Antiviral therapy for chronic hepatitis C in patients with inherited bleeding disorders: an international, multicenter cohort study

Summary. Background: Hepatitis C is a major co‐morbidity in patients with hemophilia. However, there is little information on the efficacy of antiviral therapy and long‐term follow‐up after treatment.Objectives: To assess the effect of interferon‐based (IFN‐based) therapy on hepatitis C virus (HCV) eradication, to identify determinants associated with treatment response, and to assess the occurrence of end‐stage liver disease (ESLD) after completing antiviral therapy.Patients and methods: In a multicenter cohort study, 295 treatment‐naïve hemophilia patients chronically infected with HCV were included. The effect of therapy was expressed as sustained virological response (SVR). Determinants associated with treatment response were expressed as odds ratios (ORs). Cumulative incidence of ESLD was assessed using a Kaplan–Meier survival table.Results: Among human immunodeficiency virus (HIV) negative patients (n = 235), SVR was 29% (29/101) for IFN monotherapy, 44% (32/72) for IFN with ribavirin, and 63% (39/62) for pegylated IFN (PegIFN) with ribavirin. In patients co‐infected with HIV (n = 60), IFN monotherapy, IFN with ribavirin, and PegIFN with ribavirin eradicated HCV in 7/35 (20%), 1/2 (50%), and 11/23 (48%), respectively. SVR increased with genotype 2 and 3 [OR 11.0, 95% CI: 5.8–20.5], and combination therapy (IFN and ribavirin OR 3.7, 95% CI: 1.7–8.4), PegIFN and ribavirin (OR 4.2, 95% CI: 1.8–9.5). Up to 15 years after antiviral treatment, none of the patients with a SVR relapsed and none developed ESLD. In contrast, among unsuccessfully treated patients the cumulative incidence of ESLD after 15 years was 13.0%.Conclusions: Successful antiviral therapy appears to have a durable effect and reduces the risk of ESLD considerably.     

New therapies for chronic hepatitis C infection: a systematic review of evidence from clinical trials

Introduction: Hepatitis C virus (HCV) affects approximately 3% of the world population. The current standard of care for treatment of HCV is a combination of pegylated interferon and ribavirin. Approximately 10% of patients will stop treatment and 30% of patients require dose reduction because of side effects. For genotype 1 HCV‐infected patients, only 40% of patients will achieve undetectable viral load 26 weeks posttreatment. Aims: The objectives of this review were to identify new treatments that are in clinical trials. These include boceprevir and telaprevir which are in routine clinical use and form part of the American Association for the Study of Liver Diseases (AASLD) 2011 guidelines as well as drugs based on observational studies, improving/modifying ribavirin or interferon‐based therapies, modifying the host response and finally the use of direct‐acting antiviral agents (DAA). Materials and methods: MEDLINE and EMBASE databases were searched from 2008 to 2011 for treatments for hepatitis C. Furthermore, abstracts and poster presentations for the annual European Association Study of the Liver, AASLD, Digestive Disease Week and Asian Pacific Association for the study of the Liver were searched for relevant material. Results: All four classes of DAA; NS3/NS4a serine protease inhibitors, cyclophilin inhibitors, NS5b polymerase inhibitors and NS5a inhibitors, show good success rates. Trials have been performed without ribavirin or interferon and demonstrate good antiviral activity with a decreased side effect profile. Combinations of DAA are a promising area of research with a high success rate. Conclusions: Clinical trials show that future HCV therapy could be personalised, achieve higher success rates with decreased adverse incidents.     

Overview of the PROVE studies evaluating the use of telaprevir in chronic hepatitis C genotype 1 patients

