Boceprevir for previously treated chronic HCV genotype 1 infection

New targets for antiviral therapy of chronic hepatitis C

Until recently, chronic hepatitis C caused by persistent infection with the hepatitis C virus (HCV) has been treated with a combination of pegylated interferon-alpha (PEG-IFNα) and ribavirin (RBV). This situation has changed with the development of two drugs targeting the NS3/4A protease, approved for combination therapy with PEG-IFNα/RBV for patients infected with genotype 1 viruses. Moreover, two additional viral proteins, the RNA-dependent RNA polymerase (residing in NS5B) and the NS5A protein have emerged as promising drug targets and a large number of antivirals targeting these proteins are at different stages of clinical development. Although this progress is very promising, it is not clear whether these new compounds will suffice to eradicate the virus in an infected individual, ideally by using a PEG-IFNα/RBV-free regimen, or whether additional compounds targeting other factors that promote HCV replication are required. In this respect, host cell factors have emerged as a promising alternative. They reduce the risk of development of antiviral resistance and they increase the chance for broad-spectrum activity, ideally covering all HCV genotypes. Work in the last few years has identified several host cell factors used by HCV for productive replication. These include, amongst others, cyclophilins, especially cyclophilinA (cypA), microRNA-122 (miR-122) or phosphatidylinositol-4-kinase III alpha. For instance, cypA inhibitors have shown to be effective in combination therapy with PEG-IFN/RBV in increasing the sustained viral response (SVR) rate significantly compared to PEG-IFN/RBV. This review briefly summarizes recent advances in the development of novel antivirals against HCV.

Specific detection of naturally occurring hepatitis C virus mutants with resistance to telaprevir and boceprevir (protease inhibitors) among treatment-naïve infected individuals

The use of telaprevir and boceprevir, both protease inhibitors (PI), as part of the specifically targeted antiviral therapy for hepatitis C (STAT-C) has significantly improved sustained virologic response (SVR) rates. However, different clinical studies have also identified several mutations associated with viral resistance to both PIs. In the absence of selective pressure, drug-resistant hepatitis C virus (HCV) mutants are generally present at low frequency, making mutation detection challenging. Here, we describe a mismatch amplification mutation assay (MAMA) PCR method for the specific detection of naturally occurring drug-resistant HCV mutants. MAMA PCR successfully identified the corresponding HCV variants, while conventional methods such as direct sequencing, endpoint limiting dilution (EPLD), and bacterial cloning were not sensitive enough to detect circulating drug-resistant mutants in clinical specimens. Ultradeep pyrosequencing was used to confirm the presence of the corresponding HCV mutants. In treatment-naïve patients, the frequency of all resistant variants was below 1%. Deep amplicon sequencing allowed a detailed analysis of the structure of the viral population among these patients, showing that the evolution of the NS3 is limited to a rather small sequence space. Monitoring of HCV drug resistance before and during treatment is likely to provide important information for management of patients undergoing anti-HCV therapy.

Future of hepatitis C therapy: development of direct-acting antivirals

PURPOSE OF REVIEW

The landscape of hepatitis C virus (HCV) therapy will change considerably over the next decade with the probable licensure of many HCV direct-acting antiviral (DAA) therapy agents. This review will outline the data on the initial two DAA agents licensed (protease inhibitors telaprevir and boceprevir) and cover potential future therapeutic strategies and challenges for DAA-based therapy, including in the context of HIV/HCV coinfection.

RECENT FINDINGS

Phase III trials evaluating the addition of telaprevir or boceprevir to pegylated interferon and ribavirin in both HCV treatment naïve and experienced populations with chronic HCV genotype 1 have demonstrated considerable improvements in sustained virological response, with many patients able to shorten total treatment duration from 48 to 24-36 weeks. Although these initial DAA-based treatment results are encouraging, additional toxicity, problematic dosing schedules, and potential drug-drug interactions pose challenges for clinical management, particularly in HIV/HCV coinfection. Phase II trials with telaprevir and boceprevir in HIV/HCV populations are underway. Subsequent DAA agents appear to have improved tolerability and dosing schedules and open the door for interferon (IFN)-free DAA-based combination therapy.

SUMMARY

Development of DAA therapy will lead to a major shift in HCV clinical management, particularly with the potential for IFN-free combination therapy.

Response-guided and -unguided treatment of chronic hepatitis C

Over time, HCV therapy with pegylated interferon and ribavirin has evolved from a fixed duration strategy to one of response guided therapy and this has enabled us to optimize treatment duration. With the evolution of protease inhibitor based therapy, the paradigm of response guided therapy has further helped in decreasing treatment duration in greater number of patients and which then translates into shorter duration of adverse events. However, several population groups have done better with extended duration therapy as opposed to response guided therapy despite early viral clearance. These include the Black population, and those with cirrhosis, decreased interferon sensitivity, and unfavorable IL28B genotypes. The proper identification of those who might benefit from extended duration HCV therapy will undoubtedly lead to optimal care and outcomes.

