-CSF in patients with alcoholic hepatitis.

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The favourable effect of G-CSF was only encountered in Asian not European studies.

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Additional data are needed to clarify the usefulness of G-CSF in severe alcoholic hepatitis, particularly in Europe.

Liver stiffness and platelet count for identifying patients with compensated liver disease at low risk of variceal bleeding

BACKGROUND & AIMS

The 2015 Baveno VI guidelines recommend against performing upper gastrointestinal endoscopy in patients with compensated cirrhosis who have a liver stiffness <20 kPa and a platelet count >150 000/mm³ because of a low prevalence of varices at risk of bleeding in this population. The aim was to synthesize the available evidence on the usefulness of the combined use of liver stiffness and platelet count to identify patients without oesophageal varices.

METHODS

Meta-analysis of trials evaluating the usefulness of a given cut-off for liver stiffness and platelet count to rule out the presence of oesophageal varices.

RESULTS

Fifteen studies were included. All studies excepting five used the Baveno VI criteria. Compared to patients with either high liver stiffness or low platelet count, those with low liver stiffness and normal platelet count had a lower risk of varices at risk of bleeding (OR=0.22, 95% CI=0.13-0.39, P<.001) with low heterogeneity between studies (I² =21%). They also had a lower risk of varices (OR=0.23, 95% CI=0.17-0.32, P<.001) with moderate heterogeneity between studies (I² =28%). In patients with low liver stiffness and normal platelet count, the pooled estimate rates for varices at risk of bleeding was 0.040 (95% CI=0.027-0.059) with low heterogeneity between studies (I² =3%).

CONCLUSIONS

Patients with low liver stiffness and normal platelet count have a lower risk of varices than those with either high liver stiffness or low platelet count. Varices at risk of bleeding are found in no more than 4% of patients when liver stiffness is <20 kPa and platelet count is normal.

"Too little, too late?" Will inhibitors of the hepatitis C virus p7 ion channel ever be used in the clinic?

Hepatitis C virus (HCV) p7 is a virus-coded ion channel, or 'viroporin'. p7 is an essential HCV protein, promoting infectious virion production, and this process can be blocked by prototypic p7 inhibitors. However, prototype potency is weak and effects in clinical trials are unsatisfactory. Nevertheless, recent structural studies render p7 amenable to modern drug discovery, with studies supporting that effective drug-like molecules should be achievable. However, burgeoning HCV therapies clear infection in the majority of treated patients. This perspective summarizes current understanding of p7 channel function and structure, pertaining to the development of improved p7 inhibitors. We ask, 'is this too little, too late', or could p7 inhibitors play a role in the long-term management of HCV disease?

New treatment strategies for hepatitis C infection

Hepatitis C infection can lead to cirrhosis and hepatocellular carcinoma and it is an important cause of mortality and morbidity. Achieving a sustained virological response has been the major aim for decades. Interferon treatment was the primarily developed therapy against the infection. Addition of the guanosine analog ribavirin to stop viral RNA synthesis increased the response rates as well as the adverse effects of the treatment. The increasing demands for alternative regimens led to the development of direct-acting antivirals (DAAs). The approval of sofosbuvir and simeprevir signaled a new era of antiviral treatment for hepatitis C infection. Although the majority of studies have been performed with DAAs in combination with interferon and resulted in a decrease in treatment duration and increase in response rates, the response rates achieved with interferon-free regimens provided hope for patients ineligible for therapy with interferon. Most DAA studies are in phase II leading to phase III. In the near future more DAAs are expected to be approved. The main disadvantage of the therapy remains the cost of the drugs. Here, we focus on new treatment strategies for hepatitis C infection as well as agents targeting hepatitis C virus replication that are in clinical development.

Viroporins: structure, function and potential as antiviral targets

The channel-forming activity of a family of small, hydrophobic integral membrane proteins termed 'viroporins' is essential to the life cycles of an increasingly diverse range of RNA and DNA viruses, generating significant interest in targeting these proteins for antiviral development. Viroporins vary greatly in terms of their atomic structure and can perform multiple functions during the virus life cycle, including those distinct from their role as oligomeric membrane channels. Recent progress has seen an explosion in both the identification and understanding of many such proteins encoded by highly significant pathogens, yet the prototypic M2 proton channel of influenza A virus remains the only example of a viroporin with provenance as an antiviral drug target. This review attempts to summarize our current understanding of the channel-forming functions for key members of this growing family, including recent progress in structural studies and drug discovery research, as well as novel insights into the life cycles of many viruses revealed by a requirement for viroporin activity. Ultimately, given the successes of drugs targeting ion channels in other areas of medicine, unlocking the therapeutic potential of viroporins represents a valuable goal for many of the most significant viral challenges to human and animal health.

Docking assay of small molecule antivirals to p7 of HCV

Protein p7 of HCV is a 63 amino acid channel forming membrane protein essential for the progression of viral infection. With this momentousness, p7 emerges as an important target for antiviral therapy. A series of small molecule drugs, such as amantadine, rimantadine, amiloride, hexamethylene amiloride, NN-DNJ and BIT225 have been found to affect the channel activity. These compounds are docked against monomeric and hexameric structures of p7 taken at various time steps from a molecular dynamics simulation of the protein embedded in a hydrated lipid bilayer. The energetics of binding identifies the guanidine based ligands as the most potent ligands. The adamantanes and NN-DNJ show weaker binding energies. The lowest energy poses are those at the site of the loop region for the monomer and hexamer. For the latter, the poses show a tendency of the ligand to face the lumen of the pore. The mode of binding is that of a balance between hydrophobic interactions and hydrogen bond formation with backbone atoms of the protein.

Aminoadamantanes versus other antiviral drugs for chronic hepatitis C

BACKGROUND

Hepatitis C virus infection affects around 3% of the world population or approximately 160 million people. A variable proportion (5% to 40%) of the infected people develop clinical symptoms. Hence, hepatitis C virus is a leading cause of liver-related morbidity and mortality with hepatic fibrosis, end-stage liver cirrhosis, and hepatocellular carcinoma as the dominant clinical sequelae. Combination therapy with pegylated (peg) interferon-alpha and ribavirin achieves sustained virological response (that is, undetectable hepatitis C virus RNA in serum by sensitivity testing six months after the end of treatment) in approximately 40% to 80% of treated patients, depending on viral genotype. Recently, a new class of drugs have emerged for hepatitis C infection, the direct acting antivirals, which in combination with standard therapy or alone can lead to sustained virological response in 80% or more of treated patients. Aminoadamantanes, mostly amantadine, are antiviral drugs used for the treatment of patients with chronic hepatitis C. We have previously systematically reviewed amantadine versus placebo or no intervention and found no significant effects of the amantadine on all-cause mortality or liver-related morbidity and on adverse events in patients with hepatitis C. Overall, we did not observe a significant effect of amantadine on sustained virological response. In this review, we systematically review aminoadamantanes versus other antiviral drugs.

OBJECTIVES

To assess the beneficial and harmful effects of aminoadamantanes versus other antiviral drugs for patients with chronic hepatitis C virus infection by conducting a systematic review with meta-analyses and trial sequential analyses of randomised clinical trials.

SEARCH METHODS

The Cochrane Hepato-Biliary Group Controlled Trials Register (1996 to December 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 11 of 12, 2013), MEDLINE (1946 to December 2013), EMBASE (1974 to December 2013), Science Citation Index EXPANDED (1900 to December 2013), the WHO International Clinical Trials Registry Platform (www.who.int/ictrp), Google Scholar, and Eudrapharm up to December 2013. Furthermore, full text searches were conducted until December 2013.

