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BACKGROUND AND PURPOSE Vascular endothelial growth factor receptor 2 (VEGFR2) is an attractive therapeutic target for the treatment of diseases such as cancer. Small-molecule VEGFR2 inhibitors of a variety of chemical classes are currently under development or in clinical use. In this study, we describe the de novo design of a new generation pyrazole-based molecule (JK-P3) that targets VEGFR2 kinase activity and angiogenesis. EXPERIMENTAL APPROACH JK-P compound series were designed using de novo structure-based identification methods. Compounds were tested in an in vitro VEGFR2 kinase assay. Using primary endothelial cells, JK-P compounds were assessed for their ability to inhibit VEGF-A-stimulated VEGFR2 activation and intracellular signalling. We tested these compounds in cell migration, proliferation and angiogenesis assays. KEY RESULTS JK-P3 and JK-P5 were predicted to bind the VEGFR2 kinase domain with high affinity, and both compounds showed pronounced inhibition of endogenous VEGFR2 kinase activity in primary human endothelial cells. Only JK-P3 inhibited VEGF-A-stimulated VEGFR2 activation and intracellular signalling. Interestingly, JK-P3 inhibited endothelial monolayer wound closure and angiogenesis but not endothelial cell proliferation. Both compounds inhibited fibroblast growth factor receptor kinase activity in vitro, but not basic fibroblast growth factor-mediated signalling in endothelial cells. CONCLUSIONS AND IMPLICATIONS This is the first report that describes an anti-angiogenic inhibitor based on such a pyrazole core. Using a de novo structure-based identification approach is an attractive method to aid such drug discovery. These results thus provide an important basis for the development of multi-tyrosine kinase inhibitors for clinical use in the near future. [ABSTRACT FROM AUTHOR]

BACKGROUND AND PURPOSE The potent pro-angiogenic growth factors VEGF-A and basic fibroblast growth factor (bFGF) exert their effects by binding VEGF receptor 2 and FGF receptor tyrosine kinases, respectively. Indolinones (e.g. SU5416 and Sutent) and anilinophthalazines (e.g. PTK787) are potent small molecule inhibitors of VEGFR2 and other tyrosine kinases, but their effects on VEGF-A- and bFGF-stimulated endothelial responses are unclear. Here we assess the ability of these compounds to inhibit pro-angiogenic responses through perturbation of receptor activity and endothelial function(s). EXPERIMENTAL APPROACH We used in silico modelling, in vitro tyrosine kinase assays, biochemistry and microscopy to evaluate the effects of small molecules on receptor tyrosine kinase activation and intracellular signalling. Primary human endothelial cells were used to assess intracellular signalling, cell migration, proliferation and tubulogenesis. KEY RESULTS We predicted that the anilinophthalazine PTK787 binds the tyrosine kinase activation loop whereas indolinones are predicted to bind within the hinge region of the split kinase domain. Sutent is a potent inhibitor of both VEGFR2 and FGFR1 tyrosine kinase activity in vitro. The compounds inhibit both ligand-dependent and -independent VEGFR2 trafficking events, are not selective for endothelial cell responses and inhibit both VEGF-A- and bFGF-mediated migration, wound healing and tubulogenesis at low concentrations. CONCLUSIONS AND IMPLICATIONS We propose that these compounds have novel properties including inhibition of bFGF-mediated endothelial responses and perturbation of VEGFR2 trafficking. Differential inhibitor binding to receptor tyrosine kinases translates into more potent inhibition of bFGF- and VEGF-A-mediated intracellular signalling, cell migration and tubulogenesis. Indolinones and anilinophthalazines thus belong to a class of multi-kinase inhibitors that show clinical efficacy in disease therapy. [ABSTRACT FROM AUTHOR]