High-throughput quantification of the anti-leukemia drug STI571 (Gleevec) and its main metabolite (CGP 74588) in human plasma using liquid chromatography-tandem mass spectrometry

Liquid chromatography-tandem mass spectrometric assay for the light sensitive tyrosine kinase inhibitor axitinib in human plasma

A bioanalytical assay for the new tyrosine kinase inhibitor axitinib was developed and validated. In addition, the light mediated trans to cis isomerization of this drug was investigated. For the quantitative assay, human plasma samples were pre-treated under light protection using protein precipitation with acetonitrile containing erlotinib as the internal standard. The extract was diluted with water and injected into the chromatographic system. The system consisted of a trifunctional bonded octadecyl silica column with isocratic elution using formic acid in a water-methanol mixture. The eluate was transferred into an electrospray interface with positive ionization and the analyte was detected and quantified using the selected reaction monitoring mode of a triple quadrupole mass spectrometer. The assay was validated in a 0.2-200ng/ml concentration range, the lowest level of this range being the lower limit of quantification. Within day precisions were 2.5-6%, between day precisions 4-9% and accuracies were between 91 and 106% for the whole calibration range. Light protected axitinib showed no isomerization and was shown to be chemically stable under all relevant conditions. Finally, the assay was successfully applied for a mouse tissue distribution study using mouse samples diluted with human plasma.

Determination of imatinib plasma levels in patients with chronic myeloid leukemia by high performance liquid chromatography-ultraviolet detection and liquid chromatography-tandem mass spectrometry: methods' comparison

The aims of this study were to validate and compare HPLC and LCMSMS analytical methods and their applicability for the quantitation of imatinib in human plasma. A total of 50 patients with chronic myeloid leukemia (CML) in chronic phase (CP) receiving 400 mg/day imatinib were enrolled in the study. Drug levels were determined by HPLC-UV and LCMSMS. HPLC intra-day accuracy ranged from 100.51 to 103.19%. LCMSMS accuracy ranged from 89.72 to 106.29%. The correlation coefficient between both methods was r(2)=0.96. HPLC can be used for imatinib levels' determinations in patients accurately and precisely.

Pharmacokinetic/pharmacodynamic correlation and blood-level testing in imatinib therapy for chronic myeloid leukemia

Imatinib is the current standard of care in the treatment of chronic myeloid leukemia (CML), inducing durable responses and prolonged progression-free survival. However, plasma exposure to the drug from a given dosing regimen can vary widely among patients. Reasons for this may include incomplete adherence, intrinsic variations in the metabolism of imatinib, and drug-drug interactions. Data from two recent studies have shown a correlation between imatinib trough plasma concentration and clinical response, leading to suggestions that maintaining imatinib blood concentrations above approximately 1000 ng/ml might be associated with improved outcomes. In patients who do not respond as well as expected to initial imatinib treatment, measurement of trough plasma concentration could assist with decisions about whether to increase the dose. Blood-level testing may also be helpful in other clinical scenarios: for example, when poor adherence is suspected, adverse reactions are unusually severe, or there is a possible drug-drug interaction. Further work is required to confirm prospectively the link between imatinib plasma concentrations and response, and to define effective trough concentrations in different patient populations. However, based on the current data, imatinib blood-level testing seems to be a useful aid when making clinical decisions in CML.

Imatinib plasma levels are correlated with clinical benefit in patients with unresectable/metastatic gastrointestinal stromal tumors

PURPOSE To study the pharmacokinetics (PK) of imatinib (IM) in patients with advanced GI stromal tumors (GISTs) treated in a randomized phase II study and to explore the potential relationship between IM plasma levels and long-term clinical outcomes. PATIENTS AND METHODS Patients were randomly assigned to receive IM at 400 mg versus 600 mg daily. IM plasma levels were analyzed in a subset of patients (n = 73) for whom PK data on day 1 and at steady-state (SS, day 29) were available. IM PK was evaluated using a population PK approach. The relationship between IM plasma exposure and clinical outcome was explored by grouping patients into quartiles according to IM trough concentration (C(min)). The clinical outcome parameters evaluated include overall objective benefit rate (OOBR; complete response plus partial response plus stable disease) time to progression (TTP), and KIT genotyping. Results IM PK exposure showed a high inter-patient variability, and clinical outcomes were correlated with IM trough levels at SS. The median TTP was 11.3 months for patients in the lowest C(min) quartile (Q1, < 1,110 ng/mL) compared with more than 30 months for Q2 to Q4 (P = .0029). OOBR was also inferior in Q1 patients. In patients with GIST with KIT exon 11 mutations (n = 39), the OOBR was 67% for Q1 patients versus 100% for all others (P = .001). CONCLUSION In patients with advanced GIST, IM trough levels at SS were associated with clinical benefit. Patients with IM C(min) below 1,100 ng/mL showed a shorter TTP and lower rate of clinical benefit (OOBR). Further studies are justified to test whether monitoring IM plasma levels might optimize clinical outcomes for patients with GIST.

Long-term efficacy of imatinib in a practical setting is correlated with imatinib trough concentration that is influenced by body size: a report by the Nagasaki CML Study Group

Imatinib has dramatically improved long-term survival of chronic myelogenous leukemia (CML) patients. To analyze its efficacy in a practical setting, we registered most of CML patients in Nagasaki Prefecture of Japan. Of these, 73 patients received imatinib as an initial therapy. The overall survival rate of these patients was 88.7% at 6 years, and the cumulative complete cytogenetic response rate was 82.5% at 18 months. These results are comparable with the data of other reports including the IRIS study; however, the administered imatinib dose was smaller in our study than that in other reports. To address these discrepancies, we measured the trough concentration of imatinib among 35 patients. Although 39% of the patients were administered less than 400 mg/day, the trough level was comparable to those of previous reports. The trough level of imatinib showed a significant relationship with its efficacy, and was clearly related to dose of imatinib administrated and dose of imatinib divided by body surface area (BSA). Considering the smaller BSA of Japanese patients as compared to those of foreign origin, the results suggest that a lower dose of imatinib could maintain enough trough level and provided excellent results for the treatment of CML in our registry.

