Background: With an increasing number of cancer patients receiving tyrosine kinase inhibitors (TKIs), therapeutic drug monitoring of these molecules is becoming more widespread today. It is mainly based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) methods with typical run times of several minutes. In an online solid phase extraction-MS/MS (SPE-MS/MS) system, the chromatography column is replaced with a reusable solid phase extraction (SPE) cartridge and the analysis time is shortened to less than half a minute. The aim of this study was to develop such a method and test the performance of this high-throughput system in the analysis of imatinib (IMA), nilotinib (NIL), and lapatinib (LAP) in human plasma.
Methods: Samples were prepared by simple protein precipitation with methanol containing deuterated internal standards. After centrifugation, the supernatant was diluted 10 fold with a mixture of methanol and water (1:1). A C4 cartridge was used for SPE and the analytes were eluted by acetonitrile. All the analytes were measured within a wide calibration range (50-5000 ng/mL for nilotinib and imatinib, 100-10,000 ng/mL for lapatinib). The method was compared with the LC-MS/MS method by the analysis of 176 clinical samples.
Results: Intraday and interday inaccuracies within 15% and a coefficient of variation less than 15% were achieved for all the TKIs that were measured. Even though the matrix effects were higher in comparison with LC-MS/MS methods, their effect on the performance of the method was eliminated by the usage of deuterated internal standards. The total run time of the new method was 29 seconds for one analysis and the results were fully comparable with LC-MS/MS.
Conclusions: Routine clinical practice requiring high-throughput methods for therapeutic drug monitoring of TKIs may benefit from the online SPE-MS/MS method that provides fast, low-cost analysis, and results that are comparable with conventional methods.