title: Application of higher throughput screening (HTS) inhibition assays to evaluate the interaction of antiparasitic drugs with cytochrome P450s.
abstract: In this study we have evaluated the application and reliability of using fluorescence (FLUO)-based high throughput screening assays with recombinant CYPs (rCYP). This was accomplished by screening 29 clinically important antiparasitic drugs for inhibition of the five major drug-metabolizing CYPs (-1A2, -2C9, -2C19, -2D6, and -3A4). Data from FLUO/rCYP assays were compared with that obtained by conventional HPLC assays using human liver microsomes (HLM) and rCYPs. The K(i) values showed good correlations: FLUO/rCYP and HPLC/rCYP (r(2) = 0.81), HPLC/rCYP and HPLC/HLM (r(2) = 0.82), and FLUO/rCYP and HPLC/HLM (r(2) = 0.72). Niclosamide had substrate-dependent contrasting effects on CYP2C9 activity with an apparent activation (400%) of 7-methoxy-4-trifluoromethylcoumarin demethylase activity and potent inhibition (K(i) = 6.00 microM) of diclofenac 4-hydroxylase activity. Potent inhibitors of CYP1A2 were artemisinin, dihydroartemisinin, thiabendazole, primaquine, and niclosamide (K(i) = 0.43, 3.67, 1.54, 0.22, and 2.70 microM, respectively). Proguanil, cycloguanil, amodiaquine, and desethylamodiaquine inhibited CYP2D6 (K(i) = 6.76, 5.97, 2.1, and 4.13 microM, respectively). Considering the C(max) of these drugs, artemisinin, thiabendazole, primaquine, amodiaquine, and desethylamodiaquine may cause clinically important interactions because they are predicted to inhibit 67 to 99% of the activities of the CYPs they interact with. In addition, our results suggest CYP1A2 inhibition as the mechanism behind the observed thiabendazole/theophylline and primaquine/antipyrine interactions in vivo.
authors: Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe.
authors: T E
authors: TE
authors: Bapiro
authors: A C
authors: AC
authors: Egnell
authors: J A
authors: JA
authors: Hasler
authors: C M
authors: CM
authors: Masimirembwa
mesh_terms: D000981:Antiprotozoal Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D013050:Spectrometry, Fluorescence
chemical_list: D000981:Antiprotozoal Agents; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System