Persistence of Resistance-Associated Substitutions

Persistence of telaprevir-resistant NS3 amino acid substitutions has been observed following treatment failure. Of a combined 255 treatment-naïve and previously treated subjects from Studies 108, 111, and C216 in whom telaprevir-resistant variants had emerged during treatment, 103 (40%) had detectable resistant variants by population sequencing at end of study (follow-up range 2-70 weeks, median 45 weeks) and results for loss of variants were similar across the three studies. In the combined studies, 46% of the telaprevir-resistant substitutions in subtype 1a and 16% of the substitutions in subtype 1b were still detected by the end of study: 29% of V36, 16% of T54, 38% of R155, 14% of A156, and 44% of V36M+R155K variants were detected at the end of study.

In a 3-year follow-up study of 56 treatment-naïve and prior treatment-failure subjects who did not achieve SVR with a telaprevir regimen in a Phase 2 study and had telaprevir-resistant variants after treatment failure, variants were detected by population sequencing in 11% (6/56) of subjects (median follow-up of 25 months). Telaprevir-resistant variants V36L/M, T54S, and R155K were detectable (present at greater than 25% of the viral population) in some subjects at 24 months. By 36 months, V36M, T54A/S, and A156N/S/T variants had fallen below the level of detection by population sequencing in all subjects. At 36 months, 3% of the subject isolates that had the R155K variant still had detectable R155K variants by population sequencing.

The lack of detection of a substitution based on a population-based assay does not necessarily indicate the substitution has declined to the pre-treatment level. The long-term clinical impact of the emergence or persistence of detectable INCIVEK resistance-associated substitutions is unknown. No data are available regarding INCIVEK efficacy among patients w