Impact of the background regimen on virologic response to etravirine: pooled 48-week analysis of DUET-1 and -2.

Purpose: This subgroup analysis of the phase 3 DUET trials examined the impact of the background regimen on virologic response to etravirine in treatment-experienced patients. Methods: Patients received etravirine 200 mg or placebo, both twice daily with a background regimen of darunavir/ritonavir, investigator-selected nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), and optional enfuvirtide. Virologic response at week 48 (viral load <50 HIV-1 RNA copies/mL) was analyzed by the number and activity of background agents. Results: Baseline phenotypic sensitivity score (PSS), enfuvirtide use, darunavir fold change in 50% effective concentration (FC), and number of baseline darunavir resistance-associated mutations (RAMs) were significant predictors of response to etravirine (P < .0001, P = .0018, P < .0001, and P = .0120, respectively). The number of active NRTIs was not a significant predictor of response (P = .0626). The highest response rates in etravirine-treated patients were associated with PSS >= 2, de novo enfuvirtide use, darunavir FC <= 10, <= 1darunavir RAM, and >= 2 active NRTIs. Virologic response was consistently higher in etravirine-treated patients than placebo-treated patients, regardless of the activity of the background regimen. Response rates according to baseline PSS were 46% to 79% in the etravirine group versus 6% to 75% in the placebo group. Conclusion: The results of this subanalysis demonstrate higher virologic response rates with increased activity of the background regimen in both treatment groups, with the highest responses achieved in patients using >= 2 active agents in addition to etravirine.