Boceprevir for previously treated chronic HCV genotype 1 infection

Treating hepatitis C: current standard of care and emerging direct-acting antiviral agents

Summary.  During the late 1990s and early 2000s, major advances were made in the treatment of patients with chronic hepatitis C virus (HCV) infection. Interferon, combination interferon plus ribavirin (RBV) and pegylated interferon plus RBV increased sustained virologic response (SVR) rates from ~5% to ~40-80%, depending on the genotype of HCV infection. Advances in molecular biology have allowed investigators to begin to understand the mechanisms of HCV infection and replication. Advances in understanding of viral kinetics have provided tools to identify patients who are most likely to attain SVR. With the advances in the science of HCV infection, the first part of the 21st century has seen the development and early introduction of a number of direct-acting antiviral (DAA) drugs. These novel medications interfere with critical steps in HCV replication and have the potential to significantly increase SVR rates. This article will review the key elements of HCV replication and evaluate the various classes of new and investigational DAA that have the potential to create a revolution in the management of patients with chronic hepatitis C.

The impact of fibrosis and steatosis on early viral kinetics in HCV genotype 1-infected patients treated with Peg-IFN-alfa-2a and ribavirin

Hepatitis C viral (HCV) kinetics after initiation of interferon-based therapy provide valuable insights for understanding virus pathogenesis, evaluating treatment antiviral effectiveness and predicting treatment outcome. Adverse effects of liver fibrosis and steatosis on sustained virological response have been frequently reported, yet their impacts on the early viral kinetics remain unclear. In this study, associations between histology status and early viral kinetics were assessed in 149 HCV genotype 1-infected patients treated with pegylated interferon alfa-2a and ribavirin (DITTO trial). In multivariate analyses adjusted for critical factors such as IL28B genotype and baseline viral load, presence of significant fibrosis (Ishak stage > 2) was found to independently reduce the odds of achieving an initial reduction (calculated from day 0 to day 4) in HCV RNA of ≥2 logIU/mL (adjusted OR 0.03, P = 0.004) but was not associated with the second-phase slope of viral decline (calculated from day 8 to day 29). On the contrary, presence of liver steatosis was an independent risk factor for not having a rapid second-phase slope, that is, ≥0.3 logIU/mL/week (adjusted OR 0.22, P = 0.012) but was not associated with the first-phase decline. Viral kinetic modelling theory suggests that significant fibrosis primarily impairs the treatment antiviral effectiveness in blocking viral production by infected cells, whereas the presence of steatosis is associated with a lower net loss of infected cells. Further studies will be necessary to identify the biological mechanisms underlain by these findings.

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.

Hepatitis C Virus: The Rising Concerns and Growing Hopes, Report From the HCV Symposium, Fourth Tehran Hepatitis Congress, November 2011, Tehran, Iran

The rising concerns for future health burden of hepatitis C virus (HCV) in global scale has continuously encouraged preventing measures particularly public awareness programs. There is an increasing necessity for allocating HCV awareness issues in public scope, especially for high risk populations and patients. Proper knowledge of health care professionals and treating physicians and their attitude with regard to hepatitis C management is also crucial. Achieving this can be a constructive step forward in controlling and hopefully eradicating hepatitis C virus in our community. Having a clear scientific grasp on treatment options and protocols, the concept of “CURE” achievement in hepatitis C and the future hopes in enhancing virological response with the coming direct antiviral agents can significantly add to the current practices of treating hepatitis C. This scientific report paper outlines the insights communicated at the HCV symposium during the 4th Tehran Hepatitis Congress, November 2011, Tehran, Iran.

Novel human SR-BI antibodies prevent infection and dissemination of HCV in vitro and in humanized mice

BACKGROUND & AIMS

Hepatitis C virus (HCV)-induced end-stage liver disease is currently the major indication for liver transplantation in the Western world. After transplantation, the donor liver almost inevitably becomes infected by the circulating virus and disease progression is accelerated in immune suppressed transplant patients. The current standard therapy, based on pegylated interferon and ribavirin, induces severe side effects and is often ineffective in this population. Therefore, new strategies to prevent graft re-infection are urgently needed. We have previously shown that monoclonal antibodies (mAbs) against the HCV co-receptor scavenger receptor class B type I (SR-BI/Cla1) inhibit infection by different HCV genotypes in cell culture.

METHODS

Using phage display libraries, we have generated a large set of novel human mAbs against SR-BI and evaluated their effectiveness in preventing HCV infection and direct cell-to-cell spread in vitro and in vivo using uPA-SCID mice with a humanized liver.

