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

Therapeutic Monitoring of Orally Administered, Small-Molecule Anticancer Medications with Tumor-Specific Cellular Protein Targets in Peripheral Fluid Spaces-A Review

Orally administered, small-molecule anticancer drugs with tumor-specific cellular protein targets (OACD) have revolutionized oncological pharmacotherapy. Nevertheless, the differences in exposure to these drugs in the systemic circulation and extravascular fluid compartments have led to several cases of therapeutic failure, in addition to posing unknown risks of toxicity. The therapeutic drug monitoring (TDM) of OACDs in therapeutically relevant peripheral fluid compartments is therefore essential. In this work, the available knowledge regarding exposure to OACD concentrations in these fluid spaces is summarized. A review of the literature was conducted by searching Embase, PubMed, and Web of Science for clinical research articles and case reports published between 10 May 2001 and 31 August 2022. Results show that, to date, penetration into cerebrospinal fluid has been studied especially intensively, in addition to breast milk, leukocytes, peripheral blood mononuclear cells, peritoneal fluid, pleural fluid, saliva and semen. The typical clinical indications of peripheral fluid TDM of OACDs were (1) primary malignancy, (2) secondary malignancy, (3) mental disorder, and (4) the assessment of toxicity. Liquid chromatography-tandem mass spectrometry was most commonly applied for analysis. The TDM of OACDs in therapeutically relevant peripheral fluid spaces is often indispensable for efficient and safe treatments.

Discontinuation of tyrosine kinase inhibitors in pediatric chronic myeloid leukemia

BACKGROUND

The feasibility of tyrosine kinase inhibitor (TKI) discontinuation in pediatric chronic myeloid leukemia (CML) remains to be fully elucidated.

PROCEDURES

TKI was prospectively discontinued in patients who were diagnosed with CML at <20 years of age, treated with TKI for ≥3 years, and sustained molecular response 4.0 (MR4.0) for ≥2 years. Molecular relapse was defined as a single loss of major molecular response (MMR) (BCR-ABL1^IS >0.1%). Relapsed patients resumed the same TKI therapy administered before discontinuation.

RESULTS

Twenty-two patients with chronic-phase CML were enrolled, and the median ages at diagnosis and at TKI discontinuation were 9 (range: 1-14) years and 16 (5-26) years, respectively. The median follow-up time after TKI discontinuation was 37 months (range: 24-41 months). The median duration of TKI treatment before discontinuation was 100 (42-178) months, and that of MR4.0 was 53.5 (25-148) months. The treatment-free remission (TFR) rate at 12 months was 50.0% (90% confidence interval: 31.7%-65.8%). Eleven patients experienced loss of MMR within 4 months after TKI discontinuation and resumed TKI as originally prescribed. No progression was observed, and all 11 patients regained MR4.0 after TKI resumption. No patient had a withdrawal syndrome. The quality-of-life analysis suggested that successful TFR may improve academic performance in some patients. In patients who discontinued TKI therapy before puberty, the possibility of improvement in growth velocity upon TKI discontinuation was observed.

CONCLUSIONS

TKI could be discontinued safely in patients with pediatric CML showing a sustained deep MR.

Tandem mass spectrometry of small-molecule signal transduction inhibitors: Accurate-m/z data to adapt structure proposals of product ions

Protein kinases inhibitors or, more generally, signal transduction inhibitors (STIs) can be used to treat diseases in which deregulation of the protein kinase activity plays a role, such as in cancer. A wide variety of drugs has been developed and/or is under investigation to act as protein kinase inhibitors, especially in tyrosine kinase inhibition. The bioanalysis of STIs has received considerable attention in the past 20 years. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) in selected-reaction monitoring (SRM) mode is the method-of-choice in such studies. In several of these studies from us and others, structures are proposed for the product ions applied in SRM. A critical review of these proposed structures is presented using accurate-m/z data, which we have now generated with a linear-ion-trap-Orbitrap hybrid mass spectrometer. This led to adaptation and new structural proposals of 18 product ions for 13 STIs. Our investigation endorses the power of accurate-m/z analysis in structure elucidation of product ions in bioanalytical LC-MS-MS studies and for which the SRM mode in tandem-quadrupole instruments is apparently less suitable.