Host genomics and HCV treatment response

In 2009, an association between the interleukin-28B (IL28B) polymorphism and treatment outcome for genotype 1 (G1) hepatitis C virus (HCV) infection, as well as spontaneous clearance of HCV, was reported. Since the initial publications, over 100 articles have appeared in the peer-reviewed literature, with many more manuscripts in press and abstracts presented at scientific meetings. Despite the proliferation of data concerning the IL28B polymorphism and HCV infection, there remain many critical unanswered questions about clinical implications and the underlying biological mechanisms. In this review, we discuss the basic principles of genome-wide association study methodologies that are important for interpreting the results of genetic association studies. We then review the current literature concerning the association between IL28B variants and interferon (IFN) treatment response in patients with chronic HCV infection, as well as spontaneous HCV clearance. We consider the relevance of the IL28B polymorphism to non-G1 HCV, as well as the special treatment populations of HIV/HCV co-infection and recurrent HCV post-liver transplantation. We review current knowledge of the biological mechanisms underlying this genetic association, including the link to liver IFN-stimulated gene expression, and identify continuing gaps in our knowledge and key research priorities. Finally, pegylated-IFN and ribavirin is no longer the standard of care for the treatment of G1 HCV, and we conclude by considering the relevance of IL28B polymorphisms in the era of direct-acting antivirals.

Hepatitis C and non-Hodgkin lymphoma: the clinical perspective

Hepatitis C virus (HCV) is a commonly transmitted infection that has both hepatic and extrahepatic repercussions. These range from the inflammatory to the oncologic with an undisputed link to hepatitis, liver cirrhosis, and hepatocellular carcinoma. Its role in the development of B cell non-Hodgkin lymphoma (B-NHL) is becoming better understood, leading to opportunities for research, therapy, and even prevention. Research in the field has progressed significantly over the last decade, with the number of patients diagnosed with HCV and B-NHL rising incrementally. It is therefore becoming crucial to fully understand the pathobiologic link of HCV in B cell lymphomagenesis and its optimal management in the oncologic setting.

Advances in the treatment of hepatitis C virus infection

Therapy for chronic hepatitis C virus (HCV) infection with pegylated interferon α and ribavirin leads to suboptimal rates of viral eradication in patients with genotype 1 HCV, the most common viral strain in the United States and many other countries. Recent advances in the study of viral kinetics, host factors that predict response to antiviral therapy, and viral protein structure have established the foundation of a new era in the treatment of HCV infection. The HCV NS3/4A protease inhibitors boceprevir and telaprevir, the first 2 agents in a new and promising generation of direct-acting antiviral agents to have completed phase III studies, were approved by the US Food and Drug Administration in May 2011. The addition of these HCV protease inhibitors to standard therapy has been demonstrated to dramatically improve sustained virologic response rates, both in treatment-naïve patients and in prior relapsers and nonresponders. These novel agents represent only the beginning of a revolution in HCV therapy, which will include additional protease inhibitors as well as other classes of drugs currently under investigation, such as polymerase inhibitors, NS5A inhibitors, and host factor inhibitors such as cyclophilin antagonists. The future of HCV therapy holds promise for significantly higher sustained virologic response rates with shorter treatment durations, as well as the intriguing potential to achieve virologic cure with interferon-free combination therapy regimens.

Resistance-associated variants in chronic hepatitis C patients treated with protease inhibitors

Direct-acting antiviral agents in combination with pegylated interferon (PEG-IFN) and ribavirin (RBV) significantly improve sustained virologic response rate and reduce duration of therapy among both treatment-naïve and treatment-experienced patients with genotype 1 chronic hepatitis C. One of the most important considerations with both boceprevir and telaprevir is the potential development of resistant variants with therapy. Patients with poor intrinsic responsiveness to interferon, and those with incomplete virological suppression on protease inhibitor therapy, appear to be at higher risk for resistance. In this article we will define antiviral resistance and review the data on both in vitro and in vivo resistance to protease inhibitors, concentrating on data on boceprevir and telaprevir. We will also explore the significance of resistant variants present at the baseline, as well as the fate of the resistant variants and the ways to minimize the development of resistance to protease inhibitors.

IL28B genetic polymorphism testing in the era of direct acting antivirals therapy for chronic hepatitis C: ten years too late?

An association between variations at the IL28B gene locus and HCV clearance (spontaneous recovery or sustained virological response under pegylated interferon (PEG-IFN) and ribavirin (RBV) has been extensively described. In genotype 1-infected patients, the new direct antiviral agents (DAA) including the two approved protease inhibitors boceprevir and telaprevir, in association with the PEG-IFN/RBV combination is the new standard of care making it necessary to redefine the interest of the IL28B genotype in the decision to treat and how to treat genotype 1-infected patients. In treatment-naïve patients, IL28B status can certainly identify those with a high probability of achieving SVR with response guided therapy and probably in whom the duration of treatment can be markedly reduced. In experienced patients, the impact of IL28B genotypes is limited and cancelled by early viral kinetics. However, the decision to initiate or withhold therapy remains a clinical one. In summary, although it was a major milestone in the treatment of patients with PEG-IFN/RBV, IL28B polymorphism testing entered the clinical arena almost 10 years too late.

