A Rapid and Selective UPLC-MS/MS Assay for Accurate Analysis of Apatinib in Rat Plasma and its Application to a Pharmacokinetic Study

Objective: Apatinib, a novel small-molecule Tyrosine Kinase Inhibitor (TKI), is under development to treat advanced gastric cancer. For the pharmacokinetic evaluation and routine drug monitoring of apatinib, a quantitative ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method in rat plasma was developed with tinidazole used as an internal standard (IS). Methods: Protein precipitation (PPT) was selected as a sample pre-treatment method to extract apatinib. Then, chromatography was performed on a Kinetex C8 column (2.1x100 mm, 2.6 μm) using a constant mobile phase including 0.2% formic acid and 10 mM ammonium acetate in water and methanol (30:70, v/v) with a gradient flow rate from 0.2 mL/min to 0.4 mL/min. Chromatographic analysis was performed in only 4.5 min. Mass spectrometric detection was carried on positive electrospray ionization (ESI+) mode with Multiple-Reaction Monitoring (MRM). Results: The standard calibration curve showed good linearity in 2-1000 ng/mL with the correlation coefficient (R²) > 0.99. The Lower Limit of Quantitation (LLOQ) was 2 ng/mL. The precision, accuracy, extraction recovery, matrix effect, stability and carryover were all within the acceptable range. Conclusion: This method was simple, accurate, selective and successfully used for a pharmacokinetic study following seven rats orally administrated a single of 60 mg/kg apatinib.