Highly active antiretroviral therapy (HAART) has demonstrated the ability to suppress viral activity for extended periods and to prolong survival in patients with HIV infections. The proven efficacy of HAART has stimulated efforts to develop even more effective therapy, including more potent and better tolerated agents within existing drug classes and more convenient regimens. The protease inhibitor (PI) fosamprenavir [GW 433908], a water-soluble prodrug of amprenavir, allows for reductions in pill size and count, compared with the parent compound, factors that could improve patient compliance. The efficacy of fosamprenavir in treatment-experienced and antiretroviral-naive patients was demonstrated in two separate studies presented at the 10th Conference on Retroviruses and Opportunistic Infections [Boston, US; February 2003]. The first study, CONTEXT, demonstrated that the combination of fosamprenavir plus ritonavir was not inferior to lopinavir/ritonavir ['Kaletra'] in PI-experienced patients. Extended follow-up data from the NEAT study showed that fosamprenavir achieved better viral suppression than nelfinavir in treatment-naive patients. An analysis of resistance data from the NEAT and SOLO studies showed a lack of cross-resistance with other PIs, suggesting fosamprenavir was suitable for first-line use.