The purpose of this study is to compare 4 different combinations of anti-HIV drugs and to determine the number of people whose HIV blood levels decrease to 200 copies/ml or less while on the treatment. This study evaluates the safety of these drug combinations, which include an experimental protease inhibitor (PI), amprenavir.

Despite the success that many patients have had with PI treatment regimens, there is still a possibility that patients receiving PIs may continue to have high HIV blood levels. Because of this possibility, alternative drug combinations containing PIs are being studied. It appears that amprenavir, when taken with 3 or 4 other anti-HIV drugs, may be effective in patients with prior PI treatment experience.

A number of studies both within and outside the ACTG have been initiated or are in development to try to address the issue of alternative treatments for patients who either do not achieve or lose virologic control while receiving protease inhibitors (PIs). Amprenavir (APV) is an attractive candidate to investigate as part of salvage regimens because: 1) it has substantial antiretroviral activity; 2) there are preliminary in vitro and in vivo data that suggest that resistance to this agent may be mediated in part by a unique mutation (I50V); and 3) its cross-resistance profile to the approved PIs is uncertain.

Patients are selectively randomized to 1 of 4 study arms based on prior PI experience. Those randomized to Arms A, B, or C receive 2 PIs, 1 of which is amprenavir (APV), and those randomized to Arm D receive a single PI (APV) as part of their treatment regimen, as follows:

Arm A: APV plus saquinavir soft gel capsule (SQVsgc) plus abacavir (ABC) plus efavirenz (EFV) plus adefovir (ADV).

Arm B: APV plus indinavir (IDV) plus ABC plus EFV plus ADV. Arm C: APV plus nelfinavir (NFV) plus ABC plus EFV plus ADV. Arm D: APV plus placebo (NFV, IDV, or SQVsgc) plus ABC plus EFV plus ADV. All patients receive L-carnitine supplementation. All patients receive clinical physical assessments and laboratory testing during study as follows: Weeks 2, 4, and every 4 weeks thereafter. A primary analysis is performed after the last patient has reached 24 weeks. [AS PER AMENDMENT 3/2/00: At that time, all patients are unblinded to their original treatment assignment.] Patients who experience virologic failure are unblinded and may choose 1 of the following 3 options: Continue study medications open-label, permanently discontinue study medications, or selectively continue study medications [AS PER AMENDMENT 3/2/00: from the arm the patient was originally randomized to] and combine with other approved antiretroviral agents. [AS PER AMENDMENT 3/2/00: For patients adding didanosine (ddI) to their regimens, monitoring for the development of pancreatitis is crucial.] Final evaluations are required for those patients who are off drug during the immediate 8-week period following the last dose of study treatment. Beyond 8 weeks, they are followed for incidence of death, cancer, congenital anomalies, and permanent disabilities. [AS PER AMENDMENT 3/2/00: Gilead Sciences has terminated its U.S. development of ADV for HIV infection. Gilead will continue to supply ADV for patients in ACTG 398 until the study closes. Patients who are receiving ADV at the completion of the study may continue to access ADV through the Expanded Access Program, provided that the physician and patient have determined that continued use of ADV is beneficial.]

Inclusion Criteria

Patients may be eligible for this study if they:

• Are HIV-positive.
• Have current virologic failure (2 consecutive HIV blood levels above 1,000 copies/ml) while on PIs.
• Are over 13 years of age (consent of parent or guardian required if under 18).
• Agree to practice abstinence or use effective methods of birth control during the study and for 90 days after.

Exclusion Criteria

Patients will not be eligible for this study if they:

• Have hepatitis within 90 days prior to study entry.
• Have a history of a peripheral neuropathy within 60 days of study entry.
• Have an unexplained temperature for a 7-day period.
• Have chronic diarrhea within 30 days prior to study entry.
• Have cancer requiring chemotherapy.
• Received any therapy for infection or other illness within 30 days prior to study entry.
• Have received certain other medications.
• Are pregnant or breast-feeding.