Efficacy and safety profile of imatinib mesylate (ST1571) in Japanese patients with advanced gastrointestinal stromal tumors: a phase II study (STI571B1202)

BACKGROUND

Imatinib mesylate, an inhibitor of KIT, ABL protein, and platelet-derived growth factor receptor alpha (PDGFRalpha) tyrosine kinase, has recently been found to have a dramatic antitumor effect on gastrointestinal stromal tumor (GIST). The aim of this study was to assess the efficacy and safety of imatinib mesylate in Japanese patients with advanced GIST.

METHODS

Patients with measurable lesions were enrolled between April 1, 2002, and September 20, 2002, using a design based on previous phase II studies in the United States and the European Union. The diagnosis of GIST was proven histologically with positive immunostaining for KIT (CD117). Imatinib mesylate was administered at a dose of either 400 mg or 600 mg once a day. Pharmacokinetic parameters and mutation analysis of c-kit were also assessed in a subgroup of patients.

RESULTS

A total of 74 patients (28 receiving imatinib mesylate at 400 mg/day; 46 receiving 600 mg/day); median age, 56.0 years, were enrolled. No patient had a complete response, 51 patients (69%) had a partial response, and 19 patients (26%) had stable disease. The median progression-free survival time was 96 weeks. The estimated 3-year overall survival (Kaplan-Meier) rate for all patients was 73.6%. The most frequent adverse effects related to the drug were nausea (78%), diarrhea (70%), dermatitis (62%), facial edema (61%), edema of the lower limbs (58%), vomiting (54%), and eyelid edema (51%). Most of the adverse effects were mild and manageable.

CONCLUSION

Imatinib mesylate is generally safe and has significant activity in the treatment of advanced GIST in Japanese patients.

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 (Cmins) 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 Cmin 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). Cmin 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.

Effects of imatinib (Glivec) on the pharmacokinetics of metoprolol, a CYP2D6 substrate, in Chinese patients with chronic myelogenous leukaemia

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Imatinib, a tyrosine kinase inhibitor, exhibits a competitive inhibition on the CYP450 2D6 isozyme with a K(i) value of 7.5 microm. However, the clinical significance of the inhibition and its relevance to 2D6 polymorphisms have not been evaluated. The pharmacokinetics of imatinib have been well studied in Caucasians, but not in a Chinese population. Metoprolol, a CYP2D6 substrate, has different clearances among patients with different CYP2D6 genotypes. It is often used as a CYP2D6 probe substrate for clinical drug-drug interaction studies.

WHAT THIS STUDY ADDS

Co-administration of imatinib at 400 mg twice daily increased the plasma AUC of metoprolol by approximately 23% in 20 Chinese patients with chronic myeloid leukaemia (CML), about 17% increase in CYP2D6 intermediate metabolizers (IMs) (n = 6), 24% in extensive metabolizers (EMs) (n = 13), and 28% for the subject with unknown 2D6 status (n = 1) suggesting that imatinib has a weak to moderate inhibition on CYP2D6 in vivo. * The clearance of imatinib in Chinese patients with CML showed no difference between CYP2D6 IMs and EMs, and no major difference from Caucasian patients with CML based on data reported in the literature. AIMS To investigate the effect of imatinib on the pharmacokinetics of a CYP2D6 substrate, metoprolol, in patients with chronic myeloid leukaemia (CML). The pharmacokinetics of imatinib were also studied in these patients.

METHODS

Patients (n = 20) received a single oral dose of metoprolol 100 mg on day 1 after an overnight fast. On days 2-10, imatinib 400 mg was administered twice daily. On day 8, another 100 mg dose of metoprolol was administered 1 h after the morning dose of imatinib 400 mg. Blood samples for metoprolol and alpha-hydroxymetoprolol measurement were taken on study days 1 and 8, and on day 8 for imatinib.

RESULTS

Of the 20 patients enrolled, six patients (30%) were CYP2D6 intermediate metabolizers (IMs), 13 (65%) extensive metabolizers (EMs), and the CYP2D6 status in one patient was unknown. In the presence of 400 mg twice daily imatinib, the mean metoprolol AUC was increased by 17% in IMs (from 1190 to 1390 ng ml(-1) h), and 24% in EMs (from 660 to 818 ng ml(-1) h). Patients classified as CYP2D6 IMs had an approximately 1.8-fold higher plasma metoprolol exposure than those classified as EMs. The oral clearance of imatinib was 11.0 +/- 2.0 l h(-1) and 11.8 +/- 4.1 l h(-1) for CYP2D6 IMs and EMs, respectively.

CONCLUSIONS

Co-administration of a high dose of imatinib resulted in a small or moderate increase in metoprolol plasma exposure in all patients regardless of CYP2D6 status. The clearance of imatinib showed no difference between CYP2D6 IMs and EMs.

Phase I and Pharmacokinetic Study of Imatinib Mesylate in Patients With Advanced Malignancies and Varying Degrees of Liver Dysfunction: A Study by the National Cancer Institute Organ Dysfunction Working Group

Purpose

To develop dosing guidelines and to evaluate the pharmacokinetics of imatinib in patients with liver dysfunction (LD).

Patients and Methods

Patients (N = 89) with varying solid tumors and liver function were stratified into four groups according to serum total bilirubin and AST and were treated with escalating doses of imatinib. Plasma and urine were assayed for concentrations of imatinib and its active metabolite, CGP74588 .

Results

In the mild LD group, dose-limiting toxicity, specifically nausea/vomiting and fatigue, occurred in two patients at the 600 mg/d dose level. In the moderate and severe LD groups, the maximal dose evaluated was 300 mg/d. Grade 3 to 4 toxicities consisted primarily of liver function test elevations (24%), nausea/vomiting (10%), fatigue (6%), and edema (5%). After the first imatinib dose, the mean (± SD) dose-normalized areas under the plasma concentration-time curve from time 0 to infinity (AUC0-∞) were 162 ± 155, 171 ± 72, 182 ± 157, and 185 ± 172 (μg/mL × h)/mg for normal, mild, moderate, and severe LD groups, respectively. Renal excretion of imatinib was less than 10% of the total dose in all groups.

Conclusion

Imatinib exposure (as measured by the dose-normalized AUC) did not differ between patients with normal liver function and those with LD. The maximal recommended dose of imatinib for patients with mild LD is 500 mg/d. Dosing guidelines for patients with moderate and severe LD remain undetermined.

