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

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.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.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, ≤1 darunavir 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.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.