Phase III results of Boceprevir in treatment naïve patients with chronic hepatitis C genotype 1

INTRODUCTION

Chronic hepatitis C virus infection affects approximately 2% of the world population and can result in cirrhosis and hepatocellular carcinoma. Until 2011, the standard of care (SOC) has been therapy with pegylated interferon alfa and ribavirin (PEG-IFN/RBV). Sustained virologic response rates (SVR) after SOC in patients infected with genotype 1 have been 40-50%. The development of new direct antiviral agents (DAA) is vital. The first drugs that specifically target the HCV protease have been approved in 2011. This review summarizes the results of SPRINT-2, a phase III double blind, placebo controlled study in which the efficacy and safety of Boceprevir, a new HCV protease inhibitor, was compared to SOC.

DESIGN

A total of 1097 treatment-naïve, genotype 1, chronic hepatitis C patients were randomized into three different groups. All patients received a 4-week lead in phase with peginterferon alfa-2b and ribavirin. A total of 363 patients were randomized to the control group and received 44 additional weeks of PEG-IFN/RBV; of the 368 patients randomized to group 2, the response-guided treatment regimen (RGT), patients with undetectable HCV RNA through week 8 and 24 received 24 weeks of triple therapy (PEG-IFN/RBV/Boceprevir); patients whose HCV-RNA was detectable between weeks 8 and 24 but undetectable at week 24 received subsequently 20 weeks of (PEG-IFN/RBV); 366 patients in group 3 were treated with lead-in followed by triple therapy through week 48.

RESULTS

Treatment with Boceprevir triple therapy increased SVR to 63-66% compared to 38% receiving PEG-IFN/RBV therapy. Non-Black patients achieved higher SVR rates compared to Black patients. Responsiveness to interferon in the lead-in phase was predictive for SVR. SVR rates did not differ between patients randomized to RGT with Boceprevir and those treated with a fixed duration. Anaemia was the most important adverse event leading to dose reduction of RBV in 13% of controls and 21% of Boceprevir recipients.

CONCLUSION

Triple therapy of Boceprevir in combination with PEG-IFN 2b/RBV is more effective than SOC alone. RGT is possible without reducing the SVR rates. Management of anaemia has to be considered.

Management of chronic hepatitis C infection in children

PURPOSE OF REVIEW

Chronic hepatitis C infection remains a global public health burden and has important clinical implications due to progressive liver fibrosis and development of cirrhosis and its complications. The role of antiviral therapy in infected children is an area of controversy due to an indolent clinical course in the majority of children, and a low likelihood of viral eradication in response to an intensive interferon-based treatment course that is associated with a wide spectrum of adverse effects. This review summarizes new concepts in the epidemiology, natural history, and management of chronic hepatitis C infection in children.

RECENT FINDINGS

In the past 18 months, two large prospective studies demonstrated high rates of sustained virologic response in children with chronic hepatitis C infection, estimated at 53% in genotype 1 with peginterferon α-2b-ribavirin, and 47% in genotype 1 with peginterferon α-2a-ribavirin. On this basis, both combination regimens have been recently approved by the Food and Drug Administration (FDA) for use in children.

SUMMARY

Children with hepatitis C infection may benefit from early treatment, and the decision to pursue antiviral therapy should be based on individual assessment of host and viral characteristics, and stage of liver fibrosis.

Triple therapy for HCV genotype 1 infection: telaprevir or boceprevir?

Boceprevir and telaprevir are the first two protease inhibitors available for the treatment of patients infected with hepatitis C virus (HCV) genotype 1. A sustained virological response (SVR) of 70-80% is observed when either of these protease inhibitors is utilized with pegylated interferon (PEG-IFN) and ribavirin (RBV) in treatment naïve patients. Both agents are also highly effective in patients who failed to achieve a SVR during previous treatment with PEG-IFN/RBV. A rapid virological response (RVR) is observed in 56-60% of treatment naïve patients. Patients who achieve a RVR can be treated with a shorter course of therapy (24-28 weeks) and still achieve a SVR rate of 90% or higher. Patients who do not achieve a RVR, those with cirrhosis and certain prior non-responders should be treated for 48 weeks. Although the SVR rates observed with boceprevir and telaprevir are quite similar both globally and within sub-populations, the treatment algorithms for the two agents are unique. The decision of which protease inhibitor to use should assess several factors including the treatment scheme, duration of therapy, adverse event profile, cost and the likelihood of achieving a RVR. The latter is highly dependent upon IFN sensitivity and the IL28B genotype.