RESULTS

Eleven human monoclonal antibodies were generated that specifically recognize SR-BI. Two antibodies, mAb8 and mAb151, displayed the highest binding and inhibitory properties and also interfered with direct cell-to-cell spread in vitro. Studies in humanized mice showed that both antibodies were capable of preventing HCV infection and could block intrahepatic spread and virus amplification when administered 3 days after infection. Interestingly, anti-SR-BI therapy was effective against an HCV variant that escaped the control of the adaptive immune response in a liver transplant patient.

CONCLUSIONS

The anti-SR-BI mAbs generated in this study may represent novel therapeutic tools to prevent HCV re-infection of liver allografts.

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.

TMC647055, a potent nonnucleoside hepatitis C virus NS5B polymerase inhibitor with cross-genotypic coverage

Hepatitis C virus (HCV) infection is a major global health burden and is associated with an increased risk of liver cirrhosis and hepatocellular carcinoma. There remains an unmet medical need for efficacious and safe direct antivirals with complementary modes of action for combination in treatment regimens to deliver a high cure rate with a short duration of treatment for HCV patients. Here we report the in vitro inhibitory activity, mode of action, binding kinetics, and resistance profile of TMC647055, a novel and potent nonnucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase. In vitro combination studies with an HCV NS3/4A protease inhibitor demonstrated potent suppression of HCV RNA replication, confirming the potential for combination of these two classes in the treatment of chronic HCV infection. TMC647055 is a potent nonnucleoside NS5B polymerase inhibitor of HCV replication with a promising in vitro biochemical, kinetic, and virological profile that is currently undergoing clinical evaluation.

The HCV non-nucleoside inhibitor Tegobuvir utilizes a novel mechanism of action to inhibit NS5B polymerase function

Tegobuvir (TGV) is a novel non-nucleoside inhibitor (NNI) of HCV RNA replication with demonstrated antiviral activity in patients with genotype 1 chronic HCV infection. The mechanism of action of TGV has not been clearly defined despite the identification of resistance mutations mapping to the NS5B polymerase region. TGV does not inhibit NS5B enzymatic activity in biochemical assays in vitro, suggesting a more complex antiviral mechanism with cellular components. Here, we demonstrate that TGV exerts anti-HCV activity utilizing a unique chemical activation and subsequent direct interaction with the NS5B protein. Treatment of HCV subgenomic replicon cells with TGV results in a modified form of NS5B with a distinctly altered mobility on a SDS-PAGE gel. Further analysis reveals that the aberrantly migrating NS5B species contains the inhibitor molecule. Formation of this complex does not require the presence of any other HCV proteins. The intensity of the aberrantly migrating NS5B species is strongly dependent on cellular glutathione levels as well as CYP 1A activity. Furthermore analysis of NS5B protein purified from a heterologous expression system treated with TGV by mass spectrometry suggests that TGV undergoes a CYP- mediated intracellular activation step and the resulting metabolite, after forming a glutathione conjugate, directly and specifically interacts with NS5B. Taken together, these data demonstrate that upon metabolic activation TGV is a specific, covalent inhibitor of the HCV NS5B polymerase and is mechanistically distinct from other classes of the non-nucleoside inhibitors (NNI) of the viral polymerase.

Antiviral strategies in hepatitis C virus infection

Resolution of the three-dimensional structures of several hepatitis C virus (HCV) proteins, together with the development of replicative cell culture systems, has led to the identification of a number of potential targets for direct-acting antiviral (DAA) agents. Numerous families of drugs that potently inhibit the HCV lifecycle in vitro have been identified, and some of these molecules have reached early to late clinical development. Two NS3/4A protease inhibitors, telaprevir and boceprevir, were approved in Europe and the United States in 2011 in combination with pegylated interferon (IFN)-α and ribavirin for the treatment of chronic hepatitis C related to HCV genotype 1, in both treatment-naïve and treatment-experienced patients. Sustained virological response rates in the range of 6675% and 5966% (2988% if the response to the first course of therapy is taken into account) have been achieved in these two patient populations, respectively, with treatment durations of 24 to 48 weeks. A number of other DAAs are at the clinical developmental stage in combination with pegylated IFN-α and ribavirin or with other DAAs in IFN-free regimens, with or without ribavirin. They include second-wave, first-generation, and second-generation NS3/4A protease inhibitors, nucleoside/nucleotide analogue inhibitors and non-nucleoside inhibitorsof HCVRNA-dependent RNA polymerase, inhibitors of nonstructural protein 5A (NS5A) and host-targeted compounds, such as cyclophilin inhibitors and silibinin. The proof of concept that IFN-free regimens may lead to HCV eradication has recently been brought. However, new drugs may be associated with troublesome side effects and drugdrug interactions, and the ideal IFN-free DAA combination remains to be found.