Quantification of imatinib and related compounds using capillary electrophoresis-tandem mass spectrometry with field-amplified sample stacking

A quantification method for imatinib (IM), its major metabolite N-desmethyl imatinib (NDI), and a degradation by-product was developed using CE-MS combined with an online concentration technique. The use of multiple reaction monitoring (MRM)-MS/MS further improved the sensitivity of this technology. Liquid-liquid extraction (LLE) using tertiary butyl methyl ether yielded high recovery and reproducibility for the pretreatment of serum samples. The recovery rate exceeded 83% for all three analytes, and was 90% for IM. To improve quantification results, a conductivity-induced online analyte concentration technique, field-amplified sample stacking (FASS), was used. The S/N ratios were improved at least 10-fold when compared with conventional capillary zone electrophoresis. The detection limits were 0.2 ng/mL for IM, 0.4 ng/mL for NDI, and 4 ng/mL for the degradation by-product. These results are superior to those previously obtained by other reported methods. The new method was validated in terms of its selectivity, intra- and interday repeatability and accuracy, and sample storage stability, following the guidelines issued by the European Medicines Agency. Considering the convenient pretreatment procedure (LLE), superior sensitivity, and fast analysis speed (<15 min), this method can be useful in the determination of imatinib levels in blood.

D609 protects retinal pigmented epithelium as a potential therapy for age-related macular degeneration

Accumulated oxidative damage may lead to irreversible retinal pigmented epithelium (RPE) cell death, which is considered to be the primary cause of dry age-related macular degeneration (AMD), leading to blindness in the elderly. However, an effective therapy for this disease is lacking. Here, we described a robust high-content screening procedure with a library of 814 protective compounds and found that D609 strongly protected RPE cells from sodium iodate (SI)-induced oxidative cell death and prolonged their healthy survival. D609 effectively attenuated excessive reactive oxygen species (ROS) and prevented severe mitochondrial loss due to oxidative stress in the RPE cells. Surprisingly, the potent antioxidative effects of D609 were not achieved through its own reducibility but were primarily dependent on its ability to increase the expression of metallothionein. The injection of this small water-soluble molecule also showed an explicit protective effect of the RPE layer in an SI-induced AMD mouse model. These findings suggested that D609 could serve as a novel antioxidative protector of RPE cells both in vitro and in vivo and unveiled a novel antioxidative mechanism of D609, which may ultimately have clinical applications for the treatment of AMD.

Imatinib trough levels: a potential biomarker to predict cytogenetic and molecular response in newly diagnosed patients with chronic myeloid leukemia

Therapeutic drug monitoring of imatinib in patients with chronic myeloid leukemia (CML) is an ongoing debate. We studied the influence of imatinib trough levels on therapeutic response in 206 newly diagnosed patients with CML. We also compared the drug levels in patients taking branded and generic imatinib. Imatinib levels were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Marked inter-individual variability was seen in imatinib levels (coefficient of variation = 69%). Trough levels were significantly higher in patients who attained complete cytogenetic response than those who did not (2213.9 ± 1101 vs. 1648.6 ± 1403.4ng/mL; p < .001). Patients with major molecular response (MMR) had higher trough levels than those without MMR (2333.4 ± 1112 vs. 1643.4 ± 1383.9ng/mL; p = .001). Patients with trough levels ≤1000ng/mL were at high risk for failure of imatinib therapy [RR =1.926; 95%CI (1.562, 2.374); p < .001]. Trough levels emerged as an independent predictor of imatinib response in multivariate analysis. To conclude, imatinib trough levels significantly influence cytogenetic and molecular response and might emerge as a potential biomarker for therapeutic response in CML.

Imatinib quantification in human serum with LC-MS3 as an effective way of protein kinase inhibitor analysis in biological matrices

BACKGROUND

As imatinib gained a lot of attention in the field of medicine, appropriate methods are needed for drug analysis. LC-MS/MS combined with complex sample preparation and column enrichment is usually the method of choice when high sensitivity is necessary. The application of LC-MS3 in imatinib quantification has not been discussed in the literature.

