Clinical relevance of HCV antiviral drug resistance

Evolution of drug resistance against antiviral agents that target cellular factors

Antiviral drugs have classically been developed by directly disrupting the functions of viral proteins. However, this strategy has been largely unsuccessful due to the rapid generation of viral escape mutants. It has been well established that as compared to the virus-centric approach, the strategy of developing antiviral drugs by targeting host-dependency factors (HDFs) minimizes drug resistance. However, recent reports have indicated that drug resistance against some of the host-targeting antiviral agents can in fact occur under some circumstances. Long-term selection pressure of a host-targeting antiviral agent may induce the virus to use an alternate cellular factor or alters its affinity towards the target that confers resistance. Alternatively, virus may synchronize its life cycle with the patterns of drug therapy. In addition, virus may subvert host's immune system to perpetuate under the limiting conditions of the targeted cellular factor. This review describes novel potential mechanisms that may account for the acquiring resistance against agents that target HDFs.

Medicinal chemistry strategies for discovering antivirals effective against drug-resistant viruses

During the last forty years we have witnessed impressive advances in the field of antiviral drug discovery culminating with the introduction of therapies able to stop human immunodeficiency virus (HIV) replication, or cure hepatitis C virus infections in people suffering from liver disease. However, there are important viral diseases without effective treatments, and the emergence of drug resistance threatens the efficacy of successful therapies used today. In this review, we discuss strategies to discover antiviral compounds specifically designed to combat drug resistance. Currently, efforts in this field are focused on targeted proteins (e.g. multi-target drug design strategies), but also on drug conformation (either improving drug positioning in the binding pocket or introducing conformational constraints), in the introduction or exploitation of new binding sites, or in strengthening interaction forces through the introduction of multiple hydrogen bonds, covalent binding, halogen bonds, additional van der Waals forces or multivalent binding. Among the new developments, proteolysis targeting chimeras (PROTACs) have emerged as a valid approach taking advantage of intracellular mechanisms involving protein degradation by the ubiquitin-proteasome system. Finally, several molecules targeting host factors (e.g. human dihydroorotate dehydrogenase and DEAD-box polypeptide 3) have been identified as broad-spectrum antiviral compounds. Implementation of herein described medicinal chemistry strategies are expected to contribute to the discovery of new drugs effective against current and future threats due to emerging and re-emerging viral pandemics.

Challenges and perspectives of direct antivirals for the treatment of hepatitis C virus infection

Treatment of chronic hepatitis C virus infection has been revolutionised by the development of direct-acting antivirals (DAAs). All-oral, once-daily, 8- to 12-week treatment regimens are now standard of care, with viral eradication possible in >95% of patients across different populations. Despite these advances, several unresolved issues remain, including treatment of patients with hepatitis C virus genotype 3, chronic kidney disease, and those in whom DAA therapy has previously failed. Glecaprevir/pibrentasvir and sofosbuvir/velpatasvir/voxilaprevir are the most recently approved DAA regimens. Given the overwhelming success of modern DAA-based therapies, glecaprevir/pibrentasvir and sofosbuvir/velpatasvir/voxilaprevir are also likely to represent the last DAAs to be approved. Both are pangenotypic, once-daily, all-oral DAA combinations that have the potential to close the gaps in the current DAA treatment portfolio. Herein, we review the challenges associated with current DAAs and how these two regimens may be implemented in existing treatment algorithms.

Comparison of antiviral resistance across acute and chronic viral infections

Antiviral therapy can lead to drug resistance, but multiple factors determine the frequency of drug resistance mutations and the clinical consequences. When chronic infections caused by Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV) and Hepatitis B Virus (HBV) are compared with acute infections such as influenza virus, respiratory syncytial virus (RSV), and other respiratory viruses, there are similarities in how and why antiviral resistance substitutions occur, but the clinical significance can be quite different. Emergence of resistant variants has implications for design of new therapeutics, treatment guidelines, clinical trial design, resistance monitoring, reporting, and interpretation. In this discussion paper, we consider the molecular factors contributing to antiviral drug resistance substitutions, and a comparison is made between chronic and acute infections. The implications of resistance are considered for clinical trial endpoints and public health, as well as the requirements for therapeutic monitoring in clinical practice with acute viral infections.

