Selection of HIV-1 for Resistance to Fifth Generation Protease Inhibitors Reveals Two Independent Pathways to High-Level Resistance

Darunavir (DRV) is exceptional among potent HIV-1 protease inhibitors (PIs) in the high drug concentrations that are achived in vivo. Little is known about the de novo resistance pathway for DRV. We have selected for resistance to high drug concentrations against ten PIs and their structural precursor DRV. Mutations accumulated through two pathways (anchored by protease mutations I50V or I84V). Small chemical changes in the inhibitor P1 side chain led to preferential use of one pathway over the other. Changes in the inhbitor P2 side chain determined differences in potency that were retained in the resistant viruses. Viral variants from the two pathways showed differential selection of compensatory mutations in Gag cleavage sites. These results reveal the high level of selective pressure that is attainable with fourth generation PIs, and how features of the inhibitor affect both the resistance pathway and the residual potency in the face of resistance.