Faldaprevir combined with pegylated interferon alfa-2a and ribavirin in treatment-naïve patients with chronic genotype 1 HCV: SILEN-C1 trial

Drug-drug interactions with oral anti-HCV agents and idiosyncratic hepatotoxicity in the liver transplant setting

Studies of boceprevir and telaprevir based antiviral therapy in liver transplant (LT) recipients with hepatitis C genotype 1 infection have demonstrated dramatic increases in tacrolimus, cyclosporine, and mTOR inhibitor exposure. In addition to empiric dose reductions, daily monitoring of immunosuppressant blood levels is required when initiating as well as discontinuing the protease inhibitors to maximize patient safety. Although improved suppression of HCV replication is anticipated, 20 to 40% of treated subjects have required early treatment discontinuation due to various adverse events including anemia (100%), infection (30%), nephrotoxicity (20%) and rejection (5 to 10%). Simeprevir and faldaprevir will likely have improved efficacy and safety profiles but potential drug interactions with other OATP1B1 substrates and unconjugated hyperbilirubinemia are expected. In contrast, sofosbuvir and daclatasvir based antiviral therapy are not expected to lead to clinically significant drug-drug interactions in LT recipients but confirmatory studies are needed. Liver transplant recipients may also be at increased risk of developing drug induced liver injury (DILI). Establishing a diagnosis of DILI in the transplant setting is very difficult with the variable latency, laboratory features and histopathological manifestations of hepatotoxicity associated with a given drug, the need to exclude competing causes of allograft injury, and the lack of an objective and verifiable confirmatory test. Nonetheless, a heightened awareness of the possibility of DILI is warranted in light of the large number of medications used in LT recipients and the potential adverse impact that DILI may have on patient outcomes.

Chronic hepatitis C genotype 1 virus: who should wait for treatment?

Elucidation of the natural history of chronic hepatitis C (CHC) and the identification of risk factors for its progression to advanced liver disease have allowed many physicians to recommend deferral treatment (triple therapy) in favour of waiting for new drug availability for patients who are at low risk of progression to significant liver disease. Newer generation drugs are currently under development, and are expected to feature improved efficacy and safety profiles, as well as less complex and shorter duration delivery regimens, compared to the current standards of care. In addition, patients with cirrhosis and prior null responders have a low rate (around 15%) of achieving sustained virological response (SVR) with triple therapy, and physicians must also consider the decision to wait for new treatments in the future for these patients as well. Naïve patients are the most likely to achieve a close to 100% SVR rate; therefore, it may be advisable to recommend that patients with mild to moderate CHC should wait for the newer therapy options. In contrast, patients with advanced fibrosis and cirrhosis will be those with the greatest need for expedited therapeutic intervention. There remains a need, however, for establishing definitive clinical management guidelines to maximize the benefit of waiting for new drugs and minimize risk of side effects and non-response to the current triple therapy.

Bridging in vitro and in vivo metabolism and transport of faldaprevir in human using a novel cocultured human hepatocyte system, HepatoPac

An increased appreciation of the importance of transporter and enzyme interplay in drug clearance and a desire to delineate these mechanisms necessitates the utilization of models that contain a full complement of enzymes and transporters at physiologically relevant activities. Additionally, the development of drugs with longer half-lives requires in vitro systems with extended incubation times that allow characterization of metabolic pathways for low-clearance drugs. A recently developed coculture hepatocyte model, HepatoPac, has been applied to meet these challenges. Faldaprevir is a drug in late-stage development for the treatment of hepatitis C. Faldaprevir is a low-clearance drug with the somewhat unique characteristic of being slowly metabolized, producing two abundant hydroxylated metabolites (M2a and M2b) in feces (∼40% of the dose) without exhibiting significant levels of circulating metabolites in humans. The human HepatoPac model was investigated to characterize the metabolism and transport of faldaprevir. In human HepatoPac cultures, M2a and M2b were the predominant metabolites formed, with extents of formation comparable to in vivo. Direct glucuronidation of faldaprevir was shown to be a minor metabolic pathway. HepatoPac studies also demonstrated that faldaprevir is concentrated in liver with active uptake by multiple transporters (including OATP1B1 and Na(+)-dependent transporters). Overall, human HepatoPac cultures provided valuable insights into the metabolism and disposition of faldaprevir in humans and demonstrated the importance of enzyme and transporter interplay in the clearance of the drug.

