To determine the safety and tolerance of low-dose versus high-dose cysteamine administered concurrently with zidovudine (AZT). To determine the pharmacokinetics and effects on immune function and viral load in patients receiving these drug regimens.

Patients receive high or low doses of cysteamine plus AZT or placebo plus AZT. The target dose of cysteamine is determined by titration of the dose over a 6-week period, after which the patient receives 24 additional weeks of treatment. An initial cohort of 36 patients will be enrolled in a 10-week pilot phase. Accrual will be temporarily suspended while data from the pilot phase is assessed.

Inclusion Criteria

Concurrent Medication:

Allowed:

• Chemoprophylaxis for Pneumocystis carinii pneumonia, candidiasis, Mycobacterium tuberculosis, and herpes as prescribed by the investigator.
• Recombinant erythropoietin and G-CSF if clinically indicated.

Patients must have:

• Documented HIV infection.
• CD4 count 300 - 500 cells/mm3.
• Prior AZT therapy for at least 3 months but less than 12 months prior to study entry.
• No past or current AIDS-defining opportunistic infection.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Kaposi's sarcoma requiring systemic therapy.
• Active malignancy other than basal cell carcinoma or in situ cervical carcinoma.

Concurrent Medication:

Excluded:

• Antiretroviral therapy other than AZT.
• Immunosuppressive drugs.
• Investigational HIV drugs/therapies other than study drug.
• Interferon.
• Steroids.
• Hematopoietins.
• Cytotoxic chemotherapy including Adriamycin, bleomycin, and vincristine.

Concurrent Treatment:

Excluded:

• Radiation therapy.

Patients with the following prior condition are excluded:

History of treatment-limiting intolerance to 500-600 mg AZT daily as manifested by the same recurrent grade 3 toxicity or any prior grade 4 toxicity.

Prior Medication:

Excluded:

• Prior antiretroviral therapy other than AZT.

Required:

• AZT for at least 3 months but no more than 12 months prior to study entry.