Grazoprevir and elbasvir plus ribavirin for chronic HCV genotype-1 infection after failure of combination therapy containing a direct-acting antiviral agent

BACKGROUND & AIMS

The Phase-2 C-SALVAGE study evaluated an investigational interferon-free combination of grazoprevir (a NS3/4A protease inhibitor) and elbasvir (a NS5A inhibitor) with ribavirin for patients with chronic HCV genotype-1 infection who had failed licensed DAA-containing therapy.

METHODS

C-SALVAGE was an open-label study of grazoprevir 100 mg and elbasvir 50 mg QD with weight-based ribavirin BID for 12 weeks in cirrhotic and non-cirrhotic patients with chronic HCV genotype-1 infection who had not attained SVR after ⩾4 weeks of peginterferon and ribavirin plus either boceprevir, telaprevir, or simeprevir. Exclusion criteria included decompensated liver disease, hepatocellular carcinoma, and HIV or HBV co-infection. The primary efficacy outcome was SVR12 defined as a HCV RNA level below the assay limit of quantification 12 weeks after the end of treatment.

RESULTS

Of the 79 patients treated with ⩾1 dose of study drug, 66 (84%) patients had a history of virologic failure on a regimen containing a NS3/4A protease inhibitor; 12 of the other 13 patients discontinued prior treatment because of adverse experiences. At entry, 34 (43.6%) of 78 evaluable patients harbored NS3 RAVs. SVR12 rates were 76/79 (96.2%) overall, including 28/30 (93.3%) patients with genotype 1a infection, 63/66 (95.5%) patients with prior virologic failure, 43/43 (100%) patients without baseline RAVs, 31/34 (91.2%) patients with baseline NS3 RAVs, 6/8 (75.0%) patients with baseline NS5A RAVs, 4/6 (66.7%) patients with both baseline NS3 and RAVs, and 32/34 (94.1%) cirrhotic patients. None of the five reported serious adverse events were considered drug-related.

CONCLUSIONS

Grazoprevir and elbasvir plus ribavirin for 12 weeks provides a promising new treatment option for patients after failure of triple therapy containing an earlier-generation protease inhibitor.

Susceptibilities of genotype 1a, 1b, and 3 hepatitis C virus variants to the NS5A inhibitor elbasvir

Elbasvir is an investigational NS5A inhibitor with in vitro activity against multiple HCV genotypes. Antiviral activity of elbasvir was measured in replicons derived from wild-type or resistant variants of genotypes 1a, 1b, and 3. The barrier to resistance was assessed by the number of resistant colonies selected by exposure to various elbasvir concentrations. In a phase 1b dose-escalating study, virologic responses were determined in 48 noncirrhotic adult men with chronic genotype 1 or 3 infections randomized to placebo or elbasvir from 5 to 50 mg (genotype 1) or 10 to 100 mg (genotype 3) once daily for 5 days. The NS5A gene was sequenced from plasma specimens obtained before, during, and after treatment. Elbasvir suppressed the emergence of resistance-associated variants (RAVs) in vitro in a dose-dependent manner. Variants selected by exposure to high elbasvir concentrations typically encoded multiple amino acid substitutions (most commonly involving loci 30, 31, and 93), conferring high-level elbasvir resistance. In the monotherapy study, patients with genotype 1b had greater reductions in HCV RNA levels than patients with genotype 1a at all elbasvir doses; responses in patients with genotype 3 were generally less pronounced than for genotype 1, particularly at lower elbasvir doses. M28T, Q30R, L31V, and Y93H in genotype 1a, L31V and Y93H in genotype 1b, and A30K, L31F, and Y93H in genotype 3 were the predominant RAVs selected by elbasvir monotherapy. Virologic findings in patients were consistent with the preclinical observations. NS5A-RAVs emerged most often at amino acid positions 28, 30, 31, and 93 in both the laboratory and clinical trial. (The MK-8742 P002 trial has been registered at ClinicalTrials.gov under identifier NCT01532973.).

