Imatinib Levels Research Articles

Contribution of the α1-Acid Glycoprotein in Drug Pharmacokinetics: The Usefulness of α1-Acid Glycoprotein-Knockout Mice.

α1-Acid glycoprotein (AGP) is a primary binding protein for many basic drugs in plasma. The number of drugs that bind to AGP, such as molecular target anticancer drugs, has been continuously increasing. Since the plasma level of AGP fluctuates under various pathological conditions such as inflammation, it is important to evaluate the contribution of AGP to drug pharmacokinetics. Here, we generated conventional AGP-knockout (AGP-KO) mice and used them to evaluate the contribution of AGP. The pharmacokinetics of drugs that bind to two AGP variants (F1*S or A variants) or albumin were evaluated. Imatinib (a F1*S-binding drug) and disopyramide (an A-binding drug) or ibuprofen (an albumin-binding drug) were administered to wild-type (WT) and AGP-KO. The plasma level of imatinib and disopyramide decreased rapidly in AGP-KO as compared to WT. In AGP-KO, AUC and t1/2 were decreased, then CLtot was increased. Compared with disopyramide, imatinib pharmacokinetics showed more marked changes in AGP-KO as compared to WT. The results seemed to be due to the difference in plasma level of each AGP variant (F1*S:A = 2-3:1). No differences were observed in ibuprofen pharmacokinetics between the WT and AGP-KO mice. In vitro experiments using plasma from WT and AGP-KO showed that unbound fractions of imatinib and disopyramide were higher in AGP-KO. These results suggest that the rapid elimination of imatinib and disopyramide in AGP-KO could be due to decreased protein binding to AGP. Taken together, the AGP-KO mouse could be a potential animal model for evaluating the contribution of AGP to the pharmacokinetics of various drugs.

Relationship of body mass index and plasma imatinib levels in CML patients and mitigation of clinical impact using PK-guided dosing strategy.

e18522 Background: Imatinib is a mainstay of treatment for patients with chronic myeloid lymphoma (CML). Exposure-response relationships have been demonstrated and trough levels between 800 and 1000 ng/ml are usually associated with Major Molecular Response (MMR), prolonged survival and acceptable safety. The extent to which body mass index (BMI) might influence drug pharmacokinetics (PK) and clinical outcome remains to be investigated. Methods: Therapeutic drug monitoring was performed in 60 adult patients (56 years, M33/27F) starting imatinib (400 mg QD) for CML, and baseline deviation from target Cmin was used to subsequently adjust dosing using Monolix software. Baseline BMI was calculated and collected along with other patient characteristics and comedications likely to alter imatinib PK. Response (MMR at 3 months) and drug-related toxicity (CTCAE grading) were recorded. Patients were divided into three subgroups: BMI<18.5; 18.5<BMI<24.5, and BMI>24.5. The association between BMI and trough imatinib levels at baseline, further differences in toxic events and response rate between cohorts, as well as differences in dosing after PK-guided dose adjustment, were all tested using appropriate statistical analysis. Results: Mean imatinib trough levels at baseline were 1172 (754-4737), 870 (276-1767) and 820 (334-2217) ng/ml for patients with BMI<18.5, 18.5<BMI<24.5 and BMI>24.5, respectively. Patients with BMI<18.5 were statistically overexposed (p<0.01, ANOVA). Conversely, there was a trend towards lower exposure in patients with BMI>24.5, but this was not statistically significant. Multivariate analysis confirmed that low BMI was an independent factor for overexposure with imatinib. After PK-guided dosing, a statistically significant difference in dosing after correction was observed, as overexposed patients had their dose reduced to an average of 330 mg QD, whereas underexposed patients had their dose increased to an average of 500 mg QD (p<0.01, paired t-test). Consequently, when comparing in the three different cohorts the incidence of both response and toxic events, no difference was observed among patients (p=0.33 and p=0.911 for efficacy and toxicity respectively, Chi-2 test). Conclusions: Low BMI (<18.5) puts patients at risk of significant overexposure to imatinib, whereas there is a trend towards lower exposure in patients with high BMI (>24.5). This could potentially lead to either increased toxicity or lack of efficacy is no adjustment in dosing is performed. Here, TDM with subsequent adaptive dosing helps to correct the dose according to the initial deviation from target, thus smoothing the clinical impact of the differences in exposure observed at the start of treatment.

Association between plasma imatinib levels and response to treatment of chronic myeloid leukemia in patients from Manaus, Brazil.

