Simultaneous determination of SYL-1119 and SYL-1119-P in rat plasma using HPLC coupled with tandem mass spectrometry

SYL-1119 is a sphingosine-1-phosphate receptor 1 modulator for the treatment of autoimmune disease with better selectivity, while SYL-1119-P is its active phosphate. A sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous determination of SYL-1119 and SYL-1119-P in rat plasma. SYL-1110, an analogue of SYL-1119, was used as the internal standard. Plasma samples were prepared by protein precipitation using acetonitrile. The analytes and internal standard were separated on a Zorbax SB-C18 column (3.5 μm, 100mm × 2.1 mm) with a gradient mobile phase consisting of methanol and water containing 0.1% formic acid at a flow rate of 0.2 ml/min with an operating temperature of 20 °C. The detection was performed on a triple quadrupole tandem mass spectrometer with positive electrospray ionization in multiple reaction monitoring mode of the transitions at m/z 364 → 259 for SYL-1119, m/z 444 → 259 for SYL-1119-P, and m/z 378 → 273 for the IS. Calibration curves were linear in the range of 0.2–50 ng/ml for SYL-1119 and 10–1000 ng/ml for SYL-1119-P. The lower limit of quantification (LLOQ) was 0.2 ng/ml for SYL-1119 and 10 ng/ml for SYL-1119-P. The intra- and inter-day precisions were 5.4–12.8% for two analytes with accuracies within ±10%. The recoveries for two compounds were 91.3–104.5%. The analytes were proved to be stable during all sample storage, preparation, and analytic procedures. The method was successfully applied to the pharmacokinetic study of SYL-1119 and SYL-1119-P in rats after oral administration of SYL-1119.