Host APOBEC3G protein inhibits HCV replication through direct binding at NS3

Human APOBEC3G (hA3G) is a cytidine deaminase that restricts replication of certain viruses. We have previously reported that hA3G was a host restriction factor against hepatitis C virus (HCV) replication, and hA3G stabilizers showed a significant inhibitory activity against HCV. However, the molecular mechanism of hA3G against HCV remains unknown. We show in this study that hA3G’s C-terminal directly binds HCV non-structural protein NS3 at its C-terminus, which is responsible for NS3’s helicase and NTPase activity. Binding of hA3G to the C-terminus of NS3 reduced helicase activity, and therefore inhibited HCV replication. The anti-HCV mechanism of hA3G appeared to be independent of its deamination activity. Although early stage HCV infection resulted in an increase in host hA3G as an intracellular response against HCV replication, hA3G was gradually diminished after a long-term incubation, suggesting an unknown mechanism(s) that protects HCV NS3 from inactivation by hA3G. The process represents, at least partially, a cellular defensive mechanism against HCV and the action is mediated through a direct interaction between host hA3G and HCV NS3. We believe that understanding of the antiviral mechanism of hA3G against HCV might open an interesting avenue to explore hA3G stabilizers as a new class of anti-HCV agents.

Hepatitis C NS5A protein: two drug targets within the same protein with different mechanisms of resistance

The era of interferon-free antiviral treatments for hepatitis C virus infection has arrived. With increasing numbers of approved antivirals, evaluating all parameters that may influence response is necessary to choose optimal combinations for treatment success. Targeting NS5A has become integral in antiviral combinations in clinical development. Daclatasvir and ledipasvir belong to the NS5A inhibitor class, which directly target the NS5A protein. Alisporivir, a host-targeting antiviral, is a cyclophilin inhibitor that indirectly targets NS5A by blocking NS5A/cyclophilin A interaction. Resistance to daclatasvir and ledipasvir differs from alisporivir, with mutations arising in NS5A domains I and II, respectively. Combining these two classes acting on distinct NS5A domains represents an attractive strategy for potentially effective interferon-free treatments for chronic hepatitis C infection.

Virologic resistance analysis from a phase 2 study of MK-5172 combined with pegylated interferon/ribavirin in treatment-naive patients with hepatitis C virus genotype 1 infection

BACKGROUND

Virologic failure following treatment of hepatitis C virus (HCV) genotype 1 with direct-acting antiviral agents is often accompanied by the emergence of resistant variants. MK-5172 is an investigational once-daily protease inhibitor. We analyzed variants in treatment-naive noncirrhotic patients with virologic failure on MK-5172 (100-800 mg/day) plus pegylated interferon alfa/ribavirin (peg-IFN/RBV) during a phase 2 trial.

METHODS

Population and selective clonal sequencing were performed at baseline and at virologic failure in the 4 MK-5172 dosing arms. MK-5172 activity was determined using a mutant replicon assay.

RESULTS

Six of 266 (2.3%) MK-5172 recipients satisfied prespecified criteria for virologic failure, all with genotype 1a infection. Five patients with virologic failure were in the MK-5172 100-mg arm, including 4 patients with low plasma MK-5172 levels documented during triple therapy. Variants associated with >4-fold loss of potency were detected in 3 of the 4 patients with genotype 1a breakthrough while on MK-5172. The fifth patient had undetectable HCV-RNA levels at the end of triple therapy but subsequently broke through during the peg-IFN/RBV tail 16 weeks after completion of MK-5172. Three patients had D168 variants at virologic failure, including 2 with the D168A variant associated with a 95-fold loss of potency. The sole apparent relapse was actually a genotype 3a reinfection in the MK-5172 200-mg group.

CONCLUSIONS

Virologic failure occurred uncommonly (6/266 [2.3%]) in MK-5172/peg-IFN/RBV recipients. The most prevalent treatment-emergent variants were detected at the D168 locus. D168A variants conferring approximately 2-log reduction in MK-5172 susceptibility emerged in 2 of the 4 evaluable patients with genotype 1a breakthrough. Clinical Trials Registration. NCT01353911.

