The Potential for CYP2D6 Inhibition Screening Using a Novel Scintillation Proximity Assay-Based Approach

Author:

Delaporte Enock1,Slaughter Donald E.1,Egan Marjorie A.2,Gatto Gregory J.2,Santos Albie3,Shelley Joanne3,Price Elizabeth3,Howells Leighton4,Dean Dennis C.2,Rodrigues A. David1

Affiliation:

1. Department of Drug Metabolism, Merck Research Laboratories, West Point, PA

2. Department of Drug Metabolism, Merck Research Laboratories, Rahway, NJ

3. Amersham Pharmacia Biotech, Cardiff Laboratories, Whitchurch, Cardiff, UK

4. Amersham Pharmacia Biotech, Piscataway, NJ

Abstract

High throughput inhibition screens for human cytochrome P450s (CYPs) are being used in preclinical drug metabolism to support drug discovery programs. The versatility of scintillation proximity assay (SPA) technology has enabled the development of a homogeneous high throughput assay for cytochrome P450 2D6 (CYP2D6) inhibition screen using [O-methyl-'4C]dextromethorphan as substrate. The basis of the assay was the trapping of the 0- demethylation product, [14C]HCHO, on SPA beads. Enzyme kinetics parameters Vm,,. and apparent Ki,, determined using pooled human liver microsomes and microsomes from baculovirus cells coexpressing human CYP2D6 and NADPH-cytochrome P450 reductase, were 245 pmol [14C]HCHO/min/mg protein and 11,tM, and 27 pmol ['4C]HCHO/min/pmol and 1.6,uM, respectively. In incubations containing either pooled microsomes or recombinant CYP2D6, [14C]dextromethorphan 0-demethylase activity was inhibited in the presence of quinidine (IC50 = 1.0,uM and 20 nM, respectively). By comparison, inhibitors selective for other CYP isoforms were relatively weak (IC50 > 25 tM). In agreement, a selective CYP2D6 inhibitory monoclonal antibody caused greater than 90% inhibition of [14C]dextromethorphan O-demethylase activity in human liver microsomes, whereas CYP2C9/19- and CYP3A4/5-selective antibodies elicited a minimal inhibitory effect. SPA-based [14C]dextromethorphan 0-demethylase activity was also shown to correlate (r2 = 0.6) with dextromethorphan O-demethylase measured by high-performance liquid chromatography in a bank of human liver microsomes (N = 15 different organ donors). In a series of known CYP2D6 inhibitors/substrates, the SPA-based assay resolved potent inhibitors (IC50 <2 μM) from weak inhibitors (IC50 ≥ 20 μM). It is concluded that the SPA-based assay described herein is suitable for CYP2D6 inhibition screening using either native human liver microsomes or cDNA-expressed CYP2D6.

Publisher

Elsevier BV

Cited by 21 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. CYP Inhibition Methods;Drug-Like Properties;2016

2. In VitroApproaches to Study Drug–Drug Interactions;Methods and Principles in Medicinal Chemistry;2014-07-11

3. Modern methods of cytochrome P450 analysis;Biochemistry (Moscow) Supplement Series B: Biomedical Chemistry;2013-04

4. Higher-Throughput Screening Methods to Identify Cytochrome P450 Inhibitors and Inducers: Current Applications and Practice;High-Throughput Screening Methods in Toxicity Testing;2013-03-04

5. Mass spectrometric determination of the quantity and enzyme activity of cytochromes P450;Russian Journal of Bioorganic Chemistry;2011-03

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