Basic answers to complicated questions for the course of chronic hepatitis C treatment

Hepatitis C virus infection is a long-lasting disease, which causes chronic hepatitis, liver cirrhosis and hepatocellular carcinoma, thus leading to liver-related death. Currently, the optimal treatment for chronic hepatitis C infection is the combination of pegylated interferon and ribavirin. The aim of this review is to assess the long-term clinical outcomes of interferons alone or in combination with ribavirin in the management of chronic hepatitis C.

Prevalence of hepatitis C virus variants resistant to NS3 protease inhibitors or the NS5A inhibitor (BMS-790052) in hepatitis patients with genotype 1b

BACKGROUND

Hepatitis C virus (HCV) of genotype 1b is the most prevalent worldwide, and the least responsive to interferon-based treatments. A combination therapy with two direct-acting antivirals has shown promising results in patients with HCV-1b, but the prevalence of drug-resistant variants before treatment is not known in the Japanese population.

OBJECTIVES

To detect HCV variants resistant to NS3 protease inhibitors or the NS5A inhibitor (BMS-790052) in hepatitis patients infected with HCV-1b.

STUDY DESIGN

Drug-resistant mutations were determined in the 362 hepatitis patients infected with HCV-1b who had not received direct-acting antivirals before.

RESULTS

Amino-acid substitutions resistant to NS3 inhibitors (V36A, T54S, Q80H and D168E) were detected in 15 of the 307 (4.9%) patients, who had been examined, and T54S (3.3%) predominated over V36A (0.3%), Q80R (0.7%) and D168E (0.7%) in them. Amino-acid substitutions resistant to BMS-790052 (L31M and/or Y93H) were detected in 33 of the 294 (11.2%) patients, and Y93H (8.2%) predominated over L31M (2.7%). One of the 239 (0.4%) patients, who had been examined for amino-acid substitutions in both NS3 and NS5A regions, possessed HCV-1b variants resistant to NS3 inhibitors (T54S) and BMS-790052 (L31M).

CONCLUSIONS

Mutations conferring resistance to NS3 inhibitors or BMS-790052 were frequent in our treatment-naive study population, but double mutants with possible resistance to both drugs were rare. Since single mutations did not result in treatment failure in a previous pilot trial combining BMS-790052 and an NS3 inhibitor, larger trials of this drug regimen appear warranted in the Japanese population.

A predictive model of treatment outcome in patients with chronic HCV infection using IL28B and PD-1 genotyping

BACKGROUND & AIMS

The advent of new chronic hepatitis C virus (HCV) therapies requires characterization of patients in order to predict adequate treatment. A good candidate marker is Programmed Cell Death-1 (PD-1) which is involved in progression of HCV infection. The aim of this study was to analyse the effect of several single nucleotide polymorphisms of PD-1 gene and several previously associated factors (IL28B and KIR receptors) on treatment responses.

METHODS

407 HCV chronic infected patients treated with PEG-IFN-α and ribavirin were recruited and classified according to their response to treatment. They were genotyped for PD-1 and IL28B polymorphisms, killer immunoglobulin-like receptors (KIR) and HLA genes. A multivariate logistic regression analysis and a Chi-squared Automatic Interaction Detector (CHAID) prediction model of response included these and other clinical parameters.

RESULTS

Our results showed that PD-1.3/A allele was significantly associated with sustained virological response (SVR) in a multivariate logistic regression analysis (p<0.01, OR=2.57). Additionally, IL28B C/C genotype was the most significant predictor of an SVR to treatment in all HCV genotypes (74.5%). In IL28B C/C patients, the presence of PD-1.3/A allele increased the probability of an SVR to 93.3%. Moreover, when this analysis was made only with patients infected by HCV-1, the predictive value of IL28B C/C genotype with PD-1.3/A allele was 90%.

CONCLUSIONS

PD-1.3/A allele is associated with SVR to treatment and notably increases the predictive value of IL28B C/C genotype. Both markers in conjunction could be a useful tool, more relevant than HCV genotype in some cases, in clinical practice.

