title: Determination of regorafenib (BAY 73-4506) and its major human metabolites BAY 75-7495 (M-2) and BAY 81-8752 (M-5) in human plasma by stable-isotope dilution liquid chromatography-tandem mass spectrometry.
abstract: BACKGROUND
  Regorafenib (BAY 73-4506, commercial name Stivarga(®)) is an oral multikinase inhibitor developed by Bayer Pharma AG (Germany) that targets angiogenic, stromal and oncogenic receptor tyrosine kinases. An isotope dilution liquid chromatography-tandem mass spectrometry method has been developed and validated for the simultaneous determination of regorafenib and its two major metabolites BAY 75-7495 (M-2) and BAY 81-8752 (M-5) in lithium-heparinized human plasma.
  
  
  RESULTS
  Analysis was performed after protein precipitation on a triple-quadrupole tandem mass spectrometer. The validated concentration range was from 2.00 (lower limit of quantitation) to 2000 µg/l for all the analytes. Selectivity and specificity in the presence of four potential comedications were demonstrated. Interassay accuracy and precision coefficient of variation ranged from 91.2% (at LLOQ of M-5) to 105% and 3.59 to 14.1%, respectively.
  
  
  CONCLUSIONS
  The method proved to be selective, specific, sufficiently sensitive, highly reproducible and robust for the analysis of large numbers of samples. The method performance met current guidelines on bioanalytical method validation.
authors.affiliation: Drug Metabolism & Pharmacokinetics, Pharmaceutical Research Center, Bayer HealthCare AG, Aprather Weg 18A, D-42096 Wuppertal, Germany.
authors.forename: Frank-Thorsten
authors.initials: FT
authors.lastname: Hafner
authors.forename: Daniel
authors.initials: D
authors.lastname: Werner
authors.forename: Michael
authors.initials: M
authors.lastname: Kaiser
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D007201:Indicator Dilution Techniques; D007554:Isotopes / Q000032:analysis; D057230:Limit of Detection; D008297:Male; D010671:Phenylurea Compounds / Q000032:analysis / Q000097:blood* / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000032:analysis / Q000097:blood* / Q000378:metabolism*; D011725:Pyridines / Q000032:analysis / Q000097:blood* / Q000378:metabolism*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D007554:Isotopes; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C559147:regorafenib