To assess the dose-related antiviral effects of SC-48334 and zidovudine (AZT) administered in combination or individually in HIV-1 positive patients with 200 - 500 CD4+ cells/mm3. To determine the safety of escalating doses of SC-48334 when administered in combination with any of three doses of AZT to symptomatic HIV-1 positive patients with 200 - 500 CD4+ cells/mm3, and to assess the pharmacokinetics of the two drugs, given separately and in combination.

Inclusion Criteria

Patients must have:

• Documented HIV infection.
• CD4 cell count 200 - 500 cells/mm3.
• Prior therapy with 12 - 48 weeks of AZT.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Clinically significant diarrhea without definable cause (> 3 liquid stools per day for more than 7 days within 6 months prior to study entry).
• Diarrhea, as above, with known non-HIV-related cause occurring within 1 month prior to study entry.
• Symptoms meeting CDC criteria for AIDS classification.
• Fever as a constitutional sign of HIV disease (> 38.5 degrees C persisting for more than 14 consecutive days or for more than 15 days in any given 30-day period prior to study entry).
• Malignancies, other than basal cell carcinoma and Kaposi's sarcoma (provided patient has fewer than 10 Kaposi's sarcoma lesions, no non-skin lesions, and no requirement for systemic treatment).
• Significant organ dysfunction.
• Known hypersensitivity to SC-48334 or AZT or related compounds.

Concurrent Medication:

Excluded:

• Any investigational drug other than SC-48334.
• Any anti-HIV drug other than AZT.
• Cancer chemotherapy.

Patients with the following prior conditions are excluded:

• History of cataracts or known increased risk of cataract formation.
• Known hypersensitivity to SC-48334 or AZT or related compounds.
• History of lactose intolerance.

Prior Medication:

Excluded:

• Prior SC-48334.
• Cancer chemotherapy within 6 months prior to study entry.
• Treatment with any investigational drug or any drug with anti-HIV activity, other than AZT, within 30 days prior to study entry.

Prior Treatment:

Excluded:

Whole-body irradiation within 6 months prior to study entry. Current use of illicit substances, or abuse of alcohol, which would limit compliance with the protocol.