Efficacy of PREZISTA co-administered with 100 mg ritonavir in treatment-experienced patients The evidence of efficacy of PREZISTA co-administered with ritonavir (600/100 mg b.i.d.) in treatment-experienced patients is based on the 48 weeks analysis of the Phase III trial TITAN in treatment-experienced lopinavir naïve patients and on the analyses of 96 weeks data from the Phase IIb trials POWER 1, 2 and 3 in patients with high level of PI resistance.