 With this structural change, the stereochemistry around the bis-THF moiety confers orientational changes, that allows for continued binding with the protease which has developed a resistance for amprenavir.All the FDA approved protease inhibitors are listed below.All the HIV protease inhibitors on the market contain a central core motif consisting of a hydroxyethylen scaffold, with the only exception being the central core of tipranavir, which is based on a coumarin scaffold.