Antiviral Activity of and Resistance to Lamivudine in Combination With Zidovudine, Stavudine, or Didanosine

To evaluate the efficacy, safety, and pharmacokinetics of lamivudine (3TC) combined with zidovudine (AZT), stavudine (d4T), or didanosine (ddI) in comparison with d4T or ddI monotherapy in HIV-infected patients with no prior nucleoside therapy. 3TC may be uniquely effective in combination with AZT due to the interaction of AZT and 3TC resistance mutations. One explanation is that the M184V mutation, which confers resistance to 3TC, suppresses AZT resistance. This benefit of 3TC may not extend to combination therapy with other nucleoside analogs. 3TC may be uniquely effective in combination with AZT due to the interaction of AZT and 3TC resistance mutations. One explanation is that the M184V mutation, which confers resistance to 3TC, suppresses AZT resistance. This benefit of 3TC may not extend to combination therapy with other nucleoside analogs. Patients are randomized to either a ddI limb or d4T limb, then randomized a second time to one of six treatment arms, as follows: ddI alone, d4T alone, 3TC/AZT (on both ddI and d4T limbs), 3TC/ddI, and 3TC/d4T. Treatment is given for 48 weeks. At study week 24, patients on monotherapy will have 3TC added to their regimen (in a blinded fashion). PER AMENDMENT 10/18/96: A treatment extension phase has been added to the study design in order to allow subjects who complete 48 weeks of therapy to remain on their same blinded treatment until approximately 2 months after the last enrolled subject completes 48 weeks on the study.