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Detoxication vs. Bioactivation Pathways of Lapatinib In Vitro
Author(s) -
Nardone Dasean,
Jackson Klarissa
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.03460
Subject(s) - glucuronidation , lapatinib , sulfotransferase , microsome , chemistry , glutathione , biochemistry , sulfation , glucuronosyltransferase , glucuronide , enzyme , pharmacology , cytochrome p450 , metabolite , cancer , biology , medicine , trastuzumab , breast cancer
Lapatinib (Tykerb®) is an orally administered tyrosine kinase inhibitor of EGFR and HER‐2 approved for the treatment of HER2+ breast cancer. Metabolic activation of lapatinib by cytochrome P450 3A enzymes leads to formation of a reactive quinoneimine intermediate, which is implicated in the development of lapatinib‐induced hepatotoxicity. However, less is known about the potential detoxication pathways of lapatinib. In preclinical species (rat and dog), the O‐debenzylated metabolite of lapatinib (M1) has been shown to undergo glucuronidation and sulfation. Human recombinant UDP‐glucuronosyltransferases (UGTs) were also reported to catalyze M1 glucuronidation in vitro. The objectives of this study were to identify the major UGT enzymes involved in lapatinib M1 glucuronidation and elucidate the inter‐species differences in the conjugation vs. bioactivation pathways of M1. Reaction phenotyping experiments were conducted using human recombinant UGT enzymes and human liver microsomes with enzyme‐selective chemical inhibitors. Metabolites were analyzed by LC‐MS/MS. The results of these studies demonstrated that UGT1A1 was the major hepatic UGT enzyme involved in lapatinib M1 glucuronidation; recombinant UGT1A8 (ex‐hepatic) also formed the M1‐glucuronide. In liver microsomal incubations supplemented with glutathione (GSH), NADPH, and UDPGA, levels of the M1‐glucuronide and quinoneimine‐GSH conjugate were similar across species (human, rat, and dog). However, in microsomal incubations with GSH and NADPH alone, formation of the quinoneimine‐GSH conjugate was highest in human liver microsomes compared to rat and dog. We also observed inter‐species differences in the biotransformation of M1 in liver S9 fractions via glucuronidation, sulfation, and aldehyde oxidase‐mediated oxidation. Collectively, these findings indicate that multiple non‐P450 pathways are involved in the biotransformation of O‐debenzylated lapatinib in vitro, and these routes may represent a protective mechanism against formation of the potentially toxic quinoneimine intermediate.