title: Biochemical characterization of TAK-593, a novel VEGFR/PDGFR inhibitor with a two-step slow binding mechanism.
abstract: Inhibition of tumor angiogenesis leads to a lack of oxygen and nutrients in the tumor and therefore has become a standards of care for many solid tumor therapies. Dual inhibition of vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) protein kinase activities is a popular strategy for targeting tumor angiogenesis. We discovered that TAK-593, a novel imidazo[1,2-b]pyridazine derivative, potently inhibits tyrosine kinases from the VEGFR and PDGFR families. TAK-593 was highly selective for these families, with an IC(50) >1 μM when tested against more than 200 protein and lipid kinases. TAK-593 displayed competitive inhibition versus ATP. In addition, TAK-593 inhibited VEGFR2 and PDGFRβ in a time-dependent manner, classifying it as a type II kinase inhibitor. Analysis of enzyme-inhibitor preincubation experiments revealed that the binding of TAK-593 to VEGFR2 and PDGFRβ occurs via a two-step slow binding mechanism. Dissociation of TAK-593 from VEGFR2 was extremely slow (t(1/2) >17 h), and the affinity of TAK-593 at equilibrium (K(i)*) was less than 25 pM. Ligand displacement analysis with a fluorescent tracer confirmed the slow dissociation of TAK-593. The dissociation rate constants were in good agreement between the activity and ligand displacement data, and both analyses supported slow dissociation of TAK-593. The long residence time of TAK-593 may achieve an extended pharmacodynamic effect on VEGFR2 and PDGFRβ kinases in vivo that differs substantially from its observed pharmacokinetic profile.
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd., 2-17-85, Jusohonmachi Yodogawa-ku, Osaka 532-8686, Japan.
authors.forename: Hidehisa
authors.initials: H
authors.lastname: Iwata
authors.forename: Shinichi
authors.initials: S
authors.lastname: Imamura
authors.forename: Akira
authors.initials: A
authors.lastname: Hori
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hixon
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miki
mesh_terms: D053961:Azabicyclo Compounds / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D015394:Molecular Structure; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D053961:Azabicyclo Compounds; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; C557405:TAK 593; D017479:Receptors, Platelet-Derived Growth Factor; D040262:Receptors, Vascular Endothelial Growth Factor