GS-7977: a promising nucleotide analog NS5B polymerase inhibitor of HCV

Despite the approval of the protease inhibitors telaprevir and boceprevir, the treatment of hepatitis C remains difficult to manage and sustained virologic response rates have room for further improvement. GS-7977 is a nucleotide analog NS5B inhibitor currently in Phase III trials. It offers great hope in addressing the problems currently associated with pegylated interferon and protease inhibitor-based therapies. The purpose of this article is to review the development of GS-7977, the information currently available in the public domain concerning its pharmacokinetic, clinical efficacy and side-effect profile, and to evaluate the future of this drug and its integration into the hepatitis C treatment paradigm.

Utilization of hepatitis C antibody-positive livers: genotype dominance is virally determined

Because of the unrelenting donor shortage, utilization of all potential liver donors is essential. However, when utilizing marginal donors it is critical to precisely characterize the risks, inform recipients of those risks, and allocate these higher risk organs to appropriate candidates. Towards this goal, we need to determine the safety and potential consequences, if any, of utilizing hepatitis C (HCV) antibody-positive donors in HCV infected recipients. To further characterize HCV antibody-positive donors, we analyzed prospectively collected serum samples from HCV antibody-positive donors transplanted into HCV RNA-positive recipients from 5/1993 to 10/2008 for HCV viral load (Roche Cobas AmpliPrep/Cobas Taqman HCV Assay) and genotype (Siemens Versant 2.0 LiPA HCV 5' UTR/Core Assay). Seventeen of 32 (53%) HCV antibody-positive donors were RNA negative. Fifteen patients received an HCV RNA-positive donor and nine donor-recipient pairs had different genotypes or subtypes for analysis. When genotype 1 competed with a non-1 genotype, it was found in 5/6 recipients. In 2/3 cases of mismatched genotype 1 subtypes, genotype 1a dominated. Kaplan-Meier analysis of patient and graft survival and fibrosis progression did not reveal differences between patients who received an HCV antibody-positive donor that was viremic or aviremic. In conclusion, approximately half of HCV antibody-positive donors were aviremic. Viral dominance in viremic donor-recipient pairs seems virally determined.

Review of boceprevir and telaprevir for the treatment of chronic hepatitis C

OBJECTIVE

To summarize and evaluate the published literature pertaining to boceprevir and telaprevir, and to provide clinicians with suggestions for use in patients with chronic hepatitis C infection.

METHODS

A standardized search strategy was performed using the MEDLINE, EMBASE, Google Scholar and International Pharmaceuticals Abstracts databases using the search terms "boceprevir", "telaprevir", "boceprevir and hepatitis C", and "telaprevir and hepatitis C". A manual search of references was performed to identify articles missed by the electronic search. Studies were included in the review if they assessed either boceprevir or telaprevir in comparison with standard of care in chronic hepatitis C patients.

RESULTS

The studies identified assessed boceprevir and telaprevir in genotype-1 hepatitis C patients. In both treatment-naive and treatment-experienced patients, sustained virological response rates were achieved more often with boceprevir or telaprevir in combination with pegylated interferon and ribavirin compared with pegylated interferon and ribavirin alone. Both medications were well tolerated, with anemia presenting as the most treatment-limiting adverse effect.

CONCLUSIONS

Boceprevir and telaprevir will revolutionize the management of hepatitis C genotype 1 patients and will most likely decrease the burden of end-stage disease worldwide. However, current clinical limitations include establishing appropriate and cost-effective treatment durations, and use in special populations such as transplant patients and patients coinfected with HIV. Future research will need to clarify these clinical obstacles to clearly define the role of these agents in hepatitis C management.

Protease inhibitors for the treatment of chronic hepatitis C genotype-1 infection: the new standard of care

For the past decade, the standard treatment for chronic hepatitis C infection has been pegylated-interferon plus ribavirin. With US Food and Drug Administration approval of boceprevir and telaprevir--two protease inhibitors--the standard-of-care treatment for genotype-1 infection, the main genotype worldwide, is now peginterferon plus ribavirin and a protease inhibitor. Rates of sustained virological response or cure with triple combination treatment have improved substantially, both in patients who have had previous treatment and in those who have not. Improvements have been most substantial in populations regarded as difficult to treat, such as individuals with cirrhosis. However, despite improved response rates, protease inhibitors have incremental toxic effects, high costs, increased pill burden, and many drug interactions. Moreover, because new antiviral drugs directly inhibit hepatitis C virus, viral resistance has become an important issue, essentially precluding use of protease inhibitor monotherapy, and potentially restricting future treatment options for patients who consequently do not achieve sustained virological response. Protease inhibitors are the first of many antiviral medications that will probably be combined in future interferon-free regimens.