Current treatment for genotype 1 HCV infection with pegylated interferon (PEG IFN) and ribavirin (RBV) is effective in less than 50% of patients. The advent of direct-acting antiviral agents that target replication of HCV promises to improve therapy for the disease. Telaprevir is a new peptidomimetic serine protease inhibitor that specifically targets the NS3/4a HCV serine protease to cause rapid reduction in HCV RNA levels. Three Phase II Protease Inhibition for Viral Evaluation (PROVE) studies have assessed the efficacy and safety of telaprevir in genotype 1 patients. The studies examined sustained virological response (SVR) rates and also the adverse events related to the use of this drug in different groups. The results of these studies suggested that the addition of this specific protease inhibitor to PEG IFN alfa-2a and RBV can significantly improve the results of treatment in patients affected with chronic HCV infection with genotype 1, when compared with the standard treatment, PEG IFN alfa-2a and RBV alone. The key observations in these Phase II trials of telaprevir were higher rate of SVR above current standard of care (61-69% for T12PR24 treatment-naive patients compared with 46-48% for standard of care in naive patients). Low rates of relapse were observed in T12PR24-treated patients (2-14% vs 22-23%). The studies suggest that the duration of treatment could be reduced for rapidly responsive naive patients from 48 to 24 weeks while maintaining improved SVR rates. RBV remains an essential component of treatment with protease inhibitors combined with PEG IFN. The main adverse reactions of note with its use were rashes, anemia and nausea.     

Implications of finding synergic in vitro drug-drug interactions between interferon-alpha and ribavirin for the treatment of hepatitis C virus

Hepatitis C virus (HCV) infections are currently treated using a combination of interferon-alpha (IFN-alpha) and ribavirin (RBV). If IFN-alpha is utilized alone, the sustained virological response (SVR) rate is approximately 20%, whereas when RBV is used alone it does not lead to an SVR. However, when IFN-alpha and RBV are used together, the combination leads to an SVR rate of approximately 40%. This clinical synergy is thought to be due to the direct antiviral effects of RBV, or to indirect effects of RBV that stimulate the immune response. Evidence for either hypothesis is limited. Recently, we undertook an in vitro drug-drug combination analysis using surrogate model systems of HCV replication and found a reproducible synergy of antiviral effects between the two drugs at physiologically relevant drug concentrations. Our findings provide experimental support for the contention that the direct effects of these drugs' antiviral activity are responsible for the clinical synergy observed in patients.     

Non-nucleoside inhibitors of the HCV polymerase

Chronic hepatitis C virus (HCV) infection is the leading cause of chronic liver disease. Current therapy using pegylated interferon-alpha with ribavirin is poorly tolerated and confers an overall sustained virological response around 56%. Compounds exhibiting an improved safety profile with similar or enhanced antiviral properties may represent future treatment options. Several drug discovery programmes are ongoing to directly target the viral enzymes involved in HCV replication. Recent clinical success using a peptidomimetic inhibitor of the viral serine protease has demonstrated proof-of-concept for the use of direct antiviral agents in reducing viral load. The RNA-dependent RNA polymerase (RdRp) of HCV is also required for viral RNA replication and thus represents an attractive drug discovery target. Preclinical characterization of several non-nucleoside inhibitors (NNIs) of the HCV RdRp have been described, including a promising series of benzothiadiazine derivatives which have been shown to efficiently block viral RNA synthesis in HCV replicon cell systems. Herein, the antiviral activity, mode of action, resistance profiling and therapeutic potential of the benzothiadiazine class of compounds for clinical development are explored.     

Nouveaux traitements de l’infection chronique par le virus de l’hépatite C

Treatment of hepatitis C virus (HCV) infection by the combination of pegylated interferon and ribavirin has been the standard of care since 1998 and has helped to achieve a sustained virologic response (SVR) in more than 50% of patients with chronic infection. SVR represents a complete recovery from the infection, but more than 50% of genotype-1-infected patients do not achieve SVR. Progress in the understanding of the viral cycle and the characterization of the viral enzymes which are possible targets have resulted in the development of new molecules including direct-acting antivirals targeted against HCV with specificity for either genotype-1 (protease inhibitors NS3/NS4A) or wider spectrum (NS5A inhibitors, polymerase inhibitors NS5B or entry inhibitors), and nonspecific antivirals (new interferons, cyclophilin inhibitors). We review the results of phase III trials, which have clearly shown a 20% to 30% increase in the SVR rate of genotype-1-infected patients, both naive and who have received previous treatments. These new drugs have been approved at the end of 2011, after an early compassionate access to cirrhotic patients who have experienced a previous relapse or partial response to the combination therapy. In the future, the main limitations of the triple therapy will be safety against adverse effects (including skin rash and anemia, which may be easily controlled), cost, adherence, viral resistances, and drug-drug interactions that we have to avoid by therapeutic education of patients and physicians.     

