Deep-Sequencing Analysis of the Gene Encoding the Hepatitis C Virus Nonstructural 3–4A Protease Confirms a Low Prevalence of Telaprevir-Resistant Variants at Baseline and the End of the REALIZE Study

Background. Population sequencing (PS) has shown that telaprevir-resistant variants are not typically detectable at baseline (prevalence, ≤5 % of patients), and most variants present at the time of treatment failure are no longer detectable at the end of the study. Methods. To gain insight into the evolution of telaprevir-resistant variants, their baseline prevalence and per-sistence after treatment was investigated using a more sensitive, deep-sequencing (DS) technique in a large number of treatment-experienced patients from the REALIZE study who were infected with hepatitis C virus genotype 1. Results. Before treatment initiation, telaprevir-resistant variants (T54A, T54S, or R155K in 1%–2 % of the viral population) were detected by DS in a fraction (2%) of patients for whom PS failed to detect resistance; these variants were not necessarily detected at the time of treatment failure. Of 49 patients in whom telaprevir-resistant variants were detected by PS at the time of treatment failure but not at the end of the study, DS revealed the presence of variants (V36A/L/M, T54S, or R155K in 1%–36 % of the viral population) in 16 patients (33%) at the end of the study. Conclusions. Similar to PS findings, DS analysis revealed that the frequency of telaprevir-resistant variants be-fore treatment was also low, and variants detected at the time of treatment failure were no longer detectable in the majority of patients during follow-up