In vitro activity: Dolutegravir(S/GSK1349572) inhibits HIV-1 integrase-catalyzed strand transfer with a 50% inhibitory concentration (IC50) of 2.7 nM. S/GSK1349572 inhibits both the HIV integration reaction strand transfer step in vitro and HIV replication in cells with similar potencies. The inhibitor has no effect on total viral DNA synthesis in infected cells but blocks the integration of viral DNA into host DNA with the same potency as its antiviral effect.
Kinase Assay: The inhibitory potencies of S/GSK1349572 and other INIs are measured in a strand transfer assay using recombinant HIV integrase. A complex of integrase and biotinylated preprocessed donor DNA-streptavidin-coated Acintillation proximity assay (SPA) beads is formed by incubating 2 μM purified recombinant integrase with 0.66 μM biotinylated donor DNA-4 mg/mL streptavidin-coated SPA beads in 25 mM sodium morpholinepropanesulfonic acid (MOPS) (pH 7.2), 23 mM NaCl, and 10 mM MgCl2 for 5 minutes at 37 °C. These beads are spun down and preincubated with diluted INIs for 60 minutes at 37 °C. Then a 3H-labeled target DNA substrate is added to give a final concentration of 7 nM substrate, and the strand transfer reaction mixture is incubated at 37 °C for 25 to 45 minutes, which allows for a linear increase in the strand transfer of donor DNA to radiolabeled target DNA. The signal is read using a Wallac MicroBeta scintillation plate reader.
Cell Assay: MT-4 cells growing exponentially at a density of 500000 or 600000 /mL are infected with HIV-1 strain IIIB at a viral multiplicity of infection of 0.001 or a 50% tissue culture infective dose of 4 to 10. The cells are then aliquoted to 96-well plates in the presence of varying concentrations of S/GSK1349572. After incubation for 4 or 5 days, antiviral activity is determined by a cell viability assay that either measured bioluminescence with a CellTiter-Glo luminescent reagent or measured absorbance at 560 and 690 nm using the yellow tetrazolium MTT reagent [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide]. | 