SELECTION CRITERIA

Randomised clinical trials assessing aminoadamantanes in participants with chronic hepatitis C virus infection.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. RevMan Analysis was used for statistical analysis of dichotomous data using risk ratio (RR) with 95% confidence intervals (CI). Methodological domains were used to assess the risk of systematic errors ('bias'). We used trial sequential analysis to assess risk of random errors ('play of chance').

MAIN RESULTS

Six randomised clinical trials with 581 participants with chronic hepatitis C were included. All trials had high risk of bias. The included trials compared amantadine versus other antiviral drugs: ribavirin, mycophenolate mofetil, interferon-alpha, or interferon-gamma. Standard antiviral therapy (interferon-alpha, interferon-alpha plus ribavirin, or peg interferon alpha) was administered equally to the intervention and the control groups in five trials, depending on when the trial was conducted. Four trials compared amantadine versus ribavirin. There were no deaths or liver-related morbidity in the two intervention groups (0/216 (0%) versus 0/211 (0%); 4 trials; very low quality of the evidence). The lower estimated risk for (serious) adverse events leading to treatment discontinuation with amantadine was imprecise (RR 0.56, 95% CI 0.27 to 1.16; based on 10/216 (5%) versus 18/211 (9%) participants in 4 trials; very low quality of the evidence). There were more participants with failure of sustained virological response in the amantadine group than in the ribavirin group (206/216 (96%) versus 176/211 (84%); RR 1.14, 95% CI 1.07 to 1.22, 4 trials; low quality of the evidence). Amantadine versus ribavirin more often failed to achieve end-of follow-up biochemical response (41/46 (89%) versus 31/46 (67%); RR 1.31, 95% CI 1.05 to 1.63; 2 trials; very low quality of the evidence). One trial compared amantadine versus mycophenolate mofetil. There were no significant differences between the two treatment groups, except that amantadine was inferior to mycophenolate mofetil regarding the outcome failure to achieve end-of treatment virological response (low quality of evidence). One trial each compared amantadine versus interferon-alpha or interferon-gamma. Both comparisons showed no significant differences in the treatment outcomes (very low quality of the evidence). The observed effects could be due to real effects, systematic errors (bias), or random errors (play of chance). This possible influence on the observed effect by play of chance is due to the fact that trial sequential analyses could not confirm our findings. We were not able to perform meta-analyses on failure of histological improvement and quality of life due to lack of valid data in all trial comparisons.

AUTHORS' CONCLUSIONS

This systematic review has identified evidence of very low quality for the key outcomes of all-cause mortality or liver-related morbidity and adverse events in people with chronic hepatitis C when treated with amantadine compared with ribavirin, mycophenolate, interferon-alpha, or interferon-gamma. The timeframe for measuring the composite outcome was insufficient in the included trials. There was low quality evidence that amantadine led to more participants who failed to achieve sustained virological response compared with ribavirin. This observation may be real or caused by systematic errors (bias), but it does not seem to be caused by random error (play of chance). Due to the low quality of the evidence, we are unable to determine definitively whether amantadine is less effective than other antivirals in patients with chronic hepatitis C. As it appears less likely that future trials assessing amantadine or potentially other aminoadamantanes for patients with chronic hepatitis C would show strong benefits, it is probably better to focus on the assessments of other direct acting antiviral drugs. We found no evidence assessing other aminoadamantanes in randomised clinical trials in order to recommend or refute their use.

Aminoadamantanes for chronic hepatitis C

BACKGROUND

Around 3% of the world's population (approximately 160 million people) are chronically infected with hepatitis C virus. The proportion of infected people who develop clinical symptoms varies between 5% and 40%. Combination therapy with pegylated interferon-alpha plus ribavirin eradicates the virus from the blood six months after treatment (sustained virological response) in approximately 40% to 80% of infected patients, depending on the viral genotype. New antiviral agents, such as boceprevir and telaprevir, in combination with standard therapy, can increase sustained virological response in genotype 1 infected patients to at least 70%. There is therefore an unmet need for drugs that can achieve a higher proportion of sustained virological response. Aminoadamantanes are antiviral drugs used for treatment of patients with chronic hepatitis C.

OBJECTIVES

To assess the beneficial and harmful effects of aminoadamantanes for patients with chronic hepatitis C infection by conducting a systematic review with meta-analyses of randomised clinical trials, as well as trial sequential analyses.

SEARCH METHODS

We conducted electronic searches of the Cochrane Hepato-Biliary Group Controlled Trials Register (1996 to December 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 11 of 12 (1995 to December 2013), MEDLINE (1946 to December 2013), EMBASE (1974 to December 2013), Science Citation Index EXPANDED (1900 to December 2013), the WHO International Clinical Trials Registry Platform (www.who.int/ictrp), Google Scholar, and Eudrapharm up to December 2013 and checked the reference lists of identified publications.

SELECTION CRITERIA

Randomised clinical trials assessing aminoadamantanes in patients with chronic hepatitis C infection.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. We assessed for risks of systematic errors ('bias') using the 'Risk of bias' tool. We analysed dichotomous data with risk ratio (RR) and continuous data with mean difference (MD) or standardised mean difference (SMD), both with 95% confidence intervals (CI). We used trial sequential analysis to assess the risk of random errors ('play of chance'). We assessed quality using the GRADE system.

MAIN RESULTS

We included 41 randomised clinical trials with 6193 patients with chronic hepatitis C. All trials had high risk of bias. All included trials compared amantadine versus placebo or no intervention. Standard antiviral therapy was administered equally to the intervention and the control groups in 40 trials. The standard antiviral therapy, which was administered to both intervention groups, was interferon-alpha, interferon-alpha plus ribavirin, and peg interferon-alpha plus ribavirin, depending on the time when the trial was conducted.When we meta-analysed all trials together, the overall results demonstrated no significant effects of amantadine, when compared with placebo or no intervention, on our all-cause mortality or liver-related morbidity composite outcome (5/2353 (0.2%) versus 6/2264 (0.3%); RR 0.90, 95% CI 0.38 to 2.17; I² = 0%; 32 trials; very low quality). There was also no significant effect on adverse events (288/2869 (10%) versus 293/2777 (11%); RR 0.98, 95% CI 0.84 to 1.14; I² = 0%; 35 trials; moderate quality). We used both fixed-effect and random-effects meta-analyses. Amantadine, when compared with placebo or no intervention, did not significantly influence the number of patients who failed to achieve a sustained virological response (1821/2861 (64%) versus 1737/2721 (64%); RR 0.98, 95% CI 0.95 to 1.02; I² = 35%; 35 trials; moderate quality). However, in the subgroup using interferon plus ribavirin, amantadine decreased the number of patients who failed to achieve a sustained virological response (422/666 (63%) versus 447/628 (71%); RR 0.89, 95% CI 0.83 to 0.96; I² = 41%; 11 trials; low quality). Similar results were found for failure to achieve an end of treatment virological response. Amantadine, when compared with placebo or no intervention, significantly decreased the number of patients without normalisation of alanine aminotransferase (ALT) serum levels at the end of treatment (671/1141 (59%) versus 732/1100 (67%); RR 0.88, 95% CI 0.83 to 0.94; I² = 47%; 19 trials; low quality). Amantadine, when compared with placebo or no intervention, did not significantly influence the end of follow-up biochemical response (1133/1896 (60%) versus 1151/1848 (62%); RR 0.95, 95% CI 0.91 to 1.00; I² = 49%; 21 trials; low quality).The observed beneficial effects could be true effects but could also be due to both systematic errors (bias) and random errors (play of chance). The latter is due to the fact that trial sequential analyses could not confirm or refute our findings. We were not able to perform meta-analyses for failure of histological improvement or quality of life due to a lack of valid data.