Modeling quasispecies and drug resistance in hepatitis C patients treated with a protease inhibitor

Telaprevir, a novel hepatitis C virus (HCV) NS3-4A serine protease inhibitor, has demonstrated substantial antiviral activity in patients infected with HCV. However, drug-resistant HCV variants were detected in vivo at relatively high frequency a few days after drug administration. Here we use a two-strain mathematical model to explain the rapid emergence of drug resistance in HCV patients treated with telaprevir monotherapy. We examine the effects of backward mutation and liver cell proliferation on the preexistence of the mutant virus and the competition between wild-type and drug-resistant virus during therapy. We also extend the two-strain model to a general model with multiple viral strains. Mutations during therapy only have a minor effect on the dynamics of various viral strains, although they are capable of generating low levels of HCV variants that would otherwise be completely suppressed because of fitness disadvantages. Liver cell proliferation may not affect the pretreatment frequency of mutant variants, but is able to influence the quasispecies dynamics during therapy. It is the relative fitness of each mutant strain compared with wild-type that determines which strain(s) will dominate the virus population. This study provides a theoretical framework for exploring the prevalence of preexisting mutant variants and the evolution of drug resistance during treatment with other HCV protease inhibitors or polymerase inhibitors.

Spanish society of liver transplantation (SETH) consensus recommendations on hepatitis C virus and liver transplantation

In November 2010, the Spanish Society of Liver Transplantation (Sociedad Española de Trasplante Hepático, SETH) held a consensus conference. One of the topics of debate was liver transplantation in patients with hepatitis C. This document reviews (i) the natural history of post-transplant hepatitis C, (ii) factors associated with post-transplant prognosis in patients with hepatitis C, (iii) the role of immunosuppression in the evolution of recurrent hepatitis C and response to antiviral therapy, (iv) antiviral therapy, both before and after transplantation, (v) follow-up of patients with recurrent hepatitis C and (vi) the role of retransplantation.

Viral hepatitis in liver transplantation

Liver transplantation is the only alternative for patients with end-stage liver disease. Viral hepatitis B and C are among the most common causes of cirrhosis and hepatocellular carcinoma and a frequent indication for liver transplantation. Hepatitis B virus immunoglobulin and nucleot(s)ide analogues have facilitated the management of patients with hepatitis B who have received liver transplants and resulted in excellent long-term outcomes. On the contrary, recurrence of hepatitis C is the main cause of graft loss in most transplant programs. Current therapeutic approaches are far from optimal, because sustained virologic responses are only achieved in one-third of treated patients, and adverse effects are common and severe. However, the rapid development of direct-acting antivirals against hepatitis C virus will change the management of this disease and in a few years prevent graft infection with this virus.

Hepatitis C and substance use: new treatments and novel approaches

PURPOSE OF REVIEW

To provide an update on new treatment approaches for patients with hepatitis C virus (HCV) infection and substance use. This issue is of extreme importance for HCV, as many patients have substance-use histories.

RECENT FINDINGS

Recent emergence of two new protease inhibitors, boceprevir and telaprevir, to enhance the modern treatment of HCV have boosted the sustained virologic response rate to about 80%, a 30% increase over prior standard of care with interferon and ribavirin. Unfortunately, many providers are reluctant to treat patients with substance-use histories unless they have demonstrated abstinence for at least 6 months, and there is a spoken and unspoken bias against these patients. Emerging new studies have shown that even current injection drug users can be treated successfully with results comparable to patients who are abstinent and those with no drug-use histories, especially with attention to the patient's substance use and other psychiatric problems.

SUMMARY

Newer treatment approaches for HCV will help many more patients than ever before to overcome the virus. Changed attitudes and innovative approaches to patients with substance-use histories are needed to bring these scientific advances to this segment of the population of patients with HCV.

The pharmacokinetics of peginterferon alfa-2a and ribavirin in African American, Hispanic and Caucasian patients with chronic hepatitis C

BACKGROUND

Amongst Caucasian, Hispanic and African Americans with genotype 1 hepatitis C virus (HCV), there is a wide variation in response to treatment with peginterferon alfa-2a (PEG-IFN alfa-2a) and ribavirin.

AIM

To evaluate the pharmacokinetics (PK) of PEG-IFN alfa-2a and ribavirin among these three groups.