Determination of imatinib mesylate and its main metabolite (CGP74588) in human plasma and murine specimens by ion-pairing reversed-phase high-performance liquid chromatography

A sensitive reversed-phase high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of imatinib, a tyrosine kinase inhibitor, and its main metabolite N-desmethyl-imatinib (CGP74588) in human plasma and relevant murine biological matrices. A simple HPLC assay for the individual quantification of imatinib and CGP74588 in murine specimens has not been reported to date. Sample pre-treatment involved liquid-liquid extraction with tert-butyl-methyl ether. Imatinib, CGP74588 (metabolite) and the internal standard 4-hydroxybenzophenone were separated using a narrow bore (2.1 x 150 mm) stainless steel Symmetry C(18) column and detected by UV at 265 nm. The mobile phase consisted of 28% (v/v) acetonitrile in 50 mM ammonium acetate buffer pH 6.8 containing 0.005 M 1-octane sulfonic acid and was delivered at 0.2 mL/min. The calibration curve was prepared in blank human plasma and was linear over the dynamic range 10 ng/mL to 10 microg/mL). The accuracy was close to 100% and the within-day and between-day precisions were within the generally accepted 15% range. The validation results showed that the assay was selective and reproducible. This method was applied to study the pharmacokinetics of imatinib and its main metabolite in human and mice.

Pharmacokinetic investigation of imatinib using accelerator mass spectrometry in patients with chronic myeloid leukemia

PURPOSE

To investigate the potential use of accelerator mass spectrometry (AMS) in the study of the clinical pharmacology of imatinib.

EXPERIMENTAL DESIGN

Six patients who were receiving imatinib (400 mg/d) as part of their ongoing treatment for chronic myeloid leukemia (CML) received a dose containing a trace quantity (13.6 kBq) of (14)C-imatinib. Blood samples were collected from patients before and at various times up to 72 h after administration of the test dose and were processed to provide samples of plasma and peripheral blood lymphocytes (PBL). Samples were analyzed by AMS, with chromatographic separation of parent compound from metabolites. In addition, plasma samples were analyzed by liquid chromatography/mass spectrometry (LCMS).

RESULTS

Analysis of the AMS data indicated that imatinib was rapidly absorbed and could be detected in plasma up to 72 h after administration. Imatinib was also detectable in PBL at 24 h after administration of the (14)C-labeled dose. Comparison of plasma concentrations determined by AMS with those derived by LCMS analysis gave similar average estimates of area under plasma concentration time curve (26 +/- 3 versus 27 +/- 11 microg/mL.h), but with some variation within each individual.

CONCLUSIONS

Using this technique, data were obtained in a small number of patients on the pharmacokinetics of a single dose of imatinib in the context of chronic dosing, which could shed light on possible pharmacologic causes of resistance to imatinib in CML.

High-performance liquid chromatography method with ultraviolet detection for the quantification of the BCR-ABL inhibitor nilotinib (AMN107) in plasma, urine, culture medium and cell preparations

An isocratic and sensitive HPLC assay was developed allowing the determination of the new anticancer drug nilotinib (AMN107) in human plasma, urine, culture medium and cell samples. After protein precipitation with perchloric acid, AMN107 underwent an online enrichment using a Zirchrom-PBD precolumn, was separated on a Macherey-Nagel C18-HD column and finally quantified by UV-detection at 258 nm. The total run time is 25 min. The assay demonstrates linearity within a concentration range of 0.005-5.0 microg/ml in plasma (r(2)=0.9998) and 0.1-10.0 microg/ml in urine (r(2)=0.9913). The intra-day precision expressed as coefficients of variation ranged depending on the spiked concentration between 1.27-9.23% in plasma and 1.77-3.29% in urine, respectively. The coefficients of variation of inter-day precision was lower than 10%. Limit of detection was 0.002 microg/ml in plasma and 0.01 microg/ml in urine. The described method is stable, simple, economic and is routinely used for in vivo and in vitro pharmacokinetic studies of AMN107.

Identification of imatinib mesylate degradation products obtained under stress conditions

In this paper, the decomposition of imatinib mesylate (ImM) under hydrolytic (neutral, acidic, alkaline), oxidative and photolytic conditions was studied. The imatinib mesylate is practically photostable and stable under neutral conditions. The main degradation products under acidic and alkaline conditions are compounds: 4-methyl-N3-(4-pyridin-3-yl-pyrimidyn-2-yl)-benzene-1,3-diamine (2) and 4-(4-methyl-piperazin-1-ylmethyl)-benzoic acid (3). The main degradation products under oxidation conditions, i.e. 4-[(4-methyl-4-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide (6), 4-[(4-methyl-1-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide (7) and 4-[(4-methyl-1,4-dioxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide (8), were isolated from the reaction mixtures and identified by the HPLC, 1H NMR and MS techniques. During stress study the suitability of the proposed HPLC method to control purity of the samples was verified.

Phase I trial of imatinib in children with newly diagnosed brainstem and recurrent malignant gliomas: a Pediatric Brain Tumor Consortium report

This study estimated the maximum tolerated dose (MTD) of imatinib with irradiation in children with newly diagnosed brainstem gliomas, and those with recurrent malignant intracranial gliomas, stratified according to use of enzyme-inducing anticonvulsant drugs (EIACDs). In the brainstem glioma stratum, imatinib was initially administered twice daily during irradiation, but because of possible association with intratumoral hemorrhage (ITH) was subsequently started two weeks after irradiation. The protocol was also amended to exclude children with prior hemorrhage. Twenty-four evaluable patients received therapy before the amendment, and three of six with a brainstem tumor experienced dose-limiting toxicity (DLT): one had asymptomatic ITH, one had grade 4 neutropenia and, one had renal insufficiency. None of 18 patients with recurrent glioma experienced DLT. After protocol amendment, 3 of 16 patients with brainstem glioma and 2 of 11 patients with recurrent glioma who were not receiving EIACDs experienced ITH DLTs, with three patients being symptomatic. In addition to the six patients with hemorrhages during the DLT monitoring period, 10 experienced ITH (eight patients were symptomatic) thereafter. The recommended phase II dose for brainstem gliomas was 265 mg/m(2). Three of 27 patients with brainstem gliomas with imaging before and after irradiation, prior to receiving imatinib, had new hemorrhage, excluding their receiving imatinib. The MTD for recurrent high-grade gliomas without EIACDs was 465 mg/m(2), but the MTD was not established with EIACDs, with no DLTs at 800 mg/m(2). In summary, recommended phase II imatinib doses were determined for children with newly diagnosed brainstem glioma and recurrent high-grade glioma who were not receiving EIACDs. Imatinib may increase the risk of ITH, although the incidence of spontaneous hemorrhages in brainstem glioma is sufficiently high that this should be considered in studies of agents in which hemorrhage is a concern.

