VEGFR-3-IN-1 is a potent and selective VEGFR3 inhibitor with an IC50 of 110.4 nM. VEGFR-3-IN-1 significantly inhibits proliferation and migration of VEGF-C-induced human dermal lymphatic endothelial cells (HDLEC), MDA-MB-231, and MDA-MB-436 cells by inactivating the VEGFR3 signaling pathway, and also effectively inhibits breast cancer growth.