A revolution in HCV treatment with direct-acting antivirals: From non-response to eradication

COMMENTARY ON: Preliminary study of two antiviral agents for hepatitis C genotype 1. Lok AS, Gardiner DF, Lawitz E, Martorell C, Everson GT, Ghalib R, Reindollar R, Rustgi V, McPhee F, Wind-Rotolo M, Persson A, Zhu K, Dimitrova DI, Eley T, Guo T, Grasela DM, Pasquinelli C. N Engl J Med 2012 January 19;366(3):216–24. Copyrigth (2012). Abstract reprinted with permission from the Massachusetts Medical Society. http://www.ncbi.nlm.nih.gov/pubmed/22256805 Abstract: Background: Patients with chronic hepatitis C virus (HCV) infection who have not had a response to therapy with peginterferon and ribavirin may benefit from the addition of multiple direct-acting antiviral agents to their treatment regimen. Methods: This open-label, phase 2a study included an exploratory cohort of 21 patients with chronic HCV genotype 1 infection who had not had a response to previous therapy (i.e., had not had ⩾2 log(10) decline in HCV RNA after ⩾12weeks of treatment with peginterferon and ribavirin). We randomly assigned patients to receive the NS5A replication complex inhibitor daclatasvir (60mg once daily) and the NS3 protease inhibitor asunaprevir (600mg twice daily) alone (group A, 11 patients) or in combination with peginterferon alfa-2a and ribavirin (group B, 10 patients) for 24weeks. The primary end point was the percentage of patients with a sustained virologic response 12weeks after the end of the treatment period. Results: A total of 4 patients in group A (36%; 2 of 9 with HCV genotype 1a and 2 of 2 with genotype 1b) had a sustained virologic response at 12weeks after treatment and also at 24weeks after treatment. Six patients (all with HCV genotype 1a) had viral breakthrough while receiving therapy, and resistance mutations to both antiviral agents were found in all cases; 1 patient had a viral response at the end of treatment but had a relapse after the treatment period. All 10 patients in group B had a sustained virologic response at 12weeks after treatment, and 9 had a sustained virologic response at 24weeks after treatment. Diarrhea was the most common adverse event in both groups. Six patients had transient elevations of alanine aminotransferase levels to more than three times the upper limit of the normal range. Conclusions: This preliminary study involving patients with HCV genotype 1 infection who had not had a response to prior therapy showed that a sustained virologic response can be achieved with two direct-acting antiviral agents only. In addition, a high rate of sustained virologic response was achieved when the two direct-acting antiviral agents were combined with peginterferon alfa-2a and ribavirin. (Funded by Bristol-Myers Squibb; ClinicalTrials.gov number, NCT01012895.). © European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Approximately 170 million people are infected with hepatitis C virus (HCV) worldwide. Treatment of genotype 1 naïve chronic hepatitis C with peginterferon alfa (PegIFN) and ribavirin (RBV) for 48 weeks results in sustained virologic response (SVR) in approximately 40% of patients. Retreatment of previous non-responders to PegIFN/RBV therapy with triple therapy, a protease inhibitor (telaprevir or boceprevir), PegIFN/RBV, results in an SVR in less than 30% of cases [1Zeuzem S. Andreone P. Pol S. et al.Telaprevir for retreatment of HCV infection.N Engl J Med. 2011; 364: 2417-2428Crossref PubMed Scopus (1449) Google Scholar, 2Bacon B.R. Gordon S.C. Lawitz E. et al.Boceprevir for previously treated chronic HCV genotype 1 infection.N Engl J Med. 2011; 364: 1207-1217Crossref PubMed Scopus (1526) Google Scholar]. Direct-acting antivirals (DAAs) with different viral targets, including NS3 protease inhibitors, nucleoside/nucleotide analogues and non-nucleoside inhibitors of the RNA-dependent RNA polymerase, and NS5A