A Six-Month Safety and Antiviral Study in HIV-1 Seropositive, AZT-Experienced Patients With CD4 Counts Less Than or Equal to 50 Cells/mm3 to Evaluate MK-639 Alone Versus Zidovudine (AZT) and 3TC Versus the Combination of MK-639 With AZT/3TC

Inclusion Criteria

Concurrent Medication:

Allowed for all patients:

• Standard prophylaxis for opportunistic infections.
• Continuation of treatment for opportunistic infection.

Allowed for open-label study patients:

• Rifampin.

Patients must have:

• HIV positivity.
• CD4 count <= 50 cells/mm3.
• More than 6 months of prior AZT (blinded study only).

NOTE:

• Patients on the open-label study must have AZT intolerance or have < 6 months of prior AZT.

Prior Medication:

Required for blinded study patients:

• > 6 months of prior AZT.

Required for open-label study patients:

• < 6 months of prior AZT.

Allowed for open-label study patients:

• Prior 3TC.

Exclusion Criteria

Concurrent Medication:

Excluded in all patients:

• Immunosuppressants.

Excluded in blinded study patients:

• AZT, ddI, ddC, or d4T.
• Rifampin.

Excluded in open-label study patients:

• 3TC.

Prior Medication:

Excluded in all patients:

• Prior protease inhibitors.
• Investigational agents and immunomodulators within 30 days prior to study entry.
• Immunosuppressants within 2 weeks prior to study entry.

Excluded in blinded study patients:

• Any prior 3TC.
• AZT, ddI, ddC, or d4T within 2 weeks prior to study entry.

Excluded in open-label study patients:

3TC within 30 days prior to study entry.