Population pharmacokinetics of imatinib and the role of alpha-acid glycoprotein

AIMS

The aims of this observational study were to assess the variability in imatinib pharmacokinetics and to explore the relationship between its disposition and various biological covariates, especially plasma alpha1-acid glycoprotein concentrations.

METHODS

A population pharmacokinetic analysis was performed using NONMEM based on 321 plasma samples from 59 patients with either chronic myeloid leukaemia or gastrointestinal stromal tumours. The influence of covariates on oral clearance and volume of distribution was examined. Furthermore, the in vivo intracellular pharmacokinetics of imatinib was explored in five patients.

RESULTS

A one-compartment model with first-order absorption appropriately described the data, giving a mean (+/-SEM) oral clearance of 14.3 l h-1 (+/-1.0) and a volume of distribution of 347 l (+/-62). Oral clearance was influenced by body weight, age, sex and disease diagnosis. A large proportion of the interindividual variability (36% of clearance and 63% of volume of distribution) remained unexplained by these demographic covariates. Plasma alpha1-acid glycoprotein concentrations had a marked influence on total imatinib concentrations. Moreover, we observed an intra/extracellular ratio of 8, suggesting substantial uptake of the drug into the target cells.

CONCLUSION

Because of the high pharmacokinetic variability of imatinib and the reported relationships between its plasma concentration and efficacy and toxicity, the usefulness of therapeutic drug monitoring as an aid to optimizing therapy should be further investigated. Ideally, such an approach should take account of either circulating alpha1-acid glycoprotein concentrations or free imatinib concentrations.

Population pharmacokinetics of imatinib and the role of alpha-acid glycoprotein

AIMS

The aims of this observational study were to assess the variability in imatinib pharmacokinetics and to explore the relationship between its disposition and various biological covariates, especially plasma alpha1-acid glycoprotein concentrations.

METHODS

A population pharmacokinetic analysis was performed using NONMEM based on 321 plasma samples from 59 patients with either chronic myeloid leukaemia or gastrointestinal stromal tumours. The influence of covariates on oral clearance and volume of distribution was examined. Furthermore, the in vivo intracellular pharmacokinetics of imatinib was explored in five patients.

RESULTS

A one-compartment model with first-order absorption appropriately described the data, giving a mean (+/-SEM) oral clearance of 14.3 l h-1 (+/-1.0) and a volume of distribution of 347 l (+/-62). Oral clearance was influenced by body weight, age, sex and disease diagnosis. A large proportion of the interindividual variability (36% of clearance and 63% of volume of distribution) remained unexplained by these demographic covariates. Plasma alpha1-acid glycoprotein concentrations had a marked influence on total imatinib concentrations. Moreover, we observed an intra/extracellular ratio of 8, suggesting substantial uptake of the drug into the target cells.

CONCLUSION

Because of the high pharmacokinetic variability of imatinib and the reported relationships between its plasma concentration and efficacy and toxicity, the usefulness of therapeutic drug monitoring as an aid to optimizing therapy should be further investigated. Ideally, such an approach should take account of either circulating alpha1-acid glycoprotein concentrations or free imatinib concentrations.

Simultaneous determination of AMN107 and Imatinib (Gleevec®, Glivec®, STI571) in cultured tumour cells using an isocratic high-performance liquid chromatography procedure with UV detection

A reversed phase high-performance liquid chromatographic (HPLC) method with UV detection was developed for the simultaneous determination of imatinib (Gleevec, Glivec, STI571) and AMN107 in cultured tumour cells, using clozapine as an internal standard. The compounds of interest were extracted by liquid-liquid extraction using TOXI-TUBES((R)) A extraction tubes. Chromatographic separation was performed on a Phenomenex Gemini C18 reversed phase column (150 mm x 2.0 mm, 5 microm particle size), using a mixture of 65% CH(3)OH (methanol) and 35% NH(4)Ac (Ammonium acetate) buffer (20mM, pH 10). Separation was achieved under isocratic conditions at a flow rate of 0.5 ml/min. Imatinib, clozapine and AMN107 are detected by UV detection at 260 nm. Calibration curves were linear from 50 to 7500 ng/ml with correlation coefficients (r(2)) better than 0.998. The limit of quantitation (LOD) was 50 ng/ml. The method has been successfully applied to a cellular kinetics study.

Pharmacokinetic-Pharmacodynamic Relationships of Imatinib and Its Main Metabolite in Patients with Advanced Gastrointestinal Stromal Tumors

PURPOSE

This study explored factors affecting the pharmacokinetic variability of imatinib and CGP 74588, and the pharmacokinetic-pharmacodynamic correlations in patients with advanced gastrointestinal stromal tumors.

EXPERIMENTAL DESIGN

Thirty-five patients with advanced gastrointestinal stromal tumors received 400 mg of imatinib daily. Six blood samples were drawn: before intake, during 1- to 3- and 6- to 9-hour intervals after intake on day 1, and before intake on days 2, 30, and 60. Plasma imatinib and CGP 74588 concentrations were quantified by reverse-phase high-performance liquid chromatography coupled with tandem mass spectrometry, and analyzed by the population pharmacokinetic method (NONMEM program). The influence of 17 covariates on imatinib clearance (CL) and CGP 74588 clearance (CLM/fm) was studied. These covariates included clinical and biological variables and occasion (OCC = 0 for pharmacokinetic data corresponding to the first administration, or OCC = 1 for the day 30 or 60 administrations).

