This two-part study, conducted by Franco Lori, et al., first analyzed the efficacy of beginning treatment soon after HIV infection occurs, a period known as primary infection. In the primary infection study ten patients with a very high average baseline viral load of 551,217 copies were treated with hydroxyurea (HU), ddI and the protease inhibitor indinavir. Patients began treatment within 1.7 months (mean) after infection. All patients' viral loads reached undetectable levels (under 50 copies) within 4 to 16 weeks, and after a mean treatment period of 46 weeks their T-cells counts had increased an average of 154 cells. An special analysis of the T-cells found them to be anti-HIV-specific.

In the parallel study, 12 patients with chronic HIV infection and a mean baseline viral load of 51,795 copies were treated with HU and ddI for a mean period of 122 weeks. Not all patients reached undetectable levels with this treatment: the mean viral load after 122 weeks 186, and the mean T0-cell increase was just 30 cells.