Simultaneous measurement of imatinib, nilotinib and dasatinib in dried blood spot by ultra high performance liquid chromatography tandem mass spectrometry

Imatinib, dasatinib and nilotinib are three tyrosine kinase inhibitors currently used to treat Bcr-Abl1 positive chronic myelogenous leukaemia (CML). However, achieving maximum benefit with these drugs may require optimal dosing and adherence to therapy. In those cases, therapeutic drug monitoring (TDM) can be a useful tool in managing patients with CML. The paper presents simple and high throughput method for simultaneous determination of all three TKIs in dried blood spot (DBS) samples from CML patients. DBS samples were prepared by applying 10 μL of spiked whole blood onto an Agilent DBS cards. Whole blood spot was punched out of the card, transferred to a well in a 96-well Captiva ND Lipids filter plate. After the addition of isotopically labelled internal standard, the drug was extracted with 0.1% formic acid in methanol. The collected extract (1 μL) was injected onto a Phenomenex Kinetex 50 mm × 2.1 mm C18 column and eluted with acetonitrile gradient into a triple quadrupole ESI-MS/MS Agilent 6460 operated in positive mode. The total run time was only 2.6 min. The method was validated in terms of linearity, selectivity, specificity, accuracy, precision, absolute and relative matrix effect and stability. The effect of haematocrit (Hct) on the accurate concentration determination was also examined. The method was linear in the range of 50-5000 μg/L for imatinib and nilotinib and in the range of 2.5-250 μg/L for dasatinib, with correlation coefficient values higher than 0.997. Lower limits of quantification (LLOQ) were 50 μg/L for imatinib and nilotinib and 2.5 μg/L for dasatinib. The method proved to be accurate (% bias < 13.2) and precise (CV < 10.3%) on intra- as well as on inter-day basis. Sample matrix (% ME=94.5-106.7) and different Hct values had no significant effect on the accuracy of measured concentrations. Samples proved to be stable whilst stored on DBS cards at room temperature or in the refrigerator; however, at 40 °C the stability of dasatinib was compromised. The method presented was successfully applied to clinical samples.