Prediction of sustained virological response by ribavirin plasma concentration at week 4 of therapy in hepatitis C virus genotype 1 patients

BACKGROUND: Pegylated interferon/ribavirin combination is currently the standard treatment for chronic hepatitis C virus (HCV) infection. Body weight adjustment of ribavirin is crucial for response. However, previous studies found no relation between ingested dose and plasma concentration. The aim of this study was to define the ribavirin trough plasma concentration at week 4 (W4) associated with sustained virological response (SVR). METHODS: Thirty-one HCV genotype 1 patients (8 naive and 23 non-responders to a previous pegylated interferon/ribavirin therapy) were treated with pegylated interferon/ribavirin and assessed by HPLC for ribavirin plasma concentration at W4. RESULTS: Eleven patients (35%) achieved SVR, whereas 20 (65%) were non-responders. The median ribavirin plasma concentration at W4 (1.90 mg/l) varied from 1.62 mg/l in patients with subsequent non-response to 2.28 mg/l in sustained responders (P=0.007). Receiver operating characteristic curve analysis indicated that the 2.01 mg/l threshold gave the best sensitivity and specificity (73% and 80%, respectively, area under the curve =0.80; P=0.007). Sixty-seven percent of patients with median ribavirin plasma concentration >2 mg/l achieved SVR versus only 16% below this level (P=0.007). Multivariate regression analysis indicated that a ribavirin plasma concentration >2 mg/l at W4 was associated with SVR independent of gender, age, weight, baseline viral load and response to previous therapy. CONCLUSION: These results, which remain to be confirmed in large clinical trials, highlight the potential relevance of ribavirin plasma level monitoring at an early stage of treatment. This monitoring could be of help in guiding antiviral therapy by offering dose adjustment in patients with ribavirin plasma level below the 2 mg/l threshold.     

Improving anti-hepatitis C virus therapy

The estimated prevalence of hepatitis C virus (HCV) infection is 2%, representing 123 million infected individuals worldwide. HCV infection burdens public health in relation to hepatic (cirrhosis and its complications in 20% of patients) and extrahepatic (vasculitis) complications, and lessens quality of life. Major progress has been made in the last two decades for the diagnosis and treatment of HCV, including more appropriate screening strategies for HCV infection (improved sensitivity of serological and virological tests); a better evaluation of the impact of chronic HCV infection on the liver (semi-quantitative scoring systems of necro-inflammation and fibrosis on liver biopsy, non-invasive evaluation of fibrosis with biochemical markers and elastometry); and improved therapeutic regimens. This progress provides a better definition of who to treat (clinical impact or significant fibrosis); how to treat; tailoring therapies for doses and durations of the pegylated interferon plus ribavirin combination according to virological (mainly genotype and early viral kinetics, but also baseline viral load) and hosts factors (fibrosis, immune status, weight); and how to monitor efficacy and tolerance of therapy. The progress has now resulted in a 50% rate of complete HCV eradication, ranging 45 - 90% according to the genotype and especially in those patients with early viral response. New therapies, specifically HCV protease or polymerase inhibitors, in combination with pegylated interferon, or more potent and less toxic new formulations of interferons or ribavirin, will increase these encouraging results in the future.     

Improving anti-hepatitis C virus therapy

The estimated prevalence of hepatitis C virus (HCV) infection is 2%, representing 123 million infected individuals worldwide. HCV infection burdens public health in relation to hepatic (cirrhosis and its complications in 20% of patients) and extrahepatic (vasculitis) complications, and lessens quality of life. Major progress has been made in the last two decades for the diagnosis and treatment of HCV, including more appropriate screening strategies for HCV infection (improved sensitivity of serological and virological tests); a better evaluation of the impact of chronic HCV infection on the liver (semi-quantitative scoring systems of necro-inflammation and fibrosis on liver biopsy, non-invasive evaluation of fibrosis with biochemical markers and elastometry); and improved therapeutic regimens. This progress provides a better definition of who to treat (clinical impact or significant fibrosis); how to treat; tailoring therapies for doses and durations of the pegylated interferon plus ribavirin combination according to virological (mainly genotype and early viral kinetics, but also baseline viral load) and hosts factors (fibrosis, immune status, weight); and how to monitor efficacy and tolerance of therapy. The progress has now resulted in a 50% rate of complete HCV eradication, ranging 45 – 90% according to the genotype and especially in those patients with early viral response. New therapies, specifically HCV protease or polymerase inhibitors, in combination with pegylated interferon, or more potent and less toxic new formulations of interferons or ribavirin, will increase these encouraging results in the future.     