inhibitors are under development [[3]Asselah T. Marcellin P. Direct acting antivirals for the treatment of chronic hepatitis C: one pill a day for tomorrow.Liver Int. 2012; 32: 88-102Crossref PubMed Scopus (121) Google Scholar]. Gane and colleagues found that a combination of two DDAs can suppress HCV RNA in genotype 1 non-responder patients but the treatment with the DAAs combination was limited to 13 days and was followed immediately by treatment with PegIFN/RBV, thus preventing the assessment of SVR with DAAs alone [[4]Gane E. Roberts S. Stedman C. et al.Oral combination therapy with a nucleoside polymerase inhibitor (RG7128) and danoprevir for chronic hepatitis C genotype 1 infection (INFORM-1): a randomised, double-blind, placebo-controlled, dose-escalation trial.Lancet. 2010; 376: 1467-1475Abstract Full Text Full Text PDF PubMed Scopus (312) Google Scholar]. Studies of DAAs combinations in the genotype 1 non-responder population are warranted. Recently, Lok et al., in a preliminary study including patients with HCV genotype 1 infection who were non-responders to prior therapy, showed that an SVR could be achieved with two DAAs [[5]Lok A.S. Gardiner D.F. Lawitz E. et al.Preliminary study of two antiviral agents for hepatitis C genotype 1.N Engl J Med. 2012; 366: 216-224Crossref PubMed Scopus (548) Google Scholar]. Daclatasvir (BMS-790052) is a first-in-class, highly selective HCV NS5A replication complex inhibitor with picomolar potency in vitro [[6]Gao M. Nettles R.E. Belema M. et al.Chemical genetics strategy identifies an HCV NS5A inhibitor with a potent clinical effect.Nature. 2010; 465: 96-100Crossref PubMed Scopus (855) Google Scholar]. NS5A is a membrane-associated phosphoprotein present in basally phosphorylated (p56) and hyperphosphorylated (p58) forms. It was previously reported that only p58-defective mutants could be complemented in trans, and NS5A is involved in HCV virion production, suggesting that different forms of NS5A exert multiple functions at various stages of the viral life cycle. The N terminus of NS5A (domain I) has been crystallized in alternative dimeric forms and contains both zinc- and RNA-binding domains, properties that have been demonstrated in vitro. Daclatasvir is active at picomolar concentrations in vitro towards replicons expressing a broad range of HCV genotypes and acts in an additive to synergistic way with interferon and other small molecule antiviral compounds [6Gao M. Nettles R.E. Belema M. et al.Chemical genetics strategy identifies an HCV NS5A inhibitor with a potent clinical effect.Nature. 2010; 465: 96-100Crossref PubMed Scopus (855) Google Scholar, 7Asselah T. NS5A inhibitors: a new breakthrough for the treatment of chronic hepatitis C.J Hepatol. 2011; 54: 1069-1072Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar]. The resistance profile of BMS-790052 reveals that inhibitor sensitivity maps to the N terminus of domain 1 of NS5A [6Gao M. Nettles R.E. Belema M. et al.Chemical genetics strategy identifies an HCV NS5A inhibitor with a potent clinical effect.Nature. 2010; 465: 96-100Crossref PubMed Scopus (855) Google Scholar, 7Asselah T. NS5A inhibitors: a new breakthrough for the treatment of chronic hepatitis C.J Hepatol. 2011; 54: 1069-1072Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar, 8Fridell R.A. Wang C. Sun J.H. et al.Genotypic and phenotypic analysis of variants resistant to hepatitis C virus nonstructural protein 5A replication complex inhibitor BMS-790052 in humans: in vitro and in vivo correlations.Hepatology. 