AUTHORS' CONCLUSIONS

This systematic review does not demonstrate any significant effects of amantadine on all-cause mortality or liver-related morbidity composite outcome and on adverse events in patients with hepatitis C; however, the median trial duration was 12 months, with a median follow-up of six months, which is not long enough to assess the composite outcome sufficiently. Overall, we did not see an effect of amantadine on failure to achieve a sustained virological response. Subgroup analyses demonstrated that the combination of amantadine plus interferon-alpha and ribavirin seems to increase the number of patients achieving a sustained virological response. This finding may be caused by both systematic errors (bias) and risks of random errors (play of chance), but it could also be real. Based on the results of the overall evidence, it appears less likely that future trials assessing amantadine for patients with chronic hepatitis C will show strong benefits. Therefore, it is probably advisable to wait for the results of trials assessing other direct-acting antiviral drugs. In the absence of convincing evidence of benefit, the use of amantadine is justified in the context of randomised clinical trials assessing the effects of combination therapy. We found a lack of evidence on other aminoadamantanes than amantadine.

Citation networks of related trials are often disconnected: implications for bidirectional citation searches

BACKGROUND AND OBJECTIVES

Reports of randomized controlled trials (RCTs) should set findings within the context of previous research. The resulting network of citations would also provide an alternative search method for clinicians, researchers, and systematic reviewers seeking to base decisions on all available evidence. We sought to determine the connectedness of citation networks of RCTs by examining direct (referenced trials) and indirect (through references of referenced trials, etc) citation of trials to one another.

METHODS

Meta-analyses were used to create citation networks of RCTs addressing the same clinical questions. The primary measure was the proportion of networks where following citation links between RCTs identifies the complete set of RCTs, forming a single connected citation group. Other measures included the number of disconnected groups (islands) within each network, the number of citations in the network relative to the maximum possible, and the maximum number of links in the path between two connected trials (a measure of indirectness of citations).

RESULTS

We included 259 meta-analyses with a total of 2,413 and a median of seven RCTs each. For 46% (118 of 259) of networks, the RCTs formed a single connected citation group-one island. For the other 54% of networks, where at least one RCT group was not cited by others, 39% had two citation islands and 4% (10 of 257) had 10 or more islands. On average, the citation networks had 38% of the possible citations to other trials (if each trial had cited all earlier trials). The number of citation islands and the maximum number of citation links increased with increasing numbers of trials in the network.

CONCLUSION

Available evidence to answer a clinical question may be identified by using network citations created with a small initial corpus of eligible trials. However, the number of islands means that citation networks cannot be relied on for evidence retrieval.

Protective role of amantadine in mitochondrial dysfunction and oxidative stress mediated by hepatitis C virus protein expression

Amantadine is an antiviral and antiparkinsonian drug that has been evaluated in combination therapies against hepatitis C virus (HCV) infection. Controversial results have been reported concerning its efficacy, and its mechanism of action remains unclear. Data obtained in vitro suggested a role of amantadine in inhibiting HCV p7-mediated cation conductance. In keeping with the fact that mitochondria are responsible to ionic fluxes and that HCV infection impairs mitochondrial function, we investigated a potential role of amantadine in modulating mitochondrial function. Using a well-characterized inducible cell line expressing the full-length HCV polyprotein, we found that amantadine not only prevented but also rescued HCV protein-mediated mitochondrial dysfunction. Specifically, amantadine corrected (i) overload of mitochondrial Ca²⁺; (ii) inhibition of respiratory chain activity and oxidative phosphorylation; (iii) reduction of membrane potential; and (iv) overproduction of reactive oxygen species. The effects of amantadine were observed within 15 min following drug administration and confirmed in Huh-7.5 cells transfected with an infectious HCV genome. These effects were also observed in cells expressing subgenomic HCV constructs, indicating that they are not mediated or only in part mediated by p7. Single organelle analyzes carried out on isolated mouse liver mitochondria demonstrated that amantadine induces hyperpolarization of the membrane potential. Moreover, amantadine treatment increased the calcium threshold required to trigger mitochondrial permeability transition opening. In conclusion, these results support a role of amantadine in preserving cellular bioenergetics and redox homeostasis in HCV-infected cells and unveil an effect of the drug which might be exploited for a broader therapeutic utilization.

Structure-guided design affirms inhibitors of hepatitis C virus p7 as a viable class of antivirals targeting virion release

Current interferon-based therapy for hepatitis C virus (HCV) infection is inadequate, prompting a shift toward combinations of direct-acting antivirals (DAA) with the first protease-targeted drugs licensed in 2012. Many compounds are in the pipeline yet primarily target only three viral proteins, namely, NS3/4A protease, NS5B polymerase, and NS5A. With concerns growing over resistance, broadening the repertoire for DAA targets is a major priority. Here we describe the complete structure of the HCV p7 protein as a monomeric hairpin, solved using a novel combination of chemical shift and nuclear Overhauser effect (NOE)-based methods. This represents atomic resolution information for a full-length virus-coded ion channel, or "viroporin," whose essential functions represent a clinically proven class of antiviral target exploited previously for influenza A virus therapy. Specific drug-protein interactions validate an allosteric site on the channel periphery and its relevance is demonstrated by the selection of novel, structurally diverse inhibitory small molecules with nanomolar potency in culture. Hit compounds represent a 10,000-fold improvement over prototypes, suppress rimantadine resistance polymorphisms at submicromolar concentrations, and show activity against other HCV genotypes.

CONCLUSION

This proof-of-principle that structure-guided design can lead to drug-like molecules affirms p7 as a much-needed new target in the burgeoning era of HCV DAA.

Meta-analysis: the impact of IL28B polymorphisms on rapid and sustained virological response in HCV-2 and -3 patients

BACKGROUND

Recent studies suggested that IL28B polymorphisms may affect rapid and sustained virological response rates in HCV patients infected with genotype 2 or 3.

AIM

To assess the role of IL28B polymorphisms on the virological response in HCV-2 and -3 patients.

METHODS

We performed meta-analysis of studies evaluating the impact of rs12979860 and rs8099917 polymorphisms on rapid and sustained virological response in HCV-2 or -3 patients.

RESULTS

Twenty-three studies involving 3042 patients were included. The first meta-analysis evaluated the impact of rs12979860 polymorphism and included 1963 patients. When compared with rs12979860 CT/TT patients, CC patients had a higher rapid virological response rate (mean difference: 12.9%, 95% CI: 6.5-19.4%, P < 0.001) and a higher sustained virological response rate (mean difference: 4.9%, 95% CI: 0.1-9.8%, P = 0.046). The second meta-analysis evaluated the impact of rs8099917 polymorphism and included 2246 patients. When compared with rs8099917 TG/GG patients, TT patients had a higher rapid virological response rate (mean difference: 14.8%, 95% CI: 7.2-22.4%, P < 0.001) and a higher sustained virological response rate (mean difference: 5.5%, 95% CI: 0.4-10.6%, P = 0.033). When considering only patients treated for 24 weeks, results were unchanged. No potential sources of between-study heterogeneity were identified.

CONCLUSIONS

Favourable IL28B polymorphisms are associated with higher rapid and sustained virological response rates in HCV-2 and -3 patients. However, as the impact on a sustained response is very limited, it is unlikely that IL28B polymorphisms provide additional predictive value when considering other predictors of a sustained response.

