Development and validation of an assay for a novel ghrelin receptor inverse agonist PF-5190457 and its major hydroxy metabolite (PF-6870961) by LC-MS/MS in human plasma

PF-5190457 is a selective and potent ghrelin receptor inverse agonist presently undergoing clinical trials to treat alcohol use disorder (AUD). We describe the development and validation of a selective and sensitive liquid chromatography-tandem mass spectrometry-based method for quantification of PF-5190457 and its recently discovered hydroxy metabolite PF-6870961 in human plasma. Analytes were extracted after simple protein precipitation using methanol (2.5 ng mL(-1) tacrine as an internal standard). A gradient liquid chromatography method was used to separate the analytes on an Acquity UPLC BEH C18 analytical column. The separation was achieved at a flow rate of 0.25 mL min(-1) and the total chromatographic runtime was 11.30 min. Positive electrospray ionization and multiple reaction monitoring mode were used for the quantification of all the analytes. The calibration curves from six validation runs were linear with a correlation coefficient of >= 0.996 for the concentration range of 1-1000 ng mL(-1) and 2-250 ng mL(-1) for PF-5190457 and PF-6870961, respectively. The retention time for PF-5190457, PF-6870961 and tacrine were 4.4, 3.8, and 4.6 min, respectively. The lower limit of quantification for PF-5190457 and PF-6870961 was 1 and 2 ng mL(-1), respectively. The inter-assay precision and accuracy results obtained were within the Food and Drug Administration recommended +/- 15% limit of nominal values. All the analytes were found to be stable under varied stability conditions. The recovery of PF-5190457 and PF-6870961 ranged from 95 to 103%. Further, the application of the method was demonstrated by measuring the concentration of PF-5190457 and its hydroxy metabolite in patient plasma samples from 100 mg dose.