METHODS

Forty-seven patients with genotype 1 CHC (17 African Americans, 14 Hispanics and 16 Caucasians) received 8 weeks of PEG-IFN alfa-2a (180 μg/week) and ribavirin (1000 or 1200 mg/day). PEG-IFN alfa-2a serum concentrations and ribavirin plasma concentrations were measured following the first dose and at week 8. Pharmacokinetic parameters (C(max), T(max), AUC, CL/F) were estimated using noncompartmental methods.

RESULTS

There was no difference in the pharmacokinetic parameters for PEG-IFN alfa-2a following single-dose or steady-state administration between African American or Hispanic patients compared with Caucasian patients. Ribavirin pharmacokinetic parameters were similar between Hispanic and Caucasian patients for single-dose and steady-state administration. The single-dose C(max) was 33% lower (P < 0.05) in African American compared with Caucasian patients. Other ribavirin single-dose and steady-state pharmacokinetic parameters were slightly decreased (approximately 20% lower) in African American patients, but were not considered clinically meaningful.

CONCLUSIONS

No differences were observed in PEG-IFN alfa-2a pharmacokinetic parameters between African American or Hispanic patients compared with Caucasian patients. For ribavirin, no differences were observed in pharmacokinetic parameters between Hispanic and Caucasian patients. While a trend towards increased ribavirin clearance and decreased exposure was observed in African American patients vs. Caucasian patients, the differences were small and not considered clinically meaningful (Clinical Trial Number: NP17354).

Telaprevir for retreatment of HCV infection: review of the REALIZE trial

An estimated 170 million people are chronically infected with HCV, which is a leading cause of cirrhosis, hepatocellular carcinoma and liver transplantation in North America. However, in patients infected with HCV genotype 1, 48 weeks of pegylated IFN-α and ribavirin treatment results in a sustained virologic response of only 40–50%. Therefore, development of effective regimens to eradicate HCV has been an urgent priority, especially in those patients who have a predicted low treatment response, partial responders and nonresponders. Telaprevir is a reversible, selective, orally bioavailable inhibitor of the HCV NS3/4A serine protease, and resembles the HCV polypeptide that is cleaved by the viral protease, a necessary step in replication. The REALIZE trial was a Phase III, randomized, double-blind, placebo-controlled study of patients who were previously treated with pegylated IFN-α and ribavirin unsuccessfully for chronic genotype 1 HCV infection, with the aim to compare the efficacy, safety and tolerability of telaprevir. This article reviews the background, study design and results of the REALIZE trial, and discusses the significance of these findings in the rapidly evolving treatment regimens for genotype 1 chronic HCV.

Anti-hepatitis C virus drugs in development

Development of robust cell culture models for hepatitis C viral infection has greatly increased our understanding of this virus and its life cycle. This knowledge has led to the development of many drugs that target specific elements of viral replication, including viral proteins and host factors required for replication. The NS3/4A serine protease inhibitors were the first of these to be used in the clinic, and reagents that target other elements of the viral lifecycle are in advanced stages of clinical development. These include new NS3/4A protease inhibitors, NS5B RNA-dependent RNA polymerase inhibitors, NS5A inhibitors, and host-directed antivirals, such as cyclophilin inhibitors. Alternative interferons with possibly improved tolerability, specifically interferon-λ1 (interleukin-29), are also under development. These new reagents against hepatitis C virus should lead to highly effective, well-tolerated, and likely interferon-sparing therapies in the next several years.

Current standards in the treatment of chronic hepatitis C

BACKGROUND

In Germany, 400 000 to 500 000 people are chronically infected with the hepatitis C virus (HCV), 70% to 80% of them with HCV genotype 1. Combined treatment with peginterferon-alfa and ribavirin leads to a sustained virologic response (SVR) in 40% to 50% of patients with genotype 1 and 70% to 80% of patients with genotypes 2 and 3. The HCV protease inhibitors boceprevir and telaprevir were approved for clinical use in Germany in 2011.

METHODS

Selective literature review.

RESULTS

Treatment with peginterferon and ribavirin is recommended for a variable length of time depending on the HCV genotype (24 to 72 weeks for genotype 1, 16 to 48 weeks for genotypes 2 and 3), the baseline HCV-RNA concentration (greater or less than 600 000 to 800 000 IU/mL), and the decline in HCV-RNA concentration after 4 and 12 weeks of treatment. Either boceprevir or telaprevir is given in addition to peginterferon and ribavirin. In the approval studies, these triple combinations were shown to yield higher SVR rates than dual treatment for genotype 1 (66% to 75% versus 37% to 44%). If there is a favorable early decline in HCV-RNA, the treatment can be shortened to 24 to 28 weeks in 44% to 65% of patients with genotype 1. The SVR rates in genotype 1 patients who failed previous dual therapy were 69% to 88% for prior relapsers, 52% to 59% for partial responders, and 33% for null responders. Triple combination therapy is associated with new adverse events.