Generating an in vitro-in vivo correlation for metabolism and liver enrichment of a hepatitis C virus drug, faldaprevir, using a rat hepatocyte model (HepatoPac)

Hepatocytes provide an integrated model to study drug metabolism and disposition. As a result of a loss of polarity or a significant decrease in the expression of enzymes and transporters, suspended and sandwich-cultured hepatocytes have limitations in determining hepatocellular drug concentrations. Underprediction of the extent of glucuronidation is also a concern for these hepatocyte models. Faldaprevir is a hepatitis C virus protease inhibitor in late-stage development that has demonstrated significant liver enrichment in in vivo rat models based on quantitative whole-body autoradiography (QWBA) and liver-to-plasma area under-the-curve ratio. In bile duct cannulated rats, the primary biliary metabolite was a glucuronide. Owing to ethical concerns, it is difficult to assess liver enrichment in humans, and a lack of in vitro and in vivo correlation of glucuronidation has been reported. The current study was conducted to verify whether a hepatocyte model, rat HepatoPac, could overcome some of these limitations and provide validity for follow-up studies with human HepatoPac. With rat HepatoPac, liver enrichment values averaged 34-fold and were consistent with rat QWBA (26.8-fold) and in vivo data (42-fold). In contrast, liver enrichment in suspended hepatocytes was only 2.8-fold. Furthermore, the extent of faldaprevir glucuronidation in HepatoPac studies was in agreement with in vivo results, with glucuronidation as the major pathway (96%). Suspended rat hepatocytes did not generate the glucuronide or two key hydroxylated metabolites that were observed in vivo. Overall, our studies suggest that HepatoPac is a promising in vitro model to predict in vivo liver enrichment and metabolism, especially for glucuronidation, and has demonstrated superiority over suspended hepatocytes.

Direct-acting Antiviral Agents for the Treatment of Chronic Hepatitis C Virus Infection

Hepatitis C virus (HCV) is a leading cause of cirrhosis and hepatocellular carcinoma (HCC) in the US and Japan. Therefore, eradication of HCV may reduce the occurrence of HCC in HCV-infected individuals. In 2011, the use of first-generation HCV NS3/4A protease inhibitors such as telaprevir and boceprevir was initiated for clinical treatment of HCV. Administration of telaprevir and boceprevir plus peginterferon and ribavirin increased rates of sustained virological response (SVR) in HCV genotype 1-infected patients. However, this treatment regimen also led to severe adverse events. Second-generation direct-acting antiviral agents (DAAs) for HCV, such as simeprevir plus peg-interferon and ribavirin also resulted in higher SVR rates, with similar adverse events to other peg-interferon and ribavirin treatments. Higher SVR rates in HCV genotype 1- and 2-infected patients were achieved with 12-16 weeks of sofosbuvir plus other class DAAs with/without ribavirin and 12 weeks of sofosbuvir plus ribavirin, respectively. For "difficult-to-treat" HCV-infected patients, more therapeutic options are needed. Further studies examining the efficacy and adverse effects of such therapies will be required for the development of additional treatments.

Enzyme-transporter interplay in the formation and clearance of abundant metabolites of faldaprevir found in excreta but not in circulation

Faldaprevir is a hepatitis C virus protease inhibitor that effectively reduces viral load in patients. Since faldaprevir exhibits slow metabolism in vitro and low clearance in vivo, metabolism was expected to be a minor clearance pathway. The human [(14)C] absorption, distribution, metabolism, and excretion study revealed that two monohydroxylated metabolites (M2a and M2b) were the most abundant excretory metabolites in feces, constituting 41% of the total administered dose. To deconvolute the formation and disposition of M2a and M2b in humans and determine why the minor change in structure [the addition of 16 atomic mass units (amu)] produced chemical entities that were excreted and were not present in the circulation, multiple in vitro test systems were used. The results from these in vitro studies clarified the formation and clearance of M2a and M2b. Faldaprevir is metabolized primarily in the liver by CYP3A4/5 to form M2a and M2b, which are also substrates of efflux transporters (P-glycoprotein and breast cancer resistance protein). The role of transporters is considered important for M2a and M2b as they demonstrate low permeability. It is proposed that both metabolites are efficiently excreted via bile into feces and do not enter the systemic circulation to an appreciable extent. If these metabolites permeate to blood, they can be readily taken up into hepatocytes from the circulation by uptake transporters (likely organic anion transporting polypeptides). These results highlight the critical role of drug-metabolizing enzymes and multiple transporters in the process of the formation and clearance of faldaprevir metabolites. Faldaprevir metabolism also provides an interesting case study for metabolites that are exclusively excreted in feces but are of clinical relevance.

Antiviral therapy of hepatitis C in 2014: do we need resistance testing?

