Structure-Based Design, Synthesis, and Characterization of Dual Hotspot Small-Molecule HIV-1 Entry Inhibitors

Cellular infection by HIV-1 is initiated with a binding event between the viral envelope glycoprotein gp120 and the cellular receptor protein CD4. The CD4–gp120 interface is dominated by two hotspots: a hydrophobic gp120 cavity capped by Phe43CD4 and an electrostatic interaction between residues Arg59CD4 and Asp368gp120. The CD4 mimetic small-molecule NBD-556 (1) binds within the gp120 cavity; however, 1 and related congeners demonstrate limited viral neutralization breadth. Herein, we report the design, synthesis, characterization, and X-ray structures of gp120 in complex with small molecules that simultaneously engage both binding hotspots. The compounds specifically inhibit viral infection of 42 tier 2 clades B and C viruses and are shown to be antagonists of entry into CD4-negative cells. Dual hotspot design thus provides both a means to enhance neutralization potency of HIV-1 entry inhibitors and a novel structural paradigm for inhibiting the CD4–gp120 protein–protein interaction.