Characterization of Kinetic Binding Properties of Unlabeled Ligands via a Preincubation Endpoint Binding Approach.
The dissociation rates of unlabeled drugs have been well studied by kinetic binding analyses. Since kinetic assays are laborious, we developed a simple method to determine the kinetic binding parameters of unlabeled competitors by a preincubation endpoint assay. The probe binding after preincubation of a competitor can be described by a single equation as a function of time. Simulations using the equation revealed the degree of IC50 change induced by preincubation of a competitor depended on the dissociation rate koff of the competitor but not on the association rate kon To validate the model, an in vitro binding assay was performed using a smoothened receptor (SMO) and [(3)H]TAK-441, a SMO antagonist. The equilibrium dissociation constants (KI) and koff of SMO antagonists determined by globally fitting the model to the concentration-response curves obtained with and without 24 h preincubation correlated well with those determined by other methods. This approach could be useful for early-stage optimization of drug candidates by enabling determination of binding kinetics in a high-throughput manner because it does not require kinetic measurements, an intermediate washout step during the reaction, or prior determination of competitors' KI values.
Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa, Japan yuuji.shimizu@takeda.com.
Yuji
Y
Shimizu
Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa, Japan.
Kazumasa
K
Ogawa
Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa, Japan.
Masaharu
M
Nakayama
D001667:Binding, Competitive; D006801:Humans; D007700:Kinetics; D008024:Ligands; D011725:Pyridines / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D011869:Radioligand Assay / Q000379:methods*; D000072086:Smoothened Receptor / Q000037:antagonists & inhibitors* / Q000737:chemistry
D008024:Ligands; D011725:Pyridines; D011758:Pyrroles; C491023:SMO protein, human; D000072086:Smoothened Receptor; C577980:TAK-441
binding kinetics; computer simulations; law of mass action; smoothened receptor