title: Identification of human liver cytochrome P450 isoforms involved in autoinduced metabolism of the antiangiogenic agent (Z)-5-[(1,2-dihydro-2-oxo-3H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-propanoic acid (TSU-68).
abstract: (Z)-5-[(1,2-Dihydro-2-oxo-3H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-propanoic acid (TSU-68) is a new anticancer drug that inhibits angiogenic receptor tyrosine kinases, which play a crucial role in tumor-induced vascularization. TSU-68 undergoes hepatic oxidation and glucuronidation. Incubation of TSU-68 with human liver microsomes in the presence of NADPH resulted in the formation of three major metabolites: 5-, 6-, and 7-hydroxyindolinone derivatives. The 5-, 6-, and 7-hydroxylation followed simple Michaelis-Menten kinetics with V(max)/K(m) values (an indicator of intrinsic clearance) of 13, 25, and 6 microl/min/mg, respectively. Of the 10 cDNA-expressed human cytochrome P450 isoforms examined, only CYP1A1 and CYP1A2 exhibited appreciable TSU-68 hydroxylation activity. Inhibition studies with alpha-naphthoflavone (a selective CYP1A2 inhibitor) and anti-CYP1A2 antibody also indicated the almost exclusive role of CYP1A2 in microsomal TSU-68 hydroxylation. Treatment of human hepatocytes with 10 microM TSU-68 resulted in a 28- to 140-fold increase in CYP1A1/2-mediated ethoxyresorufin O-deethylase activity. The protein levels of CYP1A2 were increased in TSU-68-treated hepatocytes, and those of CYP1A1, which were undetectable in control hepatocytes, were also increased to detectable levels in the TSU-68-treated hepatocytes. Thus, TSU-68 was shown to induce CYP1A1/2 expression, which was responsible for its hydroxylation. The observation that TSU-68 treatment resulted in a 10- to 45-fold increase in 5-, 6-, and 7-hydroxylation directly demonstrated the autoinduced hydroxylation of TSU-68. In conclusion, TSU-68 has the potential to cause induction of its own CYP1A1/2-mediated oxidative metabolism in humans. This autoinductive effect provides a clear explanation for the clinically observed decrease in TSU-68 plasma concentrations during repeated administration of the drug.
authors.affiliation: Pharmacokinetics Research Laboratory, Taiho Pharmaceutical Co., Ltd., 224-2, Ebisuno, Hiraishi, Kawauchi-cho, Tokushima 771-0194, Japan. r-kitamura@taiho.co.jp
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Kitamura
authors.forename: Hisae
authors.initials: H
authors.lastname: Asanoma
authors.forename: Sekio
authors.initials: S
authors.lastname: Nagayama
authors.forename: Masaki
authors.initials: M
authors.lastname: Otagiri
mesh_terms: D020533:Angiogenesis Inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D020719:Glucuronides / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation; D007211:Indoles / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D000078183:Oxindoles; D011422:Propionates / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D011758:Pyrroles
chemical_list: D020533:Angiogenesis Inhibitors; D020719:Glucuronides; D007211:Indoles; D000078183:Oxindoles; D011422:Propionates; D020033:Protein Isoforms; D011758:Pyrroles; D003577:Cytochrome P-450 Enzyme System; C412603:orantinib