2-(Trihydroxyphenyl)thienopyrimidinones as Key Scaffolds for Targeting a Novel Allosteric Site of HIV-1 Integrase

A promising novel class of 2-(trihydroxyphenyl)thieno[2,3-d]pyrimidin-4(3H)-ones as HIV-1 integrase (IN) allosteric inhibitors is reported. All compounds were considerably more effective than the control compound LEDGIN-6, showing an inhibitory activity in the low micromolar range in both the HIV-1 integrase LEDGF/p75-dependent and independent activity assays. Selected compounds 6, 9, 10, and 12 were also able to affect the exchange of the HIV-1 IN-IN subunit and the interaction between IN and LEDGF/p75. Differently from LEDGINs, small-molecule inhibitors were able to interact with the IN binding domain (IBD) of Lens-Epithelium-derived Growth Factor/p75 (LEDGF/p75) and HIV-1 IN, and none of these compounds was able to induce multimerization, suggesting a different mechanism of action. In silico experiments carried out on compounds 6 and 10 suggest that a region adjacent to the sucrose binding site (SBS), together with a second nearby cavity, may represent relevant allosteric regions for their interaction with IN. In vitro experiments performed in the presence and absence of sucrose on selected IN mutants are qualitatively consistent with this model, although further structural and biophysical studies will be required to define the exact binding mode.