Background. The pre-existence of minority hepatitis C virus (HCV) variants and their impact on treatment outcome, as well as the persistence of emerging resistant variants posttreatment in patients failing treatment with simeprevir/peginterferon/ribavirin (SMV/PR), were assessed by deep sequencing (DS). Methods. Population sequencing (PS) and Illumina DS were performed on HCV genotype 1 isolates from patients treated with SMV/PR in Phase 2b (PILLAR [NCT00882908] and ASPIRE [NCT00980330]) and Phase 3 (QUEST-1 [NCT01289782], QUEST-2 [NCT01290679], and PROMISE [NCT01281839]) trials. Results. Minority polymorphisms (ie, detected pretreatment by DS only) reducing SMV activity in vitro were uncommon (3.6%, 19 of 534 patients). These SMV-resistant minority polymorphisms were detected in similar proportions of patients achieving (3.7%) and not achieving (3.3%) sustained virologic response with SMV/PR and generally did not emerge as major variants at time of failure. SMV-resistant variants emerging at time of failure were no longer detected at end of study in 69.3% and 52.0% of the patients by PS and DS, respectively. Conclusions. Minority polymorphisms did not impact outcome of SMV/PR treatment. The majority of emerging variants that became undetectable at end of study by PS were also undetectable by DS. These results suggest no added value of DS for clinical usage of SMV.
Keywords: HCV; deep sequencing; minority (viral) variants; resistance; simeprevir.