P450 Bioactivation of Analogs of Fluoro-iodoaniline Assessed by GSH Trapping Studies: Insight into Mechanism of P450 Oxidation

摘要

Bioactivation of drugs by P450 can result in formation of reactive electrophiles that could react to cellular components with toxic consequences. In pharmaceutical companies, attention is being paid to bioactivation and there are efforts to identify and remove this liability as early as possible in drug discovery. Here we studied bioactivation of fluoro-iodoaniline analogs and the result is insightful for the mechanism of aniline bioactivation. For 2-fluoro-4-iodoaniline, the major GSH conjugate was the addition of GSH conjugate with concomitant loss of fluorine. The minor metabolite was the addition of GSH and oxygen. For the analog which had fluorine at the C-3 position (next to iodine), the metabolic profile changes to the GSH conjugates of the hydroxylated ring with and without loss of fluorine ion. This points to the two competing mechanisms of oxidation that includes 2,5-cyclohexadien-1-iodo-4-imino and arene-oxide intermediates. The loss of fluorine without the addition of oxygen atom only takes place when the fluorine is on the carbon next to the C-1 aniline. This is consistent with formation of reactive metabolite 2,5-cyclohexadien-1-iodo-4-imino and the GSH reaction at the ipso position (to the carbon attached to amino group). The thiol from GSH would then react with C-2 followed by loss of HF.