The treatment of chronic hepatitis C has fundamentally changed since the approval of the first direct-acting antivirals (DAA) in 2011. In addition to telaprevir and boceprevir, in 2014 two new NS3 protease inhibitors (simeprevir and faldaprevir), one non-nucleoside polymerase inhibitor (sofosbuvir) and one NS5a replication complex inhibitor (daclatasvir) have expanded the treatment options for chronic hepatitis C. Resistance-associated variants (RAV) are naturally produced during the HCV life cycle. The frequency of RAVs within HCV quasispecies mainly depends on their replicational fitness. Variants conferring resistance to nucleos(t)ide analogues have not been detected, and the majority of NS3 protease-resistant variants are present at low frequencies (0.1-3%) before initiation of DAA-based therapies. However, the Q80K variant conferring resistance to simeprevir has been observed in 9-48% of untreated HCV genotype 1a-infected patients, leading to reduced SVR rates. Resistant variants are detectable in the majority of patients with treatment failure to NS3 protease inhibitor- or NS5a inhibitor-based antiviral therapy. Long-term follow-up studies by population-based sequence analysis have shown the disappearance of resistant variants in the majority of patients, with median times to loss of mutations of 4-64weeks. For the nucleotide analogue sofosbuvir, the emergence of the S282T resistant variant has been observed only in single patients, with reversion to wild-type within several weeks. Data are sparse on retreatment of patients with the same DAA or the same class of DAAs. However, retreatment with a different class of DAAs after failure of NS3 protease inhibitor-based therapy has been successful in small studies. This article forms part of a symposium in Antiviral Research on "Hepatitis C: next steps toward global eradication."

Entry inhibitors and future treatment of hepatitis C

Hepatitis C virus (HCV) is a major cause of liver cirrhosis and hepatocellular carcinoma. Furthermore, HCV-induced liver disease is the leading indication for liver transplantation. The recent introduction of direct-acting antivirals (DAAs) has revolutionized HCV treatment by making possible the cure of the majority of patients. However, their efficacy and safety in difficult-to-treat patients such as patients receiving immunosuppression, those with advanced liver disease, co-morbidity and HIV/HCV-co-infection remain to be determined. Furthermore, prevention of liver graft infection remains a pressing issue. HCV entry inhibitors target the very first step of the HCV life cycle and efficiently inhibit cell-cell transmission - a key prerequisite for viral spread. Because of their unique mechanism of action on cell-cell transmission they may provide a promising and simple perspective for prevention of liver graft infection. A high genetic barrier to resistance and complementary mechanism of action compared to DAAs makes entry inhibitors attractive as a new strategy for treatment of multi-resistant or difficult-to-treat patients. Clinical studies are needed to determine the future role of entry inhibitors in the arsenal of antivirals to combat HCV infection. This article forms part of a symposium in Antiviral Research on "Hepatitis C: next steps toward global eradication."

Mass balance and metabolite profiling of steady-state faldaprevir, a hepatitis C virus NS3/4 protease inhibitor, in healthy male subjects

The pharmacokinetics, mass balance, and metabolite profiles of faldaprevir, a selective peptide-mimetic hepatitis C virus NS3/NS4 protease inhibitor, were assessed at steady state in 7 healthy male subjects. Subjects received oral doses of 480 mg faldaprevir on day 1, followed by 240 mg faldaprevir on days 2 to 8 and 10 to 15. [14C]faldaprevir (240 mg containing 100 μCi) was administered on day 9. Blood, urine, feces, and saliva samples were collected at intervals throughout the study. Metabolite profiling was performed using radiochromatography, and metabolite identification was conducted using liquid chromatography-tandem mass spectrometry. The overall recovery of radioactivity was high (98.8%), with the majority recovered from feces (98.7%). There was minimal radioactivity in urine (0.113%) and saliva. Circulating radioactivity was predominantly confined to plasma with minimal partitioning into red blood cells. The terminal half-life of radioactivity in plasma was approximately 23 h with no evidence of any long-lasting metabolites. Faldaprevir was the predominant circulating form, accounting for 98 to 100% of plasma radioactivity from each subject. Faldaprevir was the only drug-related component detected in urine. Faldaprevir was also the major drug-related component in feces, representing 49.8% of the radioactive dose. The majority of the remainder of radioactivity in feces (41% of the dose) was accounted for in almost equal quantities by 2 hydroxylated metabolites. The most common adverse events were nausea, diarrhea, and constipation, all of which were related to study drug. In conclusion, faldaprevir is predominantly excreted in feces with negligible urinary excretion.

Genome-wide association study to characterize serum bilirubin elevations in patients with HCV treated with GS-9256, an HCV NS3 serine protease inhibitor

BACKGROUND

Protease inhibitors for the treatment of HCV can cause mild and reversible elevations of unconjugated bilirubin. We sought to characterize genetic determinants of bilirubin elevations using a genome-wide approach among patients with genotype 1 HCV who received combination therapy that included GS-9256, a novel potent inhibitor of HCV NS3 serine protease, as part of a Phase IIb trial.

METHODS

Of the 200 patients sampled, 176 had confirmed European ancestry and were included in the analysis. Infinium HumanOmni5BeadChip (Illumina, Inc., San Diego, CA, USA) was used for genotyping. A categorical analysis of low (grade 0-1) versus high (grade 2-4) bilirubin toxicity grade and a quantitative trait locus mapping of peak bilirubin concentrations was performed.