Boceprevir: an oral protease inhibitor for the treatment of chronic HCV infection

Chronic hepatitis C (CHC) virus infection affects more than 170 million people globally. The aim of treatment of CHC is to affect sustained elimination of the virus (a sustained virological response [SVR]). The success and duration of therapy with interferon is dependent on HCV genotype. The current standard of care comprises combined treatment with pegylated interferon and ribavirin. Rates of SVR in patients with genotype 1 infection, the least responsive group, are less than 50%. Boceprevir is a ketoamide protease inhibitor that binds reversibly to the HCV nonstructural NS3 protease active site inhibiting intracellular viral replication. Phase III clinical studies have demonstrated that, in combination with the current standard of care, boceprevir significantly increases the SVR rate in both treatment-naive and previously treated patients with genotype 1 CHC. Both the US FDA and EMA have approved boceprevir for the treatment of genotype 1 CHC: the first directly-acting antiviral drug to be licensed for this indication. This article will review the pharmacology and pharmacodynamics of boceprevir, the efficacy and safety of the drug, and explore possible future developments in the management of CHC.     

A case of successful treatment with telaprevir-based triple therapy for hepatitis C infection after treatment failure with vaniprevir-based triple therapy

Recently direct-acting antiviral agents, such as hepatitis C virus (HCV) non-structural 3/4A (NS3/4A) protease inhibitors (PI), have been introduced, and triple therapy regimens that include PI with conventional pegylated interferon α and ribavirin have significantly improved the sustained virological response (SVR) rate, up to 80% for both treatment-naïve and treatment-experienced patients with HCV genotype 1. We here report for the first time a case of the successful treatment of HCV genotype 1 infection with a first generation PI drug (telaprevir) based triple therapy after treatment failure with a second generation PI drug (vaniprevir) based triple therapy. A 67-year-old treatment-naïve Japanese man with HCV genotype 1b infection took part in a phase III clinical trial of vaniprevir-based triple therapy. His serum HCV RNA had become undetectable at week 2 and SVR was highly expected, but HCV RNA reappeared at week 4 after vaniprevir treatment. Polymerase chain reaction direct sequence of the HCV NS3/4A gene at week 8 after vaniprevir treatment showed the emergence of a vaniprevir-resistance mutation (D168V), the probable reason for the treatment failure. Six months later, retreatment with telaprevir-based triple therapy was started. Although the dosages of telaprevir and ribavirin had to be reduced due to severe anemia, the patient achieved an SVR. This case shows the value of repeating PI-based triple therapy with a different drug, a process that would reduce the chance of drug resistant mutation.     

Treatment options for nonresponders and relapsers to initial therapy for hepatitis C

As treatment for chronic hepatitis C virus (HCV) infection has advanced over the past decade, efforts have evolved to retreat patients who did not achieve a sustained virologic response to previous antiviral regimens. Retreating nonresponders to interferon alfa monotherapy with a combination of interferon and ribavirin yields a sustained virologic response in 9% to 32% of patients, whereas retreatment with peginterferon alfa plus ribavirin yields a sustained virologic response in up to 30% to 40% of patients. Sustained virologic response is more likely in retreated patients with HCV genotype 2 or 3, low serum HCV RNA levels, and lack of response to prior interferon monotherapy. Retreatment of nonresponders to interferon-ribavirin combination therapy is associated with lower response rates (< or = 20%). Despite treatment advances, the efficacy of current antiviral regimens for nonresponders remains inadequate. The next few years will see more-targeted antiviral regimens for these patients and therapies focused on slowing the progression of liver disease rather than viral eradication.     

