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Antagonizing vascular endothelial growth factor receptor 2 (VEGFR2) to block angiogenesis has been applied toward cancer therapy for its role in promoting cancer growth and metastasis. However, most these clinical anticancer drugs have unexpected side effects. Development of novel VEGFR2 inhibitors with less toxicity remains an urgent need. In this study, we describe a novel, well-tolerated, and orally active VEGFR2 inhibitor, YLT192, which inhibits tumor angiogenesis and growth. YLT192 significantly inhibited kinase activity of VEGFR2 and suppressed proliferation, migration, invasion, and tube formation of human umbilical vascular endothelial cells (HUVEC) in vitro. In addition, it inhibited VEGF-induced phosphorylation of VEGFR2 and its downstream signaling regulator in HUVEC. Zebrafish embryonic models and alginate-encapsulated tumor cell assays indicated YLT192 also inhibited angiogenesis in vivo. Moreover, YLT192 could directly inhibit proliferation and induce apoptosis of cancer cells in vitro and in vivo. Oral administration of YLT192 at a dose of 100 mg/kg/day could markedly inhibited human tumor xenograft growth without causing obvious toxicities. It decreased microvessel densities (MVD) in tumor sections. It also shows good safety profiles in the studies with mice and rats. Taken together, these preclinical evaluations suggest that YLT192 inhibits angiogenesis and may be a promising anticancer drug candidate.

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Background and Purpose Targeted chemotherapy using small‐molecule inhibitors of angiogenesis and proliferation is a promising strategy for cancer therapy. Experimental Approach YL529 was developed via computer‐aided drug design, de novo synthesis and high‐throughput screening. The biochemical, pharmacodynamic and toxicological profiles of YL529 were investigated using kinase and cell viability assays, a mouse tumour cell‐containing alginate bead model, a zebrafish angiogenesis model and several human tumour xenograft models in athymic mice. Key Results In vitro, YL529 selectively inhibited the activities of VEGFR2/VEGFR3 and serine/threonine kinase RAF kinase. YL529 inhibited VEGF165‐induced phosphorylation of VEGFR2, as well as the proliferation, migration, invasion and tube formation of human umbilical vascular endothelial cells. It also significantly blocked vascular formation and angiogenesis in the zebrafish model. Moreover, YL529 strongly attenuated the proliferation of A549 cells by disrupting the RAF/mitogen‐activated protein (MAP) or extracellular signal‐regulated kinase (Erk) kinase (MEK) kinase kinase/MAPK pathway. Oral administration of YL529 (37.5–150 mg−1·kg−1·day−1) to nude mice bearing established tumour xenografts significantly prevented the growth (60–80%) of A549, SPC‐A1, A375, OS‐RC‐2 and HCT116 tumours without detectable toxicity. YL529 markedly reduced microvessel density and increased tumour cell apoptosis in the tumours formed in mice inoculated with the lung cancer cells, SPC‐A1 and A549, and the colon carcinoma cells, HCT116. Conclusions and Implications YL529, an orally active multikinase inhibitor, shows therapeutic potential for solid tumours, and warrants further investigation as a possible anticancer agent.

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