Darunavir (TMC114, 1a) has a stability comparable to other protease inhibitors. Darunavir (TMC114, UIC-94017) blocks the infectivity and replication of each of HIV-1 NL4-3 variants exposed to and selected for resistance to Ro 31-8959, MK-639, AG1341, or ABT 538 at concentrations up to 5 μM (IC 50 s, 0.003 to 0.029 μM), although it was less active against HIV-1 NL4-3 variants selected for resistance to VX-478 (IC 50 , 0.22 μM).