Three phase III trials of Raltegravir in treatment experienced patients have been conducted (BENCHMRK trials). In both of these studies, more than 75 percent of patients receiving Raltegravir plus optimized background therapy (OBT) achieved viral load (HIV RNA) reductions to less than 400 copies/mL compared to more than 40 percent of patients receiving placebo plus OBT. Both studies also showed that Raltegravir plus OBT was generally well tolerated.