37 Clinical experience Efficacy of PREZISTA co-administered with 100 mg ritonavir in ART-naïve patients The evidence of efficacy of PREZISTA/ritonavir 800/100 mg q.d. is based on the analyses of 48 week data from the ongoing, randomised, controlled, open-label Phase III trial ARTEMIS in antiretroviral treatment-naïve HIV-1 infected patients comparing PREZISTA/ritonavir 800/100 mg q.d. with lopinavir/ritonavir 800/200 mg per day (given as a twice-daily or as a once-daily regimen).