RESULTS

The best regression formulas were: CL (L/h) = 7.97 (AAG/1.15)(-0.52), and CLM/fm (L/h) = 58.6 (AAG/1.15)(-0.60) x 0.55(OCC), with the plasma alpha1-acid glycoprotein (AAG) levels indicating that both clearance values decreased at a higher AAG level. A significant time-dependent decrease in CLM/fm was evidenced with a mean (+SD) CGP 74588/imatinib area under the curve (AUC) ratio of 0.25 (+/-0.07) at steady state, compared with 0.14 (+/-0.03) on day 1. Hematologic toxicity was correlated with pharmacokinetic variables: the correlation observed with the estimated unbound imatinib AUC at steady-state (r = 0.56, P < 0.001) was larger than that of the total imatinib AUC (r = 0.32, NS).

CONCLUSIONS

The plasma AAG levels influenced imatinib pharmacokinetics. A protein-binding phenomenon needs to be considered when exploring the correlations between pharmacokinetics and pharmacodynamics.

Thymidine-phosphorothioate oligonucleotides induce activation and apoptosis of CLL cells independently of CpG motifs or BCL-2 gene interference

We compared antisense phosphorothioate oligonucleotides (PS-ODN) that target BCL-2 such as Genasense (G3139-PS), with other PS-ODN or phosphodiester-ODN (PO-ODN) in their relative capacity to induce apoptosis of chronic lymphocytic leukemia (CLL) B cells in vitro. Surprisingly, we found that thymidine-containing PS-ODN, but not PO-ODN, induced activation and apoptosis of CLL cells independent of BCL-2 antisense sequence or CpG motifs. All tested thimidine-containing PS-ODN, irrespective of their primary sequences, reduced the expression of Bcl-2 protein and increased the levels of the proapoptotic molecules p53, Bid, Bax in CLL cells. Apoptosis induced by thymidine-containing PS-ODN was preceded by cellular activation, could be blocked by the tyrosine-kinase inhibitor imatinib mesylate (Gleevec), and was dependent on ABL kinase. We conclude that thymidine-containing PS-ODN can activate CLL cells and induce apoptosis via a mechanism that is independent of BCL-2 gene interference or CpG motifs.

A 96-well single-pot protein precipitation, liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of muraglitazar, a novel diabetes drug, in human plasma

A 96-well single-pot protein precipitation, liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the determination of muraglitazar, a PPAR alpha/gamma dual agonist, in human plasma. The internal standard, a chemical analogue, was dissolved in acetonitrile containing 0.1% formic acid. The solvent system was also served as a protein precipitation reagent. Human plasma samples (0.1 mL) and the internal standard solution (0.3 mL) were added to a 96-well plate. The plate was vortexed for 1 min and centrifuged for 5 min. Then the supernatant layers were directly injected into the LC/MS/MS system. The chromatographic separation was achieved isocratically on a Phenomenox C18(2) Luna column (2 mm x 50 mm, 5 microm). The mobile phase contained 20/80 (v/v) of water and acetonitrile containing 0.1% formic acid. Detection was by positive ion electrospray tandem mass spectrometry on a Sciex API 3000. The standard curve, which ranged from 1 to 1000 ng/mL, was fitted to a 1/x weighted quadratic regression model. This single-pot approach effectively eliminated three time consuming sample preparation steps: sample transfer, dry-down, and reconstitution before the injection, while it preserved all the benefits of the traditional protein precipitation. By properly adjusting the autosampler needle offset level, only the supernatant was injected, without disturbing the precipitated proteins in the bottom. As a result, the quality of chromatography and column life were not compromised. After more than 600 injections, there was only slightly increase of column back-pressure. The validation results demonstrated that this method was rugged and provide satisfactory precision and accuracy. The method has been successfully applied to analyze human plasma samples in support of a first-in-man study. This method has also been validated in monkey and mouse plasma for the determination of muraglitazar.

Imatinib (Gleevec®, Glivec®) tumour tissue analysis by measurement of sediment and by liquid chromatography tandem mass spectrometry

The analysis of the signal transduction inhibitor imatinib in patient tumour tissue using LC and MS/MS is described. The anticancer agent is eluted over RP-C18 within 2 mm together with its internal standard STI571-d8. Calibration curves were prepared in red blood cells (RBC). For quantitative isolation of the RBC, measurement of sediment was applied. There were no indications of signal suppression by substances originating in the biological matrix. The limit of determination in tumour tissue was in the range of those recorded for RBC and plasma. The assay is selective and sensitive, with its robustness favouring the experimental application in clinical oncology and its routine use in animal experiments. The LOD was 4.5 ng per gram in tumour tissue.

Clinical pharmacokinetics of imatinib

Imatinib is a potent and selective inhibitor of the protein tyrosine kinase Bcr-Abl, platelet-derived growth factor receptors (PDGFRalpha and PDGFRbeta) and KIT. Imatinib is approved for the treatment of chronic myeloid leukaemia (CML) and gastrointestinal stromal tumour (GIST), which have dysregulated activity of an imatinib-sensitive kinase as the underlying pathogenetic feature. Pharmacokinetic studies of imatinib in healthy volunteers and patients with CML, GIST and other cancers show that orally administered imatinib is well absorbed, and has an absolute bioavailability of 98% irrespective of oral dosage form (solution, capsule, tablet) or dosage strength (100 mg, 400 mg). Food has no relevant impact on the rate or extent of bioavailability. The terminal elimination half-life is approximately 18 hours. Imatinib plasma concentrations predictably increase by 2- to 3-fold when reaching steady state with 400mg once-daily administration, to 2.6 +/- 0.8 microg/mL at peak and 1.2 +/- 0.8 microg/mL at trough, exceeding the 0.5 microg/mL (1 micromol/L) concentrations needed for tyrosine kinase inhibition in vitro and leading to normalisation of haematological parameters in the large majority of patients with CML irrespective of baseline white blood cell count. Imatinib is approximately 95% bound to human plasma proteins, mainly albumin and alpha1-acid glycoprotein. The drug is eliminated predominantly via the bile in the form of metabolites, one of which (CGP 74588) shows comparable pharmacological activity to the parent drug. The faecal to urinary excretion ratio is approximately 5:1. Imatinib is metabolised mainly by the cytochrome P450 (CYP) 3A4 or CYP3A5 and can competitively inhibit the metabolism of drugs that are CYP3A4 or CYP3A5 substrates. Interactions may occur between imatinib and inhibitors or inducers of these enzymes, leading to changes in the plasma concentration of imatinib as well as coadministered drugs. Hepatic and renal dysfunction, and the presence of liver metastases, may result in more variable and increased exposure to the drug, although typically not necessitating dosage adjustment. Age (range 18-70 years), race, sex and bodyweight do not appreciably impact the pharmacokinetics of imatinib.