A human monoclonal antibody targeting scavenger receptor class B type I precludes hepatitis C virus infection and viral spread in vitro and in vivo

Endstage liver disease caused by chronic hepatitis C virus (HCV) infection is the leading indication for liver transplantation in the Western world. However, immediate reinfection of the grafted donor liver by circulating virus is inevitable and liver disease progresses much faster than the original disease. Standard antiviral therapy is not well tolerated and usually ineffective in liver transplant patients, whereas anti-HCV immunotherapy is hampered by the extreme genetic diversity of the virus and its ability to spread by way of cell-cell contacts. We generated a human monoclonal antibody against scavenger receptor class B type I (SR-BI), monoclonal antibody (mAb)16-71, which can efficiently prevent infection of Huh-7.5 hepatoma cells and primary hepatocytes by cell-culture-derived HCV (HCVcc). Using an Huh7.5 coculture system we demonstrated that mAb16-71 interferes with direct cell-to-cell transmission of HCV. Finally we evaluated the in vivo efficacy of mAb16-71 in "human liver urokinase-type plasminogen activator, severe combined immune deficiency (uPA-SCID) mice" (chimeric mice). A 2-week anti-SR-BI therapy that was initiated 1 day before viral inoculation completely protected all chimeric mice from infection with serum-derived HCV of different genotypes. Moreover, a 9-day postexposure therapy that was initiated 3 days after viral inoculation (when viremia was already observed in the animals) suppressed the rapid viral spread observed in untreated control animals. After cessation of anti-SR-BI-specific antibody therapy, a rise of the viral load was observed.

CONCLUSION

Using in vitro cell culture and human liver-chimeric mouse models, we show that a human mAb targeting the HCV coreceptor SR-BI completely prevents infection and intrahepatic spread of multiple HCV genotypes. This strategy may be an efficacious way to prevent infection of allografts following liver transplantation in chronic HCV patients, and may even hold promise for the prevention of virus rebound during or following antiviral therapy.

Boceprevir and telaprevir for the treatment of chronic hepatitis C: safety management in clinical practice

Effective management of adverse events (AEs) is important to prevent treatment discontinuation and optimize hepatitis C virus infection eradication rates. The addition of direct-acting antiviral agents, telaprevir (TVR) or boceprevir to pegylated interferon (PEG-IFN) and ribavirin (RBV) represents a new era of therapy associated with an improvement in treatment response rates and an impairment of the safety profile compared to PEG-IFN/RBV. An increase in the frequency and severity of anaemia was reported in clinical trials for both drugs, and skin disorders including rash and pruritus occurred more frequently with the TVR-based regimen. These AEs are generally manageable and do not lead to early discontinuation. The management of anaemia has not been clearly established, and the impact of RBV dose reductions and erythropoietin alpha use on treatment efficacy and safety must be clarified. The management of rashes, which were mild and moderate in more than 90% of the cases, is well planned, does not require TVR discontinuation and can be treated using emollients and topical corticosteroids. However, approximately 5% of rashes were severe, and a few cases were classified as severe cutaneous adverse reactions leading to treatment discontinuation.

Future treatment of patients with HCV cirrhosis

Of all hepatitis C virus (HCV) patients, those with cirrhosis are most in need of treatment because of increased morbidity and mortality. Treatment with pegylated-interferon (PEG-IFN) and ribavirin (RBV) (PR) has definitely shown the benefits of successful treatment by improving fibrosis, causing the regression of cirrhosis and reducing and preventing cirrhosis-related complications. However, the sustained virological response (SVR) is lower in patients with cirrhosis. First generation protease inhibitors (boceprevir and telaprevir) in combination with PR are a major advancement in the treatment of both naïve and treatment-experienced genotype 1 patients. In naïve patients, the SVR rate with the triple regimen with boceprevir was increased by 14% in patients with severe fibrosis or cirrhosis compared with PR. This benefit was lower than that observed in patients with mild or moderate fibrosis (30%). The SVR rate of the triple regimen with telaprevir was increased by 10-30% compared with PR in patients with severe fibrosis or cirrhosis compared with nearly 30% in patients with mild or moderate fibrosis. In treatment-experienced patients, previous relapsers have the highest increase in SVR with the triple regimen compared with PR, whatever the status of fibrosis. Previous partial or non-responder patients with cirrhosis had lower SVR rates than those without cirrhosis. However, the benefits of telaprevir and boceprevir vs PR was maintained. Previous non-responder patients with cirrhosis benefited the least from treatment. The relapse rate was always higher and side effects were more frequent in patients with cirrhosis compared with those without. First generation protease inhibitors plus PR appear to be a new step forward in the management of HCV genotype 1 patients with cirrhosis.

Single- and multiple-ascending-dose studies of the NS3 protease inhibitor asunaprevir in subjects with or without chronic hepatitis C

