A Chemoproteomic Platform To Assess Bioactivation Potential of Drugs

Reactive
metabolites (RM) formed from bioactivation of drugs can
covalently modify liver proteins and cause mechanism-based inactivation
of major cytochrome P450 (CYP450) enzymes. Risk of bioactivation of
a test compound is routinely examined as part of lead optimization
efforts in drug discovery. Here we described a chemoproteomic platform
to assess in vitro and in vivo bioactivation
potential of drugs. This platform enabled us to determine reactivity
of thousands of proteomic cysteines toward RMs of diclofenac formed
in human liver microsomes and living animals. We pinpointed numerous
reactive cysteines as the targets of RMs of diclofenac, including
the active (heme-binding) sites on several key CYP450 isoforms (1A2,
2E1 and 3A4 for human, 2C39 and 3A11 for mouse). This general platform
should be applied to other drugs, drug candidates, and xenobiotics
with potential hepatoxicity, including environmental organic substances,
bioactive natural products, and traditional Chinese medicine.