Liquid chromatography-mass spectrometry for the quantitative bioanalysis of anticancer drugs

The monitoring of anticancer drugs in biological fluids and tissues is important during both pre-clinical and clinical development and often in routine clinical use. Traditionally, liquid chromatography (LC) in combination with ultraviolet (UV), fluorescence, or electrochemical detection is employed for this purpose. The successful hyphenation of LC and mass spectrometry (MS), however, has dramatically changed this. MS detection provides better sensitivity and selectivity than UV detection and, in addition, is applicable to a significantly larger group of compounds than fluorescence or electrochemical detection. Therefore, LC-MS has now become the method of first choice for the quantitative bioanalysis of many anticancer agents. There are still, however, a lot of new developments to be expected in this area, such as the introduction of more sensitive and robust mass spectrometers, high-throughput analyses, and further optimization of the coupled LC systems. Many articles have appeared in this field in recent years and are reviewed here. We conclude that LC-MS is an extremely powerful tool for the quantitative analysis of anticancer drugs in biological samples.

Quantification of Imatinib in Human Plasma by High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Imatinib, also known as Gleevec or Glivec, is a selective tyrosine kinase inhibitor currently used for the treatment of Philadelphia chromosome-positive chronic myeloid leukemia (CML) and for other malignant pathologies. We have developed a LC-MS-MS [corrected] method that could be used for imatinib therapeutic drug monitoring in plasma. After a liquid-liquid extraction, the imatinib and its deuterated internal standard were eluted on an XTerra RP18 column with a gradient of acetonitrile-ammonium formiate buffer 4 mmol/L, pH 3.2. Imatinib was detected by electrospray ionization mass spectrometry with multiple reaction-monitoring mode. The calibration curves were linear over the range 10-5000 ng/mL. The limit of quantification was set at 10 ng/mL. The bias was lower than 8%. Intra-day and inter-day precisions were lower than 8%. The extraction recovery was higher than 90%. This method is simple, adapted to routine application, and allows accurate therapeutic monitoring of imatinib. It can be used to evaluate patient adherence to daily oral therapy, drug-drug interactions, or pharmacokinetic/pharmacodynamic relationships.

Population pharmacokinetics of imatinib mesylate in patients with chronic-phase chronic myeloid leukaemia: results of a phase III study

AIMS

This study was designed to investigate the biochemical and physiological covariates or comedications that affect the pharmacokinetics of imatinib mesylate in patients with chronic-phase chronic myeloid leukaemia (CP CML).

METHODS

Pharmacokinetic data were analyzed in 371 patients receiving 400 mg imatinib once daily during a phase III trial of imatinib vs interferon-alfa plus cytarabine for the treatment of newly diagnosed CP CML. Covariates included age, weight, sex, ethnicity, haemoglobin (Hb) concentration, white blood cell (WBC) count, liver function, and creatinine concentration. Blood samples for imatinib analysis were taken on treatment days 1 and 29. Nonlinear mixed effects modelling was used for the population pharmacokinetic analysis.

RESULTS

Population mean estimates (95% confidence interval) at day 1 for apparent clearance (CL) and apparent volume of distribution (V) of imatinib were 14 (13-15) l h(-1) and 252 (237-267) l, respectively. Modelling suggested that CL decreased by 4 (3-5) l h(-1) from day 1 to day 29, whereas V remained unchanged. Interindividual variability in CL and V was 32% and 31%, respectively. Weight, Hb, and WBC count demonstrated small effects on CL and V. Doubling body weight or Hb or halving the WBC count was associated with a 12%, 86% and 8% increase in CL, respectively, and a 32%, 60% and 5% increase in V, respectively. Comedications showed no clear effects on imatinib CL.

CONCLUSIONS

Population covariates and coadministered drugs minimally affected imatinib pharmacokinetics in newly diagnosed CP CML patients.

Metabolism and disposition of imatinib mesylate in healthy volunteers

Imatinib mesylate (GLEEVEC, GLIVEC, formerly STI571) has demonstrated unprecedented efficacy as first-line therapy for treatment for all phases of chronic myelogenous leukemia and metastatic and unresectable malignant gastrointestinal stromal tumors. Disposition and biotransformation of imatinib were studied in four male healthy volunteers after a single oral dose of 239 mg of (14)C-labeled imatinib mesylate. Biological fluids were analyzed for total radioactivity, imatinib, and its main metabolite CGP74588. Metabolite patterns were determined by radio-high-performance liquid chromatography with off-line microplate solid scintillation counting and characterized by liquid chromatography-mass spectrometry. Imatinib treatment was well tolerated without serious adverse events. Absorption was rapid (t(max) 1-2 h) and complete with imatinib as the major radioactive compound in plasma. Maximum plasma concentrations were 0.921 +/- 0.095 mug/ml (mean +/- S.D., n = 4) for imatinib and 0.115 +/- 0.026 mug/ml for the pharmacologically active N-desmethyl metabolite (CGP74588). Mean plasma terminal elimination half-lives were 13.5 +/- 0.9 h for imatinib, 20.6 +/- 1.7 h for CGP74588, and 57.3 +/- 12.5 h for (14)C radioactivity. Imatinib was predominantly cleared through oxidative metabolism. Approximately 65 and 9% of total systemic exposure [AUC(0-24 h) (area under the concentration time curve) of radioactivity] corresponded to imatinib and CGP74588, respectively. The remaining proportion corresponded mainly to oxidized derivatives of imatinib and CGP74588. Imatinib and its metabolites were excreted predominantly via the biliary-fecal route. Excretion of radioactivity was slow with a mean radiocarbon recovery of 80% within 7 days (67% in feces, 13% in urine). Approximately 28 and 13% of the dose in the excreta corresponded to imatinib and CGP74588, respectively.