New antiviral therapies in the management of HCV infection

Improved knowledge of the HCV life cycle and of structural features of HCV proteins have led to the discovery of numerous potential targets for antiviral therapy. Viral replication and polyprotein processing have been tagged as promising viral targets. Clathrin-mediated endocytosis, fusion of HCV with cellular membranes, translation of viral RNA, virus production and release as well as several host cell factors may provide alternative targets for future anti-HCV therapies. Several compounds are currently under investigation in clinical trials and showed high antiviral activity in patients with chronic hepatitis C. Recently, Phase III studies for two protease inhibitors, telaprevir and boceprevir, each given in combination with pegylated interferon (standard of care [SOC]), were completed. In HCV-genotype-1-infected patients, the addition of telaprevir or boceprevir to SOC increased sustained virological response rates from <50% to >70%. Nucleoside/nucleotide inhibitors of the HCV NS5B polymerase have shown antiviral activity against different HCV genotypes, and have a higher barrier to resistance than protease inhibitors. In addition, several allosteric binding sites have been identified for non-nucleoside inhibitors of the NS5B polymerase. Inhibitors of NS5A are potentially active against all HCV genotypes. Among the different host cell-targeting compounds, cyclophilin inhibitors have shown promising results. Future hope lies in the combination of direct-acting antiviral agents with the possibility of interferon-free treatment regimens.     

Dasabuvir (ABT333) for the treatment of chronic HCV genotype I: a new face of cure,an expert review

Hepatitis C virus (HCV) affects nearly 1.3% of US population and around 2% of people worldwide. It is associated with serious complication of Cirrhosis and Hepatocellular carcinoma leading to significant morbidity and mortality. Until now the only treatment option for this serious disease was interferon based therapy which had poor tolerance and at best SVR (Sustained virological response) in only 50% of cases. With the introduction of other direct – acting antiviral agents the treatment of HCV has been revolutionized with significantly high rates of cure. Among novel Direct acting antivirals are non-nucleoside inhibitor NS5B which is highly effective in treatment of HCV genotype 1 a and 1b including those with compensated cirrhosis achieving high cure rates with SVR more than 97 % in pooled analysis from six different phase 3 trials. This review will discuss the DAA – Dasabuvir, a non – nucleoside NS5B inhibitor, its mechanism of action, efficacy, safety & tolerance, and drug resistance. Dasabuvir is approved by FDA in combination with other DAA agents called as the 3D(Viekira Pak) in various interferon free regimens achieving high cure rates (SVR >95%) with low adverse effects. In Europe, it is approved by European medicines agency for use in combination with Ombitasvir, Paritaprevir, and ritonavir with or without ribavirin. The drug is used in treatment naive as well as previously treated patient with high success rates. It is also approved in patients with compensated cirrhosis, patients with HIV co-infection and liver transplant recipients which were in the past were excluded from treatment with interferon based therapy. Dasabuvir is extensively evaluated in large clinical trials and shown excellent SVR among HCV genotype1 patient population in combination with other oral DAAs, with good safety profile and tolerance. Its drawback is its genotype restriction, need for ribavirin (RBV) for 1a genotype, low resistance barrier and high cost. It is well tolerated with less than 1 % of patients permanently discontinuing treatment and 2% of patient experiencing a serious adverse reaction. It is contraindicated in patients with known hypersensitivity to ritonavir (e.g. Steven – Johnson syndrome) and strong inducers of CYP3A and CYP2CB.     

MK-5172, a selective inhibitor of hepatitis C virus NS3/4a protease with broad activity across genotypes and resistant variants

HCV NS3/4a protease inhibitors are proven therapeutic agents against chronic hepatitis C virus infection, with boceprevir and telaprevir having recently received regulatory approval as add-on therapy to pegylated interferon/ribavirin for patients harboring genotype 1 infections. Overcoming antiviral resistance, broad genotype coverage, and a convenient dosing regimen are important attributes for future agents to be used in combinations without interferon. In this communication, we report the preclinical profile of MK-5172, a novel P2-P4 quinoxaline macrocyclic NS3/4a protease inhibitor currently in clinical development. The compound demonstrates subnanomolar activity against a broad enzyme panel encompassing major hepatitis C virus (HCV) genotypes as well as variants resistant to earlier protease inhibitors. In replicon selections, MK-5172 exerted high selective pressure, which yielded few resistant colonies. In both rat and dog, MK-5172 demonstrates good plasma and liver exposures, with 24-h liver levels suggestive of once-daily dosing. When administered to HCV-infected chimpanzees harboring chronic gt1a or gt1b infections, MK-5172 suppressed viral load between 4 to 5 logs at a dose of 1 mg/kg of body weight twice daily (b.i.d.) for 7 days. Based on its preclinical profile, MK-5172 is anticipated to be broadly active against multiple HCV genotypes and clinically important resistance variants and highly suited for incorporation into newer all-oral regimens.     

