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Drug Metabolism Letters


ISSN (Print): 1872-3128
ISSN (Online): 1874-0758

Inhibitory Properties of Trapping Agents: Glutathione, Potassium Cyanide, and Methoxylamine, Against Major Human Cytochrome P450 Isoforms

Author(s): Chenghong Zhang, Susan Wong, Erlie M. Delarosa, Jane R. Kenny, Jason S. Halladay, Cornelis E. Hop and Siamak Cyrus Khojasteh-Bakht

Volume 3, Issue 2, 2009

Page: [125 - 129] Pages: 5

DOI: 10.2174/187231209788654126

Price: $65


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 IC50 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).

Keywords: Trapping agents, glutathione, cyanide, methoxylamine, P450 inhibition, reactive metabolites

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