Clinical trials in adults and children suggest that SQV-SGC has advantages over other protease inhibitors in terms of tolerability, safety, and effectiveness in patients who have failed therapy with other protease inhibitors. [AS PER AMENDMENT 11/24/99: Pharmacokinetic data from this study demonstrate lower than expected plasma SQV exposures, particularly in Arm 1. Based on these data, patients in the study will be offered the opportunity to adjust their doses. Ritonavir added to the Arm 1 regimen is expected to significantly increase SQV-SGC plasma levels and allow twice-daily dosing for SQV-SGC.]

Patients are randomized to one of two study arms. Patients in Arm 1 receive SQV-SGC plus two [AS PER AMENDMENT 11/24/99: one or two] NRTIs of choice. Patients in Arm 2 receive SQV-SGC plus NFV plus one or two NRTIs of choice. All participants are evaluated by physical examinations and laboratory tests during the study and are followed for incidence of death, cancer, or fetal abnormality. NRTIs are not provided as part of this study. [AS PER AMENDMENT 11/24/99: This study is closed to accrual. All subjects on follow-up (Cohort 1) are given the option of either discontinuing participation in ACTG 397 or participating in the next phase of the study (version 2.0). Those electing to continue participation constitute Cohort 1A. The adjusted Arm 1 regimen consists of SQV-SGC plus ritonavir plus one or two NRTIs. Ritonavir is not provided as part of this study. The Arm 2 regimen study drugs have not changed but the maximum allowable dose of SQV-SGC has increased from 1,200 mg twice-daily to 1,600 mg twice-daily. Participants continue to be followed with physical examinations and laboratory evaluations that include an intensive pharmacokinetics study on Day 14 of the new regimen.]