RESULTS

A total of 4,466,809 genetic markers were analysed. No single variant showed a statistically significant association with observed bilirubin elevations in this patient population. In a targeted analysis of single nucleotide polymorphisms in genes known to be involved in bilirubin transport, no significant differences in allele frequency between high and low bilirubin toxicity grade were observed.

CONCLUSIONS

These results indicate that risk for bilirubin elevation in patients receiving GS-9256 is unlikely to be strongly influenced by common genetic variants with large effects. The current study cannot rule out a role for common variants of weak effect, or a more complex model, including multiple contributing factors, such as rare variants and as yet unidentified environmental influences.

Second-wave IFN-based triple therapy for HCV genotype 1 infection: simeprevir, faldaprevir and sofosbuvir

With the approval of second-wave direct-acting antivirals simeprevir, sofosbuvir and faldaprevir in 2014-2015, for genotype 1 hepatitis C, patients and doctors will have more treatment options. During a first period, these treatments will still be used with peginterferon and ribavirin. The second wave of IFN-based triple therapy will have benefits and risk. These treatments have the following advantages: higher efficacy with more patient candidates for a shorten treatment duration (12-24 weeks, instead of 48 weeks). These new treatments appear to have a better safety profile than first generation, with no additional increase in anaemia over peginterferon/ribavirin. Then, these treatments are to take for patients with a decrease in pill burden (these three direct-acting antivirals are given orally one pill a day). Simeprevir and sofosbuvir may be approved in the US and Europe, in 2014, at the time this manuscript will be released. Approval of faldaprevir will follow. These direct-acting antivirals with many others will hopefully be combined in future interferon-free regimens. The goal of this review to summarize the results and safety of simeprevir, faldaprevir and sofosbuvir, to advise physicians and to inform patients on the benefits and risks of these second-wave IFN-based regimens for HCV genotype infection.

HCV F1/F2 patients: treat now or continue to wait

The treatment of chronic HCV is evolving rapidly. In 2014, three new oral antiviral agents, simeprevir, faldeprevir and sofosbuvir will become available for patients with HCV genotype 1. These agents have far less side effects than the first generation protease inhibitors telaprevir and boceprevir. Treatment will therefore be easier for patients to tolerate but still require peginterferon and ribavirin (PEGINF/RBV). The first IFN free therapy, sofosbuvir (SOF) and ribavirin (RBV), will also become available in 2014. This treatment is highly effective for patients with HCV genotype 2. However, SVR rates with SOF/RBV appear to be similar to that achieved with PEGINF/RBV in patients with HCV genotype 3. The first IFN-free all oral antiviral therapy combination for patients with HCV genotype 1 may be available late in 2014 or early 2015. The factors which should be considered when deciding whether to treat a patient with HCV now or to delay treatment until IFN free therapies are available is discussed.

Role of IL28B for chronic hepatitis C treatment toward personalized medicine

Genome-wide association studies recently revealed that certain interleukin-28B (IL28B) polymorphisms are strongly associated with responses to pegylated interferon (PEG-IFN) and ribavirin (RBV) therapy in patients chronically infected with hepatitis C virus (HCV) genotype 1, as well as with spontaneous clearance of HCV. Subsequent reports revealed that IL28B genotypes also affect treatment efficacy in chronic infection with other HCV genotypes. Furthermore, there have been several reports that implicate IL28B genotypes in inflammatory status, progression of fibrosis and adverse clinical outcomes in chronic hepatitis C (CHC). Therapy of CHC recently entered a new era with the deployment of direct-acting antivirals. These include nonstructural 3/4A protease inhibitors which have shown promise in combination with PEG-IFN/RBV in several clinical trials. IFN-free therapy is expected to be useful especially in IFN-resistant patients and may become the standard of care in the future. Several clinical trials have revealed an association between IL28B genotype and treatment efficacy in triple therapy or IFN-free regimens. On the other hand the mechanism of the effect of IL28B on HCV infection has not yet been elucidated. Recently, it was shown that the polymorphism of IFN-lambda 4 (IFNL4) is in high linkage disequilibrium with that of near IL28B, and more strongly associated with spontaneous or treatment-induced HCV clearance than IL28B genotypes, especially in individuals of African ancestry. This finding provides new insights into the genetic regulation of HCV clearance and its clinical management. IL28B genotyping will be also useful for personalized CHC treatment in the forthcoming era of direct-acting antivirals.

Treating HCV in HIV 2013: on the cusp of change

Treating hepatitis C virus (HCV) in HIV/HCV co-infected patients is a challenge. Even if the benefits of achieving a sustained virological response are clear, the rates achieved with the combination of pegylated-interferon and ribavirin are disappointing. The addition of direct acting antiviral agents (DAAs) to the treatment of hepatitis C is revolutionizing the treatment of HCV in mono-infected patients. Even if there have not been any agents approved for the treatment of co-infected patients, many studies specifically designed for this population are ongoing. This article reviews available data on the use of DAAs in co-infected patients and the challenges associated with these new drugs.

