CYP Ki Determinations

 

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)

CYP Isoforms
CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 (other isoforms are available)

Matrix
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

Detection Method
LC-MS/MS of specific probe metabolites

Deliverables
Ki, Standard error of Ki, Inhibition modality, detailed Report

Turnaround Time
5 Days

Compound requirements
Depending on IC50 values but typically 2 mg solid