METHODS

An LC-MS3 imatinib quantification method was developed and validated in human serum. The sample preparation was based on the liquid-liquid extraction of 50 μL human serum. Chromatographic separation was performed using a Luna 5 μm C18 (2) 100 A, 150 mm×2 mm column and the elution was done using a mobile phase consisting of A (H2O/methanol=95/5, v/v) and B (H2O/methanol=3/97, v/v), both with 10 mM ammonium acetate and 0.1% acetic acid.

RESULTS

The conditions applied resulted in a limit of detection/quantification value of 0.14/0.45 ng/mL reached without a sophisticated sample preparation technique or enrichment column application. It could be demonstrated that MS3 detection is a very effective way of sensitive imatinib quantification. Further, it could be stated that the strategy presented can be very useful for a sensitive analysis of other protein kinase inhibitors, because their molecule structure is appropriate for MS3 detection.

CONCLUSIONS

The presented analytical strategy is an effective way of protein kinase inhibitor analysis in human serum.

Simultaneous quantification of imatinib and its main metabolite N-demethyl-imatinib in human plasma by liquid chromatography-tandem mass spectrometry and its application to therapeutic drug monitoring in patients with gastrointestinal stromal tumor

The aim of this study was to improve and validate a more stable and less time-consuming method based on liquid chromatography and tandem mass spectrometry (LC- MS/MS) for the quantitative measurement of imatinib and its metabolite N-demethyl-imatinib (NDI) in human plasma. Separation of analytes was performed on a Waters XTerra RP₁₈ column (50 × 2.1 mm i.d., 3.5 μm) with a mobile phase consisting of methanol-acetonitrile-water (65:20:15, v/v/v) with 0.05% formic acid at a flow-rate of 0.2 mL/min. The Quattro MicroTM triple quadruple mass spectrometer was operated in the multiple-reaction-monitoring mode via positive electrospray ionization interface using the transitions m/z 494.0 → 394.0 for imatinib, m/z 479.6 → 394.0 for NDI and m/z 488.2 → 394.0 for IS. The method was linear over 0.01-10 μg/mL for imatinib and NDI. The intra- and inter-day precisions were all <15% in terms of relative standard deviation, and the accuracy was within ±15% in terms of relative error for both imatinib and NDI. The lower limit of quantification was identifiable and reproducible at 10 ng/mL. The method was sensitive, specific and less time-consuming and it was successfully applied in gastrointestinal stromal tumor patients treated with imatinib.

Influence of MDR1 and CYP3A5 genetic polymorphisms on trough levels and therapeutic response of imatinib in newly diagnosed patients with chronic myeloid leukemia

Polymorphisms in genes coding for imatinib transporters and metabolizing enzymes may affect imatinib pharmacokinetics and clinical response. Aim of this study was to assess the influence of polymorphisms in MDR1 and CYP3A5 genes on imatinib trough levels, cytogenetic and molecular response in patients with CML. Newly diagnosed patients with chronic-phase CML started on imatinib therapy were enrolled and followed up prospectively for 24 months. The following single nucleotide polymorphisms were genotyped; C1236T, C3435T, G2677T/A in MDR1 gene and A6986G in CYP3A5 gene. Genotyping was done using PCR-RFLP method and validated by direct gene sequencing. Trough levels of imatinib were measured using LC-MS/MS. Cytogenetic response was assessed by conventional bone-marrow cytogenetics. Molecular response was assessed by qRTPCR using international scale. A total of 173 patients were included, out of which 71 patients were imatinib responders, while 102 were non-responders. Marked inter-individual variability in trough levels of imatinib was seen. Patients with GG genotype for CYP3A5-A6986G (P=0.016) and TT genotype for MDR1-C3435T (P=0.013) polymorphisms had significantly higher trough levels of imatinib. Patients with AA genotype for CYP3A5-A6986G [RR=1.448, 95% CI (1.126, 1.860), P=0.029] and CC genotype for MDR1-C1236T [RR=1.397, 95% CI (1.066, 1.831), P=0.06] &MDR1-C3435T [RR=1.508, 95% CI (1.186, 1.917), P=0.018] polymorphisms were at high risk for failure of imatinib therapy. Patients with CGC haplotype for MDR1 polymorphisms had significantly lower imatinib trough levels and were at a higher risk of imatinib failure [RR=1.547, 95% CI (1.324, 1.808), P<0.001]. GG vs. non-GG genotype for CYP3A5-A6986G [adjusted OR: 0.246; 95% CI (0.116, 0.519); P<0.001] and TT vs. non-TT genotype for MDR1-C1236T [adjusted OR: 0.270; 95% CI (0.110, 0.659); P=0.004] &MDR1-C3435T [adjusted OR: 0.289; 95% CI (0.135, 0.615); P=0.001] polymorphisms were independent factors predicting imatinib response in multivariate analysis. To conclude, MDR1 and CYP3A5 genetic polymorphisms significantly influence plasma trough levels and therapeutic response of imatinib in patients with CML. Genotyping of these polymorphisms could be of value to individualize the therapy and optimize the clinical outcomes.

