High throughput lead optimization requires simple, homogeneous cell-based assays capable of defining the drug-like properties of first-round screening hits. Induction and inhibition of the Phase I drug-metabolizing enzymes are central to this process. We report here an assay for induction and inhibition of cytochrome P-450 (CYP) isozyme 1A2 that meets these requirements. It utilizes HepG2/C3A, a human liver cell line, and ethoxyresorufiln. Using methylcholanthrene, CYP1A2 can be induced dramatically, and it is inhibited by furafylline, a mechanism-based inhibitor of this enzyme.
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