A liquid chromatographic–tandem mass spectrometric method for the determination of two selective thymidylate synthase inhibitors, BGC945 and BGC638, in mouse plasma

A LC–tandem mass spectrometry method to quantify the quinazoline-based thymidylate synthase inhibitors BGC945 and BGC638 in mouse plasma was developed. BGC945 and BGC638 were extracted from mouse plasma using protein precipitation with acetonitrile. Chromatography was performed on a Fluophase RP 5 μm, 100 mm × 2.0 mm i.d. column using a gradient of ammonium acetate and acetonitrile as a mobile phase with a flow rate of 0.2 mL min−1. The injection volume for each sample was 20 μL with a total run time of 7.5 min. This method was validated in the range 25–4000 nM (r2 = 0.99). The analytical assay performance showed that the method was accurate (mean intra- and inter-day assay R.E. were below 12% and 11%, respectively), reproducible (mean intra- and inter-day R.S.D. were less than 13% and 5% for all quality control levels, respectively) and sensitive (lower limit of quantification was 25 nM) in the range studied. This validated method has been used to define the first pharmacokinetic report of BGC945 and BGC638 in mice.