Clinical Implications of Detectable Baseline Hepatitis C Virus-Genotype 1 NS3/4A-Protease Variants on the Efficacy of Boceprevir Combined With Peginterferon/Ribavirin

Background

 We analyzed the impact of pretreatment variants conferring boceprevir-resistance on sustained virologic response (SVR) rates achieved with boceprevir plus peginterferon-α/ribavirin (P/R) for hepatitis C virus (HCV)-genotype-1 infection.

Methods

 NS3-protease-polymorphisms emerging coincident with virologic failure on boceprevir/P/R regimens were identified as resistance-associated variants (RAVs). Baseline samples pooled from 6 phase II or phase III clinical trials were analyzed for RAVs by population sequencing. Interferon (IFN)-responsiveness was predefined as >1 log reduction in HCV-RNA level during the initial 4-week lead-in treatment with P/R before boceprevir was added. The effective boceprevir-concentration inhibiting RAV growth by 50% (EC₅₀) was determined using a replicon assay relative to the wild-type referent.

Results

 Sequencing was performed in 2241 of 2353 patients (95.2%) treated with boceprevir. At baseline, RAVs were detected in 178 patients (7.9%), including 153 of 1498 genotype-1a infections (10.2%) and 25 of 742 genotype-1b infections (3.4%) (relative risk, 3.03; 95% confidence interval [CI], [2.01, 4.58]). For IFN-responders, SVR₂₄ (SVR assessed 24 weeks after discontinuation of all study medications) rates were 78% and 76% with or without RAVs detected at baseline, respectively. For the 510 poor IFN-responders, SVR₂₄ rates were 8 of 36 subjects (22.2% [11.7%, 38.1%]) when baseline RAVs were detected vs 174 of 474 subjects (36.7% [32.5%, 41.1%]) when baseline RAVs were not detected (relative likelihood of SVR₂₄ [95% CI], 0.61 [0.32, 1.05]). Sustained virologic response was achieved in 7 of 8 (87.5%) IFN-nonresponders with baseline variants exhibiting ≤2-fold increased EC₅₀ for boceprevir in a replicon assay, whereas only 1 of 15 (7%) IFN-nonresponders with baseline RAVs associated with ≥3-fold increased EC₅₀ achieved SVR.

Conclusions

 Baseline protease-variants appear to negatively impact SVR rates for boceprevir/P/R regimens only when associated with decreased boceprevir susceptibility in vitro after a poor IFN-response during the lead-in period.

Molecular docking investigation of the binding interactions of macrocyclic inhibitors with HCV NS3 protease and its mutants (R155K, D168A and A156V)

Hepatitis C Virus (HCV) non-structural protein 3 (NS3) protease drug resistance poses serious challenges on the design of an effective treatment. Substrate Envelope Hypothesis, "the substrates of HCV NS3/4A protease have a consensus volume inside the active site called substrate envelope" is used to design potent and specific drugs to overcome this problem. Using molecular docking, we studied the binding interaction of the different inhibitors and protein and evaluated the effect of three different mutations (R155K, D168A and A156V) on the binding of inhibitors. P2-P4 macrocycles of 5A/5B and modified 5A/5B hexapeptide sequences have the best scores against the wild-type protein -204.506 and -206.823 kcal/mole, respectively. Also, charged P2-P4 macrocycles of 3/4A and 4A/4B hexapeptide sequences have low scores with the wild-type protein -200.467 and -203.186 kcal/mole, respectively. R155K mutation greatly affects the conformation of the compounds inside the active site. It inverts its orientations, and this is because the large and free side chain of K155 which restricts the conformation of the large P2-P4 macrocycle. The conformation of charged P2-P4 macrocycle of 3/4A hexapeptide sequence in wild-type, A156V and D168A proteins is nearly equal; while that of charged P2-P4 macrocycle of 4A/4B hexapeptide sequence is different. Nevertheless, these compounds have a slight increase of Van der Waals volume compared to that of substrates, they are potent against mutations and have good scores. Therefore, the suggested drugs can be used as an effective treatment solving HCV NS3/4A protease drug resistance problem.

