1-aryl-3-[4-(thieno[3,2-d]pyrimidin-4-yloxy)phenyl]ureas as VEGFR-2 tyrosine kinase inhibitors: synthesis, biological evaluation, and molecular modelling studies

The vascular endothelial growth factor receptor-2 (VEGFR-2) is a tyrosine kinase receptor involved in the growth and differentiation of endothelial cells that are implicated in tumor-associated angiogenesis. In this study, novel 1-aryl-3-[4-(thieno[3,2-d]pyrimidin-4-yloxy)phenyl]ureas were synthesized and evaluated for the VEGFR-2 tyrosine kinase inhibition. Three of these compounds showed good VEGFR-2 inhibition presenting low IC50 values (150-199 nM) in enzymatic assays, showing also a significant proliferation inhibition of VEGF-stimulated human umbilical vein endothelial cells (HUVECs) at low concentrations (0.5-1 µM), using the Bromodeoxyuridine (BrdU) assay, not affecting cell viability. The determination of the total and phosphorylated (active) VEGFR-2 was performed by western blot, and it was possible to conclude that the compounds significantly inhibit the phosphorylation of the receptor at 1 µM pointing to their antiproliferative mechanism of action in HUVECs. The molecular rationale for inhibiting the tyrosine kinase domain of VEGFR-2 was also performed and discussed using molecular docking studies.The authors would like to acknowledge Foundation for the Science and Technology (FCT Portugal) for financial support through the NMR Portuguese network (Bruker 400 Avance III-Univ Minho). FCT and European Fund for Regional Development (FEDER)-COMPETE-QREN-EU for financial support through the research unities PEstC/QUI/UI686/2011, PEst-OE/SAU/UI0038/2011, and PEstOE/AGR/UI0690/2011, the research project PTDC/QUIQUI/111060/2009, and the post-Doctoral Grant attributed to Ricardo C. Calhelha (SFRH/BPD/68344/2010) also financed by Human Potential Operational Programme (POPH) and Social European Fund (FSE)