Inhibitory properties of trapping agents: glutathione, potassium cyanide, and methoxylamine, against major human cytochrome p450 isoforms.
In the early stages of drug discovery, the formation of reactive metabolites is often assessed by co-incubating the drug in liver microsomes with a trapping agent in the presence of NADPH. Our group assessed the capability of commonly used trapping agents to reversibly inhibit major cytochrome P450 (CYP) isoforms. Glutathione and cyanide did not inhibit the enzymes at concentrations up to 10 mM; however methoxylamine did show inhibition, with IC(50) values of 0.53 mM for CYP1A2, 4.12 mM for CYP2C9, 2.04 mM for CYP2C19, 9.72 mM for CYP2D6, and 1.26 and >10 mM for CYP3A4/5 (for testosterone and midazolam, respectively, as substrates).
Zhang
Chenghong
C
Drug Metabolism and Pharmacokinetics Department, Genentech, Inc., 1 DNA Way, MS 412a, South San Francisco, CA 94080, USA.
Wong
Susan
S
Delarosa
Erlie M
EM
Kenny
Jane R
JR
Halladay
Jason S
JS
Hop
Cornelis E
CE
Khojasteh-Bakht
Siamak Cyrus
SC
D065607:Cytochrome P-450 Enzyme Inhibitors; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery / Q000379:methods; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005978:Glutathione / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D006898:Hydroxylamines / Q000008:administration & dosage / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D008874:Midazolam / Q000378:metabolism; D011190:Potassium Cyanide / Q000008:administration & dosage / Q000494:pharmacology*; D013739:Testosterone / Q000378:metabolism
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D006898:Hydroxylamines; D007527:Isoenzymes; D013739:Testosterone; C005214:methoxyamine; D005978:Glutathione; D011190:Potassium Cyanide; D008874:Midazolam