In vitro activity: Telatinib has 0.66, 0.17, and 2.5 times higher IC50 values for VEGFR3, c-Kit, and PDGFRβ than VEGFR2, respectively, while Vatalanib exhibits 18, 20, and 16 times higher IC50 values, respectively, indicating that Telatinib has potential benefit over Vatalanib. Telatinib inhibits VEGFR2 autophosphorylation in a whole-cell assay with an IC50 of 19 nM, suppresses VEGF-dependent proliferation of human umbilical vein endothelial cells with an IC50 of 26 nM, and blocks PDGF-stimulated growth of human aortic smooth muscle cells with an IC50 of 249 nM. Telatinib displays little inhibitory activity against the Raf kinase pathway, epidermal growth factor receptor family, the fibroblast growth factor receptor (FGFR) family, and the Tie-2 receptor.

Kinase Assay: The vanadate (Vi)-sensitive ATPase activity of ABCG2 in the membrane of High Five insect cells is measured. Briefly, membrane (2 μg/0.06 mL) are incubated in ATPase assay buffer with or without 0.4 mM vanadate at 37°C for 5 min and then incubated with varying concentrations of telatinib at 37°C for 5 min. The ATPase reaction is started by the addition of 4 mM Mg-ATP. After incubating at 37°C for 10 min, the reactions are stopped by adding 0.05 mL of 10% SDS solution. The liberated inorganic phosphate is measured.

Cell Assay: Telatinib has low affinity for the Raf kinase pathway, epidermal growth factor receptor family, the fibroblast growth factor receptor (FGFR) family, or the Tie-2 receptor. Telatinib is metabolized by various cytochrome P450 (CYP) isoforms including CYP3A4/3A5, CYP2C8, CYP2C9, and CYP2C19 as well as by uridine diphosphate glucuronosyltransferase 1A4 (UGT1A4), with the formation of the N-glucuronides of telatinib as the major biotransformation pathway in man. In vitro studies show telatinib to be a weak substrate of the adenosine triphosphate binding cassette (ABC) B1 (ABCB1) transporter. Telatinib at 1 μM significantly enhances the intracellular accumulation of [3H]-mitoxantrone (MX) in ABCG2-overexpressing cell lines. In addition, telatinib at 1 μM significantly reduces the rate of [3H]-MX efflux from ABCG2-overexpressing cells. Furthermore, telatinib significantly inhibits ABCG2-mediated transport of [3H]-E217βG in ABCG2 overexpressing membrane vesicles.