Absorption and elimination of imatinib through the rat intestine in vitro.

Imatinib is a potent selective inhibitor of tyrosine kinases and is used primarily in the treatment of chronic myeloid leukemia and the gastrointestinal stromal tumour. Although, it is well established that imatinib is a substrate of several transport proteins which are also active in the intestinal mucosa, the mechanisms of imatinib intestinal absorption and elimination were not systematically investigated yet. To do that, we used a Sweetana-Grass type of diffusion chambers with segments of rat intestine as a model of the intestinal mucosa, measured the permeability coefficients of imatinib and its major metabolite (N-desmethyl imatinib) in both directions with and without specific and general inhibition of active transport, and calculated the efflux ratios. The results show that the good bioavailability of imatinib is highly likely achieved by its active absorption from the intestine and that its active elimination through the intestinal mucosa is mediated by a synergistic activity of organic cation transporter 1 in the basolateral membrane and the added activity of two efflux proteins (P-glycoprotein and breast cancer resistant protein) in the apical membrane of enterocytes of the rat ileum. Interestingly, it was found that N-desmethyl imatinib is only transported by P-glycoprotein.

Monitoring of imatinib targeted delivery in human leukocytes.

The success of imatinib therapy in chronic myeloid leukemia is highly influenced by its active transport into target cells. However, the methodology for analytical evaluation of intracellular drug concentration is rare and usually reliant upon the use of radioactively labeled drugs. More specifically, there is no published method available in the literature for the determination of imatinib concentration in granulocytes. To gain further insight into the intracellular drug uptake a very reliable two-stage sample concentration procedure was devised and coupled with a sensitive ultra-high performance liquid chromatography tandem mass spectrometry. The reliability of this sample preparation and sensitivity of the analysis was confirmed by a successful validation of all necessary method parameters to an impressive lower limit of quantification of 0.5 ng imatinib per 10(6) cells still at the signal to noise ratio of 670. The usefulness of the method is further improved with only 6 mL of blood being necessary for patient analysis. The method has been applied to blood samples of 13 CML patients treated with imatinib and all the measured intracellular drug concentrations were within the validated range. These and further measurements will enable the research of factors which may, besides blood plasma concentration, influence the individual's response to imatinib therapy. Furthermore, individualisation of dosing based on the directly measured targeted drug delivery could be possible.

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.