Increased replicative fitness can lead to decreased drug sensitivity of hepatitis C virus

Passage of hepatitis C virus (HCV) in human hepatoma cells resulted in populations that displayed partial resistance to alpha interferon (IFN-α), telaprevir, daclatasvir, cyclosporine, and ribavirin, despite no prior exposure to these drugs. Mutant spectrum analyses and kinetics of virus production in the absence and presence of drugs indicate that resistance is not due to the presence of drug resistance mutations in the mutant spectrum of the initial or passaged populations but to increased replicative fitness acquired during passage. Fitness increases did not alter host factors that lead to shutoff of general host cell protein synthesis and preferential translation of HCV RNA. The results imply that viral replicative fitness is a mechanism of multidrug resistance in HCV. Importance: Viral drug resistance is usually attributed to the presence of amino acid substitutions in the protein targeted by the drug. In the present study with HCV, we show that high viral replicative fitness can confer a general drug resistance phenotype to the virus. The results exclude the possibility that genomes with drug resistance mutations are responsible for the observed phenotype. The fact that replicative fitness can be a determinant of multidrug resistance may explain why the virus is less sensitive to drug treatments in prolonged chronic HCV infections that favor increases in replicative fitness.

Combination of vaniprevir with peginterferon and ribavirin significantly increases the rate of SVR in treatment-experienced patients with chronic HCV genotype 1 infection and cirrhosis

BACKGROUND & AIMS

The combination of vaniprevir (a NS3/4A protease inhibitor) with peginterferon and ribavirin was shown to increase rates of sustained virologic response (SVR) significantly, compared with peginterferon and ribavirin alone, in treatment-experienced patients with chronic hepatitis C virus (HCV) genotype 1 infection without cirrhosis. We performed a blinded, randomized, controlled trial of the effects of vaniprevir with peginterferon and ribavirin in patients with cirrhosis who did not respond to prior therapy with peginterferon and ribavirin.

METHODS

Treatment-experienced patients (88% white and 35% prior null responders) with HCV genotype 1 infection and compensated cirrhosis were assigned randomly to groups given vaniprevir (600 mg twice daily) with peginterferon and ribavirin for 24 weeks (n = 16), vaniprevir (600 mg twice daily) for 24 weeks with peginterferon and ribavirin for 48 weeks (n = 14), vaniprevir (300 mg twice daily) with peginterferon and ribavirin for 48 weeks (n = 15), vaniprevir (600 mg twice daily) with peginterferon and ribavirin for 48 weeks (n = 15), or placebo with peginterferon and ribavirin for 48 weeks (n = 14, control). Cirrhosis was documented by liver biopsy (84%) or noninvasive methods (16%). Before randomization, participants were stratified based on their historical response to peginterferon and ribavirin.

RESULTS

In the primary analysis, SVR rates among patients in the respective vaniprevir groups were 9 of 15 (60.0%), 9 of 13 (69.2%), 8 of 15 (53.3%), and 10 of 13 (76.9%), compared with 2 of 14 (14.3%) in the control group (pairwise P values ≤ .016). Cirrhotic patients with null or partial responses to prior therapy achieved SVR less often than patients with prior breakthrough or relapse, although 42.1% of prior null responders in the vaniprevir groups achieved SVRs. Patients in the vaniprevir groups more frequently experienced mild-moderate nausea, vomiting, and diarrhea than controls; 5% developed grade 2 anemia compared with none in the control group (no patient developed grade 3 or 4 anemia). Among patients in the vaniprevir groups who experienced virologic failure, resistance-associated variants were detected predominantly at positions 155, 156, and 168 in the HCV protease gene.

CONCLUSIONS

In a controlled phase 2B trial, vaniprevir with peginterferon and ribavirin significantly increased rates of SVR among treatment-experienced patients with chronic HCV genotype 1 infection, compared with re-treatment with peginterferon and ribavirin alone. Vaniprevir generally was well tolerated for up to 48 weeks in patients with compensated cirrhosis. ClinicalTrials.gov number, NCT00704405.

