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Identification of the enzyme isoforms responsible for in vitro metabolism of the anti‐cancer agent TG100435 using human liver microsomes and recombinant enzymes
Author(s) -
Kousba Ahmed A,
Soll Richard,
Hu Steven,
Noronha Glenn,
Tabak Arek,
Yee Shiyin
Publication year - 2006
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.20.5.lb108-a
Subject(s) - cyp3a4 , microsome , cytochrome p450 , ketoconazole , metabolism , biochemistry , cyp1a2 , enzyme , isozyme , incubation , biology , metabolite , gene isoform , drug metabolism , microbiology and biotechnology , chemistry , gene , antifungal
The current study identified the enzyme isoforms responsible for the in vitro metabolism of the anti‐cancer agent TG100435. The metabolism of TG100435 was evaluated following its co‐incubation with human liver microsomes (HLM), cDNA‐expressed human CYP or Flavin‐containing monooxygenases (FMO) isoforms. Subsequent experiments involved the co‐incubation of TG100435 with HLM or the cDNA‐expressed isoforms in the presence of ketoconazole (a specific CYP3A4 inhibitor; 10–20μM), 1‐aminobenzotriazole (non‐specific CYP inhibitor; 2 mM), CYP3A4 monoclonal antibody (15 μL/0.5ml), or methimazole (FMO competitive inhibitor; 3 mM). CYP3A4 was the only CYP isoform metabolized TG100435. The other studied isoforms (CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP2E1) did not metabolize TG100435. TG100435 metabolism was completely inhibited following its co‐incubation with human recombinant CYP3A4 in the presence of ketoconazole, 1‐aminobenzotriazol, or monoclonal antibody. In contrast, co‐incubation of TG100435 with HLM in the presence of ketoconazole or 1‐aminobenzotriazole inhibited only 40% of TG100435 total metabolism. Subsequent metabolic studies indicated that FMO (FMO1 and FMO3, but not FMO5) were responsible for the remaining metabolism of TG100435. Similarly, TG100435 metabolism induced by FMO was completely inhibited following co‐incubation of TG100435 with HLM in the presence of methimazole.