HCV direct-acting antiviral agents: the best interferon-free combinations

For HCV infection, there have been major advancements during last several years with large numbers of ongoing trials with various direct-acting antivirals (DAA) showing high potency, favourable tolerability profile, higher barrier to resistance, shortened treatment duration, all oral regimen, pan-genotypic, fewer drug interactions and reduced pill burden. By 2014, several DAAs are anticipated to complete successful phase III trials and will be commercially available. Initially, a wave of IFN-based regimen (sofosbuvir, faldaprevir and simeprevir) will be available for treatment of HCV genotype 1. In the near future, combination of antiviral agents with additive potency that lack cross-resistance with good safety profile will likely be the new recommended regimens, making HCV, the first chronic viral infection to be eradicated worldwide with a finite duration of combination DAA therapy without IFN or ribavirin. The aim of this review was to summarize the results obtained from recent DAA combination studies without IFN.

Treatment of hepatitis C with an interferon-based lead-in phase: a perspective from mathematical modelling

BACKGROUND

The standard of care for HCV genotype 1 is a protease inhibitor (telaprevir or boceprevir) combined with pegylated interferon (PEG-IFN) and ribavirin (RBV). A lead-in phase of PEG-IFN/RBV therapy before addition of the protease inhibitor has been used, with the aim of improving response rates by reducing the development of protease inhibitor resistance. However, whether such a strategy can bring benefit to patients is unclear.

METHODS

A viral dynamic model was used to compare in silico HCV dynamics in patients treated with a period of PEG-IFN/RBV lead-in therapy followed by the addition of a protease inhibitor versus immediate triple therapy without lead-in.

RESULTS

The model predicts that both regimens result in a similar end-of-treatment viral load change (viral decline or breakthrough). Thus, the current lead-in strategy may not decrease the rate of viral breakthrough/relapse or increase the rate of sustained virological response. This agrees with available data from clinical trials of several HCV protease inhibitors, such as telaprevir, boceprevir and faldaprevir.

CONCLUSIONS

These results suggest that current PEG-IFN/RBV lead-in strategies may not improve treatment outcomes. However, viral kinetics during a period of PEG-IFN/RBV therapy, combined with other factors, such as the IL28B polymorphism and baseline viral load, can identify IFN-sensitive patients and help develop response-guided therapies.

SVR12 is higher than SVR24 in treatment-naïve hepatitis C genotype 1 patients treated with peginterferon plus ribavirin

BACKGROUND

Randomized clinical trials (RCTs) of interventions for the hepatitis C virus have historically used sustained virological response (SVR) at 24 weeks after treatment (SVR24) as the key effect measure. However, recent RCTs investigating the efficacy of new direct acting agents (DAAs) have used SVR at 12 weeks after treatment (SVR12). While there is evidence to suggest SVR24 and SVR12 are similar in patients receiving new DAAs, this is unlikely to be true for patients receiving backbone peginterferon-ribavirin control treatment. Establishing the difference between SVR12 and SVR24 for patients receiving peginterferon-ribavirin treatment is therefore necessary to avoid biased interpretations of the benefits of newer DAAs.

METHODS

We searched the MEDLINE®, Embase™, and Cochrane CENTRAL for RCTs with a peginterferon-ribavirin arm that used SVR24 and/or SVR12. As no RCTs reported on both, we pooled SVR12 and SVR24 proportions using conventional meta-analysis. Proportions were pooled separately for peginterferon alpha-2a and alpha-2b. Further, a Bayesian meta-regression model was employed to estimate the difference between SVR12 and SVR24.

RESULTS

Thirty-five RCTs including a peginterferon arm were identified. Twenty-four trials included a peginterferon alpha-2a plus ribavirin arms, of which 20 reported SVR24 and five reported SVR12. Seventeen trials included a peginterferon alpha-2b plus ribavirin arm, of which 16 reported SVR24 and one reported SVR12. Using Bayesian meta-regression, the pooled SVR12 was 6% higher than SVR24 with peginterferon alpha-2a (53% versus 47%) and 5% higher with peginterferon alpha-2b (45% versus 40%) and 95% credible intervals (CrIs) were only marginally overlapping. The meta-regression also demonstrated a marginally significant relative risk of 1.13 (95% CrI 0.99-1.26) of SVR12 versus SVR24. The conventional pairwise meta-analyses were consistent with these findings.

CONCLUSION

Considering the relatively large difference observed between SVR12 and SVR24, it seems reasonable to insist that future clinical trials report both to allow for complete transparency and clarity in their interpretation.

