Identification of CYP2B6 as a principal human enzyme involved in the metabolic bioactivation of chlorfenapyr to tralopyril.

Chlorfenapyr (Chl) poisoning is characterized by delayed clinical deterioration, high fatality, and the absence of a specific antidote, yet the metabolic mechanism underlying its severe toxicity remains incompletely understood. Chl is a pro-insecticide whose toxic effects depend on metabolic activation to the toxic metabolite tralopyril (Tral); however, the key human enzyme responsible for this process remains unidentified. Our studies confirmed the involvement of cytochrome P450s in Chl activation. Molecular docking and recombinant enzyme assays further identified CYP2B6 as the principal human enzyme catalyzing Chl bioactivation to Tral. Subsequent in vivo studies using CYP2B10, the murine ortholog of human CYP2B6, showed that CYP2B10 induction accelerated Chl clearance and increased Tral formation, whereas CYP2B10 inhibition delayed Chl clearance and reduced Tral formation. These findings support a central role of CYP2B6-mediated activation in Chl toxicity. To our knowledge, this study is the first to identify CYP2B6 as the principal human CYP isoform mediating Chl bioactivation, providing a mechanistic basis for its delayed toxicity and suggesting this pathway as a potential target for future intervention strategies.