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

A lower dosage of imatinib in patients with gastrointestinal stromal tumors with toxicity of the treatment

This study investigated the efficiency and safety of imatinib in the lower dose (300 mg/d) in patients with gastrointestinal stromal tumor (GIST) who cannot tolerate imatinib in the standard dose (400 mg/d).Steady-state imatinib trough concentration (Cmin) values in 18 patients with GIST who were taking 300 mg/d or 400 mg/d imatinib were measured. The clinical features, toxicity data, and follow-up data were collected.Around 18 patients with GIST were investigated in which 9 patients received 300 mg/d imatinib. The mean imatinib Cmin value of the 18 patients was 1841 ng/mL (1018-3897 ng/mL). The difference between the patients treated with 400 mg/d (n=9) and those treated with 300 mg/d (n = 9), which have imatinib Cmin values of 2122±1003 ng/mL and 1559±478 ng/mL, respectively, was not significant (P = 0.148). In total, 12 of the 18 patients had complete resection of the primary tumor, 8 of whom received postoperative imatinib 300 mg/d. After the average follow-up of 15.4 months, no recurrence was documented. Of the 6 patients with unresected GIST, 1 received imatinib 300 mg/d for 13 months. The tumor size of this patient continued to decrease. In contrast to patients treated with imatinib 400 mg/d, patients treated with imatinib 300 mg/d notably exhibited lesser drug-related side effects.Patients with GIST who exhibited intolerance to the standard dose of imatinib (400 mg/d), a lower dose of 300 mg/d could provide not only sufficient plasma Cmin and good disease control but also the alleviation of the side effects.

Therapeutic drug monitoring and tyrosine kinase inhibitors

The therapeutic activity of drugs can be optimized by establishing an individualized dosage, based on the measurement of the drug concentration in the serum, particularly if the drugs are characterized by an inter-individual variation in pharmacokinetics that results in an under- or overexposure to treatment. In recent years, several tyrosine kinase inhibitors (TKIs) have been developed to block intracellular signaling pathways in tumor cells. These oral drugs are candidates for therapeutic drug monitoring (TDM) due to their high inter-individual variability for therapeutic and toxic effects. Following a literature search on PubMed, studies on TKIs and their pharmacokinetic characteristics, plasma quantification and inter-individual variability was studied. TDM is commonly used in various medical fields, including cardiology and psychiatry, but is not often applied in oncology. Plasma concentration monitoring has been thoroughly studied for imatinib, in order to evaluate the usefulness of TDM. The measurement of plasma concentration can be performed by various analytical techniques, with liquid chromatography-mass spectrometry being the reference method. This method is currently used to monitor the efficacy and tolerability of imatinib treatments. Although TDM is already being used for imatinib, additional studies are required in order to improve this practice with the inclusion of other TKIs.