Nonaqueous capillary electrophoresis method for the analysis of gleevec and its main metabolite in human urine

The viability of nonaqueous capillary electrophoresis (NACE) was investigated for determination of gleevec and its main metabolite in human urine using a fused-silica capillary. Baseline separation of the studied solutes was obtained using a nonaqueous solution composed of 12 mM ammonium acetate and 87.6 mM acetic acid in methanol-acetonitrile (ACN) (80:20, v:v) providing analysis time shorter than 3 min. Different aspects including stability of the solutions, linearity, accuracy and precision were studied in order to validate the method in the urine matrix. Detection limits of 24 microg L(-1) for gleevec and its metabolite were obtained. A robustness test of the method was carried out using the Plackett-Burman fractional factorial model with a matrix of 15 experiments. The developed method is simple, rapid and sensitive and has been used to determine gleveec and its metabolite at clinically relevant levels in human urine. Before NACE determination, a solid-phase extraction (SPE) procedure with a C18 cartridge was necessary. Real determination of these analytes in two patient urines were done.

Candidate-based proteomics in the search for biomarkers of cardiovascular disease

The key concept of proteomics (looking at many proteins at once) opens new avenues in the search for clinically useful biomarkers of disease, treatment response and ageing. As the number of proteins that can be detected in plasma or serum (the primary clinical diagnostic samples) increases towards 1000, a paradoxical decline has occurred in the number of new protein markers approved for diagnostic use in clinical laboratories. This review explores the limitations of current proteomics protein discovery platforms, and proposes an alternative approach, applicable to a range of biological/physiological problems, in which quantitative mass spectrometric methods developed for analytical chemistry are employed to measure limited sets of candidate markers in large sets of clinical samples. A set of 177 candidate biomarker proteins with reported associations to cardiovascular disease and stroke are presented as a starting point for such a 'directed proteomics' approach.

Imatinib pharmacokinetics in patients with gastrointestinal stromal tumour: a retrospective population pharmacokinetic study over time. EORTC Soft Tissue and Bone Sarcoma Group

Imatinib pharmacokinetics (PK) may be affected by a number of factors that are related to the disease being treated and to the response of that disease to imatinib. Patients in the phase I and phase II trials conducted by the EORTC in patients with gastrointestinal stromal tumours (GISTs) and other sarcomas had detailed blood sampling for imatinib PK on day 1 and on day 29. Patients with GISTs also had repeat sampling, using a limited sampling strategy, after approximately 12 months on therapy. This population PK study was carried out to examine what covariates affected imatinib PK in GIST patients and what PK changes occurred over time. In the model producing the best fit, low clearance (CL) correlated with low body weight and high granulocyte count, whereas low haemoglobin correlated with low volume of distribution. For a patient with 77% of the median body weight or with 1.87 times the median granulocyte count, the apparent CL is 6.53 l/h, about 70% of the typical apparent CL of 9.33 l/h; for a patient of 84% of the typical haemoglobin level, the volume of distribution is about 70%. Total white blood cell count correlated closely with granulocyte count and there was a moderate correlation between haemoglobin and albumin (r = 0.454). There was a trend towards increased imatinib clearance after chronic exposure over 12 months. The typical apparent CL increased 33% from day 1. Nevertheless, the approximate 95% confidence interval of the increase of the typical apparent CL was 33 +/- 34.6%, which contains zero. It is not yet clear whether this is a significant factor in the amelioration of imatinib toxicity that occurs with time or is related to disease control, and further work is required to confirm this observation.

Development and validation of a simple liquid chromatographic method with ultraviolet detection for the determination of imatinib in biological samples

The aim of this study was to develop a rapid and sensitive HPLC method with UV detection for the estimation of imatinib from the plasma of patients with chronic myeloid leukemia (CML). The robustness of the method was checked by conducting first dose pharmacokinetics on blood samples from four patients who had been administered Gleevec (100 mg) in an oral dose. Samples were prepared in a simple and single step by precipitating the plasma proteins with methanol and injecting 50 microl aliquot from supernatant was subjected for analysis. Assay was conducted using a C8 column (250 mm x 4.6 mm, 5 microm particle size) under isocratic elution with 0.02 M potassium dihydrogen phosphate-acetonitrile (7:3, v/v) at a flow rate of 1 ml/min and detected using photodiode array at 265 nm. Calibration plots in spiked plasma were linear in a concentration range of 0.05-25 microg/ml. The inter and intra-day variation of standard curve was <4% (R.S.D.). This method could be a simple and quick method for the estimation of imatinib from the patient's plasma.

Voltammetric behavior and quantification of the anti-leukemia drug imatinib in bulk form, pharmaceutical formulation, and human serum at a mercury electrode

Imatinib (GleevecTM, ST1571) exemplifies the successful development of a rationally designed molecularly targeted therapy for treatment of a specific cancer. It is a highly promising new drug for the treatment of chronic myelogenous leukemia in blast crisis, in the accelerated or chronic phase after interferon failure or intolerance. The electrochemical behavior of imatinib was studied in Britton–Robinson (B–R) buffers of pH 2 to 11 by means of cyclic voltammetry at a hanging mercury drop electrode. The voltammograms showed a single 2-electron irreversible cathodic peak, which may be attributed to reduction of the C=O double bond of the imatinib molecule. Imatinib exhibited a strong adsorption onto the electrode surface especially in B–R buffers of pH 6 and 7. The adsorptive response of the drug was optimized with respect to the pH of the electrolysis medium, accumulation variables, and instrumental parameters using a square-wave stripping voltammetry technique. A fully validated, simple, sensitive, precise, and selective square-wave adsorptive cathodic stripping voltammetric procedure is described for trace determination of imatinib. The limits of detection (LOD) and quantitation (LOQ) of the bulk imatinib, following preconcentration for 150 s onto the hanging mercury drop electrode, were found to be 2.6 × 10–10 and 8.7 × 10–10 mol/L, respectively. The proposed procedure was successfully applied for quantitation of imatinib in pharmaceutical formulation (Glivec®) and spiked human serum, without the necessity for sample pretreatment or time-consuming extraction or evaporation steps prior to analysis of the drug. LOD and LOQ of 4.6 × 10–10 and 1.5 × 10–9 mol/L, respectively, were achieved after 120 s of preconcentration of the drug spiked in human serum.Key words: imatinib, GleevecTM, Glivec®, ST1571, cyclic voltammetry, square-wave stripping voltammetry, electrochemical behavior, quantification, pharmaceutical formulation, human serum.

