Preclinical characterization of anlotinib, a highly potent and selective vascular endothelial growth factor receptor‐2 inhibitor

Abrogating tumor angiogenesis by inhibiting vascular endothelial growth factor receptor‐2 ( VEGFR 2) has been established as a therapeutic strategy for treating cancer. However, because of their low selectivity, most small molecule inhibitors of VEGFR 2 tyrosine kinase show unexpected adverse effects and limited anticancer efficacy. In the present study, we detailed the pharmacological properties of anlotinib, a highly potent and selective VEGFR 2 inhibitor, in preclinical models. Anlotinib occupied the ATP ‐binding pocket of VEGFR 2 tyrosine kinase and showed high selectivity and inhibitory potency ( IC 50 <1 nmol/L ) for VEGFR 2 relative to other tyrosine kinases. Concordant with this activity, anlotinib inhibited VEGF ‐induced signaling and cell proliferation in HUVEC with picomolar IC 50 values. However, micromolar concentrations of anlotinib were required to inhibit tumor cell proliferation directly in vitro. Anlotinib significantly inhibited HUVEC migration and tube formation; it also inhibited microvessel growth from explants of rat aorta in vitro and decreased vascular density in tumor tissue in vivo. Compared with the well‐known tyrosine kinase inhibitor sunitinib, once‐daily oral dose of anlotinib showed broader and stronger in vivo antitumor efficacy and, in some models, caused tumor regression in nude mice. Collectively, these results indicate that anlotinib is a well‐tolerated, orally active VEGFR 2 inhibitor that targets angiogenesis in tumor growth, and support ongoing clinical evaluation of anlotinib for a variety of malignancies.