The weighted genotypic scoring algorithm optimizes resistance interpretations for etravirine and guides treatment decisions regarding its use in treatment-experienced patients.

Simeprevir treatment failure was usually associated with emerging high-level resistance mutations, which became undetectable over time in half of the patients.

The contribution of E138 mutations to etravirine resistance was investigated. Amino acids at position E138 after failure with etravirine in DUET were A (n = 1), G (n = 5), K (n = 3), P (n = 1), Q (n = 5), and V (n = 2). At baseline, only E138A and Q were found at 3.0% and 2.5%, respectively. Virologic response (less than 50 copies/mL) was observed in six of 12 and eight of 10 patients with E138A and E138Q, respectively. Site-directed mutants harboring E138A/G/K/Q/R or S showed etravirine fold change values of 2.9, 2.4, 2.6, 3.0, 3.6, and 2.8, respectively. E138G, K, and Q were added to the existing etravirine-weighted genotypic score including 17 etravirine resistance-associated mutations.

NCT01479868.

The randomized, placebo-controlled Phase III DUET studies enrolled treatment-experienced, HIV-1-infected patients. We examined the genotypic and phenotypic changes at endpoint relative to baseline, including the emergence of individual reverse transcriptase (RT) mutations, in patients who received the non-nucleoside reverse transcriptase inhibitor (NNRTI) etravirine and experienced virologic failure by rebound by the time of the Week 96 analysis. Patients received etravirine 200 mg twice-daily in combination with a background regimen containing darunavir/ritonavir, investigator-selected nucleoside reverse transcriptase inhibitors, and optional enfuvirtide. Virologic failure by rebound occurred in 93 (15.5%) etravirine-treated patients (compared with 170 [28.1%] placebo-treated patients). Patients experiencing virologic failure had more baseline antiretroviral resistance and lower activity of the background regimen relative to those not experiencing failure. Emergence of NNRTI resistance-associated mutations was observed in 55 of 93 patients. The most frequently emerging RT mutations were V179F, V179I, and Y181C, with positions K101 and E138 also showing frequent changes. Mutations usually emerged in a background of multiple other NNRTI mutations and were, in most cases, associated with a decrease in phenotypic sensitivity to etravirine at endpoint. Further analysis is needed to clarify the role of mutations at position 138 as determinants of etravirine resistance.