In a randomized, parallel arm, open-label study, the effect of switching from ritonavir to either nelfinavir or nelfinavir plus saquinavir as part of a triple antiretroviral regimen was investigated in 16 patients with undetectable HIV-1 loads. Patients continued to use the same nucleoside reverse transcriptase inhibitors as before the switch of protease inhibitor. The period of follow-up was 48 weeks. In all patients HIV-1 load remained undectable, whereas CD4 cell counts remained stable. Furthermore, lipid markers improved after the switch.

In 1998 there were manufacturing problems with the capsule formulation of ritonavir, one of the frequently prescribed protease inhibitors (PI). For a number of patients switching from the capsule to the liquid formulation of the drug was not an alternative because of side-effects of the liquid ritonavir. Such patients were asked to participate in the ESCAPE study [early switch from ritonavir-containing regimens to a nelfinavir or nelfinavir plus saquinavir soft gelatin capsule (SGC) formulation of saquinavir-containing regimen producing a sustained virological and immunological effect].