OBJECTIVE:The objective of this study was to examine the potential of once-daily dosing with darunavir/ritonavir 800/100 mg in a HIV-infected, treatment-experienced patient population with no baseline darunavir resistance-associated mutations (RAMs). METHODS:Patients in the randomized controlled POWER 1 and 2 trials were treatment experienced, with ≥1 International AIDS Society-USA primary protease inhibitor (PI) mutation. The virological and immunological responses in patients with no baseline darunavir RAMs receiving darunavir/r 800/100 mg once daily (n = 23), darunavir/r 600/100 mg twice daily (n = 29), or currently available PI(s) (n = 28) plus an optimized background regimen were compared. RESULTS:The proportion of patients achieving HIV RNA <50 copies per milliliter at week 24 was 67% for the group receiving darunavir/r 800/100 mg once daily and 62% for the group receiving darunavir/r 600/100 mg twice daily (P = 0.774); both were superior to control PI(s) (11%; P < 0.0001). Mean HIV RNA change from baseline was 22.39 and 22.35 log10 copies per milliliter for the group receiving darunavir/r 800/100 mg once daily and for the group receiving 600/100 mg twice daily, respectively (P = 0.895); mean CD4 increases were 88 and 111 cells per milliliter, respectively (P = 0.526). CONCLUSIONS:Treatment-experienced, HIV-infected patients with no baseline darunavir RAMs achieved similar high responses with darunavir/r 800/100 mg once daily and 600/100 mg twice daily. This suggests that once-daily darunavir/r 800/100 mg therapy, which has been shown effective in treatment-naive patients and is currently being studied in treatment-experienced patients, shows potential in patients with no darunavir RAMs.