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

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. 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. 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.