AMENDED: 8/29/90 Inclusion of asymptomatic patients with CD4 counts less than 200 cells/mm3. Standardization of baseline evaluation schedule to allow 14 days prior to study dosing. Reduction in frequency and intensity of follow-up evaluations. Standardization of study endpoints. Inclusion of toxicity scoring and management for amylase and triglyceride elevations. Clarification of concomitant medication use. Original design: To determine the effectiveness of didanosine (ddI) in patients with AIDS or advanced AIDS related complex (ARC) who have documented hematologic intolerance to zidovudine (AZT) therapy. To determine if the efficacy of ddI increases with increasing doses.

AZT is effective in reducing mortality in patients with AIDS who receive the drug after the first episode of Pneumocystis carinii pneumonia (PCP) and in patients with advanced ARC. However, AZT therapy has been associated with significant toxicities. In addition, the effectiveness of AZT appears to decrease during the second and third years of therapy. For these reasons, the development of alternative therapy that would be at least as effective but less toxic is of great importance. The drug ddI is an antiviral agent that inhibits replication (reproduction) of HIV with less apparent toxicity than AZT. The major dose-limiting toxicities found in the Phase I studies have been pains in the feet and legs of 2 patients initially receiving 12 mg/kg/day and 12 patients receiving daily doses of 25.8 to 51.2 mg/kg; symptoms began 8 to 27 weeks after initiating ddI treatment. These neuropathy-like symptoms have generally not been associated with significant abnormalities in nerve conduction studies and patients have reported marked improvement in symptoms within 1 to 2 weeks of discontinuing ddI. Some patients have resumed ddI treatment at a reduced dose after resolution of their symptoms. Studies indicate that ddI remains active in the body for at least 12 hours. This indicates that benefits of ddI might be achieved with a low frequency of drug administration.

AZT is effective in reducing mortality in patients with AIDS who receive the drug after the first episode of Pneumocystis carinii pneumonia (PCP) and in patients with advanced ARC. However, AZT therapy has been associated with significant toxicities. In addition, the effectiveness of AZT appears to decrease during the second and third years of therapy. For these reasons, the development of alternative therapy that would be at least as effective but less toxic is of great importance. The drug ddI is an antiviral agent that inhibits replication (reproduction) of HIV with less apparent toxicity than AZT. The major dose-limiting toxicities found in the Phase I studies have been pains in the feet and legs of 2 patients initially receiving 12 mg/kg/day and 12 patients receiving daily doses of 25.8 to 51.2 mg/kg; symptoms began 8 to 27 weeks after initiating ddI treatment. These neuropathy-like symptoms have generally not been associated with significant abnormalities in nerve conduction studies and patients have reported marked improvement in symptoms within 1 to 2 weeks of discontinuing ddI. Some patients have resumed ddI treatment at a reduced dose after resolution of their symptoms. Studies indicate that ddI remains active in the body for at least 12 hours. This indicates that benefits of ddI might be achieved with a low frequency of drug administration.

Patients are randomized to one of three ddI treatment groups; within each group, doses will be adjusted according to patient's weight at study entry. Stratification is by diagnosis of AIDS or AIDS related complex (ARC) and Medical Center. Data will be tabulated for the Data and Safety Monitoring Board at 3 month intervals.

Inclusion Criteria

Concurrent Medication:

Required:

• Aerosolized pentamidine (300 mg every 4 weeks). In the event of physiological intolerance, alternative PCP prophylaxis may be trimethoprim/sulfamethoxazole 1 DS tab per day or dapsone 50 - 100 mg per day.

Allowed:

• Chronic suppressive treatment for toxoplasmosis, Pneumocystis carinii pneumonia (PCP), cryptococcal meningitis, herpes simplex virus, cytomegalovirus, coccidioidomycosis, and histoplasmosis (absorption of ketoconazole or dapsone may be inhibited if given at the same time as the buffered solution of ddI, and should be taken 2 hours before or 2 hours after taking ddI; oral acidifying agents are not allowed). Isoniazid is permitted only if no acceptable alternative therapy is available. Metronidazole may be used for single courses not to exceed 14 days within consecutive 90 day intervals, the first of which begins at the initiation of the study. Erythropoietin for patients under the relevant treatment IND. Intravenous acyclovir for short courses of therapy.

Patients must:

• Have documented hematologic intolerance to zidovudine (AZT).
• Have the diagnosis of AIDS or advanced AIDS related complex (ARC).
• Have ended treatment for acute Pneumocystis carinii pneumonia (PCP) at least 2 weeks before study entry.

Have previous intolerance on at least two courses of AZT therapy (one of which must have been at daily doses of 500 mg of AZT or less).

• Be able to provide informed consent (and/or guardian as appropriate).
• Be available for follow-up for at least 6 months.
• Have baseline laboratory values as measured within 7 days before initial drug dosing.
• Allowed:
• Development of new opportunistic infections during the study - patients remain in the protocol.

Prior Medication:

Required:

• Prior use and intolerance to zidovudine (AZT).
• Allowed:
• Intralesional agents.

Exclusion Criteria

Co-existing Condition:

Patients with the following are excluded:

• Presence of Kaposi's sarcoma (KS) with known or suspected visceral disease or where KS requires chemotherapy.
• Active AIDS defining opportunistic infections not specifically allowed.
• Intractable diarrhea.
• Stage 2 AIDS-dementia complex.
• History of intolerance to aerosolized pentamidine.
• Grade 2 neuropathy, based on the Neuropathy Targeted Symptom Questionnaire, or any moderate abnormality indicative of peripheral neuropathy, particularly impaired sensation of sharp pain, light touch, or vibration in the lower extremities, distal extremity weakness, or distal extremity hyporeflexia.
• Prior history of acute or chronic pancreatitis.
• History of seizures within past 2 years or currently requiring anticonvulsants for control.
• Any other clinical conditions or prior therapy which, in the opinion of the investigator, would make the patient unsuitable for study or unable to comply with the dosing requirements.

Concurrent Medication:

Excluded:

• Isoniazid (INH).

Patients with the following are excluded:

• Active AIDS-defining opportunistic infections not specifically allowed.
• Intractable diarrhea.
• AIDS-dementia complex = or > stage 2.
• History of intolerance to aerosolized pentamidine. Grade 2 neuropathy, based on the Neuropathy Targeted Symptom Questionnaire, or any moderate abnormality indicative of peripheral neuropathy, particularly impaired sensation of sharp pain, light touch, or vibration in the lower extremities, distal extremity weakness, or distal extremity hyporeflexia.
• Prior history of acute or chronic pancreatitis.
• History of seizures within past 2 years or currently requiring anticonvulsants for control.
• Any other clinical conditions or prior therapy which, in the opinion of the investigator, would make the patient unsuitable for study or unable to comply with the dosing requirements.
• Previous participation in any Phase I ddI study.
• Life expectancy < 6 months.

Prior Medication:

Excluded:

• Chronic therapy for cytomegalovirus infection with ganciclovir.
• ddI.
• d4T.
• ddC.

Excluded within 2 weeks of study entry:

• Zidovudine (AZT).

Excluded within 1 month of study entry:

• Therapy with any other antiretroviral drug or investigational agent not specifically allowed, including interferon and immunomodulating drugs.
• Ganciclovir.
• Neurotoxic drugs.

Excluded within 3 months of study entry:

• Ribavirin.
• Cytotoxic anticancer therapy.

Prior Treatment:

Excluded within 2 weeks of study randomization:

• Transfusion.

Active alcohol or drug abuse that is sufficient, in investigator's opinion, to prevent adequate compliance with study therapy.