CYP Ki Determinations
The thermodynamic inhibition constant, Ki, is the recommended parameter by the FDA for investigating the clinical potential for CYP-related DDI. The value of [I]/Ki is important to predict potential DDI, where [I] represents the mean steady-state Cmax of the drug. A value of [I]/Ki >0.1 indicate potential in vivo DDI.
Detailed enzyme kinetic measurement at various inhibitor and substrate concentrations will yield the Ki value and the mode of inhibition (competitive, non-competitive, uncompetitive and mixed).
CYP Ki Determinations: Standard Assay Conditions (Customizable)
CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 (other isoforms are available)
Pooled human liver microsomes
Testing Compound Concentration
0, 0.25xIC50, 0.5xIC50, 0.75xIC50, 1xIC50, 2.5xIC50, 5xIC50, 10xIC50
Testing Substrate Concentration
0.3xKm, 1xKm, 3xKm, 6xKm and 10xKm
LC-MS/MS of specific probe metabolites
Ki, Standard error of Ki, Inhibition modality, detailed Report
Depending on IC50 values but typically 2 mg solid