<qa>  What is a pro-drug of amprenavir?GW433908 fosamprenavir; FPVis a pro-drug of amprenavir APV which is more water soluble and can be formulated into a tablet with a reduced pill burden four 700mg tablets of FPV versus sixteen 150mg capsules daily for APV. This study is designed to provide additional information on long term safety and tolerability of FPV containing regimens for those subjects who received FPV in previous GlaxoSmithKline studies. 