Imatinib mesylate (STI571) for treatment of children with Philadelphia chromosome-positive leukemia: results from a Children's Oncology Group phase 1 study

The purpose of this study was to determine dose-limiting toxicities and pharmacokinetics of imatinib in children with refractory or recurrent Philadelphia chromosome-positive (Ph(+)) leukemias. Oral imatinib was administered daily at dose levels ranging from 260 to 570 mg/m(2). Plasma pharmacokinetic studies were performed on days 1 and 8 of course 1. There were 31 children who received 479 courses of imatinib. The most common toxicities encountered, which occurred in less than 5% of courses, were grade 1 or 2 nausea, vomiting, fatigue, diarrhea, and reversible increases in serum transaminases. One patient at the 440-mg/m(2) dose level had dose-limiting weight gain. There were no other first-course dose-limiting toxicities. A maximum tolerated dosage was not defined. Among 12 chronic myeloid leukemia (CML) patients evaluable for cytogenetic response, 10 had a complete response and 1 had a partial response. Among 10 acute lymphoblastic leukemia (ALL) patients evaluable for morphologic response, 7 achieved an M1 and 1 achieved an M2 bone marrow. We observed marked interpatient variability in the pharmacokinetic parameters. In conclusion, we found that daily oral imatinib is well tolerated in children at doses ranging from 260 to 570 mg/m(2). Doses of 260 and 340 mg/m(2) provide systemic exposures similar to those of adults who are treated with daily doses of 400 and 600 mg, respectively.

Determination of imatinib (Gleevec®) in human plasma by solid-phase extraction–liquid chromatography–ultraviolet absorbance detection

A sensitive HPLC method has been developed for the assay of imatinib in human plasma, by off-line solid-phase extraction followed by HPLC coupled with UV-Diode Array Detection. Plasma (750 microl), with clozapine added as internal standard, is diluted 3 + 1 with water and subjected to a solid-phase extraction on a C18 cartridge. After matrix components elimination with 2000 microl of water (in two aliquots of 1000 microl), imatinib is eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 180 microl 50% methanol. A 50 microl volume is injected onto a Nucleosil 100-5 microm C18 AB column. Imatinib is analyzed using a gradient elution program with solvent mixture constituted of methanol and water containing both 0.05% ammonium acetate. Imatinib is detected by UV at 261 nm. The calibration curves are linear between 0.1 and 10 microg/ml. The limit of quantification and detection are 0.05 and 0.01 microg/ml, respectively. The mean absolute recovery of imatinib is 96%. The method is precise with mean inter-day CVs within 1.1-2.4%, and accurate (range of inter-day deviations -0.6 to +0.7%). The method has been validated and is currently being applied in a clinical study assessing the imatinib plasma concentration variability in a population of chronic myeloid leukemia- and gastro-intestinal stromal tumor-patients.

Pharmacokinetics and pharmacodynamics of imatinib in a phase I trial with chronic myeloid leukemia patients

PURPOSE

To evaluate the basic pharmacokinetic (PK) characteristics of imatinib mesylate and assess the relationship between the PK and pharmacodynamic (PD) properties of the drug.

PATIENTS AND METHODS

The PK and PD properties of imatinib were investigated during a phase I trial that included 64 adult patients with Philadelphia chromosome-positive leukemias. Patients received imatinib orally once or twice daily. PK parameters of imatinib, derived from the plasma concentration-time curves, were determined. PD response, defined as the WBC after 1 month of treatment with imatinib, was used to develop an efficacy model. A maximum inhibition-effect model was used to describe the relationship between reduction in WBC and drug exposure parameters.

RESULTS

Imatinib exposure was dose proportional after oral administration for the dose range of 25 to 1,000 mg. There was a 1.5- to three-fold drug accumulation after repeated once-daily dosing. Mean plasma trough concentration was 0.57 microg/mL (approximately 1 micromol/L) 24 hours after administration of 350 mg of imatinib at steady-state, which exceeds the 50% inhibitory concentration required to inhibit proliferation of Bcr-Abl-positive leukemic cells. Analysis of PK/PD relationships indicates that the initial hematologic response depends on the administered dose for patients with chronic myeloid leukemia.

CONCLUSION

Drug exposure (area under the concentration-time curve) is dose proportional for the dose range of 25 to 1,000 mg, and there is a 1.5- to three-fold drug accumulation at steady-state after once-daily dosing. Analysis of the relationship between PD (WBC reduction) and PK parameters at steady-state indicates that a dose of 400 mg or greater is required for maximal PD effect.

Experimental design in reversed-phase high-performance liquid chromatographic analysis of imatinib mesylate and its impurity

For the determination of the optimal RP-HPLC chromatographic conditions for the separation of imatinib mesylate and its impurity STI 509-00 experimental design 2(4) was applied. All the factors that affect imatinib mesylate/STI 509-00 separation, as well as their mutual interactions were investigated. Methanol and triethylamine content in the mobile phase, pH of the mobile phase and column temperature were independent variables or factors to be investigated in two levels: "low" and "high". Capacity factor was chosen as a dependent variable. From the experimentally determined capacity factor values, it was defined the factors that affect to chromatographic system the most. Applying response surface methodology the appropriate graphs were constructed from experimental points and optimal chromatographic conditions for the separation were defined. Optimal conditions for the separation of imatinib mesylate and STI 509-00 were obtained using X Terra 150 mm x 4.6 mm, particle size 5 microm column at 25 degrees C. Mobile phase consisted of 250 ml of methanol, 740 ml of water and 10 ml of triehylamine. pH of water phase was adjusted to 2.4 with 85% orthophosphoric acid and then methanol was added.

Reversed-phase liquid chromatography analysis of imatinib mesylate and impurity product in Glivec® capsules

The reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for the simultaneous determination of imatinib mesylate and of the impurity product in Glivec capsules (Novartis, Switzerland). Separations were performed on a X Terra 150 mm x 4.6 mm, 5 microm particle size column at 25 degrees C. The mobile phase was a mixture of methanol-water-triethylamine (25:74:1, v/v/v) with flow rate of 1.0 ml min(-1). pH value of water-triethylamine (TEA) was adjusted to 2.4 with orthophosphoric acid before adding of methanol. UV detection was performed at 267 nm. Acetaminophen was used as an internal standard. The method was validated statistically for its selectivity, linearity, precision, accuracy and robustness. Due to its speed and accuracy, the method may be used for quality control analyses.