S/GSK1349572 is a Potent Next Generation HIV Integrase Inhibitor

Background: S/GSK1349572 was selected as lead molecule from a series of two-metal binding integrase inhibitor scaffolds. We report here its antiviral potency, mechanism of action, and resistance profile. Methods: Antiviral activity of S/GSK1349572 was measured against different HIV strains in various cell lines. Mechanism of action was determined using in vitro integrase strand transfer and binding assays, effects on viral DNA integration, and resistance passage experiments. Fold change (FC) in susceptibility against integrase inhibitor (INI)-resistant mutants was determined with a HeLa-CD4 cell line assay. Results: S/GSK1349572 inhibited HIV integrase in an in vitro strand transfer assay. In PBMC cells, the antiviral EC50 and EC90 values were 0.51 and 2.0 nM, respectively. In MT-4 antiviral assays, the potency shift extrapolated to 100% human serum was 75-fold, resulting in estimated PA-EC90 of 152 nM in PBMCs. S/GSK1349572 had low nM potency against a broad clade panel of HIV-1 isolates representing Groups M and O, and against HIV-2. The mean EC50 against HIV-1 from thirteen subtype B clinical isolates was 0.52 nM. In cellular assays, S/GSK1349572 blocked viral DNA integration with a concomitant increase in 2-LTR circles. When virus was passaged in the presence of S/GSK1349572, highly resistant mutants were not isolated, but mutations which conferred low FC (maximum FC=4.1) were identified within the integrase active site. S/GSK1349572 demonstrated low fold change in activity against raltegravir resistant site directed molecular clones, including Y143R (S/GSK1349572 FC=1.4 and RAL FC=16), Q148K (S/GSK1349572 FC=1.1 and RAL FC=83), N155H (S/GSK1349572 FC=1.2 and RAL FC=11), and G140S, Q148H (S/GSK1349572 FC=2.6 and RAL FC=>130). Conclusions: S/GSK1349572 was a potent inhibitor of HIV integrase in vitro and in cellular HIV replication assays. S/GSK1349572 had a markedly different resistance profile as evidenced by limited cross-resistance to raltegravir resistant molecular clones and the low level maximum resistance to S/GSK1349572 in serial passage. 1 10