To determine the tolerance and antiviral response of two different doses of atevirdine mesylate (U-87201E) in symptomatic HIV-positive patients with CD4 counts of 50-350 cells/mm3, who also take zidovudine (AZT).

Patients are randomized to 1 of 3 treatment groups: U-87201E at 1 of 2 doses or placebo administered every 8 hours. Patients must have taken AZT for at least 3 months prior to randomization.

Inclusion Criteria

Concurrent Medication:

Allowed:

• Primary or secondary prophylaxis for opportunistic infections.

Patients must have:

• HIV infection.
• Symptoms (currently or prior to enrollment) included in Category B or C of CDC classification, although THE FOLLOWING CURRENT ACUTE MEDICAL CONDITIONS ARE NOT ALLOWED:
• Cryptococcosis
• Pneumocystis carinii pneumonia
• Herpes zoster
• Histoplasmosis
• CMV
• Hepatic or renal disease
• Lymphoma.
• CD4 count 50 - 350 cells/mm3 within 14 days prior to study entry.
• Ongoing therapy with AZT at 500 - 600 mg total daily dose for at least 3 months prior to study entry.
• Consent of parent, guardian, or person with power of attorney if less than 18 years of age.

Exclusion Criteria

Co-existing Condition:

Patients with the following conditions are excluded:

• Intolerance to AZT.
• Current diagnosis of malignancy for which systemic therapy will be required during the study.

Concurrent Medication:

Excluded:

• Any other investigational drugs.

Prior Medication:

Excluded:

• Cytotoxic chemotherapy within 1 month prior to study entry.
• Prior U-87201E or any other non-nucleoside antiretroviral medications, including but not limited to nevirapine, TIBO R-82150 or TIBO R-82913, L-697639 or L-696229, U-90152S, or any protease inhibitors.
• Antiretroviral agents other than AZT within 3 months prior to study entry.

Required:

• AZT for at least 3 months prior to study entry. Present use of excessive alcohol or illicit drugs.