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      Hepatitis C Virus NS3/4A Protease Inhibitors: A Light at the End of the Tunnel

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          Abstract

          Hepatitis C virus (HCV) infection is a serious and growing threat to human health. The current treatment provides limited efficacy and is poorly tolerated, highlighting the urgent medical need for novel therapeutics. The membrane-targeted NS3 protein in complex with the NS4A comprises a serine protease domain (NS3/4A protease) that is essential for viral polyprotein maturation and contributes to the evasion of the host innate antiviral immunity by HCV. Therefore, the NS3/4A protease represents an attractive target for drug discovery, which is tied in with the challenge to develop selective small-molecule inhibitors. A rational drug design approach, based on the discovery of N-terminus product inhibition, led to the identification of potent and orally bioavailable NS3 inhibitors that target the highly conserved protease active site. This review summarizes the NS3 protease inhibitors currently challenged in clinical trials as one of the most promising antiviral drug class, and possibly among the first anti-HCV agents to be approved for the treatment of HCV infection.

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          Most cited references41

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          IL28B is associated with response to chronic hepatitis C interferon-alpha and ribavirin therapy.

          Hepatitis C virus (HCV) infects 3% of the world's population. Treatment of chronic HCV consists of a combination of PEGylated interferon-alpha (PEG-IFN-alpha) and ribavirin (RBV). To identify genetic variants associated with HCV treatment response, we conducted a genome-wide association study of sustained virological response (SVR) to PEG-IFN-alpha/RBV combination therapy in 293 Australian individuals with genotype 1 chronic hepatitis C, with validation in an independent replication cohort consisting of 555 individuals. We report an association to SVR within the gene region encoding interleukin 28B (IL28B, also called IFNlambda3; rs8099917 combined P = 9.25 x 10(-9), OR = 1.98, 95% CI = 1.57-2.52). IL28B contributes to viral resistance and is known to be upregulated by interferons and by RNA virus infection. These data suggest that host genetics may be useful for the prediction of drug response, and they also support the investigation of the role of IL28B in the treatment of HCV and in other diseases treated with IFN-alpha.
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            Peginterferon-alpha2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose.

            Treatment with pegylated interferon (peginterferon) and ribavirin for 48 weeks is more effective than conventional interferon and ribavirin in patients with chronic hepatitis C. To assess the efficacy and safety of 24 or 48 weeks of treatment with peginterferon-alpha2a plus a low or standard dose of ribavirin. Randomized, double-blind trial. 99 international centers. 1311 patients with chronic hepatitis C. Peginterferon-alpha2a, 180 microg/wk, for 24 or 48 weeks plus a low-dose (800 mg/d) or standard weight-based dose (1000 or 1200 mg/d) of ribavirin. Sustained virologic response: undetectable HCV RNA concentration at the end of treatment and during 12 to 24 weeks of follow-up. Overall and in patients infected with HCV genotype 1, 48 weeks of treatment was statistically superior to 24 weeks and standard-dose ribavirin was statistically superior to low-dose ribavirin. In patients with HCV genotype 1, absolute differences in sustained virologic response rates between 48 and 24 weeks of treatment were 11.2% (95% CI, 3.6% to 18.9%) and 11.9% (CI, 4.7% to 18.9%), respectively, between standard- and low-dose ribavirin. Sustained virologic response rates for peginterferon-alpha2a and standard-dose ribavirin for 48 weeks were 63% (CI, 59% to 68%) overall and 52% (CI, 46% to 58%) in patients with HCV genotype 1. In patients with HCV genotypes 2 or 3, the sustained virologic response rates in the 4 treatment groups were not statistically significantly different. Treatment with peginterferon-alpha2a and ribavirin may be individualized by genotype. Patients with HCV genotype 1 require treatment for 48 weeks and a standard dose of ribavirin; those with HCV genotypes 2 or 3 seem to be adequately treated with a low dose of ribavirin for 24 weeks.
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              Telaprevir with peginterferon and ribavirin for chronic HCV genotype 1 infection.

              Current therapy for chronic hepatitis C virus (HCV) infection is effective in less than 50% of patients infected with HCV genotype 1. Telaprevir, a protease inhibitor specific to the HCV nonstructural 3/4A serine protease, rapidly reduced HCV RNA levels in early studies. We randomly assigned patients infected with HCV genotype 1 to one of three telaprevir groups or to the control group. The control group (called the PR48 group) received peginterferon alfa-2a (180 microg per week) and ribavirin (1000 or 1200 mg per day, according to body weight) for 48 weeks, plus telaprevir-matched placebo for the first 12 weeks (75 patients). The telaprevir groups received telaprevir (1250 mg on day 1 and 750 mg every 8 hours thereafter) for 12 weeks, as well as peginterferon alfa-2a and ribavirin (at the same doses as in the PR48 group) for the same 12 weeks (the T12PR12 group, 17 patients) or for a total of 24 weeks (the T12PR24 group, 79 patients) or 48 weeks (the T12PR48 group, 79 patients). The primary outcome was a sustained virologic response (an undetectable HCV RNA level 24 weeks after the end of therapy). The rate of sustained virologic response was 41% (31 of 75 patients) in the PR48 group, as compared with 61% (48 of 79 patients) in the T12PR24 group (P=0.02), 67% (53 of 79 patients) in the T12PR48 group (P=0.002), and 35% (6 of 17 patients) in the T12PR12 group (this group was exploratory and not compared with the control group). Viral breakthrough occurred in 7% of patients receiving telaprevir. The rate of discontinuation because of adverse events was higher in the three telaprevir-based groups (21%, vs. 11% in the PR48 group), with rash the most common reason for discontinuation. Treatment with a telaprevir-based regimen significantly improved sustained virologic response rates in patients with genotype 1 HCV, albeit with higher rates of discontinuation because of adverse events. (ClinicalTrials.gov number, NCT00336479.) 2009 Massachusetts Medical Society
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                Author and article information

                Journal
                Viruses
                Viruses
                Molecular Diversity Preservation International (MDPI)
                1999-4915
                August 2010
                20 August 2010
                : 2
                : 8
                : 1752-1765
                Affiliations
                Institut de Recherche en Immunologie et en Cancérologie (IRIC), Montréal, Québec, H3T 1J4, Canada; E-Mails: laurent.chatel.chaix@ 123456umontreal.ca (L.C.-C.); martin.baril@ 123456umontreal.ca (M.B.)
                Author notes
                [†]

                These authors contributed equally to this work.

                [* ]Author to whom correspondence should be addressed; E-Mail: daniel.lamarre@ 123456umontreal.ca ; Tel.: +1-514-343-7127; Fax: +1-514-343-2165.
                Article
                viruses-02-01752
                10.3390/v2081752
                3185733
                21994705
                0522bd21-2bca-4585-ad08-5d04b9622599
                © 2010 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 3 June 2010
                : 12 August 2010
                : 18 August 2010
                Categories
                Review

                Microbiology & Virology
                antiviral therapy,hcv,hcv replicon,ns3 protease,protease inhibitor,clinical trial

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