A Phase I Concentration-Controlled Trial to Assess the Safety, Tolerance, Pharmacokinetics and Development of Decreased HIV-1 Susceptibility to the Combination of Atevirdine Mesylate (U-87201E), Zidovudine (AZT), and Didanosine (ddI)

Part I: To determine the pharmacokinetic dose for atevirdine mesylate ( U-87201E ) when used in combination with zidovudine ( AZT ). To determine the pharmacokinetic profiles of U-87201E and AZT over a 12-week period. Part II: To determine whether or not decreased viral susceptibility to U-87201E develops when the drug is administered concomitantly with AZT for 12 weeks. Part III: To evaluate the pharmacokinetic effects of ddI/AZT/U-87201E therapy and to assess changes in viral susceptibility to U-87201E. Interest exists in the development of antiretroviral agents that possess different mechanisms of action from nucleoside analogs such as AZT. U-87201E is a non-nucleoside reverse transcriptase (RT) inhibitor that has demonstrated activity against HIV-1; however, an emerging characteristic of non-nucleoside RT inhibitors is the development of rapid resistance to HIV isolates. Whether this resistance can be prevented in the presence of nucleoside analogs such as AZT and ddI has yet to be determined.