Hepatitis C virus (HCV) protease inhibitors combined with pegylated alfa interferon-ribavirin have demonstrated improved efficacy compared with pegylated alfa interferon-ribavirin alone for the treatment of chronic hepatitis C. Asunaprevir (BMS-650032), a novel HCV NS3 protease inhibitor in clinical development, was evaluated for safety, antiviral activity, and resistance in four double-blind, placebo-controlled, sequential-panel, single- and multiple-ascending-dose (SAD and MAD) studies in healthy subjects or subjects with chronic HCV genotype 1 infection. In SAD studies, subjects (healthy or with chronic HCV infection) were randomized to receive asunaprevir in dose groups of 10 to 1,200 mg or a placebo. In MAD studies, healthy subjects were randomized to receive asunaprevir in dose groups of 10 to 600 mg twice daily or a placebo for 14 days; subjects with HCV infection received asunaprevir in dose groups of 200 to 600 mg twice daily, or a placebo, for 3 days. Across all four studies, headache and diarrhea were the most frequent adverse events in asunaprevir recipients. Asunaprevir at doses of 200 to 600 mg resulted in rapid HCV RNA decreases from the baseline; maximal mean changes in HCV RNA over time were 2.7 and 3.5 log(10) IU/ml in the SAD and MAD studies, respectively. No enrichment of signature asunaprevir-resistant viral variants was detected. In conclusion, the novel NS3 protease inhibitor asunaprevir, when administered at single or multiple doses of 200 to 600 mg twice daily, is generally well tolerated, achieving rapid and substantial decreases in HCV RNA levels in subjects chronically infected with genotype 1 HCV.

The evolution of drug resistance interpretation algorithms: ANRS, REGA and extension of resistance analysis to HIV-1 group O and HIV-2

Antiretroviral drug resistance is mostly linked to a complex interaction of several amino acids with variable importance or a single amino acid. To facilitate the interpretation of observed mutation patterns, hospital university centers have developed several interpretation systems. All the currently available interpretation algorithms evolved, are being continuously updated and have been improved during the last decade. Some discrepancies are still evident that are partially smoothened by link of the individual programs with other systems. After the interpretation of HIV-1 group M subtype B mutations, a refined algorithm for the other group M subtypes was developed followed by the interpretation of HIV-1 group O and HIV-2 mutations. The process of improvement is ongoing, due to the better understanding and interpretation of single and cluster mutations and the availability of new antiretroviral substances. The knowledge gained from the experience of HIV drug resistance testing has been used to establish the interpretation of HBV polymerase mutations and will be extended for the treatment of HCV infected with protease inhibitors.

Current treatment options and response rates in children with chronic hepatitis C

Vertical transmission has become the most common mode of transmission of hepatitis C virus (HCV) in children. The rate of perinatal transmission from an HCV-infected mother to her child ranges from 2% to 5% and the prevalence of HCV in children in developed countries ranges between 0.1% and 0.4%. Spontaneous viral clearance seems to be dependent on the genotype and has been reported between 2.4%-25%. For chronically infected patients, treatment with recombinant polyethylene glycol (PEG)-interferon α-2b and daily ribavirin has now been approved as standard treatment for children 2-17 years of age. In five large prospective studies, a total of 318 children and adolescents aged 3-17 years were treated either with subcutaneous PEG-interferon α-2b at a dose of 1-1.5 μg/kg or 60 μg/m² once a week in combination with oral ribavirin (15 mg/kg per day) or PEG-interferon α-2a with ribavirin. Subjects with genotype 1 and 4 received the medication for 48 wk and individuals with genotype 2 and 3 mainly for 24 wk. Overall sustained viral response (SVR) was achieved in 193/318 (60.7%) of treated patients. Stratified for genotype; 120/234 (51%) with genotype 1, 68/73 (93%) with genotype 2/3, and 6/11 (55%) with genotype 4 showed SVR. Relapse rate was between 7.7% and 17%. Overall, treatment was well tolerated; however, notable side effects were present in approximately 20%. According to recent experiences in the treatment of chronic hepatitis C in children and adolescents, a combination of PEG-interferon α with ribavirin has been found to be well tolerated and highly efficacious, particularly in individuals with genotype 2/3. Thus, this treatment can be recommended as standard of care until more effective treatment options will become available for genotype 1 patients.

Does antiviral therapy prevent hepatocellular carcinoma?

Chronic infection with HBV or HCV can lead to the development of hepatocellular carcinoma (HCC). The major risk factors for HBV-related HCC are persistent presence of hepatitis B e antigen (HBeAg) and/or high serum HBV DNA levels, and cirrhosis. The major risk factor for HCV-related HCC is cirrhosis. One randomized double blind controlled trial of lamivudine in patients with HBeAg and/or high serum HBV DNA levels showed that antiviral therapy prevented disease progression and reduced the incidence of HCC. A beneficial effect of antiviral therapy on the risk of HCC has also been shown in cohort studies and meta-analyses, particularly among responders. Several randomized controlled trials of interferon in patients with HCV-related cirrhosis showed that treated patients had a lower incidence of HCC. A greater effect was observed in patients who achieved sustained virological response, while the benefit in non-responders is unclear. Antiviral therapies for hepatitis B and hepatitis C can prevent but not completely eliminate HCC. Improvement in identification of infected persons, accessibility of care and affordability of treatment is needed for antiviral therapy to have a major impact on the global incidence of HCC.