CONCLUSION

Individualized treatment durations are recommended for the treatment of chronic hepatitis C with peginterferon and ribavirin. Triple therapy in combination with either boceprevir or telaprevir leads to a higher rate of SVR both in previously untreated genotype 1 patients and in those who have failed prior antiviral treatment.\

Hepatic cell-type specific gene expression better predicts HCV treatment outcome than IL28B genotype

BACKGROUND & AIMS

Cell-type specific expression patterns of hepatic interferon-stimulated genes (ISGs) and single nucleotide polymorphisms (SNPs) near the IL28B gene are associated with response to interferon-based therapy in patients with chronic hepatitis C virus (HCV) infection. It is not known how the IL28B genotype influences the ISG expression pattern and which is a better predictor of treatment response.

METHODS

Patients at the Toronto Western Hospital Liver Centre with known outcome to interferon-based treatment for HCV infection were evaluated. Analysis included hepatic gene expression profile using complementary DNA microarrays, genotype at the IL28B SNP rs12979860, and immunostaining for human myxovirus A protein 1 (MxA) in hepatocytes and macrophages.

RESULTS

The level of ISG immunostaining in hepatic macrophages correlated inversely with that of hepatocytes and was strongly associated with treatment outcome. Gene expression profiles and the IL28B genotype were associated with treatment response, but only absence of MxA staining in macrophages accurately predicted nonresponse to treatment. The positive predictive value (PPV) of the IL28B genotype was 94% and the negative predictive value (NPV) was 51% (n = 209). For messenger RNA expression, the PPV was 94% and the NPV was 54% (n = 65). For detection of MxA in macrophages, the PPV was 60% and the NPV was 98% (n = 110). Of 53 patients with undetectable macrophage MxA staining, only one had a sustained virologic response. IL28B genotype was strongly associated with cell-type specific staining for MxA. There was a stepwise increase in macrophage staining and decrease in hepatocyte staining from the TT (lack of response) to CC SNP (associated with response) in IL28B. By logistic regression, after controlling for the presence of macrophage MxA staining, the IL28B genotype was no longer associated with treatment response.

CONCLUSIONS

The cell-type-specific expression pattern of ISGs varies among patients with different IL28B genotypes and is a strong predictor of response to interferon-based treatment.

A practical guide for the use of boceprevir and telaprevir for the treatment of hepatitis C

The aim of this study is to review clinical trial data on the newly approved protease inhibitors boceprevir and telaprevir to develop consensus recommendations on the optimal use of these agents for the treatment of patients with chronic hepatitis C virus (HCV) infection. An expert panel of seven leading authorities in viral hepatitis was convened to establish and disseminate a practical guide on best practices for incorporating boceprevir and telaprevir into therapy for HCV infection in both treatment-naive and treatment-experienced patients. The topics covered include selecting candidates for boceprevir- or telaprevir-based treatments, predictors of response and early viral kinetics, response-guided therapy approaches, on-treatment management strategies to optimize the likelihood of response and minimize the risk of drug resistance, management of adverse effects during therapy and key considerations for special populations. The expert panel incorporated the best available clinical evidence into recommendations on how boceprevir and telaprevir should be used in the clinical setting. They indicated how treatment regimens may differ according to the baseline factors, such as presence of cirrhosis and when therapy may need to be modified or stopped altogether because of adverse events or poor virologic response. This practical guide will serve as a valuable resource for clinicians embarking on the new treatment paradigm of boceprevir or telaprevir in combination with peginterferon/ribavirin for chronic genotype 1 HCV infection.

Maximizing opportunities and avoiding mistakes in triple therapy for hepatitis C virus

Recently developed drugs and innovative strategies for the treatment of chronic infection with genotype 1 hepatitis C virus (HCV) have become the standard of care. The protease inhibitors telaprevir (Incivek) and boceprevir (Victrelis) are the first direct-acting antiviral (DAA) agents approved, and many more are being developed. These drugs substantially increased rates of sustained virologic response in treatment-naïve and -experienced patients, in conjunction with peginterferon and ribavirin (triple therapy), in phase 3 trials. The efficacy of triple therapy depends on appropriate selection of patients, although the population of patients that receive triple therapy could be expanded as the risk/benefit ratio improves. Attention to details that reflect the standard of care, such as appropriate dosing, anticipation of adverse effects, and strict adherence to stopping rules, will insure the success of these drugs and lead the way for new combination therapies.

