In vitro activity: Darunavir displays potent activity against HIV strains resistant to other available protease inhibitor. Darunavir inhibits P-glycoprotein-mediated efflux of calcein-acetoxymethyl ester in L-MDR1 cells with the inhibitory potency of 121 mM. Darunavir is a protein inhibits that mimics the phenylalanine sequences at positions 167 and 168 of the gag-pol polypeptide and binds to the active sites of the HIV protease, thereby inhibiting its activity. Darunavir blocks the infectivity and replication of each of the HIV-1 variants at concentrations up to 5 μM. Darunavir shows strong ARV activity against a selected panel of 19 recombinant clinical isolates carrying multiple protease mutations conferring resistance to an average of five other protien inhibitors. Darunavir inhibits 75% of 1501 PI-resistant viruses tested with a half maximal effective concentration (EC50) of < 10 nM.

Kinase Assay: Darunavir has a Ki of 1 nM for wild type HIV-1 protease.

Cell Assay: In an in vitro study in MT-2 cells, the potency of darunavir is greater than that of saquinavir, amprenavir, nelfinavir, indinavir, lopinavir and ritonavir. Darunavir is primarily metabolized by the hepatic cytochrome P450 (CYP) enzymes, primarily CYP3A. The ‘boosting’ dose of ritonavir acts an an inhibitor of CYP3A, thereby increasing darunavir bioavailability