Mechanism of function of viral channel proteins and implications for drug development

Viral channel-forming proteins comprise a class of viral proteins which, similar to their host companions, are made to alter electrochemical or substrate gradients across lipid membranes. These proteins are active during all stages of the cellular life cycle of viruses. An increasing number of proteins are identified as channel proteins, but the precise role in the viral life cycle is yet unknown for the majority of them. This review presents an overview about these proteins with an emphasis on those with available structural information. A concept is introduced which aligns the transmembrane domains of viral channel proteins with those of host channels and toxins to give insights into the mechanism of function of the viral proteins from potential sequence identities. A summary of to date investigations on drugs targeting these proteins is given and discussed in respect of their mode of action in vivo.

Impact of insulin resistance on sustained response in HCV patients treated with pegylated interferon and ribavirin: a meta-analysis

BACKGROUND & AIMS

Recent studies suggested that SVR rates might be lower in HCV patients with insulin resistance (IR) than in patients without IR, but the extent of the impact of IR on treatment response has not been established. We aimed to confirm the role of IR assessed by the homoeostasis model assessment (HOMA-IR) on SVR and to determine its magnitude.

METHODS

We performed meta-analysis of studies evaluating the impact of IR in HCV patients treated with pegylated interferon and ribavirin.

RESULTS

Fourteen studies involving 2732 patients were included. SVR was less frequent in patients with IR than in patients without IR (mean difference: -19.6%, 95% CI: -29.9% to -9.4%, p<0.001). In sensitivity analyses according to HCV-1 patients, patients with IR also less frequently attained a SVR than patients without IR (mean difference: -13.0%, 95% CI: -22.6% to -3.4%, p=0.008). In addition, the baseline HOMA-IR index was lower in responders than in non-responders (mean difference: -0.92, 95% CI: -1.53 to -0.32, p<0.001). In sensitivity analyses restricted to HCV-1 patients, the baseline HOMA-IR index remained lower in responders than in non-responders (mean difference: -0.63, 95% CI: -1.13 to -0.14, p<0.001).

CONCLUSIONS

HCV patients with IR have a 20% lower SVR than patients without IR. The baseline HOMA-IR index is a major determinant of SVR.

Efficacy of interferon-based antiviral therapy in patients with chronic hepatitis C infected with genotype 5: a meta-analysis of two large prospective clinical trials

The characteristics and response rate to pegylated interferon and ribavirin (PEG-INF + RBV) of patients with chronic hepatitis C infected with genotype 5 are poorly documented. A meta-analysis of two large phase III/IV prospective randomized clinical trials conducted in Belgium in patients with chronic hepatitis C (n = 1,073 patients) was performed in order to compare the response to antiviral therapy of hepatitis C virus (HCV) genotype 5 with that of other HCV genotypes. A subset of HCV-1 infected patients selected from within the study database were selected to match the HCV-5 sample for known prognostic factors. In Belgium HCV-5 is responsible for a significant minority of cases of chronic hepatitis C CHC (4.5%) and is characterized by a more advanced age (58.4 years), a high frequency of cirrhosis (27.7%), a specific mode of HCV acquisition, and a particular geographic origin (66.7% of patients from West Flanders). The primary comparative analysis showed that response to treatment with PEG-INF + RBV of HCV-5 is similar to HCV-1 and lower compared to HCV-2/3. The analysis of the matched patient subgroup demonstrates that the HCV-5 "intrinsic sensitivity" to PEG-IFN + RBV therapy is identical to HCV-1, with a sustained virological response of 55% in both groups. In contrast to previous publications, this meta-analysis suggests that HCV-5 response to treatment is closer to HCV-1 than to HCV-2/3 and suggests that in Belgium HCV-5 infection should be treated with the same antiviral regimen as HCV-1.

Resistance mutations define specific antiviral effects for inhibitors of the hepatitis C virus p7 ion channel

The hepatitis C virus (HCV) p7 ion channel plays a critical role during infectious virus production and represents an important new therapeutic target. Its activity is blocked by structurally distinct classes of small molecules, with sensitivity varying between isolate p7 sequences. Although this is indicative of specific protein-drug interactions, a lack of high-resolution structural information has precluded the identification of inhibitor binding sites, and their modes of action remain undefined. Furthermore, a lack of clinical efficacy for existing p7 inhibitors has cast doubt over their specific antiviral effects. We identified specific resistance mutations that define the mode of action for two classes of p7 inhibitor: adamantanes and alkylated imino sugars (IS). Adamantane resistance was mediated by an L20F mutation, which has been documented in clinical trials. Molecular modeling revealed that L20 resided within a membrane-exposed binding pocket, where drug binding prevented low pH-mediated channel opening. The peripheral binding pocket was further validated by a panel of adamantane derivatives as well as a bespoke molecule designed to bind the region with high affinity. By contrast, an F25A polymorphism found in genotype 3a HCV conferred IS resistance and confirmed that these compounds intercalate between p7 protomers, preventing channel oligomerization. Neither resistance mutation significantly reduced viral fitness in culture, consistent with a low genetic barrier to resistance occurring in vivo. Furthermore, no cross-resistance was observed for the mutant phenotypes, and the two inhibitor classes showed additive effects against wild-type HCV.

CONCLUSION

These observations support the notion that p7 inhibitor combinations could be a useful addition to future HCV-specific therapies.

Mixing the right hepatitis C inhibitor cocktail

Therapy for hepatitis C virus (HCV) infection is on the cusp of a new era. Until now, standard-of-care therapy has involved interferon (IFN) and ribavirin. With the first successful Phase III trials of specific targeted antiviral therapy for HCV (STAT-C) compounds, as well as three trials in progress giving the first glimpse of IFN-free combinations of STAT-C agents, this review looks ahead to the new classes of anti-HCV agents currently in clinical development. Successful pharmacologic control of HIV and TB frames the discussion, as well as consideration of the mutation frequency of HCV replication. Maximizing synergy between agents and minimizing cumulative toxicity will be critical to the design of future IFN-free STAT-C regimens.

Influence of amantadine on CD81 expression on lymphocytes in chronic hepatitis C

INTRODUCTION

Interferon alpha (IFN) down regulates CD81 expression on peripheral blood mononuclear cells (PBMC) in patients with chronic hepatitis C virus (HCV) infection. Aim of our study was to investigate whether amantadine alters IFN associated down regulation of CD81 expression on PBMC in patients with chronic hepatitis C.

METHODS

Nineteen patients with chronic HCV infection received peginterferon alpha-2a/ribavirin (SOC) for 48 weeks. Patients were randomised to 12 weeks amantadine therapy (n=12) or no additional treatment (n=7). FACS analysis of CD81 expression on CD4(+), CD8(+), CD19(+), and CD56(+) cells was performed at baseline, week (TW) 4, TW12, and TW24 of antiviral therapy.

RESULTS

A significant decline of CD81 expression was observed on CD4(+), CD8(+), and CD56(+) cells (p=0.011, p<0.001, p=0.015, respectively) but not on CD19(+) cells (p>0.2). CD81 expression on CD4(+), CD8(+), CD19(+), and CD56(+) cells was not different between patients treated with SOC plus amantadine and patients treated with SOC alone.

CONCLUSION

The current study confirms that CD81 expression is down regulated by SOC on CD4(+), CD8(+) and CD56(+) cells. Amantadine treatment was not associated with CD81 expression. Interaction between amantadine and CD81 is unlikely to be involved in potential antiviral activity of amantadine in chronic HCV infection.

