Volumetric dried blood microsampling for monitoring imatinib mesylate therapy: Method development and clinical application in patients with chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a hematologic neoplasia, characterized as a proliferative disease of the hematopoietic system. Imatinib mesylate (IM), a selective tyrosine kinase inhibitor, is considered a first-line therapy for CML, indicated for both adult and pediatric patients presenting the Philadelphia chromosome (Ph+). However, patients in treatment with IM may show different responses due to interindividual pharma-cokinetic variability. Therapeutic drug monitoring should be routinely performed to identify treatment response profile, adherence to treatment, or possible drug interactions, thus supporting better treatment management. Volumetric absorptive microsampling (VAMS) are innovative devices for blood collection whose advantages include the possibility of home collection by the patient or at the physician's office. The assay was fully validated according to bioanalytical validation guidelines. Estimated plasma concentrations of IM were not statistically different between groups according to adherence (p = 0.15), with median of 789 ng ml-1 in the group with some level of non-adherence versus 1141.9 ng ml-1 in the group with adherence, classified with the Morisky-Green questionnaire. This study included 33 patients with CML in treatment with IM. These patients answered socio-economic, sociodemographic, and adherence profile (Morisky-Green) questionnaires. Patients also received in-structions for home blood collection with VAMS devices. Afterwards, the samples were analyzed by LC-MS/MS. The mean age of the patients was 52 years, 84.8% were ingesting doses of 400 mg/day and the majority were male (69.7%). IM and its metabolite NIM were extracted from VAMS with an aqueous solution with 0.1% formic acid, followed by protein precipitation with acetonitrile. The methodology developed in this study was satis-factory for the determination of IM and NIM in VAMS and can be used in hospital and office routines for the therapeutic monitoring of patients with CML.