Treatment with PREZISTA co-administered with ritonavir (600/100 mg b.i.d.) resulted in 56.5% (POWER 1 and 2) and 52.2% (POWER 3) of responders with a decrease of at least 1 log10 in HIV RNA from baseline, 38.9% (POWER 1 and 2) and 42.1% (POWER 3) of subjects with an HIV RNA level < 50 copies/ml and 49.6% (POWER 1 and 2) and 50.0% (POWER 3) respectively of subjects with an HIV RNA level less than 400 copies/ml.