A Small-Molecule Pan-Id Antagonist Inhibits Pathologic Ocular Neovascularization

Summary: Id helix-loop-helix (HLH) proteins (Id1–4) bind E protein bHLH transcription factors, preventing them from forming active transcription complexes that drive changes in cell states. Id proteins are primarily expressed during development to inhibit differentiation, but they become re-expressed in adult tissues in diseases of the vasculature and cancer. We show that the genetic loss of Id1/Id3 reduces ocular neovascularization in mouse models of wet age-related macular degeneration (AMD) and retinopathy of prematurity (ROP). An in silico screen identifies AGX51, a small-molecule Id antagonist. AGX51 inhibits the Id1-E47 interaction, leading to ubiquitin-mediated degradation of Ids, cell growth arrest, and reduced viability. AGX51 is well-tolerated in mice and phenocopies the genetic loss of Id expression in AMD and ROP models by inhibiting retinal neovascularization. Thus, AGX51 is a first-in-class compound that antagonizes an interaction formerly considered undruggable and that may have utility in the management of multiple diseases. : Wojnarowicz et al., describe the identification, by an in silico screen, and characterization of a small molecule, AGX51, that targets Id proteins. AGX51 treatment of cells lead to Id protein degradation, cell cycle arrest, and reduced cell viability. AGX51 inhibited pathologic ocular neovascularization in mouse models, phenocopying genetic Id loss. Keywords: Id proteins, protein-protein interactions, macular degeneration, retinopathy of prematurity, angiogenesis