Treatment of chronic hepatitis C in southern Taiwan

Chronic hepatitis C virus (HCV) infection may lead to cirrhosis and hepatocellular carcinoma. Interferon (IFN)-alpha is effective in the treatment of chronic hepatitis C. The rate of response to IFN is enhanced by increasing the IFN dose. Extending the treatment duration can reduce the relapse rate. Addition of ribavirin to IFN increases the sustained virological response (SVR). Thus, combination therapy with IFN and ribavirin was adopted for the treatment of chronic hepatitis C in Kaohsiung Medical University Hospital in 1998. Approximately 60% of patients receiving IFN/ribavirin therapy gained SVR. IFN 6 million units three times per week combined with daily ribavirin for 6 months achieved SVR more frequently than combination therapy with 3 million units. Factors for SVR in these combination regimens were HCV genotype, viral load and early virological response. Long-term follow-up of patients treated with IFN has shown that SVR might reduce the risk of progression to cirrhosis and hepatocellular carcinoma. Pegylated (peg)-IFN has a longer half-life and better efficacy. Combination therapy with peg-IFN and ribavirin accomplished higher SVR than conventional IFN and ribavirin. A multicenter clinical trial was conducted in Taiwan to compare the efficacy of combination therapy between peg-IFN/ribavirin and conventional IFN/ribavirin for 6 months. SVR was higher in patients receiving peg-IFN and ribavirin, especially in those infected with HCV genotype 1b. Based on the results obtained, the national health insurance started to sponsor the combination therapy in October 2003, with a suggested duration for 6 months. Some small-scale studies in Taiwan have postulated higher SVR for treatment duration of 12 than of 6 months in patients with genotype 1b. Further investigation should be conducted in the near future.     

Antiviral Chemistry & Chemotherapy's current antiviral agents FactFile 2008 (2nd edition): RNA viruses

Among the RNA viruses, other than the retroviruses (that is, HIV), which are dealt with separately in the current FactFile, the most important targets for the development of antiviral agents at the moment are the orthomyxoviruses (that is, influenza), the hepaciviruses (that is, hepatitis C virus [HCV]) and, to a lesser extent, the picornaviruses. Although the uncoating inhibitors amantadine and rimantadine were the first known inhibitors of influenza A, the neuraminidase inhibitors oseltamivir, zanamivir and peramivir have now become the prime antiviral drugs for the treatment of influenza A and B virus infections. For HCV infections, standard treatment consists of the combination of pegylated interferon-alpha with ribavirin, but several other antivirals targeted at specific viral functions such as the HCV protease and/ or polymerase may be expected to soon take an important share of this important market. Still untapped is the potential of a variety of uncoating inhibitors, as well as protease and/or polymerase inhibitors against the wide spectrum of picornaviruses. While ribavirin has been available for 35 years as a broad-spectrum anti-RNA virus agent, relatively new and unexplored is favipiravir (T-705) accredited with activity against influenza as well as flaviviruses, bunyaviruses and arenaviruses.     

