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Quantitative determination of the cytidine deaminase inhibitor tetrahydrouridine (THU) in mouse plasma by liquid chromatography/electrospray ionization tandem mass spectrometry
Author(s) -
Parise Robert A.,
Egorin Merrill J.,
Eiseman Julie L.,
Joseph Erin,
Covey Joseph M.,
Beumer Jan H.
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3054
Subject(s) - chemistry , chromatography , electrospray ionization , tandem mass spectrometry , electrospray , cytidine deaminase , mass spectrometry , liquid chromatography–mass spectrometry , direct electron ionization liquid chromatography–mass spectrometry interface , ionization , chemical ionization , enzyme , biochemistry , ion , organic chemistry
A number of anticancer drugs are cytidine analogues that undergo metabolic deactivation catalyzed by cytidine deaminase (CD). 3,4,5,6‐Tetrahydrouridine (THU) is a potent inhibitor of CD, by acting as a transition‐state analogue of its natural substrate cytidine. However, to date its pharmacokinetic properties have not been fully characterized, which has impaired its optimal preclinical evaluation and clinical use. We report a liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the sensitive, accurate and precise quantitation of THU in mouse plasma. Validation was performed according to FDA guidelines. The assay employed deuterated THU as the internal standard and an acetonitrile protein precipitation step. Separation, based on hydrophilic interaction chromatography, was achieved with an amino column and an isocratic mobile phase of 0.1% formic acid in acetonitrile and water followed by a wash. Chromatographic separation was followed by positive‐mode electrospray ionization MS/MS detection in the multiple reaction monitoring (MRM) mode. The assay was accurate (92.5–109.9%) and precise (2.1–9.0%) in the concentration range of 0.2–50 µg/mL. Recovery from plasma was near‐complete (92.9–119.3%) and ion suppression was negligible (−17.5 to −0.2%). Plasma freeze/thaw stability (93.1–102.1%), stability for 3 months at −80°C (99.5–110.9%), and stability for 4 h at room temperature (92.1–102.4%) were all in order. This assay is currently being used to quantitate THU in ongoing pharmacokinetic studies. In addition, the assay is expected to be a useful tool in any future studies involving co‐administration of THU with cytidine analogues. Copyright © 2007 John Wiley & Sons, Ltd.