Natural prevalence of hepatitis C virus variants with decreased sensitivity to NS3.4A protease inhibitors in treatment-naive subjects.

BACKGROUND: The prevalence and clinical implications of naturally occurring variants that are resistant to hepatitis C virus (HCV) protease inhibitors in treatment-naive patients has not been reported. We report here the prevalence of such variants and their effect on clinical response. METHODS: Population sequence analysis of the NS3.4A protease was conducted in 570 treatment-naive subjects. RESULTS: Most subjects (98%) had wild-type virus. The remaining subjects had the following variants present in significant proportions (100%): V36M, 0.9%; R155K, 0.7%; V170A, 0.2%; and R109K, 0.2%. The V36M, R109K, and V170A substitutions confer low-level resistance (<7-fold) to protease inhibitors in replicon cells. The R155K substitution confers low-level resistance to telaprevir (TVR) and boceprevir and confers high-level resistance (>70-fold) to BILN 2061 and ITMN-191. Five subjects with the V36M or R109K variant were treated with 8-24 weeks of TVR and peginterferon-alpha2a (P) with or without ribavirin (R). Four achieved a sustained viral response, and 1 was lost to follow-up. In subjects with the R155K variant, TVR/PR provided greater antiviral activity than PR alone; however, the antiviral response was lower than that observed in subjects with wild-type virus. CONCLUSION: High levels of naturally occurring protease inhibitor-resistant variants were uncommon (<1% each) in HCV treatment-naive patients. TVR/PR efficiently inhibited V36M and R109K variants and contributed partial antiviral activity against the R155K variant. As new HCV agents are evaluated in clinical trials, it will be important to monitor the effect of baseline variants on sensitivity.

Preexisting resistance to nonnucleoside reverse-transcriptase inhibitors predicts virologic failure of an efavirenz-based regimen in treatment-naive HIV-1-infected subjects.

A case-cohort study was used to determine the effect of baseline nonnucleoside reverse-transcriptase inhibitor (NNRTI) resistance, as assessed by viral genotyping, on the response to efavirenz-containing regimens in AIDS Clinical Trials Group A5095. The sample included a random cohort of efavirenz-treated subjects plus unselected subjects who experienced virologic failure. Of 220 subjects in the random cohort, 57 (26%) had virologic failure. The prevalence of baseline NNRTI resistance was 5%. The risk of virologic failure for subjects with baseline NNRTI resistance was higher than that for subjects without such resistance (hazard ratio 2.27 [95% confidence interval], 1.15-4.49; P = .018). These results support resistance testing before starting antiretroviral therapy.

Performance of human immunodeficiency virus type 1 gp41 assays for detecting enfuvirtide (T-20) resistance mutations.

The performance of a gp41 assay, created using reagents designed for use with the OpenGene DNA Sequencing System, was evaluated using a panel of plasma samples obtained from enfuvirtide-naive and -experienced human immunodeficiency virus type 1-infected subjects. Resulting sequence data were highly accurate compared to a "home brew" assay and clonal sequence analysis.