The Role of IL28B Genotype Testing in the Era of Direct Acting Antiviral Agents

The new era of Hepatitis C management is marked by newly available tests for IL28B polymorphisms, US Food and Drug Administration (FDA) approval of the first direct acting antivirals (DAA; boceprevir and telaprevir), monitoring of drug-related mutations and emerging data on new classes of DAAs and second wave and second generation protease inhibitors. With the previous standard of care (pegylated interferon-alpha and ribavirin), baseline predictors were regularly used to determine treatment candidacy, and recently, IL28B genetic polymorphisms have been identified as the strongest baseline predictors of treatment response. Yet the role of IL28B genotype testing and other baseline predictors is less clear in the setting of DAAs. We will review the current literature assessing the role of IL28B genetic variation in the setting of DAAs and discuss the potential indication for IL28B genotype testing in treatment decision-making in this new therapeutic era.

Implications of rapid virological response in hepatitis C therapy in the US veteran population

BACKGROUND

Early predictors of response to hepatitis C virus (HCV) therapy, such as rapid virological response, are valuable for the identification of patients with a higher likelihood of treatment success.

AIM

To identify predictors of rapid virological response in a real world setting.

METHODS

Using the VA Clinical Case Registry, we identified patients with HCV mono-infection, without liver transplantation, who initiated peginterferon (PEG-IFN) and ribavirin (RBV) in 2007 or 2008 and had HCV RNA testing for RVR. Significant baseline characteristics from genotype specific univariate analyses were used in backwards stepwise models to identify significant independent predictors of RVR.

RESULTS

The final cohort consisted of 2424 patients with genotype 1 (G1), 666 patients with genotype 2 (G2), and 419 patients with genotype 3 (G3). Rapid virological response rates were 15% for G1, 71% for G2 and 57% for G3. Sustained virological response rates were significantly higher in patients with rapid virological response than without, increasing from 18% to 52% in G1, 39% to 71% in G2, and 40% to 60% in G3 (P < 0.0001). A baseline HCV RNA < 500,000 IU/mL positively predicted RVR across all genotypes studied. In addition, for G1, Black race, Hispanic ethnicity, aspartate aminotransferase/alanine aminotransferase (AST/ALT) ≥ 0.6, ferritin ≥ 350 ng/mL, LDL< 100 mg/dL and diabetes; for G2, BMI ≥ 30 kg/m(2), platelets < 150 K/μL, LDL< 100 mg/dL and the use of PEG-IFN alfa-2b; and for G3, AST/ALT ≥ 1.0, all negatively predicted rapid virological response.

CONCLUSION

We found several novel independent predictors of rapid virological response, including BMI, AST/ALT ratio, ferritin, platelets, LDL, diabetes and type of PEG-IFN prescribed, which may be useful in guiding treatment decisions in routine medical practice.

Identification and analysis of inhibitors targeting the hepatitis C virus NS3 helicase

This chapter describes two types of FRET-based fluorescence assays that can be used to identify and analyze compounds that inhibit the helicase encoded by the hepatitis C virus (HCV). Both assays use a fluorescently labeled DNA or RNA oligonucleotide to monitor helicase-catalyzed strand separation, and they differ from other real-time helicase assays in that they do not require the presence of other nucleic acids to trap the reaction products. The first assay is a molecular beacon-based helicase assay (MBHA) that monitors helicase-catalyzed displacement of a hairpin-forming oligonucleotide with a fluorescent moiety on one end and a quencher on the other. DNA-based MBHAs have been used extensively for high-throughput screening (HTS), but RNA-based MBHAs are typically less useful because of poor signal to background ratios. In the second assay discussed, the fluorophore and quencher are split between two hairpin-forming oligonucleotides annealed in tandem to a third oligonucleotide. This split beacon helicase assay can be used for HTS with either DNA or RNA oligonucleotides. These assays should be useful to the many labs searching for HCV helicase inhibitors in order to develop new HCV therapies that are still desperately needed.

Virologic escape during danoprevir (ITMN-191/RG7227) monotherapy is hepatitis C virus subtype dependent and associated with R155K substitution

Danoprevir is a hepatitis C virus (HCV) NS3/4A protease inhibitor that promotes multi-log(10) reductions in HCV RNA when administered as a 14-day monotherapy to patients with genotype 1 chronic HCV. Of these patients, 14/37 experienced a continuous decline in HCV RNA, 13/37 a plateau, and 10/37 a rebound. The rebound and continuous-decline groups experienced similar median declines in HCV RNA through day 7, but their results diverged notably at day 14. Plateau group patients experienced a lesser, but sustained, median HCV RNA decline. Baseline danoprevir susceptibility was similar across response groups but was reduced significantly at day 14 in the rebound group. Viral rebound in genotype 1b was uncommon (found in 2/23 patients). Population-based sequence analysis of NS3 and NS4A identified treatment-emergent substitutions at four amino acid positions in the protease domain of NS3 (positions 71, 155, 168, and 170), but only two (155 and 168) were in close proximity to the danoprevir binding site and carried substitutions that impacted danoprevir potency. R155K was the predominant route to reduced danoprevir susceptibility and was observed in virus isolated from all 10 rebound, 2/13 plateau, and 1/14 continuous-decline patients. Virus in one rebound patient additionally carried partial R155Q and D168E substitutions. Treatment-emergent substitutions in plateau patients were less frequently observed and more variable. Single-rebound patients carried virus with R155Q, D168V, or D168T. Clonal sequence analysis and drug susceptibility testing indicated that only a single patient displayed multiple resistance pathways. These data indicate the ascendant importance of R155K for viral escape during danoprevir treatment and may have implications for the clinical use of this agent.