Safety and efficacy of faldaprevir with pegylated interferon alfa-2a and ribavirin in Japanese patients with chronic genotype-1 hepatitis C infection

BACKGROUND & AIMS

Faldaprevir (BI 201335) is a potent once-daily (QD) NS3/4A protease inhibitor for the treatment of patients with genotype-1 (GT-1) hepatitis C virus (HCV). The aim of this study was to evaluate the safety, pharmacokinetics and efficacy of faldaprevir plus pegylated interferon alfa-2a (PegIFN) and ribavirin (RBV) in Japanese patients infected with chronic GT-1 HCV.

METHODS

Part 1 of this phase II study was a randomized, double-blind, placebo-controlled, dose-ascending study. Treatment-naïve patients received faldaprevir 120 or 240 mg QD, or placebo, plus PegIFN/RBV for 4 weeks, then PegIFN/RBV alone for 44 weeks. In Part 2 (open label), treatment-experienced patients received faldaprevir 240 mg QD plus PegIFN/RBV for 4 weeks, then PegIFN/RBV alone for 44 weeks. Efficacy was assessed using sustained virological response (SVR) 24 weeks after treatment completion. The pharmacokinetics, safety and tolerability of faldaprevir were also assessed.

RESULTS

SVR was achieved by 4/6 (67%) treatment-naïve patients treated with faldaprevir 120 mg QD, 5/6 (83%) patients treated with faldaprevir 240 mg QD and 2/4 (50%) patients who received placebo. Of the treatment-experienced patients, 3/6 (50%) achieved SVR. Faldaprevir was well tolerated. There was one serious adverse event, which was not considered to be treatment related. Rash and hyperbilirubinaemia were more frequently reported with faldaprevir than with placebo in treatment-naïve patients, but no cases were severe or serious and none led to discontinuation. Steady-state plasma concentrations of faldaprevir were reached within 7 days of QD dosing.

CONCLUSIONS

Faldaprevir with PegIFN/RBV was efficacious and well tolerated, supporting further evaluation of this combination in Japanese patients.

Antiviral treatment of hepatitis C virus infection and factors affecting efficacy

Hepatitis C virus (HCV) infection is the leading cause of chronic liver-related diseases, including cirrhosis, liver failure, and hepatocellular carcinoma. Currently, no effective vaccine is available for HCV infection. Polyethylene glycol interferon-α (PegIFN-α) in combination with ribavirin (RBV) is the standard of care (SOC) for chronic hepatitis C. However, the efficacy of PegIFN-α and RBV combination therapy is less than 50% for genotype 1 HCV, which is the dominant virus in humans. In addition, IFN and RBV have several severe side effects. Therefore, strategies to improve sustained virological response (SVR) rates have been an important focus for clinical physicians. The serine protease inhibitors telaprevir and boceprevir were approved by the United States Food and Drug Administration in 2011. The addition of HCV protease inhibitors to the SOC has significantly improved the efficacy of treatments for HCV infection. Several direct-acting antiviral drugs currently in late-stage clinical trials, both with and without peg-IFN and RBV, have several advantages over the previous SOC, including higher specificity and efficacy, fewer side effects, and the ability to be administered orally, and might be optimal regimens in the future. Factors affecting the efficacy of anti-HCV treatments based on IFN-α include the HCV genotype, baseline viral load, virological response during treatment, host IL28B gene polymorphisms and hepatic steatosis. However, determining the effect of the above factors on DAA therapy is necessary. In this review, we summarize the development of anti-HCV agents and assess the main factors affecting the efficacy of antiviral treatments.

Faldaprevir (BI 201335) for the treatment of hepatitis C in patients co-infected with HIV

Chronic HCV infection affects 130-170 million individuals worldwide and there are currently 34 million people living with HIV/AIDS. The aim of treatment of HCV is the elimination of the virus (sustained virological response). With development of drugs that specifically target HCV replication, direct-acting agents, sustained virological response rates have dramatically changed for genotype 1 infections. Challenges in the use of direct-acting agents in patients with HIV/HCV co-infection include the potential for drug-drug interactions between HIV and HCV drugs, additional drug toxicities and the need for therapy with IFN-α. Faldaprevir (FDV), previously known as BI 201335, is a second-wave HCV NS3/4A protease inhibitor with highly potent in vitro activity against HCV GT-1a/1b and improved pharmacokinetics suitable for once-daily dosing. FDV is currently in Phase III development. This article will review the pharmacology and pharmacodynamics of FDV, the efficacy and safety of the drug and explore possible future developments in the management of chronic hepatitis C infection, focusing on HIV/HCV co-infected patients.

