In vitro activity: KRN 633, a novel quinazoline urea derivative, strongly inhibits VEGFR1, VEGFR2 and VEGFR3 receptors with IC50 values of 170 nM, 160 nM and 125 nM respectively. It shows lower inhibitory activity towards non-RTKs, such as PDGF receptor (PDGFRα and β, c-Kit, breast tumor kinase, and tunica interna endothelial cell kinase tyrosine kinases (IC50 = 965, 9850, 4330, 9200, and 9900 nM, respectively). KRN 633 potently inhibits ligand VEGF induced phosphorylation of VEGFR2 in HUVECs with an IC50 of 1.16 nM. KRN 633 also inhibits VEGF-dependent, but not bFGF-dependent, phosphorylation of the MAP kinases in endothelial cells, with IC50 values of 3.51 nM and 6.08 nM for ERK1 and ERK2, respectively. KRN633 has also been shown to inhibit the VEGF-driven proliferation of HUVECs with an IC50 of 14.9 nM, but it only suppresses FGF-driven proliferation at 3 μM weakly. KRN 633 inhibits hypoxia-induced transcriptional activation of HIF-1α in a concentration-dependent manner with an IC50 of 3.79 μM, through the inhibition of both Akt and ERK phosphorylation signaling pathways.

Kinase Assay: Cell-free kinase assays are done to obtain IC50 values against a variety of recombinant VEGF receptors. KRN633 is tested at concentrations varying from 0.3 nM to 10 μM. All assays are done in quadruplicate with 1 μM ATP.

Cell Assay: Cancer cells (A549, Ls174T, DU145, HT29, LNCap and PC-3 cell lines) are plated in media containig 10% FBS and antibiotics, at densities known to permit exponential growth over the assay period. The cells are cultured for 24 hours before adding KRN633 (0.01 to 10 μM) or just the vehicle (0.1% DMSO in medium) and then grown for a further 96 hours. Cell viability is measured using WST-1 reagent.

Mol Cancer Ther. 2004 Dec;3(12):1639-49; Cancer Lett. 2010 Oct 1;296(1):17-26; J Pharmacol Sci. 2010;112(3):290-8.