The Current Status of Time Dependent CYP Inhibition Assay and In Silico Drug-drug Interaction Predictions

Zhengyin      Yan; Gary      W. Caldwell

Abstract

Various CYP time-dependent inhibition (TDI) assays have been widely implemented in drug discovery and development which has led to great success in positively identifying compounds with mechanism-base inhibition liability. However, drug-drug interaction (DDI) predictions by various in-silico models utilizing kinetic parameters obtained from TDI assays have met with significant challenges including questionable kinetic data, over-simplified in-vitro models and unreliable mathematic algorithms. Although significant efforts have been made to standardize the TDI assay and refine mathematical models, recent evaluation studies have revealed that the kinetic parameters of TDI, the most important invitro data required by all DDI prediction models, are significantly impacted by a variety of experimental variables including microsomal protein concentration, metabolic stability, CYP-specific probes, and post-incubation time. This review attempts to provide medicinal chemists a brief overview on the current status of TDI assays, determination of kinetic parameters and in silico DDI predictions with emphasis on the complexity of the TDI kinetics and limitations of current invitro models and DDI prediction methodologies.

Keywords: Time-dependent CYP inhibition, drug-drug interactions, time-dependent inhibition (TDI) assays, drug-drug interaction (DDI), metabolic stability, CYP-specific probes, fluorescent substrate, LC/MS analysis, MBI assay