arily 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 who were previously exposed to INCIVEK, or who previously failed treatment with an INCIVEK-containing regimen.
Effect of Baseline HCV Substitutions/Polymorphisms on Treatment Response
A pooled analysis was conducted to explore the association between the detection (population-based assay) of baseline NS3/4A amino acid substitutions/polymorphisms and treatment outcome in Studies 108, 111, and C216. Baseline polymorphisms at NS3 position Q80 (Q80K, Q80L, Q80R), which are frequently observed in HCV genotype 1a-infected subjects and have been reported to reduce the activity of some HCV NS3/4A protease inhibitors, were not associated with reduced INCIVEK efficacy.
Telaprevir-associated resistance substitutions (substitutions at positions V36, T54, R155 or D168) were present at baseline in 5% (117/2217) of the available subject samples in the combined clinical trials. Given the small number of subjects with baseline telaprevir resistance substitutions, conclusions about their effect on response outcomes when these substitutions are present at baseline cannot be determined.
Cross-Resistance
Treatment-emergent NS3 amino acid substitutions detected in INCIVEK-treated subjects who did not achieve SVR in the clinical trials (substitutions at positions V36, T54, R155, A156 or D168) have been demonstrated to reduce the anti-HCV activity of boceprevir and other HCV NS3/4A protease inhibitors. The impact of prior INCIVEK exposure or treatment failure on the efficacy of boceprevir or other HCV NS3/4A protease inhibitors has not been studied. INCIVEK efficacy has not been established for patients with a history of exposure to NS3/4A protease inhibitors.
Cross-resistance is not expected between INCIVEK and interferons, or INCIVEK and ribavirin. HCV replicons expressing telaprevir-associated resistance substitutions remained fully sensitive to interferon-alfa and ribavirin, as well as other direct-acting antivirals with different mechanisms of action, such as NS5B polymerase inhibitors.
12.5 Pharmacogenomics
A genetic variant near the gene encoding interferon-lambda-3 (IL28B rs12979860, a C to T change) is a strong predictor of response to peginterferon alfa and ribavirin (PR). rs12979860 was genotyped in 454 of 1088 subjects in Study 108 (treatment-naïve) and 527 of 662 subjects in Study C216 (previously treated) [see Clinical Studies (14.2 and 14.3) for trial descriptions]. SVR rates tended to be lower in subjects with the CT and TT genotypes compared to those with the CC genotype, particularly among treatment-naïve subjects receiving PR48 (Table 9). Among both treatment-naïve and previous treatment failures, subjects of all IL28B genotypes appeared to have higher SVR rates with INCIVEK-containing regimens. The results of this retrospective subgroup analysis should be viewed with caution because of the small sample size and potential differences in demographic or clinical characteristics of the substudy population relative to the overall trial population.
Table 9: SVR Rates by rs12979860 Genotype Trial rs12979860 Genotype SVR, n/N (%)
*
Lead-in and immediate start T12/PR regimens pooled.
T12/P