A randomized controlled trial of double versus triple therapy with amantadine for genotype 1 chronic hepatitis C in Latino patients

BACKGROUND

With only a third of Latinos achieving sustained virologic response (SVR), there is a need for enhanced HCV treatment. Amantadine has been proposed to improve response rates in addition to standard therapy with peginterferon alpha and ribavirin. Our objective is to evaluate whether triple therapy with amantadine improves SVR rates in this special population.

METHOD

Treatment-naïve Latino subjects with HCV genotype 1 infection were randomized to receive peginterferon alpha-2a plus weight-based ribavirin for 48 weeks (double therapy) or the same regimen plus amantadine 200 mg daily (triple therapy). The primary endpoint was SVR. Predictors of liver fibrosis using APRI and Forns indices were also evaluated.

RESULTS

We enrolled 124 patients with chronic hepatitis C genotype 1. Sixty-three received conventional therapy and 61 patients had triple therapy with amantadine. SVR at week 72 was achieved in 25 patients (39.7%) vs. 26 patients (42.6%) in the double and triple regimen, respectively (p=0.561). After multivariate analysis, advanced fibrosis, obesity, and low pretreatment ALT levels were associated with non-response in both groups (p=0.0234, p=0.0012, p=0.0249, respectively). APRI values delimited an area under the ROC curve (AUROC) of 0.724 and Forns index with AUROC of 0.733. There was no difference between both indices in predicting significant fibrosis (Knodell index: F3-F4).

CONCLUSION

Our study demonstrates that the addition of amantadine to standard treatment of chronic HCV does not improve SVR rates in Latino patients with genotype 1. Further research to improve response rates in this special population is needed.

Ion channels as antivirus targets

Ion channels are membrane proteins that are found in a number of viruses and which are of crucial physiological importance in the viral life cycle. They have one common feature in that their action mode involves a change of electrochemical or proton gradient across the bilayer lipid membrane which modulates viral or cellular activity. We will discuss a group of viral channel proteins that belong to the viroproin family, and which participate in a number of viral functions including promoting the release of viral particles from cells. Blocking these channel-forming proteins may be "lethal", which can be a suitable and potential therapeutic strategy. In this review we discuss seven ion channels of viruses which can lead serious infections in human beings: M2 of influenza A, NB and BM2 of influenza B, CM2 of influenza C, Vpu of HIV-1, p7 of HCV and 2B of picornaviruses.

No beneficial effects of amantadine in treatment of chronic hepatitis C patients

BACKGROUND

Benefit of adding amantadine to antiviral therapy for hepatitis C is controversial.

AIMS

We aimed to examine whether such policy enhances sustained viral response in treatment-naïve patients.

METHODS

297 naïve hepatitis C patients were randomized for treatment with amantadine 200mg or placebo, combined with weight-based ribavirin and 12-day high-dose interferon alpha-2b induction therapy, followed by PEG-interferon alpha-2b (1.5 microg/kg/week up to 26 weeks and thereafter, 1.0 microg/kg/week until week 52). Treatment was discontinued if hepatitis C virus (HCV) RNA was positive at week 24.

RESULTS

49% of patients were (former) drug users. Genotype 1 occurred in 45%, high viral load in 70% and severe fibrosis/cirrhosis in 32%, without differences between amantadine or placebo groups. 90 patients prematurely discontinued treatment, mainly because of grade 3 or 4 toxicity. Intention-to-treat analysis revealed sustained viral response in 47% and 51% of amantadine and placebo groups (p=0.49). Amantadine did not enhance sustained viral response in patients with genotype 1 or high viral load nor did it improve primary non-response, breakthrough or relapse rates. Genotype non-1 and lower pre-treatment gamma GT levels were independent predictors for sustained viral response.

CONCLUSION

Adding amantadine to antiviral therapy of previously untreated chronic hepatitis C patients has no beneficial effects.

A novel Hepatitis C virus p7 ion channel inhibitor, BIT225, inhibits bovine viral diarrhea virus in vitro and shows synergism with recombinant interferon-alpha-2b and nucleoside analogues

The novel small molecule, BIT225 (N-[5-(1-methyl-1H-pyrazol-4-yl)-napthalene-2-carbonyl]-guanidine: CAS No. 917909-71-8), was initially identified using a screening strategy designed to detect inhibitors of Hepatitis C virus (HCV) p7 ion channel activity. Here we report that BIT225 has potent stand-alone antiviral activity against the HCV model pestivirus bovine viral diarrhea virus (BVDV) with an IC(50) of 314nM. Combinations of BIT225 with recombinant interferon alpha-2b (rIFNalpha-2b) show synergistic antiviral action against BVDV and the synergy is further enhanced by addition of ribavirin. Synergy was also observed between BIT225 and two nucleoside analogues known to inhibit the HCV RNA-dependent RNA polymerase. BIT225 has successfully completed a phase Ia dose escalating, single dose safety trial in healthy volunteers and a phase Ib/IIa trial to evaluate the safety and pharmacokinetics of repeated dosing for selected doses of BIT225 in HCV-infected persons. A modest, but statistically significant drop in patient viral load was detected over the 7 days of dosing (ref. www.biotron.com.au). Given the critical role of the p7 protein in the HCV life cycle and pathogenicity, our data indicate that molecules like BIT225, representing a new class of antiviral compounds, may be developable for therapeutic use against HCV infection, either as monotherapy, or in combination with other HCV drugs.

Clinical trial: a randomized trial of pegylated-interferon-alpha-2a plus ribavirin with or without amantadine in treatment-naïve or relapsing chronic hepatitis C patients

BACKGROUND

The combination therapy of pegylated-interferon-alpha2a plus ribavirin is considered as the standard of care for patients with chronic hepatitis C. A sustained viral response is obtained in 40-50% of naïve patients with genotype 1 and in around 80% of naïve patients with genotype 2 or 3.

AIM

To assess whether amantadine, added to the conventional combination therapy, could improve the treatment efficacy.

METHODS

In all, 630 patients (intent-to-treat population) with chronic hepatitis C were randomized into two groups: 316 patients (treatment group) received pegylated-interferon-alpha2a (180 microg once weekly) plus ribavirin (1000-1200 mg/daily) with amantadine (200 mg/daily); 314 patients (control group) received pegylated-interferon-alpha2a (180 microg once weekly) plus ribavirin (1000-1200 mg/daily) without amantadine. The duration of the treatment was 48 weeks for genotypes 1, 4, 5 and 6, and 24 weeks for genotypes 2 and 3.

RESULTS

There was no statistically significant difference between treatments groups for any of the variables tested for. Subgroups of patients likely to take advantage of the addition of amantadine were not identified.

CONCLUSIONS

This large study definitely excludes the role of amantadine in addition of conventional combination therapy in the treatment of chronic hepatitis C patients.

