MAZ51 is a potent and selective inhibitor of vascular endothelial growth factor receptor (VEGFR)-3 (Flt-4) tyrosine kinase. MAZ51 induces cell rounding and G2/M cell cycle arrest in glioma cells through phosphorylation of Akt/GSK3β and activation of RhoA. MAZ51 inhibits the proliferation and induces the apoptosis of a variety of non-VEGFR-3-expressing tumor cell lines.