KRN-633 inhibits tyrosine phosphorylation of VEGFR-1, VEGFR2, c-Kit, and PDGFR-β (IC50=11.7, 1.16, 8.01, 130 nM) in human umbilical vein endothelial cells. KRN-633 also inhibits the VEGF-driven proliferation of HUVECs (IC50=14.9 nM). KRN-633 suppresses capillary tube formation of endothelial cells.