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Updated: Jun 5, 2026
A Simple Bioassay for the Evaluation of Vascular Endothelial Growth Factors
Published on: March 15, 2016
Biochemical characterization of TAK-593, a novel VEGFR/PDGFR inhibitor with a two-step slow binding mechanism
Hidehisa Iwata1, Shinichi Imamura, Akira Hori
1Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd., 2-17-85, Jusohonmachi Yodogawa-ku, Osaka 532-8686, Japan.
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.
Insights
TAK-593, a novel inhibitor, targets tumor angiogenesis by potently inhibiting vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) kinases. Its slow dissociation from these targets suggests a prolonged therapeutic effect.
Area of Science:
- Oncology
- Pharmacology
- Biochemistry
Background:
- Tumor angiogenesis, crucial for tumor growth, is targeted by inhibiting vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR).
- Dual inhibition of VEGFR and PDGFR is a key strategy in solid tumor therapies.
Purpose of the Study:
- To investigate the inhibitory potential and mechanism of action of TAK-593, a novel imidazo[1,2-b]pyridazine derivative.
- To characterize TAK-593's selectivity and binding kinetics against VEGFR and PDGFR family kinases.
Main Methods:
- Enzyme inhibition assays were performed to determine IC(50) values against a panel of kinases.
- Kinetic studies, including time-dependent inhibition and enzyme-inhibitor preincubation experiments, were conducted.
- Ligand displacement assays were used to confirm binding and dissociation characteristics.
Main Results:
- TAK-593 demonstrated potent and selective inhibition of VEGFR and PDGFR kinases, with IC(50) >1 μM against over 200 other kinases.
- TAK-593 acts as a type II kinase inhibitor, exhibiting competitive inhibition versus ATP.
- The drug binds to VEGFR2 and PDGFRβ via a slow, two-step mechanism with extremely slow dissociation from VEGFR2 (t(1/2) >17 h) and high affinity (K(i)* < 25 pM).
Conclusions:
- TAK-593 is a novel, selective inhibitor of VEGFR and PDGFR kinases with unique slow-binding kinetics.
- The exceptionally long residence time of TAK-593 on its targets suggests potential for extended pharmacodynamic effects in vivo.
- These properties position TAK-593 as a promising candidate for anti-angiogenic cancer therapies.
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