Liquid chromatography-tandem mass spectrometry methods for quantification of roxadustat (FG-4592) in human plasma and urine and the applications in two clinical pharmacokinetic studies.

Roxadustat (FG-4592) can inhibit the hypoxia-inducible factor prolyl hydroxylase (HIF-PH) enzymes that are responsible for targeting and regulating HIF for ubiquitination and proteasomal degradation. It has been approved in China as an anti-anemia drug for treating the anemia in dialysis-dependent CKD (chronic kidney disease) patients, and is also under regulatory review in Japan. Some studies are also investigating the clinical pharmacokinetics and pharmacodynamics of roxadustat in CKD patients. To support clinical investigations, a rapid high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method, with a concentration range from 1 to 5000 ng/mL, was designed for the quantification of roxadustat in human plasma and urine. Liquid-liquid extraction (LLE) was applied to sample clean-up followed by a chromatographic separation conducted on a Waters XTerra Phenyl column with isocratic elution. The mixture consisting of acetonitrile/water/formic acid (60:40:0.1[%], v/v/v) was employed as the mobile phase (flow rate: 1.0 mL/min) with 60% post-column split. The quantitation was employed in multiple reactions monitoring (MRM) mode based on positive electrospray ionization (ESI). This proposed method was fully validated and applied to the pharmacokinetic (PK) and pharmacodynamic (PD) study of roxadustat among healthy subjects in China.