Fosamprenavir [GW433908], a water-soluble prodrug of the nonpeptide protease inhibitor amprenavir, is a new anti-HIV agent with the potential to be given once daily when combined with low-dose ritonavir. Results from a phase III study (SOLO) were presented at the Sixth International Congress on Drug Therapy in HIV Infection [Glasgow, Scotland; November 2002]. The majority of patients treated with the fosamprenavir/ritonavir combination achieved viral loads below the limits of detection, including high proportions of patients with high viral RNA levels, or low CD4+ cell counts, at baseline. Although nelfinavir had comparable efficacy in the overall patient population, the proportions of responders among nelfinavir recipients in these two subgroups was approximately 50% lower than among the patients treated with fosamprenavir/ritonavir. Furthermore, the proportion of patients experiencing virological failure at 48 weeks was higher in the nelfinavir, compared with the fosamprenavir/ritonavir, group.