Routine therapeutic drug monitoring of tyrosine kinase inhibitors by HPLC-UV or LC-MS/MS methods

Analytical methods using high performance liquid chromatography coupled to ultraviolet detection (HPLC-UV) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) have been reported for the quantification of oral tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, and dasatinib in biological fluids. An LC-MS/MS method can simultaneously assay multiple TKIs and their metabolites with high sensitivity and selectivity for low plasma concentrations less than 1 ng/mL. For quantification of imatinib, nilotinib, and dasatinib, a limit of quantification (LOQ) of less than 10 ng/mL, 10 ng/mL, and 0.1 ng/mL, respectively, in the clinical setting is necessary. Because simpler and more cost-efficient methodology is desired for clinical analysis, plasma concentrations of imatinib and nilotinib (target trough concentrations of 1000 ng/mL and 800 ng/mL, respectively) could be assayed by an HPLC-UV method after comparison with results obtained from the standard LC-MS/MS method. However, in the quantification of dasatinib, the LC-MS/MS method that has high sensitivity and selectivity and is free from interference by endogenous impurities is superior to the HPLC-UV method. Highly precise analytical methods are needed for individualized treatment via dose adjustment of oral anticancer drugs, in particular those with low target plasma concentrations less than 10 ng/mL.

Label-free absolute quantitation of oligosaccharides using multiple reaction monitoring

An absolute quantitation method for measuring free human milk oligosaccharides (HMOs) in milk samples was developed using multiple reaction monitoring (MRM). To obtain the best sensitivity, the instrument conditions were optimized to reduce the source and postsource fragmentation prior to the quadrupole transmission. Fragmentation spectra of HMOs using collision-induced dissociation were studied to obtain the best characteristic fragments. At least two MRM transitions were used to quantify and identify each structure in the same run. The fragment ions corresponded to the production of singly charged mono-, di-, and trisaccharide fragments. The sensitivity and accuracy of the quantitation using MRM were determined, with the detection limit in the femtomole level and the calibration range spanning over 5 orders of magnitude. Seven commercial HMO standards were used to create calibration curves and were used to determine a universal response for all HMOs. The universal response factor was used to estimate absolute amounts of other structures and the total oligosaccharide content in milk. The quantitation method was applied to 20 human milk samples to determine the variations in HMO concentrations from women classified as secretors and nonsecretors, a phenotype that can be identified by the concentration of 2′-fucosylation in their milk.

Therapeutic drug monitoring for imatinib: Current status and Indian experience

Imatinib is the current gold standard for treatment of chronic myeloid leukemia (CML). Recent pharmacokinetic studies have shown considerable variability in trough concentrations of imatinib due to variations in its metabolism, poor compliance, or drug-drug interactions and highlighted its impact on clinical response. A trough level close to 1000 ng/mL, appears to be correlated with better cytogenetic and molecular responses. Therapeutic Drug Monitoring (TDM) for imatinib may provide useful added information on efficacy, safety and compliance than clinical assessment alone and help in clinical decision making. It may be particularly helpful in patients with suboptimal response to treatment or treatment failure, severe or rare adverse events, possible drug interactions, or suspected nonadherence. Further prospective studies are needed to confirm relationship between imatinib plasma concentrations with response, and to define effective plasma concentrations in different patient populations.