Determinants of hepatitis C virus p7 ion channel function and drug sensitivity identified in vitro

Hepatitis C virus (HCV) chronically infects 170 million individuals, causing severe liver disease. Although antiviral chemotherapy exists, the current regimen is ineffective in 50% of cases due to high levels of innate virus resistance. New, virus-specific therapies are forthcoming although their development has been slow and they are few in number, driving the search for new drug targets. The HCV p7 protein forms an ion channel in vitro and is critical for the secretion of infectious virus. p7 displays sensitivity to several classes of compounds, making it an attractive drug target. We recently demonstrated that p7 compound sensitivity varies according to viral genotype, yet little is known of the residues within p7 responsible for channel activity or drug interactions. Here, we have employed a liposome-based assay for p7 channel function to investigate the genetic basis for compound sensitivity. We demonstrate using chimeric p7 proteins that neither the two trans-membrane helices nor the p7 basic loop individually determines compound sensitivity. Using point mutation analysis, we identify amino acids important for channel function and demonstrate that null mutants exert a dominant negative effect over wild-type protein. We show that, of the three hydrophilic regions within the amino-terminal trans-membrane helix, only the conserved histidine at position 17 is important for genotype 1b p7 channel activity. Mutations predicted to play a structural role affect both channel function and oligomerization kinetics. Lastly, we identify a region at the p7 carboxy terminus which may act as a specific sensitivity determinant for the drug amantadine.

Genotype-dependent sensitivity of hepatitis C virus to inhibitors of the p7 ion channel

The hepatitis C virus (HCV) p7 protein plays a critical role during particle formation in cell culture and is required for virus replication in chimpanzees. The discovery that it displayed cation channel activity in vitro led to its classification within the "viroporin" family of virus-coded ion channel proteins, which includes the influenza A virus (IAV) M2 protein. Like M2, p7 was proposed as a potential target for much needed new HCV therapies, and this was supported by our finding that the M2 inhibitor, amantadine, blocked its activity in vitro. Since then, further compounds have been shown to inhibit p7 function but the relationship between inhibitory effects in vitro and efficacy against infectious virus is controversial. Here, we have sought to validate multiple p7 inhibitor compounds using a parallel approach combining the HCV infectious culture system and a rapid throughput in vitro assay for p7 function. We identify a genotype-dependent and subtype-dependent sensitivity of HCV to p7 inhibitors, in which results in cell culture largely mirror the sensitivity of recombinant protein in vitro; thus building separate sensitivity profiles for different p7 sequences. Inhibition of virus entry also occurred, suggesting that p7 may be a virion component. Second site effects on both cellular and viral processes were identified for several compounds in addition to their efficacy against p7 in vitro. Nevertheless, for some compounds antiviral effects were specific to a block of ion channel function.

CONCLUSION

These data validate p7 inhibitors as prototype therapies for chronic HCV disease. (HEPATOLOGY 2008;48:1779-1790.).

Placebo-controlled trial of 400 mg amantadine combined with peginterferon alfa-2a and ribavirin for 48 weeks in chronic hepatitis C virus-1 infection

The impact of amantadine on virologic response rates of interferon-based treatment of chronic hepatitis C is controversial. The aim of this study was to compare virological response rates in patients with chronic hepatitis C virus (HCV)-1 infection treated with 400 mg amantadine or placebo in combination with peginterferon alfa-2a (40 kD) and ribavirin for 48 weeks. Seven hundred four previously untreated chronically HCV-1-infected patients (mean age, 46 +/- 12 years) were randomized to (A) amantadine-sulphate (400 mg/day) (n = 352) or (B) placebo (n = 352), both in combination with 180 microg peginterferon alfa-2a once weekly and ribavirin (1000-1200 mg/day) for 48 weeks. End of treatment and sustained virological response after a 24-week follow-up period were assessed by qualitative reverse transcription polymerase chain reaction (RT-PCR) (sensitivity, 50 IU/mL). Demographic and baseline virological parameters were similar in both treatment groups. In groups A and B, 231 of 352 patients (66%) and 256 of 352 patients (72%) achieved an end of treatment response, and 171 of 352 patients (49 %) and 186 of 352 patients (53 %) a sustained virological response, respectively. On-treatment dropout rate in the amantadine group was significantly higher than in the placebo group (32% versus 23%; P = 0.01). However, adverse events and laboratory abnormalities were similar between both groups. Per-protocol analysis revealed similar sustained virological response rates in both treatment groups (53% versus 55%).

CONCLUSION

In this large placebo-controlled multicenter study, amantadine even at a dose of 400 mg/day did not improve virological response rates of peginterferon alfa-2a and ribavirin in patients with chronic genotype HCV-1 infection.

Distribution and dynamics of adamantanes in a lipid bilayer

The adamantanes are a class of compounds that have found use in the treatment of influenza A and Parkinson's disease, among others. The mode of action for influenza A is based on the adamantanes' interaction with the transmembrane M2 channel, whereas the treatment of Parkinson's disease is thought to relate to a channel block of N-methyl-D-aspartate receptors. An understanding of how these compounds interact with the lipid bilayer is thus of great interest. We used molecular-dynamics simulations to calculate the potential of mean force of adamantanes in a lipid bilayer. Our results demonstrate a preference for the interfacial region of the lipid bilayer for both protonated and deprotonated species, with the protonated species proving significantly more favorable. However, the protonated species have a large free-energy barrier in the center of the membrane. In contrast, there is no barrier (compared with aqueous solution) at the center of the bilayer for deprotonated species, suggesting that the permeant species is indeed the neutral form, as commonly assumed. We discuss the results with respect to proposed mechanisms of action and implications for drug-delivery in general.

Review article: novel therapeutic options for chronic hepatitis C

BACKGROUND

The efficacy of treatment against hepatitis C virus has improved, but it is still far from ideal. Thus, new antihepatitis C virus therapies are required.

AIM

To evaluate the data on antihepatitis C virus approaches beyond the current standard combination of pegylated interferon-alpha and ribavirin.

METHOD

We reviewed the available literature regarding novel antihepatitis C virus options, given alone or in combination with existing agents.

RESULTS

New interferons and ribavirin alternatives have been tried aiming to improve the efficacy and the safety/tolerability profile of standard agents. The hepatitis C virus polymerase and NS3/4A protease have been rather popular targets for new antihepatitis C virus agents. The combination of such inhibitors with pegylated interferon-alpha and ribavirin seems to act synergistically and to prevent viral resistance, compared to monotherapies. Several novel immunomodulators are currently evaluated and may be useful in combination therapies. Alternative strategies (inhibition of hepatitis C virus protein translation, assembly/release or binding) or agents with different modes of action (statins, S-adenosylmethionine and herbs) need further evaluation.

CONCLUSIONS

Many novel promising antihepatitis C virus agents are being developed, offering hope for future therapies that may target multiple points of the viral life cycle and/or host immune response. Newer approaches should ideally provide safe, effective and more tolerable therapy to all chronic hepatitis C virus patients.

Triple therapy of initial high-dose interferon with ribavirin and amantadine for patients with chronic hepatitis C

AIMS

We previously reported the potential effect of combination therapy of an initial high-dose interferon (IFN) and amantadine on the eradication of HCV-RNA in patients with chronic hepatitis C. The additive effects of amantadine on interferon and ribavirin combination therapy remain controversial. In this study we investigated the efficacy of initial high-dose IFN with ribavirin and amantadine on the virological response in patients with chronic hepatitis C with a high viral load of genotype 1b.

METHODS

Twenty-two patients with high viral loads of genotype 1b hepatitis C virus were enrolled in this pilot study. Patients were administered IFN-beta for four weeks and then IFN-alpha2b for 22 weeks with daily oral administration of ribavirin and amantadine.

RESULTS

A sustained virological response (SVR) was shown in 31.8% (seven of 22 patients). With the naïve patients, the SVR rate was 21.4% (three of 14 patients). In patients who could not eradicate HCV-RNA by previous IFN monotherapy, the SVR rate was 50% (four of eight patients).

CONCLUSION

Triple therapy with an initial high dose of IFN with ribavirin and amantadine may be effective, especially for chronic hepatitis C IFN-retreatment patients with a high viral load of genotype 1b.

