MAZ51 is a selective inhibitor of VEGFR-3 (Flt-4) tyrosine kinase. MAZ51 inhibits VEGF-C-induced activation of VEGFR-3 without blocking VEGF-C-mediated stimulation of VEGFR2. MAZ51 had no effect on ligand-induced autophosphorylation of EGFR, IGF-1R and PDGFRβ. MAZ51 blocks proliferation and induces apoptosis in a wide variety of tumor cells. Antitumor activity.