Imatinib mesylate

Imatinib (INN), marketed by Novartis as Gleevec (United States) or Glivec (Europe/Australia/Latin America), received Food & Drug Administration (FDA) approval in May 2001 and is a tyrosine kinase inhibitor used in the treatment of multiple cancers, most notably Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia. Like all tyrosine kinase inhibitors, imatinib works by preventing a tyrosine kinase enzyme. Because the BCR-Abl tyrosine kinase enzyme exists only in cancer cells and not in healthy cells, imatinib works as a form of targeted therapy-only cancer cells are killed through the drug's action. In this regard, imatinib was one of the first cancer therapies to show the potential for such targeted action and is often cited as a paradigm for research in cancer therapeutics. This study presents a comprehensive profile of imatinib, including detailed nomenclature, formulae, physico-chemical properties, methods of preparation, and methods of analysis (including compendial, electrochemical, spectroscopic, and chromatographic methods of analysis). Spectroscopic and spectrometric analyses include UV/vis spectroscopy, vibrational spectroscopy, nuclear magnetic resonance spectrometry ((1)H and (13)C NMR), and mass spectrometry. Chromatographic methods of analyses include electrophoresis, thin layer chromatography, and high-performance liquid chromatography. Preliminary stability investigations for imatinib have established the main degradation pathways, for example, oxidation to N-oxide under oxidative stress conditions. Stability was also carried out for the formulation by exposing to different temperatures 0°C, ambient temperature, and 40°C. No remarkable change was found in the drug content of formulation. This indicates that the drug was stable at the above optimized formulation. Stability studies under acidic and alkaline conditions have established the following main degradation products: α-(4-Methyl-1-piperazinyl)-3'-{[4-(3-pyridyl)-2-pyrimidinyl] amino}-p-tolu-p-toluid-ide methanesulfonate and 4-(4-methylpiperazin-1-ylmethyl)-benzoic acid. The main degradation products under oxidation conditions, that is, 4-[(4-methyl-4-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-enzamide, 4-[(4-methyl-1-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide, and 4-[(4-methyl-1,4-dioxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-enzamide. Clinical application studies for pharmacodynamics, pharmacokinetics, mechanism of action, and clinical uses of the drug were also presented. Each of the above stages includes appropriate figures and tables. More than 50 references were given as proof of the above-mentioned studies.

Liquid chromatography-tandem mass spectrometry assay for therapeutic drug monitoring of the tyrosine kinase inhibitor, midostaurin, in plasma from patients with advanced systemic mastocytosis

We developed and validated quantitative bioanalytical liquid chromatography-tandem mass spectrometry assay for the protein kinase inhibitor, midostaurin. Plasma samples were pre-treated using a protein precipitation with methanol containing midostaurin-d5 as an internal standard. After centrifugation, 5μL of the supernatant was injected into the chromatographic system. The system consisted of a 3.5μm particle bonded octadecyl silica column, with gradient elution using a mixture of 0.1% (v/v) formic acid in acetonitrile and 10mM ammonium formate in water with 0.1% formic acid. The analyte was quantified using the selected reaction-monitoring mode of a triple quadrupole mass spectrometer equipped with a heated electrospray interface. The assay was validated in a 75-2500ng/mL calibration range. For quality control, within-day and between-day precisions were 1.2-2.8%, and 1.2-6.9%, respectively. The β-expectation tolerance limit (accuracy) met the limits of acceptance ±15% (±20% for the LLQ). The drug was sufficiently stable under all relevant analytical conditions. The assay has successfully been used to assess drug levels for therapeutic drug monitoring in patients presenting advanced systemic mastocytosis and treated with the promising midostaurin.

Bioanalytical aspects of clinical mass balance studies in oncology

Clinical mass balance studies aim to investigate the absorption, distribution, metabolism and excretion (ADME) of a(n) (often radiolabeled) drug, following a single administration to humans. They are perfectly suited to determine the disposition and major metabolic pathways of a drug, the exposure to the parent drug and its metabolites, and the rate and route of elimination. A mass balance study, however, poses interesting challenges to the analysis of parent drug and metabolites in different biological matrices. Using recent clinical mass balance studies in oncology as an example, this review focuses on the aspects of mass balance studies, from bioanalytical assay development, analysis of clinical samples to reporting of study results. Along the way, it discusses bioanalytical problems and practical solutions.

Long-term outcome following imatinib therapy for chronic myelogenous leukemia, with assessment of dosage and blood levels: the JALSG CML202 study

A prospective multicenter Phase II study was performed to examine the efficacy and safety of imatinib therapy in newly diagnosed Japanese patients with chronic-phase CML. Patients were scheduled to receive imatinib 400 mg daily. Plasma imatinib concentrations were measured by liquid chromatography-tandem mass spectrometry. In 481 evaluable patients, estimated 7-year overall survival (OS) and event-free survival (EFS) at a median follow-up of 65 months were 93% and 87%, respectively. Because imatinib dosage was reduced in many patients due mainly to adverse events, subgroup analysis was performed according to the mean daily dose during the first 24 months of treatment: ≥360 mg (400-mg group; n = 294), 270-359 mg (300-mg group; n = 90) and <270 mg (200-mg group; n = 67). There were no significant differences in OS and EFS between the 300- and 400-mg groups; however, cumulative rates of complete cytogenetic and major molecular responses differed significantly between the two groups. There were no significant differences in mean imatinib trough levels between these two groups for the patients in whom trough levels had been measured. Survival and efficacy in the 200-mg group were markedly inferior to the former two groups. These results suggest that, although a daily dose of 400 mg imatinib is associated with better outcomes, 300 mg imatinib may be adequate for a considerable number of Japanese patients who are intolerant to 400 mg imatinib. Blood level monitoring would be useful to determine the optimal dose of imatinib.