Hepatology may have problems with putative surrogate outcome measures

A surrogate outcome measure is a laboratory measurement, a physical sign, or another intermediate substitute that is able to predict an intervention's effect on a clinically meaningful outcome. A clinical outcome detects how a patient feels, functions, or survives. Surrogate outcome measures occur faster or more often, are cheaper, and/or are less invasively achieved than the clinical outcome. In practice, validation is surprisingly often overlooked, especially if a biologic plausible rationale is proposed. Surrogate outcomes must be validated before use. The first step in validation is to demonstrate a correlation between the putative surrogate and the clinical outcome, e.g., the higher the surrogate the shorter time to death. However, a correlation is not sufficient to validate the surrogate. The second step is to establish if the intervention's effect on the surrogate outcome accurately predicts the intervention's effect on the clinical outcome. In hepatology a number of putative surrogate outcomes are used both in clinical research and in clinical practice without having been properly validated. Sustained virological response to interferons and ribavirin in patients with chronic hepatitis C, serum bilirubin concentration following ursodeoxycholic acid or immunosuppressants for patients with primary biliary cirrhosis, and nutritional outcomes following artificial nutrition for liver patients may not be valid surrogates for morbidity or mortality. The challenge is to develop reliable surrogates, both to facilitate the development of new interventions and to ensure our patients and us that these interventions are effective clinically.

Viral determinants of resistance to treatment in patients with hepatitis C

Chronic hepatitis C virus (HCV) infection affects more than 170 million persons worldwide and is responsible for the development of liver cirrhosis in many cases. Standard treatment with pegylated alpha interferon (IFN-alpha) in combination with the nucleoside analogue ribavirin leads to a sustained virologic response in approximately half of the patients. IFN-alpha is classified as an indirect treatment, as it interacts with the host's immune response. The mechanism of action of ribavirin is still unknown. The benefit of triple therapy by adding other antiviral agents, e.g., amantadine, is controversial. Currently, new direct antiviral drugs (HCV protease/polymerase inhibitors) are being evaluated in phase 1/phase 2 trials. Phenotypic resistance to antiviral therapy has been attributed to amino acid variations within distinct regions of the HCV polyprotein. While sensitivity to IFN-alpha-based antiviral therapy in vivo is clearly correlated with the number of mutations within the HCV NS5A protein, the underlying functional mechanisms for this association are unknown. In turn, in vitro, several mechanisms to circumvent the host immune defense or to block treatment-induced antiviral activities have been described for different HCV proteins. By the introduction of direct antiviral drugs, hepatitis C therapy now is entering a new era in which the development of resistance may become the most important parameter for treatment success or failure.

Induction doses of interferon-alpha-2a in combination with ribavirin and/or amantadine for the treatment of chronic hepatitis C in non-responders to interferon monotherapy: a randomized trial

The benefit of the triple therapy (interferon + amantadine + ribavirim) is still unknown. The efficacy of induction doses of interferon-alpha-2a monotherapy or in combination with ribavirin and/or amantadine was evaluated in interferon non-responders with chronic hepatitis C. A total of 378 patients were randomized. All the groups received the same doses and duration of interferon-alpha-2a: (i) interferon 9 MUI/day for 4 weeks and then 3 MUI/3 t.i.w. for 44 weeks (n = 53); (ii) interferon in combination with amantadine 100 mg twice daily for 48 weeks (n = 111); (iii) interferon in combination with ribavirin 1000-1200 mg (n = 106); (iv) interferon in combination with amantadine and ribavirin (n = 108). Baseline parameters were similar in the four groups. Sustained virological and biochemical responses were 13%, 6%, 18% and 22% respectively. No significant differences were found between double ribavirin arm vs triple therapy, but the difference was significant between interferon-amantadine (P = 0.008) and triple therapy (P = 0.0005). Hence, the induction doses of interferon in combination with ribavirin or ribavirin plus amantadine showed encouraging results in patients with chronic hepatitis C who were resistant to interferon. However, triple therapy is not superior to double.

Evidence for the formation of a heptameric ion channel complex by the hepatitis C virus p7 protein in vitro

The p7 protein of hepatitis C virus functions as an ion channel both in vitro and in cell-based assays and is inhibited by amantadine, long alkyl chain imino-sugar derivatives, and amiloride compounds. Future drug design will be greatly aided by information on the stoichiometry and high resolution structure of p7 ion channel complexes. Here, we have refined a bacterial expression system for p7 based on a glutathione S-transferase fusion methodology that circumvents the inherent problems of hydrophobic protein purification and the limitations of chemical synthesis. Rotational averaging and harmonic analysis of transmission electron micrographs of glutathione S-transferase-FLAG-p7 fusion proteins in liposomes revealed a heptameric stoichiometry. The oligomerization of p7 protein was then confirmed by SDS-PAGE and mass spectrometry analysis of pure, concentrated FLAG-p7. The same protein was also confirmed to function as an ion channel in suspended lipid bilayers and was inhibited by amantadine. These data validate this system as a means of generating high resolution structural information on the p7 ion channel complex.

A 2a/1b full-length p7 inter-genotypic chimeric genome of hepatitis C virus is infectious in vitro

The p7 protein of hepatitis C virus (HCV) functions as an ion channel in planar lipid bilayers, and its function is vital for the virus life cycle. In this study, we replaced either the entire or partial p7 of genotype 2a (strain JFH1), an HCV strain that replicates and produces virus progeny in vitro, with the corresponding regions of the p7 protein from genotype 1b (Australian isolate, HCV-A). Compared to wild type, the chimeric viruses reached their peak of infectivity with a delay but they produced a comparable titer to the wild type virus and the progeny viruses were able to infect naive permissive cells. Amantadine treatment of wild type and chimeric viruses reduced the virus titers by about 50% and 45%, respectively. Therefore, in this study, for the first time, we demonstrated that genotype 2a (JFH1 strain) genome encoding a full-length genotype 1b p7 gene produces infectious particles in vitro. These chimeric viruses are valuable instruments for comparative studies of the p7 proteins.

Optimizing Treatment Outcomes in Chronic Hepatitis C: Management of Non-Response

The overarching goal in treating chronic hepatitis C (CHC) is the prevention of serious hepatic complications such as cirrhosis, end-stage liver disease and hepatocellular carcinoma. Successful eradication of the hepatitis C virus has been shown to prevent liver disease progression and even promote regression of fibrosis. The treatment of CHC has improved significantly over the past decade with the introduction of interferons (IFNs), and more recently, pegylated IFNs. Up to two-thirds of all patients treated with a pegylated IFN combined with ribavirin can now achieve viral eradication if treated according to current guidelines. Despite this success rate, limited treatment options currently exist for the growing number of patients who do not respond to this combination, and those who have previously failed treatment with conventional IFN-based regimens. There are numerous host-and viral-related factors that can contribute to these outcomes. In addition, treatment insufficiency, whether due to treatment type, side effects or non-compliance, can result in inadequate antiviral pressure and a reduced likelihood of response. This review explores putative management strategies for patients who have previously failed to achieve a response to IFN-based therapy, and summarises retreatment options that have been, and are currently being evaluated.

A randomized trial of pegylated-interferon-alpha2a plus ribavirin with or without amantadine in the re-treatment of patients with chronic hepatitis C not responding to standard interferon and ribavirin

BACKGROUND

There is yet no established treatment for chronic hepatitis C patients non-responder to standard interferon and ribavirin.

