Identification of a Small-Molecule Inhibitor of HIV-1 Assembly that Targets the Phosphatidylinositol (4,5)-bisphosphate Binding Site of the HIV-1 Matrix Protein

The development of drug resistance remains a critical problem for current HIV-1 antiviral therapies, creating a need for new inhibitors of HIV-1 replication. We previously reported on a novel anti-HIV-1 compound, N(2)-(phenoxyacetyl)-N-[4-(1-piperidinyl-carbonyl)benzyl]glycinamide (14), that binds to the highly conserved phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P(2))binding pocket of the HIV-1 matrix (MA) protein. In this study, we re-evaluate the hits from the virtual screen used to identify compound 14 and test them directly in an HIV-1 replication assay using primary human peripheral blood mononuclear cells. This study resulted in the identification of three new compounds with antiviral activity; 2-(4-{[3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl]methyl})-1-piperazinyl)-N-(4-methylphenyl)-acetamide (7), 3-(2-ethoxyphenyl)-5-[[4-(4-nitrophenyl)piperazin-1-yl]methyl]-1,2,4-oxadiazole (17), and N-[4-ethoxy-3-(1-piperidinylsulfonyl)phenyl]-2-(imidazo[2,1-b][1,3]thiazol-6-yl)acetamide (18), with compound 7 being the most potent of these hits. Mechanistic studies on 7 demonstrated that it directly interacts with and functions through HIV-1 MA. In accordance with our drug target, compound 7 competes with PI(4,5)P(2) for MA binding and, as a result, diminishes the production of new virus. Mutation of residues within the PI(4,5)P(2) binding site of MA decreased the antiviral effect of compound 7. Additionally, compound 7 displays a broadly neutralizing anti-HIV activity, with IC(50) values of 7.5–15.6 μm for the group M isolates tested. Taken together, these results point towards a novel chemical probe that can be used to more closely study the biological role of MA and could, through further optimization, lead to a new class of anti-HIV-1 therapeutics.