Plasma exposure of imatinib and its correlation with clinical response in the Tyrosine Kinase Inhibitor Optimization and Selectivity Trial

BACKGROUND

This study evaluates the correlation between imatinib trough plasma concentrations (C(min)) and clinical response and safety in patients with newly diagnosed Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase in the Tyrosine Kinase Inhibitor OPtimization and Selectivity (TOPS) trial.

DESIGN AND METHODS

Patients were randomized 1:2 to 400 mg/day or 800 mg/day imatinib. Imatinib C(min) levels were collected at pre-dose before treatment, and at the end of months 1 (day 29), 6, 9, and 12.

RESULTS

Imatinib C(min) were stable over time in the 400 mg/day dose arm, but showed a slight decrease in the 800 mg/day arm due to dose adjustments between months 1-6. The overall median imatinib C(min) levels were 1040, 1200, 1935, and 2690 ng/mL for the actual 300, 400, 600, and 800 mg/day doses, respectively. The rates of major molecular response (MMR) at 3, 6, 9, and 12 months, and complete cytogenetic response (CCyR) at 6 and 12 months were significantly lower among patients with the lowest imatinib C(min) levels at Day 29 (<1165 ng/mL, 25th percentile). There was an apparent association between high imatinib C(min) and the occurrence of grade 3/4 neutropenia and all-grade rash, diarrhea, arthralgia/myalgia, and all-cause edema. Conclusions Imatinib C(min) levels were relatively stable over time and proportional to the dose administered. Patients with an imatinib C(min) above 1165 ng/mL on Day 29 achieved MMR faster and had higher MMR and CCyR rates at 12 months. There appeared to be an association between imatinib C(min) and the frequency of some adverse events. This trial was registered at http://www.clinicaltrials.gov as NCT00124748.

Effects of imatinib mesylate on the pharmacokinetics of paracetamol (acetaminophen) in Korean patients with chronic myelogenous leukaemia

AIMS

The major objective of the present study was to investigate the effect of imatinib on the pharmacokinetics of paracetamol in patients with chronic myelogenous leukaemia (CML).

METHODS

Patients (n = 12) received a single oral dose of acetaminophen 1000 mg on day 1 (control). On days 2-8, imatinib 400 mg was administered daily. On day 8 (treatment), another 1000 mg dose of paracetamol was administered 1 h after the morning dose of imatinib 400 mg. Blood and urine samples were collected for bioanalytical analyses.

RESULTS

The area under the plasma concentration-time curve (AUC) for paracetamol, paracetamol glucuronide and paracetamol sulphate under control conditions was similar to that after treatment with imatinib; the 90% confidence interval of the log AUC ratio was within 0.8 to 1.25. Urinary excretion of paracetamol, paracetamol glucuronide and paracetamol sulphate was also unaffected by imatinib. The pharmacokinetics of paracetamol and imatinib in Korean patients with CML were similar to previous pharmacokinetic results in white patients with CML. Co-administration of a single dose of paracetamol and multiple doses of imatinib was well tolerated and safety profiles were similar to those of either drug alone.

CONCLUSIONS

The pharmacokinetics of paracetamol and its major metabolites in the presence of imatinib were similar to those of the control conditions and the combination was well tolerated. These findings suggest that imatinib can be safely administered with paracetamol without dose adjustment of either drug.

