A regimen of either efavirenz or lopinavir-ritonavir plus two nucleoside reverse-transcriptase inhibitors (NRTIs) is recommended for HIV-1 patients starting initial therapy; however, it is not known which of these two regimens has greater efficacy. The alternative regimen of lopinavir-ritonavir plus efavirenz could prevent toxic effects associated with NRTIs, the study authors noted.

An open-label study was conducted to compare the three regimens for initial therapy: efavirenz plus two NRTIs (efavirenz group), lopinavir-ritonavir plus two NRTIs (lopinavir-ritonavir group), and lopinavir-ritonavir plus efavirenz (NRTI-sparing group). Seven hundred fifty-seven patients with a median CD4 count of 191 cells per cubic millimeter and a median HIV-1 RNA level of 4.8 log10 copies per milliliter were randomly assigned to the three groups.

During follow-up of a median 112 weeks, the time to virologic failure was longer in the efavirenz group than in the lopinavir-ritonavir group (P=0.006) though it was not significantly different in the NRTI-sparing group than either of the two groups. At week 96, the proportion of patients with fewer than 50 copies of plasma HIV-1 RNA per milliliter was 89 percent in the efavirenz group, 77 percent in the lopinavir-ritonavir group and 83 percent in the NRTI-sparing group (P=0.003 for the comparison between the efavirenz group and the lopinavir-ritonavir group). There was no significant difference in the time to discontinuation due to toxic effects between the groups. At virologic failure, the NRTI-sparing group recorded more antiretroviral resistance mutations than did the other two groups.

"Virologic failure was less likely in the efavirenz group than in the lopinavir-ritonavir group," the authors concluded. "The virologic efficacy of the NRTI-sparing regimen was similar to that of the efavirenz group but was more likely to be associated with drug resistance."

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