2011; 54: 1924-1935Crossref PubMed Scopus (219) Google Scholar]. In addition, it has been demonstrated that NS5A inhibitors could block hyperphosphorylation of NS5A, which is believed to play an essential role in the viral life cycle. Asunaprevir (BMS-650032) is a highly active HCV NS3 protease inhibitor. NS3 serine protease is located at the N-terminal region of NS3. The NS3 serine protease domain associates with the NS4A co-factor to cleave four specific sites. This enzyme has been extensively characterized at the biochemical level and its structure is known [[9]Kim J.L. Morgenstern K.A. Lin C. et al.Crystal structure of the hepatitis C virus NS3 protease domain complexed with a synthetic NS4A cofactor peptide.Cell. 1996; 87: 343-355Abstract Full Text Full Text PDF PubMed Scopus (680) Google Scholar]. The serine protease activity of NS3 is an attractive target for new drugs that could effectively block viral replication. Protease inhibitors have high anti-viral efficacy and usually a low genetic barrier. The genetic barrier to resistance is defined as the number of amino acid substitutions required to confer full resistance to a drug. The genetic barrier to protease inhibitors and NS5A inhibitors is usually low. Both daclatasvir and asunaprevir produce marked declines in HCV RNA levels in patients with HCV genotype 1 infection [10Nettles R.E. Gao M. Bifano M. et al.Multiple ascending dose study of BMS-790052, a nonstructural protein 5A replication complex inhibitor, in patients infected with hepatitis C virus genotype 1.Hepatology. 2011; 54: 1956-1965Crossref PubMed Scopus (170) Google Scholar, 11Pasquinelli C. Eley T. Villegas C. et al.Safety, tolerability, pharmacokinetics and antiviral activity following single- and multiple-dose administration of BMS-650032, a novel HCV NS3 inhibitor, in subjects with chronic genotype 1 HCV infection.Hepatology. 2009; 50 (abstract): 411AGoogle Scholar] and administration of the two drugs in combination did not produce a clinically meaningful pharmacokinetic interaction [[12]Bifano M. Sevinsky H. Bedford B.R. et al.Co-administration of BMS-790052 and BMS-650032 does not result in a clinically meaningful pharmacokinetic interaction in healthy subjects.Hepatology. 2010; 52 (abstract): 719AGoogle Scholar]. In the study reported by Lok et al., patients with HCV genotype 1 infection, with no response to previous treatment with PegIFN/RBV, were randomly assigned to receive daclatasvir (60 mg once daily) and asunaprevir (600 mg twice daily) alone (group A, 11 patients) or in combination with PegIFNα-2a and RBV (group B, 10 patients) for 24 weeks [[5]Lok A.S. Gardiner D.F. Lawitz E. et al.Preliminary study of two antiviral agents for hepatitis C genotype 1.N Engl J Med. 2012; 366: 216-224Crossref PubMed Scopus (548) Google Scholar]. A total of 4 patients in group A (36%; 2 of 9 with HCV genotype 1a and 2 of 2 with genotype 1b) had an SVR 12 weeks after treatment and also 24 weeks after treatment (Fig. 1). Six patients (all with HCV genotype 1a) had a viral breakthrough while receiving therapy, and resistance mutations to both antiviral agents were found in all cases; 1 patient had a viral response at the end of treatment but relapsed after the treatment period. Viral variants in the NS5A domain included Q30R, L31M/V, and Y93C/N; variants in the NS3 protease domain included R155K and D168A/E/T/V/Y. The patient with a viral relapse had a pre-existing NS3 protease resistance variant, R155K, at baseline and at the time of viral relapse, whereas the NS5A resistance variant Q30E was only detected at relapse. Although there were only 2 patients with HCV genotype 1b infection in group A, the observation that both of the patients had an SVR with two direct-acting antiviral agents alone may reflect a higher resistance barrier for this combination of drugs in patients with HCV genotype 1b infection than in those with HCV genotype 1a infection. The high frequency of resistance seen in patients with HCV genotype 1a infection who were treated with DAAs alone suggests that studies of DAAs combinations without PegIFN/RBV in patients with HCV genotype 1a infection should proceed carefully. In group B, the inclusion of Peg IFN/RBV with daclatasvir and asunaprevir