Determination of Imatinib in the Blood Cells of Chronic Myelogenous Leukemia Patients by Ion-Trap
Mass Spectrometry

David Potěšil

Imatinib mesylate is a standard first-line therapy for patients with chronic myelogenous leukemia.
However, there is still a significant proportion of these patients who reflect sub-optimal responses
or fail imatinib therapy. Knowledge of the distribution within the studied system (e.g., peripheral
blood) may be of high importance for understanding the principles of drug action and possible
patient resistance to treatment. Intracellular, or more precisely cell-associated, imatinib
concentrations in patients, were shown to be higher compared to those in plasma, but still only
limited data related to the methodology aspects of cell-associated concentrations are available.
Herein is presented an assessment of the cell-associated imatinib determination assay by mass
spectrometry. Three approaches were evaluated to isolate cells from the peripheral blood of chronic
myelogenous leukemia patients. Erythrocyte lysis was found to cause substantial leakage of
cell-associated imatinib in the first step. Selected alternative procedures utilizing density
gradients did not affect the cell-associated imatinib concentration significantly. Cell isolates
were subjected to flow cytometry which revealed differences in the population composition of
peripheral blood cell isolates among individual patients indicating that the cell isolate
composition should be addressed with the cell-associated imatinib concentration. The proposed
approach may be utilized for the determination of intracellular concentration of imatinib and for
other drugs in which the intracellular concentration plays a key role in the therapy.