YLL545 is a type of vascular endothelial growth factor receptor 2 ( VEGFR2 ) inhibitor. YLL545 can inhibit VEGF-induced phosphorylation of VEGFR2 and the activation of downstream signaling factors (like phosphorylated STAT3 and phosphorylated ERK1/2 ) in human umbilical vein endothelial cells (HUVEC). YLL545 can suppress the proliferation, migration, invasion, and angiogenesis of HUVEC. YLL545 can induce apoptosis in breast cancer mice and inhibit tumor growth.