provided sufficient antiviral activity to suppress the emergence of resistance. All 10 patients in group B had an SVR 12 weeks after treatment, and 9 had an SVR 24 weeks after treatment. It should be noticed that among the 14 patients who had an SVR 12 weeks after treatment, a HCV RNA level of less than 25 IU/ml was detected in 1 patient 24 weeks after treatment and in 2 other patients 48 weeks after treatment. All 3 patients had undetectable HCV RNA on re-testing. These data indicate that late relapse is unlikely to occur in patients who have an SVR with the DAAs combination, 12 weeks after treatment as previously established with PegIFN/RBV treatment [[13]Martinot-Peignoux M. Stern C. Maylin S. Ripault M.P. Boyer N. Leclere L. et al.Twelve weeks posttreatment follow-up is as relevant as 24 weeks to determine the sustained virologic response in patients with hepatitis C virus receiving pegylated interferon and ribavirin.Hepatology. 2010; 51: 1122-1126Crossref PubMed Scopus (150) Google Scholar]. The most common adverse events were diarrhea, fatigue, headache, and nausea. Most adverse events were mild to moderate. There were no deaths, serious adverse events, or discontinuations of study treatment due to adverse events. Diarrhea was the most common adverse event in both groups. Six patients had transient elevation of alanine aminotransferase levels to more than three times the upper limit of the normal range. Finally, Lok et al. reported interesting results with daclatasvir and asunaprevir combination in HCV genotype 1 non-responders to previous treatment with PegIFN plus ribavirin [[5]Lok A.S. Gardiner D.F. Lawitz E. et al.Preliminary study of two antiviral agents for hepatitis C genotype 1.N Engl J Med. 2012; 366: 216-224Crossref PubMed Scopus (548) Google Scholar]. Similarly, Chayama et al. reported impressive results in a pilot study of combination therapy with asunaprevir and daclatasvir in 10 Japanese patients with HCV genotype 1b infection and who had not responded to previous therapy with PegIFN/RBV: nine patients achieved an SVR [[14]Chayama K. Takahashi S. Toyota J. et al.Dual therapy with the nonstructural protein 5A inhibitor, daclatasvir, and the nonstructural protein 3 protease inhibitor, asunaprevir, in hepatitis C virus genotype 1b-infected null responders.Hepatology. 2012; 55: 742-748Crossref PubMed Scopus (320) Google Scholar]. Several studies of DAA combinations are ongoing with different HCV targets: [3Asselah T. Marcellin P. Direct acting antivirals for the treatment of chronic hepatitis C: one pill a day for tomorrow.Liver Int. 2012; 32: 88-102Crossref PubMed Scopus (121) Google Scholar, 5Lok A.S. Gardiner D.F. Lawitz E. et al.Preliminary study of two antiviral agents for hepatitis C genotype 1.N Engl J Med. 2012; 366: 216-224Crossref PubMed Scopus (548) Google Scholar, 14Chayama K. Takahashi S. Toyota J. et al.Dual therapy with the nonstructural protein 5A inhibitor, daclatasvir, and the nonstructural protein 3 protease inhibitor, asunaprevir, in hepatitis C virus genotype 1b-infected null responders.Hepatology. 2012; 55: 742-748Crossref PubMed Scopus (320) Google Scholar, 15Zeuzem S. Asselah T. Angus P. et al.Efficacy of the protease inhibitor BI201335, polymerase inhibitor BI 207127, and ribavirin in patients with chronic HCV infection.Gastroenterology. 2011; 141: 2047-2055Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar]. Preliminary results of DAA combinations show increased antiviral efficacy, reduced resistance and a good safety profile. It is important to note that some of these drugs have pan-genotypic activity. This rapid progress strongly suggests that in the near future, IFN-free short duration DAA combinations will make HCV the first chronic viral infection to be eradicated worldwide. Tarik Asselah is a speaker and investigator for BMS, Boehring-Ingelheim, Tibotec, Janssen, Gilead, Roche and MSD.