Development and validation of an enantioselective LC-MS/MS method to quantify enantiomers of (±)-TAK-700 in rat plasma: lack of in vivo inversion of (+)-TAK-700 (Orteronel) to its antipode.

A highly sensitive, specific and enantioselective assay has been developed and validated for the estimation of TAK-700 enantiomers [(+)-TAK-700 and (-)-TAK-700] in rat plasma on LC-MS/MS-ESI in the positive-ion mode. Liquid-liquid extraction was used to extract (±)-TAK-700 enantiomers and IS (phenacetin) from rat plasma. TAK-700 enantiomers were separated using methanol and 5 mm ammonium acetate (80:20, v/v) at a flow rate of 0.7 mL/min on a Chiralcel OJ-RH column. The total run time was 7.0 min and the elution of (+)-TAK-700, (-)-TAK-700 and IS occurred at 3.71, 4.45 and 4.33 min, respectively. The MS/MS ion transitions monitored were m/z 308.2 → 95.0 for TAK-700 and m/z 180.2 → 110.1 for IS. The standard curves for TAK-700 enantiomers were linear (r(2) > 0.998) in the concentration range 2.01-2015 ng/mL for each enantiomer. The inter- and intra-day precisions were in the ranges 3.74-7.61 and 2.06-8.71% and 3.59-9.00 and 2.32-11.0% for (+)-TAK-700 and (-)-TAK-700, respectively. Both the enantiomers were found to be stable in a battery of stability studies. This novel method was applied to the study of stereoselective oral pharmacokinetics of (+)-TAK-700 and it was unequivocally demonstrated that (+)-TAK-700 does not undergo chiral inversion to its antipode in vivo.

A highly sensitive LC-MS/MS method for the determination of S-raclopride in rat plasma: application to a pharmacokinetic study in rats.

A highly sensitive and rapid assay method has been developed and validated for the estimation of S-(-)-raclopride (S-RCP) in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive ion mode. The assay procedure involves a simple liquid-liquid extraction technique for extraction of S-RCP and phenacetin (internal standard, IS) from rat plasma. Chromatographic separation was achieved with 0.2% formic acid : acetonitrile (80:20, v/v) at a flow rate of 0.30 mL/min on a Phenomenex Prodigy C(18) column with a total run time of 4.5 min. The MS/MS ion transitions monitored were 347.2 → 112.1 for S-RCP and 180.1 → 110.1 for IS. Method validation and pre-clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.05 ng/mL and the linearity range was extended from 0.05 to 152 ng/mL in rat plasma. The intra-day and inter-day precisions were 0.23-10.5 and 3.74-7.29%, respectively. This novel method was applied to a pharmacokinetic study of S-RCP in rats.