Vascular endothelial growth factor receptor 2 (VEGFR2, also known as KDR and FLK1) is a receptor tyrosine kinase that regulates angiogenesis, vascular development, and embryonic hematopoiesis in response to VEGF isoforms A, C, and D. VEGFR2 kinase inhibitor II is a reversible, cell-permeable inhibitor of VEGFR2's kinase activity (IC50 = 70 nM). It less potently inhibits the platelet-derived growth factor receptor β (PDGFRβ; IC50 = 920 nM) and related receptor and non-receptor tyrosine kinases. VEGFR2 kinase inhibitor II blocks the growth of human umbilical vein endothelial cells stimulated with either VEGF or PDGF (IC50s = 110 nM and 2 μM, respectively).