Genetic barrier and variant fitness in hepatitis C as critical parameters for drug resistance development

The approval of direct-acting antiviral agents (DAAs) has marked a pivotal change in the treatment landscape of chronic hepatitis C. As for DAAs targeting other viral diseases, there are concerns regarding the development of resistant viral variants. Their selection allows the virus to escape from drug pressure with subsequent treatment failure. The emergence of resistant variants depends on multiple factors that range from genetic barriers to mutations to the fitness of viral variants. This article illustrates the basic mechanisms underlying development of resistance to specific antiviral agents with a special emphasis on NS3 protease inhibitors. The role of fitness deficits and compensation for variant selection and persistence is discussed together with technical issues in sequencing as well as clinical implications in the use of DAAs now and in the future.

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."

Anti-hepatitis C virus dinorditerpenes from the roots of Flueggea virosa

Along with four known terpenoids (1-4), eight new dinorditerpenes (5-12) were isolated and identified from the roots of Flueggea virosa. The absolute configurations of 4-6 were determined by the Mosher's method, and that of 5 was confirmed by single-crystal X-ray diffraction analysis. Using the hepatitis C virus cell culture infection system, compounds 1, 3, 11, and 12 exhibited significant anti-HCV activity with EC50 values of 5.6, 5.0, 7.5, and 6.6 μM, respectively. Compounds 11 and 12 were nontoxic toward the tested Huh7.5 cell lines.

Emergence of resistance-associated variants after failed triple therapy with vaniprevir in treatment-experienced non-cirrhotic patients with hepatitis C-genotype 1 infection: a population and clonal analysis

BACKGROUND

Vaniprevir with P/R improved SVR rates over P/R alone in treatment-experienced patients with chronic HCV-genotype 1 infection, but treatment failure presents therapeutic challenges. We identified RAVs from non-cirrhotic patients failing to achieve SVR on vaniprevir-containing regimens from a dose/duration-ranging trial of triple-combination therapy.

METHODS

Using population analysis, resistance sequencing was performed on all baseline samples and on samples at virologic failure in the vaniprevir arms. Longitudinal clonal analyses were performed on viral isolates from six vaniprevir recipients experiencing breakthrough viremia.

RESULTS

Baseline RAVs were detected in two patients subsequently experiencing virologic failure. At virologic failure, the majority of RAVs had substitutions at R155, A156, or D168. Clonal analyses identified novel double/triple variants emerging with continuing vaniprevir dosing.

CONCLUSIONS

RAVs were predominantly observed at R155, A156, and/or D168 during virologic failure on vaniprevir/P/R. Double/triple RAVs were identified in patients remaining viremic on triple therapy, suggesting evolution of resistance under selective pressure.

Statin therapy improves response to interferon alfa and ribavirin in chronic hepatitis C: a systematic review and meta-analysis

The treatment of interferon alfa (IFN-α) and ribavirin for chronic hepatitis C virus (HCV) infection achieves limited sustained virological response (SVR). We conducted a systematic review and meta-analysis to explore the efficacy of adding statins to IFN-α and ribavirin therapy for chronic hepatitis C. Studies with data pertinent to the effect of statins on chronic hepatitis C were reviewed, and randomized controlled trials (RCTs) evaluating the efficacy of the addition of statins to IFN-α and ribavirin were included in meta-analysis. The primary outcome measure was SVR. Secondary outcome measures were rapid virological response (RVR) and early virological response (EVR). The literature was systematically searched through October 2012. After screening of the 1724 non-duplicated entries, 54 potentially relevant studies were fully reviewed. Of those, 18 studies were relevant and 5 RCTs met the inclusion criteria for meta-analysis. In comparison with IFN-α and ribavirin therapy, the addition of statins significantly increased SVR (OR=2.02, 95% CI: 1.38-2.94), RVR (OR=3.51, 95% CI: 1.08-11.42) and EVR (OR=1.89, 95% CI: 1.20-2.98). The SVR increase remained significant for HCV genotype 1 (OR=2.11, 95% CI: 1.40-3.18). There were no significant increases in adverse events and withdrawals with the addition of statins. In conclusion, the addition of statins to IFN-α and ribavirin improves SVR, RVR, and EVR without additional adverse events and thus may be considered as adjuvant to IFN-α and ribavirin for chronic hepatitis C. Statins might also be used for HCV genotypes other than genotype 1, or in patients in whom the use of protease inhibitors is contraindicated or not indicated.