Hepatitis C virus/human immunodeficiency virus coinfection in hemophiliacs: high rates of sustained virologic response to pegylated interferon and ribavirin therapy

Summary. Background: Progression of chronic hepatitis C virus (HCV) infection to end‐stage liver disease is accelerated in patients coinfected with human immunodeficiency virus (HIV). HCV/HIV‐coinfected hemophiliacs are no exception. Although eradication of HCV with pegylated interferon (Peg‐IFN) plus ribavirin (Rbv) is the only approach to halt the progression of liver disease, the rates of sustained virologic response (SVR) in coinfected patients are attenuated as compared with those in HCV‐monoinfected patients. Nonetheless, in HCV‐infected hemophiliacs, who are considered to constitute a difficult‐to‐treat population, current treatment strategies yielded rates of SVR similar to those obtained in non‐hemophiliacs. Objectives and patients: In this open‐label, prospective, multicenter study, the efficacy and safety of therapy with Peg‐IFNα2a plus Rbv was evaluated in 34 HCV/HIV‐coinfected adult hemophiliacs naive to previous antiviral therapy. Methods: Peg‐IFNα2a was administered at a dose of 180 μg subcutaneously once‐weekly plus oral Rbv 1000–1200 mg day^?1 for 48 weeks, irrespective of HCV genotype. Results: All but one patient (3%) completed the study, 15 (44%) achieved an SVR, and 13 (38%) required dose reduction of either drug. A rapid virologic response (HCV‐RNA clearance at week 4; P = 0.01), a complete early virologic response (HCV RNA clearance at week 12; P = 0.005) and absence of cirrhosis (P = 0.04) were independent predictors of SVR. During a median post‐treatment follow‐up of 3 years, a steady increase in CD4+ cell count and CD4+/CD8+ cell ratio was observed in SVR patients. Conclusions: These results strongly support the use of anti‐HCV therapy in HCV/HIV‐coinfected hemophiliacs.     

Preclinical Profile and Characterization of the Hepatitis C Virus NS3 Protease Inhibitor Asunaprevir (BMS-650032)

Asunaprevir (ASV; BMS-650032) is a hepatitis C virus (HCV) NS3 protease inhibitor that has demonstrated efficacy in patients chronically infected with HCV genotype 1 when combined with alfa interferon and/or the NS5A replication complex inhibitor daclatasvir. ASV competitively binds to the NS3/4A protease complex, with K(i) values of 0.4 and 0.24 nM against recombinant enzymes representing genotypes 1a (H77) and 1b (J4L6S), respectively. Selectivity was demonstrated by the absence of any significant activity against the closely related GB virus-B NS3 protease and a panel of human serine or cysteine proteases. In cell culture, ASV inhibited replication of HCV replicons representing genotypes 1 and 4, with 50% effective concentrations (EC(50)s) ranging from 1 to 4 nM, and had weaker activity against genotypes 2 and 3 (EC(50), 67 to 1,162 nM). Selectivity was again demonstrated by the absence of activity (EC(50), >12 μM) against a panel of other RNA viruses. ASV exhibited additive or synergistic activity in combination studies with alfa interferon, ribavirin, and/or inhibitors specifically targeting NS5A or NS5B. Plasma and tissue exposures in vivo in several animal species indicated that ASV displayed a hepatotropic disposition (liver-to-plasma ratios ranging from 40- to 359-fold across species). Twenty-four hours postdose, liver exposures across all species tested were ≥110-fold above the inhibitor EC(50)s observed with HCV genotype-1 replicons. Based on these virologic and exposure properties, ASV holds promise for future utility in a combination with other anti-HCV agents in the treatment of HCV-infected patients.     

Antiviral treatment of hepatitis C: present status and future prospects

Hepatitis C virus (HCV) infection is a major cause of chronic hepatitis. A substantial proportion of patients with chronic hepatitis C eventually develop hepatocellular carcinoma (HCC), which is one of the leading causes of death worldwide. Therefore, efficient antiviral treatments for HCV have long been needed. A recently developed combination therapy of pegylated interferon and ribavirin has dramatically improved the outcome of antiviral therapy for HCV infection. In genotype 1b HCV infection, 48 weeks of the combination therapy achieved eradication of the virus in 50% of patients, and in genotype 2 HCV infection, 24 weeks of the therapy resulted in viral eradication in 80%–90% of patients. By this eradication, an improvement in the hepatic fibrosis, an inhibition of HCC development, and an improvement in life expectancy were attained. Patients who did not respond to the combination therapy may be treated with long-term interferon monotherapy, which is not intended to eradicate HCV, but will lower the serum alanine aminotransferase (ALT) level. Thus, the treatment for HCV infection has progressed significantly, but therapies with new modalities, such as inhibitors of viral protease or RNA polymerase, are still being awaited.