Development and validation of LC-MS/MS method for imatinib and norimatinib monitoring by finger-prick DBS in gastrointestinal stromal tumor patients

Abstract

The introduction of imatinib, an oral tyrosine kinase inhibitor, as first-line standard therapy in patients with unresectable, metastatic, or recurrent gastro-intestinal stromal tumor (GIST), strongly improved their treatment outcomes. However, therapeutic drug monitoring (TDM) is recommended for this drug due to the large inter-individual variability in plasma concentration when standard dose is administered. A Cmin higher than 760 ng/mL was associated with a longer progression free survival. Thus, a LC-MS/MS method has been developed and fully validated to quantify imatinib and its active metabolite, norimatinib, in finger-prick dried blood spot (DBS). The influence of hematocrit, sample homogeneity, and spot size and the correlation between finger-prick and venous DBS measurements were also assessed. The method showed a good linearity (R2 > 0,996) between 50–7500 ng/mL for imatinib and 10–1500 ng/mL for norimatinib. Analytes were extracted from DBS samples by simply adding to 3 mm-discs 150 μL of acidified methanol containing IMA-D8. The collected extract was then injected on a LC Nexera system in-house configured for the on-line cleanup, coupled with an API-4000 QT. The chromatographic separation was conducted on a Synergi Fusion-RP column (4 μm, 2x50 mm) while the trapping column was a POROS R1/20 (20 μm, 2x30 mm). The total run time was 8.5 min. DBSs stored at room temperature in plastic envelopes containing a silica-gel drying bag were stable up to 16 months.The proposed method was applied to 67 clinical samples, showing a good correlation between patients’ finger-prick DBS and plasma concentrations, measured by the reference LC-MS/MS method, internally validated. Imatinib and norimatinib concentrations found in finger-prick DBS were adjusted by hematocrit or by an experimental correction factor to estimate the corresponding plasma measurements. At the best of our knowledge, the proposed LC-MS/MS method is the first analytical assay to measure imatinib and norimatinib in DBS samples.

Therapeutic Drug Monitoring of Tyrosine Kinase Inhibitors Using Dried Blood Microsamples

“…However, the latter was considered clinically irrelevant as the authors stated that DBS samples collected via finger-prick typically correspond to blood volumes of approximately 10-20 µL ( 44 ). In other studies, for imatinib and norimatinib ( 39 ), pazopanib ( 45 ) or MK-1775 ( 27 ) no influence of spot sizes between 10 to 40 µL, 10 to 30 µL or 30 to 50 µL, respectively, were observed. Another aspect to be evaluated is the site of punching (central versus peripheral), as non-homogeneous distribution of drugs on filter paper has been described, commonly known as the “volcano effect” ( 48 ) (accumulation of red blood cells occurs at the very outer edge of a DBS).…”

Estimation of Imatinib by Modern Analytical Techniques: A Review

“…A: liquid chromatography-mass spectrometry (MS) 5 All the LC-MS/MS measurements were made by an API-4000 QT (Sciex Brugherio, Italy) coupled to a LC Nexera system (Shimadzu Milano, Italy) in-house configured for the on-line…”

Pharmacovigilance, drug interactions, pharmacogenetics and therapeutic drug monitoring of anticancer agents: a valuable support for clinical practice

“…In the last years, relevant advancements were made especially regarding methods (e.g. mass spectrometry) to quantify concentrations of multiple drugs and their metabolites in human plasma (42,43).…”