Lookup NU author(s): Dr Sally Coulthard,
Dr Chris Redfern
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Adverse reactions and non-response are common in patients treated with thiopurine drugs. Current monitoring of drug metabolite levels for guiding treatment are limited to analysis of thioguanine nucleotides (TGNs) in erythrocytes after chemical derivatisation. Erythrocytes are not the target tissue and TGN levels show poor correlations with clinical response. We have developed a sensitive assay to quantify deoxythioguanosine (dTG) without derivatisation in the DNA of nucleated blood cells. Using liquid chromatography and detection by tandem mass spectrometry, an intra- and inter-assay variability below 7.8% and 17.0% respectively were achieved. The assay had a detection limit of 0.0003125 ng (1.1 femto-moles) dTG and was quantified in DNA samples relative to endogenous deoxyadenosine (dA) in a small group of 20 patients with inflammatory bowel disease, all of whom had been established on azathioprine (AZA) therapy for more than 25 weeks. These patients had dTG levels of 20-1360 mol dTG/10(6) mol dA; three patients who had not started therapy had no detectable dTG. This method, comparable to previous methods in sensitivity, enables the direct detection of a cytotoxic thiopurine metabolite without derivatisation in an easily obtainable, stable sample and will facilitate a better understanding of the mechanisms of action of these inexpensive yet effective drugs. (C) 2016 The Authors. Published by Elsevier B.V.
Author(s): Coulthard SA, Berry P, McGarrity S, Ansari A, Redfern CPF
Publication type: Article
Publication status: Published
Journal: Journal of Chromatography B
Print publication date: 01/01/2016
Online publication date: 15/06/2016
Acceptance date: 12/06/2016
ISSN (print): 1570-0232
ISSN (electronic): 1873-376X
Publisher: Elsevier Science
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