Higher short-term virologic efficacy of three-class versus two-class highly active antiretroviral salvage therapy in HIV-infected patients

The efficacy of two-class versus three-class antiretroviral salvage treatme nt was analyzed retrospectively in 63 HIV-infected patients in whom highly active antiretroviral therapy failed. Twenty-eight patients (group A) recei ved two-class therapy, and 35 patients (group B) received three-class thera py. After 3 months of treatment, a significantly greater proportion of pati ents in group B (23/35, 65.7%) than in group A (8/28, 28.5%) showed a great er than or equal to 1 log(10) decrease in the plasma HIV RNA level (P = 0.0 034). However, after 9-12 months, 12 of 23 (52.1%) group B responders showe d viral load rebound. The results were partially explained by the finding t hat, at baseline, the great majority (21/27, 77.7%) of group A patients sho wed mutations conferring resistance to all drugs administered, whereas in g roup B patients' susceptibility to at least two drug classes was retained. However, after 9-12 months of therapy, most (18/20, 90%) of the shortterm r esponders in group B showed emergence of additional mutations that hampered long-term response.