ABT-378/Ritonavir Plus Stavudine and Lamivudine for the Treatment of Antiretroviral-Naïve Adults with HIV-1 Infection: 48-Week Results [Murphy RL, et al. AIDS 2001;15:F1]: This is the phase II Abbott-sponsored study of lopinavir plus ritonavir in two doses. Participants had baseline RNA levels >5000 c/mL and were treatment-naïve. The regimens were lopinavir, 200 or 400 mg, plus ritonavir 100 mg q12h versus lopinavir 400 mg with ritonavir 100 - 200 mg q12h. Both groups had the addition of d4T and 3TC after three weeks. The results at 48 weeks by intent-to-treat analysis for the 68 participants receiving lopinavir in the 400 mg dose was 82% with <400 c/mL and 79% with <50 c/mL. Trough levels of lopinavir indicated concentrations that exceeded wild-type HIV-1 EC50 by 50 - 100-fold. No patient had to discontinue therapy due to toxicity or viral rebound.
Comment: This is the initial Kaletra phase II trial in treatment-naïve patients, which shows the results that have been reported at various meetings. Subsequent data has focused attention on the resistance testing among the modest number of virologic failures; these patients do not show phenotypic resistance, and the pharmacologic barrier is obviously very high, so the reason for virologic failure remains unexplained.
posted 3/8/2001

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