IC87361, chemically known as 5-hydroxy-7-morpholin-4-yl-2-phenyl-4H-chromen-4-one (Molecular Formula: C₁₉H₁₇NO₄), is a potent and selective small-molecule inhibitor targeting DNA-dependent protein kinase (DNA-PK), with an IC₅₀ of approximately 34 nM and over 50-fold selectivity compared to p110β (a PI3K isoform). Functionally, IC87361 acts as a radiosensitizer: it enhances the sensitivity of wild-type endothelial cells and significantly potentiates the effects of ionizing radiation on tumor microvasculature, particularly when administered at ~10 µM for at least 4 hours.