Quantification of OSU-2S, a novel derivative of FTY720, in mouse plasma by liquid chromatography-tandem mass spectrometry.

OSU-2S is a novel anti-cancer and immune modulatory agent designed specifically to avert the immunosuppressive effects and related toxicities observed in clinical studies with its predecessor analog, FTY720. To characterize its preclinical pharmacokinetics, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of OSU-2S in mouse plasma. Ethyl acetate extraction of samples containing OSU-2S and the internal standard, Sph-17, was followed by separation with a 6min gradient (water/0.1% formic acid and methanol/0.1% formic acid) on a reverse-phase C18 column at room temperature. Selected reaction monitoring was used for detection on a triple quadrupole mass spectrometer with positive ionization. The assay was linear over the concentration range 3-3000ng/mL with accuracy ranging from 103 to 111%, and both within- and between-run precision (CV%) ≤11%. All stability samples were within ±15% of nominal values, and replicates were within 15% CV. The assay was successfully applied to a mouse pharmacokinetic study of OSU-2S with intravenous and intraperitoneal administration. OSU-2S non-compartmental pharmacokinetic parameters, area under the concentration-time curve, clearance, and elimination half-life were estimated at 1522hμg/L, 3.06L/h/kg and 15.6h, respectively, for intravenous injection. Systemic availability after intraperitoneal injection was approximately 46%. These data demonstrate the OSU-2S compound displays acceptable pharmacokinetic properties for further in vivo pharmacologic evaluation, which can be facilitated by the validated LC-MS/MS assay.