A Comparative Study of the CYP450 Inhibition Potential of Marketed Drugs Using Two Fluorescence Based Assay Platforms Routinely Used in the Pharmaceutical Industry

Semi-automated high throughput screening for the inhibition of major human cytochrome P450 enzymes (1A2, 2C9, 2C19, 2D6 and 3A4) expressed in Escherichia Coli (Cypex bactosomes) or human lymphoblastoid cells (Gentest cDNA microsomes) using fluorescent probes has been evaluated using 68 marketed drugs. In general lower IC50 values were obtained with Cypex bactosomes compared with Gentest cDNA microsomes. This could be due to use of higher concentration of protein and also the lower activity of Gentest cDNA microsomes. Notably, when compared with in vivo clinical drug-drug interactions (cDDIs) gathered from clinical studies reported in the scientific literature Cypex bactosome data was better at predicting in vivo cDDI. Consequently, from the data obtained in this comparative study, a fluorescence based assay using Cypex bactosomes is more suitable as a front-line screen for the prediction of potential downstream CYP450 driven cDDIs.