AIM

To evaluate efficacy and safety of pegylated-interferon-alpha2a plus ribavirin with or without amantadine in such patients.

METHODS

161 non-responders to standard interferon and ribavirin were randomized into two groups: 81 patients (Group 1) were given weekly Peg-IFN-alpha2a 180 microg plus ribavirin 1,000-1,200 mg/daily for 12 months, 80 patients (Group 2) received weekly Peg-IFN-alpha2a 180 microg plus ribavirin 1,000-1,200 mg/daily and amantadine 200 mg/daily for 12 months.

RESULTS

At the end of follow-up, HCV-RNA was negative in 29.6% of Group 1 and in 21.2% of Group 2 patients (P = 0.22). Patients with genotypes 1 and 4 responded better to bi-therapy (21.7%) than to triple therapy (17.3%, P = 0.5) while among patients with genotypes 2 and 3 there was a trend towards a higher sustained virological response rate when retreated with triple treatment (80% vs. 75%, P = 0.82). On multivariate analysis, genotype 1 or 4, high body mass index and >20% reduction of Peg-interferon were associated with the treatment failure.

CONCLUSIONS

The addition of amantadine does not improve the overall SVR rate in non-responder patients retreated with Peg-IFN and ribavirin; however, about 30% of non-responders may achieve a sustained response, in particular patients with genotypes 2 and 3 show a high SVR (75%).

Triple antiviral therapy in HCV positive patients who failed prior combination therapy

AIM: To assess the efficacy of triple therapy (peginte-rferon or high dose standard interferon, plus ribavirin and amantadine) in nonresponders to prior combination therapy.

METHODS: A total of 196 patients were enrolled in a multicenter, open, randomized study. Patients were given 180 μg/wk of peginterferon-alpha-2a (40 kDa) plus ribavirin (800-1000 mg/d) and amantadine (200 mg/d) for 48 wk (group A) or interferon-alpha-2a (6 MU/d for 4 wk, 3 MU/d for 20 wk, and 3 MU tiw for 24 wk) plus ribavirin (800-1000 mg/d) and amantadine (200 mg/d) for 48 wk (group B).

RESULTS: Overall sustained virologic response (SVR) was 26.6% (32.1% and 19.5% in group A and B, P = 0.057). Baseline ALT >120 UI/L (OR 2.4; 95% CI:1.11 to 5.20; P = 0.026) and HCV RNA negativity after 12 wk (OR 8.7; 95% CI: 3.87 to 19.74; P < 0.0001) were independently associated with SVR. Therapy discontinuation occurred less frequently in patients treated with peginterferon than standard interferon (P = 0.036).

CONCLUSION: More than 25% of nonresponders to combination therapy can eradicate HCV infection when retreated with triple therapy, especially if they have a high baseline ALT and are treated with pegylated interferon.

Amino Acid Variations in Hepatitis C Virus P7 and Sensitivity to Antiviral Combination Therapy with Amantadine in Chronic Hepatitis C

Background

Formation of transmembrane ion channels by hepatitis C virus (HCV) p7 and abrogation of channel function by amantadine was demonstrated in vitro. The relevance of HCV p7 amino acid (aa) variations for response to antiviral therapy with amantadine is unknown.

Methods

HCV p7 was sequenced in 86 individuals who were infected with HCV genotype 1. Thirty-six of 86 patients received amantadine within an interferon-α (IFN-α)-based antiviral therapy. Helical wheel modelling for HCV p7 was performed.

Results

No significant correlation of overall aa variations within HCV p7 was observed with response to IFN-α-based therapy with amantadine in HCV genotype 1a/b infected patients. When analysis was restricted to non-conservative aa variations, a higher number of aa substitutions within complete HCV p7 and transmem-brane helix 2 was associated with non-response in HCV-1b-infected patients receiving therapy with amantadine ( P=0.015 and P=0.037, respectively), without amantadine ( P=0.106 and P=0.118, respectively), and in the total cohort of HCV-1b-infected patients ( P=0.00007 and P=0.011, respectively). Furthermore, substitution L20F was observed more often in non-responders than responders with HCV-1b infection and therapy with amantadine ( P=0.099). By in silico modelling, aa 20 was located toward the p7 channel lumen. Substitution L20F may impair amantadine action by altering the shape of the ion channel pore.

Conclusion

Substitution L20F within HCV p7 may be associated with non-response to combination therapy specifically with amantadine in HCV-1b-infected patients. Non-responders with HCV-1b infection showed higher numbers of non-conservative aa variations within HCV p7 than responders, irrespective of the application of amantadine.

Effect of Amantadine on Depressive Symptoms in Chronic Hepatitis C Patients Treated with Pegylated Interferon

OBJECTIVE

Assess the effect of amantadine on depressive symptoms during interferon alfa therapy for hepatitis C virus infection.

METHODS

We performed a randomized, controlled trial with 14 hepatitis C virus-infected patients, treated with pegylated interferon alfa-2a 180 microg/wk plus ribavirin 1.200 mg/d. Eight patients were randomized to receive amantadine 200 mg/d, and 6 other individuals were randomized to control group without amantadine. Severity of depression and anxiety was measured using the Hospital Anxiety and Depression Scale, before starting re-treatment, and 4, 12, and 24 weeks after immunotherapy with pegylated interferon alfa-2a. Evaluations were performed by psychiatrists blinded in reference to the state of amantadine treatment. Friedman chi(2) test for repeated measures and Mann-Whitney test for nonparametric data were used to assess significant differences.

RESULTS

From baseline to follow-up, no significant increase in mean Hospital Anxiety and Depression Scale scores of depressive symptoms were seen in amantadine group (P = 0.142), meanwhile there was a statistical increase of depression scores in the control group (P = 0.001).

CONCLUSIONS

Our randomized pilot study, though small, clearly indicates that interferon alfa-induced depressive symptoms can be prevented by the use of amantadine. However, double-blind placebo-controlled trials with a higher sample size are required to confirm these preliminary findings.

Novel approaches for therapy of chronic hepatitis C

Currently available anti-HCV therapy is effective in only half of the patients and limited by side effects that often necessitate discontinuation. Therefore, new treatment strategies are being developed including (i) the optimization of current regimens, (ii) the use of additional agents working via novel mechanisms, and (iii) anti-fibrotic strategies. Many new antiviral compounds are now being studied in preclinical and clinical trials. This review will focus on drugs that have already entered the stage of phase 2 or phase 3 studies.

Signal peptide cleavage and internal targeting signals direct the hepatitis C virus p7 protein to distinct intracellular membranes

The hepatitis C virus (HCV) p7 protein forms an amantadine-sensitive ion channel required for viral replication in chimpanzees, though its precise role in the life cycle of HCV is unknown. In an attempt to gain some insights into p7 function, we examined the intracellular localization of p7 using epitope tags and an anti-p7 peptide antibody, antibody 1055. Immunofluorescence labeling of p7 at its C terminus revealed an endoplasmic reticulum (ER) localization independent of the presence of its signal peptide, whereas labeling the N terminus gave a mitochondrial-type distribution in brightly labeled cells. Both of these patterns could be visualized within individual cells, suggestive of separate pools of p7 where the N and C termini differed in accessibility to antibody. These patterns were disrupted by preventing signal peptide cleavage. Subcellular fractionation revealed that p7 was enriched in a heavy membrane fraction associated with mitochondria as well as normal ER-derived microsomes. The complex regulation of the intracellular distribution of p7 suggests that p7 plays multiple roles in the HCV life cycle either intracellularly or as a virion component.