The purpose of this study is to compare the atazanavir and nelfinavir (NFV) treatments in their ability to reduce viral load.

In this double-blind, double-placebo, randomized, 2-arm study, atazanavir and NFV each are given in combination with 2 open-label nucleoside reverse transcriptase inhibitors (NRTIs) over 48 weeks. Patients assigned to atazanavir will receive placebo capsules which are identical in size and appearance to NFV. Patients assigned to NFV will receive placebo capsules which are identical in size and appearance to atazanavir. HIV levels are monitored.

Inclusion Criteria

Patients may be eligible for this study if they:

• Have a viral load of 1000 or more copies/ml within 3 weeks before randomization. Have a CD4 cell count of 50 or more cells/mm3 within 3 weeks prior to randomization.
• Are at least 16 years old (or the minimum age by local requirements).
• Have had more than 16 weeks of therapy with a non-nucleoside reverse transcriptase inhibitor (NNRTI) and/or nucleoside reverse transcriptase inhibitor (NRTI).
• Use effective barrier method of contraception.
• Give written informed consent.
• Are available for follow-up for at least 52 weeks.

Exclusion Criteria

Patients may not be eligible for this study if they:

• Have used a protease inhibitor (PI) treatment for more than 7 days or within 30 days prior to screening.
• Have a newly-diagnosed HIV-related infection or any medical condition requiring relatively short but intense therapy at the time of enrollment.
• Have hepatitis in the 30 days before the study. Patients with long-term hepatitis are eligible if their liver function meets certain requirements.
• Are unable to demonstrate responsiveness to a provided NRTI.
• Have had previous or expect a need for therapy with agents that may cause damage to nerve tissue, the pancreas, the liver, bone marrow, or cells within 3 months of study start.
• Use too much alcohol or drugs to be able to follow the study therapy; or if they use enough to increase the risk of developing pancreatitis or chemical hepatitis.
• Have severe diarrhea within 30 days prior to study entry.
• Are pregnant or breast-feeding.
• Have a history of hemophilia.
• Have history or signs of bilateral peripheral neuropathy.
• Have cardiomyopathy.
• Have certain heart problems.
• Cannot tolerate oral medication.
• Have any other problems that would interfere with the study.