Immunotherapies in infectious diseases

The development of an infection involves interplay between the host's immune system and the virulence of the infecting microorganism. The traditional treatment of an infection involves antimicrobial chemotherapy to kill the organism. The use of immunotherapies in infections includes treatment options that modulate the immune response and can lead to control of infections. These therapies are expected to become more important therapeutic options with the increase in infections due to multidrug-resistant organisms and the increasing number of immunocompromised patients.

Understanding silibinin's modes of action against HCV using viral kinetic modeling

BACKGROUND & AIMS

Legalon® SIL (SIL) is a chemically hydrophilized version of silibinin that has exhibited high antiviral effectiveness against hepatitis C virus (HCV). Its main mode of action (MOA) remains unclear, with contradicting in vitro studies supporting either suppression of entry and cell-to-cell spread or suppression of viral RNA synthesis as the main MOA. We sought to provide new insights into SIL's MOA in HCV genotype-1/4 patients receiving intravenous SIL monotherapy for 7 days via mathematical modeling.

METHODS

Changes in HCV RNA in 25 patients receiving 10, 15, or 20mg/kg/day of SIL were analyzed and modeled using viral kinetic methods.

RESULTS

In 15 patients, the virus declined in a biphasic manner, in which a sharp drop between days 0 and 2 was followed by a slower second phase of decline. In 10 patients, the initial decline was weaker and the virus declined in a single phase over the 7-day period. The blocking production effectiveness, ε, was dose-dependent with mean ε=0.49 and 0.89 in the 10 or 15 and 20mg/kg/day dosing groups, respectively (p=0.02). The effectiveness of blocking viral infection, η, was estimated as 0.60 with no significant differences across dosing groups. For all patients, the mean rate of viral load decline measured between days 2 and 7 was high (0.3 log(10)IU/ml/day), i.e., 4-fold higher than typically observed during the 2nd phase of (pegylated)-interferon-α±ribavirin treatment.

CONCLUSIONS

Modeling HCV kinetics in vivo suggests that SIL may block both viral infection and viral production/release with its main dose-dependent effect being blocking viral production/release.

Review and management of drug interactions with boceprevir and telaprevir

Boceprevir (BOC) and telaprevir (TPV), when added to pegylated interferon and ribavirin for the treatment of chronic hepatitis C virus (HCV) infection, increase the rates of sustained virologic response in treatment-naïve persons to approximately 70%. Though these agents represent an important advance in the treatment of chronic HCV, they present new treatment challenges to the hepatology community. BOC and TPV are both substrates and inhibitors of the hepatic enzyme, cytochrome P450 3A, and the drug transporter, P-glycoprotein, which predisposes these agents to many drug interactions. Identification and appropriate management of potential drug interactions with TPV and BOC is critical for optimizing therapeutic outcomes during hepatitis C treatment. This review highlights the pharmacologic characteristics and drug-interaction potential of BOC and TPV and provides guidance on the management of drug interactions with these agents.

Management of patients coinfected with HCV and HIV: a close look at the role for direct-acting antivirals

With the development of effective therapies against human immunodeficiency virus (HIV), hepatitis C virus (HCV) infection has become a major cause of morbidity and mortality among patients with both infections (coinfection). In addition to the high prevalence of chronic HCV, particularly among HIV-infected injection drug users, the rate of incident HIV infections is increasing among HIV-infected men who have sex with men, leading to recommendations for education and screening for HCV in this population. Liver disease is the second leading and, in some cases, a preventable cause of death among coinfected patients. Those at risk for liver disease progression are usually treated with a combination of interferon (IFN) and ribavirin (RBV), which is not highly effective; it has low rates of sustained virologic response (SVR), especially for coinfected patients with HCV genotype 1 and those of African descent. Direct-acting antivirals might overcome factors such as immunodeficiency that can reduce the efficacy of IFN. However, for now it remains challenging to treat coinfected patients due to interactions among drugs, additive drug toxicities, and the continued need for combination therapies that include pegylated IFN. Recently developed HCV protease inhibitors such as telaprevir and boceprevir, given in combination with pegylated IFN and RBV, could increase the rate of SVR with manageable toxicity and drug interactions. We review the latest developments and obstacles to treating coinfected patients.