Metabolite Profiling and Reaction Phenotyping for the in vitro Assessment of the Bioactivation of Bromfenac

Bromfenac is a non-steroidal anti-inflammatory drug that was approved and subsequently withdrawn from the market due to reported cases of acute hepatotoxicity. Recently, in vitro studies have revealed that bromfenac requires UDPGA and alamethicin supplemented human liver microsomes (HLM) to form a major metabolite, bromfenac indolinone (BI). Bromfenac and BI formed thioether adducts through a bioactivation pathway in HLM and hepatocytes. (Driscoll, et al 2018) Here cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) reaction phenotyping experiments using recombinant enzymes were performed on bromfenac and BI to identify the CYP and UGT enzymes responsible for bromfenac’s metabolism and bioactivation. It was determined that UGT2B7 converts bromfenac to BI, and that while CYP2C8, CYP2C9 and CYP2C19 catalyze the hydroxylation of bromfenac, only CYP2C9 forms thioether adducts when incubated with NAC or GSH as trapping agents. Although CYP2C9 was shown to form reactive intermediate, no inhibition of CY...