Viral resistance in hepatitis C virus genotype 1-infected patients receiving the NS3 protease inhibitor Faldaprevir (BI 201335) in a phase 1b multiple-rising-dose study

Abstract

Faldaprevir (BI 201335) is a selective NS3/4A protease inhibitor under development for the treatment of chronic hepatitis C virus (HCV) infection. NS3/4A genotyping and NS3 protease phenotyping analyses were performed to monitor the emergence of resistance in patients with HCV genotype 1 infection receiving faldaprevir alone or combined with pegylated interferon alfa 2a and ribavirin (PegIFN-RBV) during a phase 1b study. Among all baseline variants, a maximum 7-fold reduction in in vitro sensitivity to faldaprevir was observed for a rare NS3 (V/I)170T polymorphism. During faldaprevir monotherapy in treatment-naive patients, virologic breakthrough was common (77%, 20/26) and was associated with the emergence of resistance mutations predominantly carrying NS3 substitutions R155K in GT1a and D168V in GT1b. D168V conferred a greater reduction in faldaprevir sensitivity (1,800-fold) than R155K (330-fold); however, D168V was generally less fit than R155K in the absence of selective drug pressure. Treatment-experienced patients treated with faldaprevir-PegIFN-RBV triple therapy showed higher viral load reductions, lower rates of breakthrough (8%, 5/62), and less frequent emergence of resistance-associated variants compared with faldaprevir monotherapy. (This study has been registered at ClinicalTrials.gov under registration no. NCT00793793.).

Figures

Fig 1

Trial design. PegIFN-RBV, pegylated interferon α-2a and ribavirin; SVR, sustained virologic response; TE, treatment experienced; TN, treatment naive.

Fig 2

Frequency of baseline polymorphisms detected among key amino acids in the NS3 protease domain. (A) Population sequence analysis of 96 baseline samples at clinically relevant NS3 amino acid positions (21). Prevalence of population-based baseline sequences that do not carry the wild type with respect to the subtype reference sequence are shown (GT1a, AF009606; GT1b, AJ238799). (B) Prevalence of NS3 amino acids at three polymorphic residues from panel A, detected by population sequencing. (C) Baseline samples in which clonal sequencing detected an amino acid change at NS3 R155 or NS3 D168 (average of 83 clones sequenced per baseline).

Fig 3

Baseline susceptibility of NS3 protease domains isolated from patients infected with GT1a or GT1b. EC50 values for faldaprevir (A) and for IFN-α (B) for each baseline sample are shown. Each point represents ≥3 independent in vitro phenotyping experiments. (C) Fold changes of individual EC50 values were calculated relative to an EC50 reference value for wild-type replicons treated with faldaprevir (12 ± 4 nM). Wilcoxon P values are shown. Horizontal lines represent the means. One of 96 patient-derived NS3 chimeric replicons did not replicate in vitro and could not be phenotyped.

Fig 4

NS3/4A-resistant variant dynamics. Viral load profile of virologic breakthrough and percentage of clones carrying NS3 R155 and/or D168 substitutions over time for a TN GT1b-infected patient from the 20-mg dose group. WT, wild type.

Fig 5

Longitudinal clonal sequence analysis. Detection of NS3 R155K (A) or NS3 D168V (B) by clonal sequencing in patients with virologic breakthrough and post-faldaprevir treatment sequences. Each row represents one patient. Wild-type (WT) sequence represents a lack of detectable R155K or D168V substitutions. FDV, faldaprevir; P/R, PegIFN-ribavirin; TE, treatment experienced; TN, treatment naive.