Pharmacokinetic Study of Macitentan in Rat Plasma by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

Macitentan is a novel, orally active dual endothelin receptor antagonist, which is currently under investigation for the treatment of diseases associated with endothelin dysfunction, including pulmonary arterial hypertension (PAH). In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of macitentan in rat plasma was developed and validated. After addition of diazepam as an internal standard (IS), protein precipitation by acetonitrile-methanol (9:1, v/v) was used to prepare samples. Chromatographic separation was achieved on a UPLC BEH C18 column (2.1 x 100 mm, 1.7 mu m) with 0.1% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 588.9 -> 203.4 for macitentan, and m/z 285.1 -> 193.1 for IS. Calibration plots were linear throughout the range 10-4000 ng/mL for macitentan in rat plasma. Mean recoveries of macitentan in rat plasma ranged from 80.2 to 93.0%. RSD of intra-day and inter-day precision were both < 12%. The accuracy of the method was between 893 and 105.1%. The method was successfully applied to pharmacokinetic study of macitentan after either oral or intravenous administration. The bioavailability of macitentan was reported as 79.6%.