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      Quantification of imatinib in human serum: validation of a high-performance liquid chromatography-mass spectrometry method for therapeutic drug monitoring and pharmacokinetic assays

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          Abstract

          Background

          Imatinib mesylate has been a breakthrough treatment for chronic myeloid leukemia. It has become the ideal tyrosine kinase inhibitor and the standard treatment for chronic-phase leukemia. Striking results have recently been reported, but intolerance to imatinib and noncompliance with treatment remain to be solved. Molecular monitoring by quantitative real-time polymerase chain reaction is the gold standard for monitoring patients, and imatinib blood levels have also become an important tool for monitoring.

          Methods

          A fast and cheap method was developed and validated using high-performance liquid chromatography-mass spectrometry for quantification of imatinib in human serum and tamsulosin as the internal standard. Remarkable advantages of the method includes use of serum instead of plasma, less time spent on processing and analysis, simpler procedures, and requiring reduced amounts of biological material, solvents, and reagents. Stability of the analyte was also studied. This research also intended to drive the validation scheme in clinical centers. The method was validated according to the requirements of the US Food and Drug Administration and Brazilian National Health Surveillance Agency within the range of 0.500–10.0 μg/mL with a limit of detection of 0.155 μg/mL. Stability data for the analyte are also presented.

          Conclusion

          Given that the validated method has proved to be linear, accurate, precise, and robust, it is suitable for pharmacokinetic assays, such as bioavailability and bioequivalence, and is being successfully applied in routine therapeutic drug monitoring in the hospital service.

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          Most cited references 20

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          Strategies for the assessment of matrix effect in quantitative bioanalytical methods based on HPLC-MS/MS.

          In recent years, high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS/MS) detection has been demonstrated to be a powerful technique for the quantitative determination of drugs and metabolites in biological fluids. However, the common and early perception that utilization of HPLC-MS/MS practically guarantees selectivity is being challenged by a number of reported examples of lack of selectivity due to ion suppression or enhancement caused by the sample matrix and interferences from metabolites. In light of these serious method liabilities, questions about how to develop and validate reliable HPLC-MS/MS methods, especially for supporting long-term human pharmacokinetic studies, are being raised. The central issue is what experiments, in addition to the validation data usually provided for the conventional bioanalytical methods, need to be conducted to confirm HPLC-MS/MS assay selectivity and reliability. The current regulatory requirements include the need for the assessment and elimination of the matrix effect in the bioanalytical methods, but the experimental procedures necessary to assess the matrix effect are not detailed. Practical, experimental approaches for studying, identifying, and eliminating the effect of matrix on the results of quantitative analyses by HPLC-MS/MS are described in this paper. Using as an example a set of validation experiments performed for one of our investigational new drug candidates, the concepts of the quantitative assessment of the "absolute" versus "relative" matrix effect are introduced. In addition, experiments for the determination of, the "true" recovery of analytes using HPLC-MS/MS are described eliminating the uncertainty about the effect of matrix on the determination of this commonly measured method parameter. Determination of the matrix effect allows the assessment of the reliability and selectivity of an existing HPLC-MS/MS method. If the results of these studies are not satisfactory, the parameters determined may provide a guide to what changes in the method need to be made to improve assay selectivity. In addition, a direct comparison of the extent of the matrix effect using two different interfaces (a heated nebulizer, HN, and ion spray, ISP) under otherwise the same sample preparation and chromatographic conditions was made. It was demonstrated that, for the investigational drug under study, the matrix effect was clearly observed when ISP interface was utilized but it was absent when the HN interface was employed.
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            Imatinib pharmacokinetics and its correlation with response and safety in chronic-phase chronic myeloid leukemia: a subanalysis of the IRIS study.

            Imatinib at 400 mg daily is standard treatment for chronic myeloid leukemia in chronic phase. We here describe the correlation of imatinib trough plasma concentrations (C(mins)) with clinical responses, event-free survival (EFS), and adverse events (AEs). Trough level plasma samples were obtained on day 29 (steady state, n = 351). Plasma concentrations of imatinib and its metabolite CGP74588 were determined by liquid chromatography/mass spectrometry. The overall mean (+/- SD, CV%) steady-state C(min) for imatinib and CGP74588 were 979 ng/mL (+/- 530 ng/mL, 54.1%) and 242 ng/mL (+/- 106 ng/mL, 43.6%), respectively. Cumulative estimated complete cytogenetic response (CCyR) and major molecular response (MMR) rates differed among the quartiles of imatinib trough levels (P = .01 for CCyR, P = .02 for MMR). C(min) of imatinib was significantly higher in patients who achieved CCyR (1009 +/- 544 ng/mL vs 812 +/- 409 ng/mL, P = .01). Patients with high imatinib exposure had better rates of CCyR and MMR and EFS. An exploratory analysis demonstrated that imatinib trough levels were predictive of higher CCyR independently of Sokal risk group. AE rates were similar among the imatinib quartile categories except fluid retention, rash, myalgia, and anemia, which were more common at higher imatinib concentrations. These results suggest that an adequate plasma concentration of imatinib is important for a good clinical response. This study is registered at http://clinicaltrials.gov as NCT00333840.
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              Nomenclature in evaluation of analytical methods including detection and quantification capabilities (IUPAC Recommendations 1995)

               L. A. Currie (1995)
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                Author and article information

                Journal
                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                Dove Medical Press
                1177-8881
                2013
                05 August 2013
                : 7
                : 699-710
                Affiliations
                [1 ]Laboratory of Tumor Biology, University of São Paulo, São Paulo, Brazil
                [2 ]Department of Hematology, School of Medicine, University of São Paulo, São Paulo, Brazil
                Author notes
                Correspondence: Vinicius Marcondes Rezende, Laboratory of Tumor Biology, Department of Hematology, School of Medicine, University of São Paulo, Av Dr Eneas de Carvalho Aguiar 155, 1o andar, Sala 30, São Paulo, SP 05403-000, Brazil, Tel +55 11 3061 5544 ext 312, Email viniciusrezende@ 123456usp.br
                Article
                dddt-7-699
                10.2147/DDDT.S42902
                3739544
                23946646
                © 2013 Rezende et al, publisher and licensee Dove Medical Press Ltd

                This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.

                Categories
                Methodology

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