Virologic Escape during Danoprevir (ITMN-191/RG7227) Monotherapy Is Hepatitis C Virus Subtype Dependent and Associated with R155K Substitution

Abstract

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.H epatitis C virus (HCV) is a positive-strand RNA virus that infects approximately 170 million people worldwide (39). It is a major cause of chronic liver disease, cirrhosis, and primary hepatocellular carcinoma. Therapy for chronic HCV infection is based on weekly injections of pegylated alpha interferon (PEG-IFN-␣) and twice-daily orally administered ribavirin (RBV). This standard of care (SOC) is associated with significant side effects and achieves a sustained virologic response (SVR) in approximately half of treated patients (5, 28). Thus, novel therapeutic modalities are clearly needed.The addition of one or more direct-acting antiviral agents (DAA) to the SOC has become a favored strategy to improve the treatment outcome of chronic HCV therapy. The two most clinically advanced DAAs, telaprevir (Incivek) and boceprevir (Victrelis), are linear peptidomimetic inhibitors of NS3/4A protease. These two NS3/4A protease inhibitors (PIs) have demonstrated significant improvements in SVR rates in genotype 1 patients when added to SOC (1,14,32,46) and have recently been licensed for use in the treatment of chronic HCV infection in the United States and in Europe. While clearly a dramatic advance in the treatment of chronic HCV, both of these compounds...

Genotype and Subtype Profiling of PSI-7977 as a Nucleotide Inhibitor of Hepatitis C Virus

“…Results showed that PSI-7977 was active in replicons with the NS3 R155K or D168V alteration. Consistent with previous findings (12,19,21), the R155K mutation was cross resistant to both RG7227 (a macrocyclic compound) and telaprevir (a linear ketoamide compound), while D168V conferred resistance only to RG7227 and not telaprevir. PSI-7977 also retained its activity against replicons with amino acid changes of NS3 C16S, A39V (resistant to the NS3/4A inhibitor ACH-806), or NS5A Y93H (resistant to the NS5A inhibitor BMS-790052).…”

“…PSI-7977 (prodrug of 2=-F-2=-C-methyluridine monophosphate) (38), PSI-352938 (prodrug of 2=-F-2=-C-methylguanosine monophosphate) (34), PSI-6130 (2=-F-2=-C-methylcytidine) (40), R1479 (4=-azidocytidine) (13), IDX-184 and INX-189 (prodrugs of 2=-C-meth-ylguanosine monophosphate) (43,48), NS5B nonnucleoside inhibitors NNI-1 (an indole analog), NNI-2 (a thiophene analog), NNI-3 (a benzothiadiazine analog), and HCV-796 (a benzofuran analog or NNI-4) (39), NS3 protease inhibitors telaprevir and RG7227 (ITMN-191) (21,22), NS3/4a inhibitor ACH-806 (46), and NS5A inhibitor BMS-790052 (8) were synthesized at Pharmasset and shown to be Ͼ95 to 99% pure by proton nuclear magnetic resonance, mass spectroscopy, and highperformance liquid chromatography analysis. Ribavirin was obtained from Sigma-Aldrich.…”

Exploring resistance pathways for first-generation NS3/4A protease inhibitors boceprevir and telaprevir using Bayesian network learning

“…The network identified an association between drug resistance mutation R155K (Bartels et al, 2008;Larrat et al, 2015;Lontok et al, 2015) and PI-exposure, suggesting this is a major mutation, while V36M is a minor drug resistance-associated variant, dependent also on the presence of R155K. These associations were confirmed in a separate HCV1a analysis, but no in the HCV1b analysis, probably due to R155K being less prevalent since two nucleotide substitutions (instead of one) are required in HCV1b patients (Lim et al, 2012). Cross-resistance between first-and second-generation PIs has been reported for this variant (Kieffer et al, 2012).…”

Hepatitis C virus resistance to new specifically-targeted antiviral therapy: A public health perspective

“…Substitutions NS3-V36A/M and NS3-T54A/S confer a low level of resistance to both Telaprevir and Boceprevir, and NS3-V170A/T to Boceprevir. There is also some cross-resistance of mutations in positions 36, 54 and 170 with other compounds, while changes in positions NS3-80, NS3-155 and NS3-168 are implicated in resistance to macrocyclic inhibitors [17,42] . Double mutants may also be selected by STAT-C treatments, combining two resistance mutations for the same or different PI class, with a potential for broad resistance to both linear and macrocyclic inhibitors [43] .…”

“…For instance, variations in NS3-V170 are present in most HCV genotype 1 isolates, and polymorphism in NS3-D168 is characteristic of HCV genotype 3 [32] . As the development of NS3/4A PIs was based in HCV genotype 1, subtype 1b, their antiviral activity with non-1b genotypes, may be not as effective, although some PIs inhibit more than one HCV genotype [22,42,[48][49][50] . Currently neither Boceprevir nor Telaprevir should be used in patients infected with HCV genotypes other than 1.…”