Qualitative and quantitative determination of SIPI-2011 and its two major metabolites in human plasma

Abstract

SIPI-2011, a structural modification of isoquinoline alkaloid, is under investigation for treating arrhythmias. To characterize the safety and tolerability, the pharmacokinetics and metabolism of SIPI-2011 were investigated in humans. After an oral administration of 600 mg SIPI-2011, a total of 32 metabolites were detected in human plasma by UPLC-UV/Q-TOF mass spectrometry utilizing mass defect filter method. The principal biotransformation pathways included di-dehydrogenation (M8–1), dehydrogenation (M9–2), and oxidation and dehydrogenation (M10–4). Afterward, a sensitive LC-MS/MS method was developed to simultaneously determine SIPI-2011 and its two major metabolites M8–1 and M9–2 in human plasma. The isotopically labeled internal standards of the metabolites were obtained by incubating deuterated SIPI-2011 with rat liver homogenates. To achieve effective chromatographic retention and separation, three analytes were eluted on an XDB-phenyl column with alkaline mobile phase, and detected by multiple reaction monitoring (MRM) with positive electrospray ionization source. To reduce the interference from the isotope signals of M8–1 and M9–2 in the higher calibration point, [M+H+ 1]⁺ ions were selected as precursor ions of M9–2 and SIPI-2011 for MRM analysis. The assay was linear in the concentration range 15.0–3000 ng/mL for SIPI-2011, 0.500–100 ng/mL for M8–1 and 1.00–200 ng/mL for M9–2. The parameters of the method validation all met the acceptance criteria. The pharmacokinetic study indicated that SIPI-2011 was rapidly absorbed with a median T_max of 0.65 h and a terminal half-life of 15.4 h when healthy volunteers were administered a single dose of 300 mg SIPI-2011. And the plasma exposures of the two metabolites M8–1 and M9–2 were less than 10 % of that of the parent drug.