Interleukin 28B genetic polymorphisms and viral factors help identify HCV genotype-1 patients who benefit from 24-week pegylated interferon plus ribavirin therapy

BACKGROUND

Interleukin 28B (IL28B) single nucleotide polymorphism (SNP) genotypes and viral factors can predict sustained virological response (SVR) in HCV genotype-1 (HCV-1) patients receiving 48 weeks of pegylated interferon and ribavirin. Whether these factors would identify those patients who can benefit from a shorter duration of therapy remains unclear.

METHODS

Treatment-naive HCV-1 patients (n=662) receiving 24 or 48 weeks of combination therapy were enrolled. Baseline demographic data, HCV viral load, IL28B SNP genotypes (rs8099917), duration of therapy and rapid virological response (RVR) were evaluated to predict SVR. The SVR rates were further stratified by the independent factors and compared.

RESULTS

The IL28B rs8099917 TT genotype, low baseline viral load (HCV RNA≤600,000 IU/ml), RVR and 48-week therapy independently predicted SVR. In RVR patients with the IL28B rs8099917 TT genotype, the SVR rate of 24-week therapy was comparable to 48-week therapy (95% versus 99%; P=0.21) at low baseline viral load, but was inferior to 48-week therapy (70% versus 97%; P<0.001) at high baseline viral load. In non-RVR patients, the SVR rate of 24-week therapy was inferior to 48-week therapy for those with the IL28B rs8099917 TT genotype but high baseline viral load (23% versus 62%; P<0.001), and those with the IL28B rs8099917 GT/GG genotype but low baseline viral load (0% versus 33%; P=0.02).

CONCLUSIONS

HCV-1 patients simultaneously bearing the IL28B rs8099917 TT genotype, low baseline viral load and RVR can benefit from a shorter duration of combination therapy.

Predicted effect of direct acting antivirals in the current HIV-HCV-coinfected population in Spain

BACKGROUND

Direct acting antivirals (DAAs) against HCV are eagerly awaited for HIV-HCV-coinfected individuals. However, the activity of first generation drugs is limited to HCV genotype 1 and is lower in cirrhotics, subtype 1a infections, prior interferon (IFN)-α exposure or unfavourable IL28B alleles. Herein, we report the current profile of HIV-HCV-coinfected patients at our institution in an attempt to predict the effect of DAAs.

METHODS

All HIV-HCV-coinfected patients seen at our HIV outpatient clinic in 2011 were identified. Information on serum HCV RNA, HCV genotype/subtype, plasma HIV RNA, prior IFN-α experience, liver fibrosis staging and IL28B alleles was recorded.

RESULTS

A total of 424 HIV-HCV-coinfected patients were identified, of whom 174 (41%) were IFN-α-experienced. Mean serum HCV RNA was 6 log IU/ml. HCV genotype/subtype distribution was 166 (39.1%) G1a, 93 (22%) G1b, 85 (20%) G4, 49 (11.5%) G3 and 1 (<1%) G2, and 30 (7%) were unclassified. Of note, 56% of G1a were prior IFN-α-experienced patients. Overall, 37% had advanced liver fibrosis (Metavir score estimates F3-F4). Finally, 70% harboured unfavourable IL28B alleles.

CONCLUSIONS

The current profile of HIV-HCV-coinfected patients in Spain is dominated by particularly difficult-to-treat individuals, such as those infected with G1a or G4 (59%), advanced liver fibrosis (37%) and unfavourable IL28B alleles (70%). A wide use of prior anti-HCV therapy in our region most likely has resulted in hepatitis C cure of more IFN-α susceptible individuals, with accumulation of a more refractory treatment population. Thus, the use of DAAs in HIV-HCV-coinfected patients will require particular expertise and their benefit might be lower than expected.

Boceprevir and telaprevir in the management of hepatitis C virus-infected patients

Recent approval of direct-acting antiviral agents (DAAs) against hepatitis C virus (HCV) offers a major advance in the management of HCV infection. These DAAs, boceprevir and telaprevir, when given with pegylated interferon alfa (Peg-IFN) and ribavirin (RBV), result in a much higher sustained virologic response rate compared with Peg-IFN and RBV. The DAA-containing regimens are approved for HCV genotype 1 infection in HCV treatment-naive and HCV treatment-experienced patients. In this review, we present an overview of pharmacology, efficacy, adverse events, and emergence of resistance-associated variants with the use of these agents. As with all drugs, especially newly approved drugs, clinicians must consult the package insert for detailed prescribing information, list of all reported adverse events, contraindications, and drug interactions.

