Measurement and stability of FTY720 in human whole blood by high-performance liquid chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry

We report here a validated method for the quantification of a new immunosuppressant drug FTY720, using HPLC–tandem mass spectrometry. Whole blood samples (500 μl) were subjected to liquid–liquid extraction, in the presence of an internal standard (Y-32919). Mass spectrometric detection was by selected reaction monitoring with an atmospheric pressure chemical ionization source in positive ionization mode (FTY720: m/z 308.3 → 255.3). The assay was linear from 0.2 to 25 μg/l (r2 > 0.997, n = 5). The inter- and intra-day analytical recovery and imprecision for quality control samples (0.5, 7 and 15 μg/l) were 95.8–103.2 and <5.5%, respectively. At the lower limit of quantification (0.2 μg/l) the inter- and intra-day analytical recovery was 99.0–102.8% with imprecision of <7.6% (n = 5). The assay had a mean relative recovery of 100.5 ± 5.8% (n = 15). Extracted samples were stable for 16 h. FTY720 quality control samples were stable at room temperature for 16 h, at 4 °C for at least 8 days and when taken through at least three freeze–thaw cycles. In conclusion, the method described displays analytical performance characteristics that are suitable for pharmacokinetic studies in humans.