Development and validation of a UPLC-MS/MS assay for the quantification of simotinib in human plasma. 
Simotinib is a novel oral small-molecule tyrosine kinase inhibitor that has demonstrated equal or superior antineoplastic activities to erlotinib in preclinical studies.  In support of a clinical pharmacokinetic study, a sensitive and accurate liquid chromatography (LC) method with mass spectrometry detection using multiple reaction monitoring (MRM) in positive ion mode was developed and validated for the quantification of simotinib in human plasma.  The sample preparation procedure involved a simple protein precipitation with methanol.  Erlotinib was used as the internal standard.  The optimal chromatographic behavior was achieved on a Zorbax SB-C8 column (2.1 mm × 100 mm, 3.5 μm) using a mixture of 0.1% formic acid with 10 mM ammonium formate/methanol (20:80, v/v) as the mobile phase.  The total LC analysis time per injection was 4 min with a flow rate of 0.2 mL/min.  The recovery was greater than 90% and no significant matrix effect was observed.  The assay was validated over the concentration range of 1-1,000 ng/mL. The intra- and interday precision and accuracy of the quality control samples at low, medium, and high concentration levels showed at most 9.4% relative standard deviation (RSD) and -7.4 to 7.4% relative errors (RE).  Assay selectivity, freeze/thaw stability, storage stability, and dilution effects were also assessed.  The method is now used to support clinical pharmacokinetic studies in patients with non-small cell lung cancer (NSCLC) after oral administration of simotinib.