Correlation between imatinib pharmacokinetics and clinical response in Japanese patients with chronic-phase chronic myeloid leukemia

Despite the outstanding results generally obtained with imatinib mesylate (IM) in the treatment of chronic myeloid leukemia (CML), some patients show a poor molecular response. To evaluate the relationship between steady-state trough plasma IM concentration (IM-C(min)) and clinical response in CML patients, we integrated data from six independent Japanese studies. Among 254 CML patients, the mean IM-C(min) was 1,010.5 ng/ml. Importantly, IM-C(min) was significantly higher in patients who achieved a major molecular response (MMR) than in those who did not (P = 0.002). Multivariate analysis showed that an MMR was associated with both age (odds ratio (OR) = 0.97 (0.958-0.995); P = 0.0153) and with IM-C(min) (OR = 1.0008 (1.0003-1.0015); P = 0.0044). Given that patients with IM-C(min) values >1,002 ng/ml had a higher probability of achieving an MMR in our large cohort (P = 0.0120), the data suggest that monitoring of IM levels in plasma may improve the efficacy of IM therapy for CML patients.

Cross-Sectional Study of Imatinib Plasma Trough Levels in Patients With Advanced Gastrointestinal Stromal Tumors: Impact of Gastrointestinal Resection on Exposure to Imatinib

Purpose

Imatinib plasma trough levels (Cmin) have been reported to correlate with treatment outcomes in patients with gastrointestinal stromal tumors (GISTs). We therefore have evaluated the correlation between imatinib Cmin and the clinical characteristics of patients with GIST.

Patients and Methods

Steady-state imatinib Cmin in 107 patients with GIST who were taking imatinib 300 to 800 mg/d was measured.

Results

In patients treated with imatinib 400 (n = 92), 300 (n = 7), 600 (n = 2), or 800 (n = 11) mg/d, imatinib Cmin was 1,305 ± 633 ng/mL, 1,452 ± 830 ng/mL, 1,698 ± 725 ng/mL, and 3,330 ± 1,592 ng/mL, respectively. Of the 92 patients treated with 400 mg/d imatinib, 59 patients (63%) were men; the median age was 55 years (range, 28 to 76 years), and the median duration of imatinib use before sampling was 8.8 months (range, 0.5 to 67.6 months). The mean inter- and intrapatient variability rates were 44.7% and 26.5%, respectively. In univariate analyses, high Cmin was correlated with advanced age (P = .02), low creatinine clearance (P = .001), low hemoglobin (P = .03), and low albumin (P < .001) concentrations. Imatinib Cmin was also significantly lower in patients with (n = 18; 942 ± 330 ng/mL) than without (n = 74; 1,393 ± 659 ng/mL) major (ie, total or subtotal) gastrectomy (P = .002). In multivariate analysis, albumin (P = .001) concentrations, creatinine clearance (P = .002), and major gastrectomy (P = .003) were significantly correlated with Cmin.

Conclusion

In patients with GIST, imatinib Cmin at steady state was significantly associated with albumin concentration, creatinine clearance, and previous major gastrectomy. Although its clinical impact is unclear at present time, monitoring of imatinib Cmin might be particularly important for optimal treatment with imatinib in patients who have undergone major gastrectomy.

Development and validation of a sensitive assay for the quantification of imatinib using LC/LC-MS/MS in human whole blood and cell culture

We developed and validated a semi-automated LC/LC-MS/MS assay for the quantification of imatinib in human whole blood and leukemia cells. After protein precipitation, samples were injected into the HPLC system and trapped onto the enrichment column (flow 5 mL/min); extracts were back-flushed onto the analytical column. Ion transitions [M + H](+) of imatinib (m/z = 494.3 --> 394.3) and its internal standard trazodone (372.5 --> 176.3) were monitored. The range of reliable response was 0.03-75 ng/mL. The inter-day precisions were: 8.4% (0.03 ng/mL), 7.2% (0.1 ng/mL), 6.5% (1 ng/mL), 8.2% (10 ng/mL) and 4.3% (75 ng/mL) with no interference from ion suppression. Autosampler stability was 24 hs and samples were stable over three freeze-thaw cycles. This semi-automated method is simple with only one manual step, uses a commercially available internal standard, and has proven to be robust in larger studies.