Biochemical study of the comparative inhibition of hepatitis C virus RNA polymerase by VX-222 and filibuvir

Filibuvir and VX-222 are nonnucleoside inhibitors (NNIs) that bind to the thumb II allosteric pocket of the hepatitis C virus (HCV) RNA-dependent RNA polymerase. Both compounds have shown significant promise in clinical trials and, therefore, it is relevant to better understand their mechanisms of inhibition. In our study, filibuvir and VX-222 inhibited the 1b/Con1 HCV subgenomic replicon, with 50% effective concentrations (EC(50)s) of 70 nM and 5 nM, respectively. Using several RNA templates in biochemical assays, we found that both compounds preferentially inhibited primer-dependent RNA synthesis but had either no or only modest effects on de novo-initiated RNA synthesis. Filibuvir and VX-222 bind to the HCV polymerase with dissociation constants of 29 and 17 nM, respectively. Three potential resistance mutations in the thumb II pocket were analyzed for effects on inhibition by the two compounds. The M423T substitution in the RNA polymerase was at least 100-fold more resistant to filibuvir in the subgenomic replicon and in the enzymatic assays. This resistance was the result of a 250-fold loss in the binding affinity (K(d)) of the mutated enzyme to filibuvir. In contrast, the inhibitory activity of VX-222 was only modestly affected by the M423T substitution but more significantly affected by an I482L substitution.

Contribution of a mutational bias in hepatitis C virus replication to the genetic barrier in the development of drug resistance

The development of resistance to direct-acting antivirals (DAAs) targeting the hepatitis C virus (HCV) can compromise therapy. However, mechanisms that determine prevalence and frequency of resistance-conferring mutations remain elusive. Here, we studied the fidelity of the HCV RNA-dependent RNA polymerase NS5B in an attempt to link the efficiency of mismatch formation with genotypic changes observed in vivo. Enzyme kinetic measurements revealed unexpectedly high error rates (approximately 10(-3) per site) for G:U/U:G mismatches. The strong preference for G:U/U:G mismatches over all other mistakes correlates with a mutational bias in favor of transitions over transversions. Deep sequencing of HCV RNA samples isolated from 20 treatment-naïve patients revealed an approximately 75-fold difference in frequencies of the two classes of mutations. A stochastic model based on these results suggests that the bias toward transitions can also affect the selection of resistance-conferring mutations. Collectively, the data provide strong evidence to suggest that the nature of the nucleotide change can contribute to the genetic barrier in the development of resistance to DAAs.

Chronic hepatitis C: treatments of the future

The launch of first-generation protease inhibitors (PIs) was a major step forward in hepatitis C virus (HCV) treatment. However, this major advance has, up to now, only been applicable to genotype-1 patients. Second-wave and second-generation PIs appear to achieve higher antiviral potency, with pan-genotype activities, fewer side-effects and potential activity against PI-resistant mutation by second-generation PIs, through more convenient daily administration. Other direct-acting antivirals (DAAs) include NS5B inhibitors such as nucleoside/nucleotide inhibitors (NIs) and non-nucleoside inhibitors (NNIs). NIs have similar efficacy across all genotypes and present with the highest barrier to resistance of all DAAs to date. PSI-7977, a pyrimidine nucleotide analogue, also has highly potent antiviral activity across all HCV genotypes. In combination with ribavirin in an interferon-free regimen, it can achieve a 100% sustained viral response (SVR) rate in genotype 2/3 treatment-naïve patients. In association with pegylated interferon and ribavirin (PR), it achieves an SVR of 91% in genotype-1 naïve patients. NNIs in association with PR appear to be less potent, but they may nonetheless play a key role in many of the combination trials including either PIs or NIs. NS5A inhibitors also exhibit highly potent antiviral activity. Evaluation of their activity in combination with PIs demonstrated for the first time that an interferon-free regimen can cure genotype-1b null-responder patients. Furthermore, quadruple therapy with PR can achieve a 100% SVR in genotype-1 null-responder patients. Other players in the field, such as cyclophilin inhibitors and therapeutic vaccines, may have a role in combination with DAAs. The near future of HCV treatment looks promising. However, whether or not DAA combinations will lead to an interferon-free regimen for all patients remains an open question.

Antiviral activity of the new DAAs for the treatment of hepatitis C virus infection: virology and resistance

The treatment of chronic hepatitis C virus (HCV) infection has substantially evolved over the past decade, following the Consensus Conference organized by the European Association for the Study of the Liver in 1999. Since then, the standard of care (SoC) for patients with chronic hepatitis C has been the combination of pegylated interferon (pegIFN) alpha-2a or -2b and ribavirin. In patients infected with HCV genotype 1, by far the most frequent HCV genotype worldwide, such treatment leads to a cure of infection in only 40-50% of cases. After a decade in which pegIFN alpha and ribavirin therapy was the only available option, triple therapy with HCV protease inhibitors (PIs; boceprevir and telaprevir) in combination with pegIFN alpha and ribavirin has become the new SoC for genotype-1-infected patients. With PI therapy, higher cure rates can be achieved, but specific issues are also raised, such as the emergence of resistance to PIs. For this reason, the present report examines the antiviral activity of PIs and what is currently known about resistance to them, while focusing on telaprevir and boceprevir, two HCV PIs recently licensed for the treatment of treatment-naïve and treatment-experienced genotype-1 patients with chronic hepatitis C. The clinical relevance of resistance testing is also discussed.