Patients are randomized to receive six single escalating doses of 524W91 or placebo, with each dose separated by at least a 6-day washout interval. In the time between 2 of the doses, the effect of food on pharmacokinetics will be investigated, with one dose administered in conjunction with a high-fat meal and one dose administered in a fasted state.

Inclusion Criteria

Patients must have:

• Documented HIV infection.
• CD4 count >= 200 cells/mm3.
• No active opportunistic infection.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Malignancy or other condition that would confound study assessment or interfere with ability to complete the study.
• Malabsorption syndrome or other gastrointestinal dysfunction that might interfere with gastrointestinal absorption.

Concurrent Medication:

Excluded on the day of each dose:

• Antiretrovirals.
• Any prescription or over-the-counter medication.
• Alcoholic beverages.
• Coffee, tea, and other xanthine-containing beverages and foods.

Patients with the following prior conditions are excluded:

History of hepatitis, pancreatitis, or cardiomyopathy within the past 5 years.

Prior Medication:

Excluded:

• Antiretrovirals within 24 hours prior to each dose.
• Any prescription or over-the-counter medications within 48 hours prior to each dose.
• Alcoholic beverages within 48 hours prior to each dose. Current alcohol or illicit drug use that may affect patient compliance.