An update on the treatment of genotype-1 chronic hepatitis C infection: lessons from recent clinical trials

The launch of first-generation protease inhibitors (PIs) was a major step forward in hepatitis C virus (HCV) treatment. However, this major advance is, up to now, restricted to genotype-1 (GT-1) patients. However, the ongoing development of new direct-acting antiviral agents (DAAs) allows new hope for the future. The development of second-wave and second-generation PIs yields higher antiviral potency through plurigenotypic activity, more convenient daily administration, fewer side effects and, for the second-generation PIs, potential activity against resistance-associated variants. NS5B inhibitors (NS5B.I) include nucleoside/nucleotide inhibitors (NIs) and nonnucleotide inhibitors (NNIs). NIs have high efficacy across all genotypes. Sofosbuvir has highly potent antiviral activity across all genotypes in association with pegylated interferon (IFN) and ribavirin (PR), thus allowing shortened treatment duration. NS5A inhibitors (NS5A.I) have highly potent antiviral activity. It has recently been shown for the first time that NS5A.I in combination with PI can cure GT-1b null-responder patients in an IFN-free regimen. In addition, several studies demonstrate that IFN-free regimens with DAA combinations are able to cure a large number of either naïve or treatment-experienced GT-1 patients. Moreover, a quadruple regimen with PR is able to cure almost all GT-1 null-responders. The development of pan-genotypic DAAs (NIs or NS5A.I) allows new combinations with or without PR that increase the rate of sustained virological response (SVR) for all patients, even for those with cirrhosis and independently of the genotype. Therefore, the near future of HCV treatment looks promising. The purpose of this article is to provide an overview of the clinical results recently reported for HCV treatment in GT-1 patients.

Baseline hepatitis C virus (HCV) NS3 polymorphisms and their impact on treatment response in clinical studies of the HCV NS3 protease inhibitor faldaprevir

A challenge to the treatment of chronic hepatitis C with direct-acting antivirals is the emergence of drug-resistant hepatitis C virus (HCV) variants. HCV with preexisting polymorphisms that are associated with resistance to NS3/4A protease inhibitors have been detected in patients with chronic hepatitis C. We performed a comprehensive pooled analysis from phase 1b and phase 2 clinical studies of the HCV protease inhibitor faldaprevir to assess the population frequency of baseline protease inhibitor resistance-associated NS3 polymorphisms and their impact on response to faldaprevir treatment. A total of 980 baseline NS3 sequences were obtained (543 genotype 1b and 437 genotype 1a sequences). Substitutions associated with faldaprevir resistance (at amino acid positions 155 and 168) were rare (<1% of sequences) and did not compromise treatment response: in a phase 2 study in treatment-naive patients, six patients had faldaprevir resistance-associated polymorphisms at baseline, of whom five completed faldaprevir-based treatment and all five achieved a sustained virologic response 24 weeks after the end of treatment (SVR24). Among 13 clinically relevant amino acid positions associated with HCV protease resistance, the greatest heterogeneity was seen at NS3 codons 132 and 170 in genotype 1b, and the most common baseline substitution in genotype 1a was Q80K (99/437 [23%]). The presence of the Q80K variant did not reduce response rates to faldaprevir-based treatment. Across the three phase 2 studies, there was no significant difference in SVR24 rates between patients with genotype 1a Q80K HCV and those without Q80K HCV, whether treatment experienced (17% compared to 26%; P = 0.47) or treatment naive (62% compared to 66%; P = 0.72).

Managing HIV/hepatitis C co-infection in the era of direct acting antivirals

Morbidity and mortality from co-morbid hepatitis C (HCV) infection in HIV co-infected patients are increasing; hence, the management of hepatitis co-infection in HIV is now one of the most important clinical challenges. Therefore, the development of direct acting antivirals (DAAs) for treatment of HCV has been eagerly awaited to hopefully improve HCV treatment outcome in co-infected individuals. Indeed, the availability of the first HCV protease inhibitors (PI) boceprevir and telaprevir for HCV genotype 1 patients has changed the gold standard of treating hepatitis C allowing for substantially improved HCV cure rates under triple HCV-PI/pegylated interferon/ribavirin therapy. Moreover, numerous other new DAAs are currently being studied in co-infected patient populations, also exploring shorter treatment durations and interferon-free treatment approaches promising much easier and better tolerated treatment regimens in the near future. Nevertheless, numerous challenges remain, including choice of patients to treat, potential for drug-drug interactions and overlapping toxicities between HIV and HCV therapy. The dramatically improved rates of HCV cure under new triple therapy, however, warrant evaluation of these new treatment options for all co-infected patients.

Novel therapeutic approaches for hepatitis C

Chronic hepatitis C virus (HCV) infection afflicts a reported 170 million people worldwide and is often complicated by cirrhosis and hepatocellular carcinoma. Morbidity and mortality are decreased with the successful treatment of chronic HCV infection. The current standard of care in the treatment for genotype 1 chronic HCV is pegylated interferon (IFN)-alfa, termed PEG, and ribavirin (RBV) in conjunction with a protease inhibitor, either telaprevir or boceprevir, which results in 67-75% sustained viral response rates. Increased understanding of the HCV has allowed further development of new direct-acting antiviral (DAA) agents against the HCV and has also allowed the development of IFN-free oral treatment regimens. We anticipate the approval in late 2013 of the first nucleotide polymerase inhibitor regimen with RBV alone for genotypes 2/3 and in combination with a 12-week regimen of PEG+RBV for genotypes 1, 4, 5, and 6. Most of the promising new DAA regimens are discussed herein.

Drug-drug interactions during antiviral therapy for chronic hepatitis C

The emergence of direct-acting antiviral agents (DAAs) for HCV infection represents a major advance in treatment. The NS3 protease inhibitors, boceprevir and telaprevir, were the first DAAs to receive regulatory approval. When combined with PEG-IFN and ribavirin, these agents increase rates of sustained virologic response in HCV genotype 1 to ∼70%. However, this treatment regimen is associated with several toxicities. In addition, both boceprevir and telaprevir are substrates for and inhibitors of the drug transporter P-glycoprotein and the cytochrome P450 enzyme 3A4 and are, therefore, prone to clinically relevant drug interactions. Several new DAAs for HCV are in late stages of clinical development and are likely to be approved in the near future. These include the protease inhibitors, simeprevir and faldaprevir, the NS5A inhibitor, daclatasvir, and the nucleotide polymerase inhibitor, sofosbuvir. Herein, we review the clinical pharmacology and drug interactions of boceprevir, telaprevir and these investigational DAAs. Although boceprevir and telaprevir are involved in many interactions, these interactions are manageable if health-care providers proactively identify and adjust treatments. Emerging DAAs seem to have a reduced potential for drug interactions, which will facilitate their use in the treatment of HCV.

Oral antiviral therapies for chronic hepatitis C infection

The treatment of hepatitis C virus (HCV) infection with pegylated interferon alpha and ribavirin leads to a sustained virologic response in around 50% of patients with HCV genotype 1, 65% with HCV genotype 4, 75% with HCV genotype 3 and around 80% with HCV genotype 2. A better understanding of the HCV lifecycle has resulted in the development of several potential direct-acting antiviral drugs (DAAs) targeting viral proteins [NS3/4A protease inhibitors, NS5B nucleos(t)idic and non-nucleos(t)idic polymerase inhibitors, NS5A replication complex inhibitors]. This review summarizes the main clinical data for the combinations of oral DAAs. DAAs, either in combination with pegylated interferon alpha or in interferon-free regimens, have demonstrated a high level of antiviral efficacy and a generally well-tolerated safety profile in treatment-naïve patients and in prior nonresponders to pegylated interferon alpha/ribavirin. Oral combination of new DAAs is likely to become the standard of care for chronic HCV in treatment-naïve or treatment-experienced patients. However, most studies so far have included small numbers of 'easy-to-treat' patients with short post-treatment periods for defining the sustained virologic response. Extension of the number of treated patients (including 'difficult-to-treat' patients, i.e. patients infected with genotype 3, who failed to respond to first-generation protease inhibitors or with cirrhosis as well as immunocompromised patients) and of the post-treatment follow up in a real-life setting could significantly worsen the rate of recovery. In these 'difficult-to-treat' patients, the rate of virologic cure with new DAAs could be lower than expected and consequently interferons may be still necessary in combination with the new drugs.

Faldaprevir (BI 201335), deleobuvir (BI 207127) and ribavirin oral therapy for treatment-naive HCV genotype 1: SOUND-C1 final results

BACKGROUND

Faldaprevir (BI 201335) and deleobuvir (BI 207127) are direct-acting antiviral agents under development for the treatment of chronic HCV infection. This article describes the final results of the Phase Ib SOUND-C1 study that evaluated the interferon-free oral combination of faldaprevir, deleobuvir and ribavirin in 32 treatment-naive patients infected with HCV genotype 1.

METHODS

Patients were randomized to receive deleobuvir 400 mg (n=15) or 600 mg (n=17) three times daily plus faldaprevir 120 mg once daily and weight-based ribavirin for 4 weeks. Interferon-free therapy was followed by response-guided faldaprevir plus pegylated interferon-α2a/ribavirin to week 24 or 48.

RESULTS

At week 4, 73% (11/15) and 100% (17/17) of patients in the deleobuvir 400 mg and 600 mg groups achieved HCV RNA<25 IU/ml, respectively. During interferon-free treatment, virological breakthrough was reported in one patient and re-increase of HCV RNA in one patient. Both patients were successfully treated with interferon-containing therapy. The rate of sustained virological response 24 weeks after completion of treatment was 73% (11/15) in the deleobuvir 400 mg group and 94% (16/17) in the 600 mg group. During faldaprevir plus pegylated interferon-α2a/ribavirin treatment, the most common adverse events were pruritus (38% of patients), rash (31%) and asthenia (31%); these were severe in approximately 3% of patients.

CONCLUSIONS

Potent antiviral activity and favourable safety of the treatment regimen were demonstrated. Furthermore, the results suggest that patients with breakthrough at week 4 may be rescued with an interferon-containing regimen. Clinical trials.gov number NCT01132313.