Imatinib mesylate (IM) is the drug of choice for the treatment of chronic myeloid leukemia (CML). However, despite most of the results obtained with this therapy being positive, some patients still present a suboptimal therapeutic response or still develop some type of resistance. Therefore, the aim of this study was to evaluate IM plasma levels in CML patients treated at a referral unit in Manaus and correlate them with variables that might interfere with these levels. Data from 52 patients were obtained through a standardized questionnaire containing clinical, sociodemographic, lifestyle, and use of other medication information, as well as an estimate of therapeutic adherence. Additionally, blood collection was performed to measure the plasma concentration of the drug using the HPLC-UV technique. Molecular studies were done to identify the presence of polymorphism in the ABCG2 C421A membrane transporter. Most patients were male with a mean age of 52 ± 12.3 years (95% CI 49.0-55.9). There was a high variation in drug concentrations in the range from 0 to 4694 ng/mL, with a mean of 1558.59 ± 989.79 ng/mL (95% CI 1283.0-1834.1). Approximately two-thirds of patients were classified in the drug-level range considered therapeutic, and there was a correlation between plasma concentration and higher molecular response. Additionally, most individuals had the normal genotype for the ABCG2 C421A polymorphism but further studies should be performed to reveal the role of this variable in the outcome of the disease in this population.

Imatinib pharmacokinetics and creatine kinase levels in chronic myeloid leukemia patients: implications for therapeutic response and monitoring

BackgroundImatinib treatment for certain cancers can lead to elevated creatine kinase (CK) levels, potentially indicating muscle injury, and ongoing research aims to understand the correlation between imatinib levels and creatine kinase to assess its impact on treatment response.MethodsThis single-center observational study involved 76 chronic myeloid leukemia (CML) patients receiving imatinib treatment, focusing on evaluating drug and metabolite levels using liquid chromatography–mass spectrometry (LC–MS-MS) instrumentation. Serum CK and creatine kinase-MB (CK-MB) levels were assessed using Colorimetric kits.ResultsCK and CK-MB levels were measured, CK showed a median value of 211.5 IU/l and CK-MB showed a median value of 4.4 IU/l. Comparing low and high CK groups, significant differences were found in peak and trough plasma concentrations of imatinib and its metabolites. Correlations between CK levels and pharmacokinetic parameters were explored, with notable associations identified. Binary logistic regression revealed predictors influencing the therapeutic response to imatinib and categorized expected CK levels into high or low, with peak levels of imatinib emerging as a significant predictor for CK level categorization.ConclusionThe study highlights the link between imatinib’s pharmacokinetics and elevated CK levels, indicating a possible correlation between specific metabolites and improved treatment response. Individualized monitoring of CK levels and imatinib pharmacokinetics could enhance care for CML patients.

CO-RELATION OF P-GLYCOPROTEIN AND PLASMA IMATINIB IN IMATINIB RESPONDERS AND NON-RESPONDERS PATIENTS WITH CHRONIC MYELOID LEUKAEMIA

Objective: To measure and compare P-glycoprotein (P-gp) expressions in imatinib responders and non-responders with chronic myeloid leukemia-chronic phase (CML-CP) and correlate with plasma imatinib levels. Methods: Patients were classified into two groups based on their haematological and cytogenetic responses to imatinib: responders and non-responders. Liquid chromatography-mass spectrometry was used to measure plasma imatinib levels, while flow cytometry was used to evaluate leucocyte P-gp expression. Results: The median plasma imatinib trough levels in non-responders were 496 (217-3150) ng/ml compared to 2245 (454-4270) ng/ml in the responders, which was statistically significant (p=0.0003). The proportion of patients expressing P-gp in granulocytes was higher in the non-responder group than in the responder group (75% vs. 62.5%). The ratio of mean fluorescence intensity (RFI) revealed that non-responders had higher median P-gp expression than did respondents MFI (1.16(1.06-1.50) and 1.12(1.01-1.38), respectively; p = 0. 2307). In both groups, there was a negative correlation between P-gp expression and plasma imatinib trough levels (-0.4384 vs.-0.2848). Conclusion: Imatinib median plasma trough levels in non-responders were considerably lower. This was highly supported by P-gp expression in granulocytes, which is inversely related to imatinib plasma trough levels; however, the difference was not statistically significant, which could be attributed to the small number of patients. This could be the cause of imatinib resistance in non-responder CML-CP patients, and P-gp levels should be evaluated to optimize treatment in patients who do not achieve hematologic or cytogenetic response.

Pharmacokinetics of Four Tyrosine Kinase Inhibitors in Adult and Paediatric Chronic Myeloid Leukaemia Patients.

Tyrosine kinase inhibitors work by blocking the tyrosine kinases responsible for the dysregulation of intracellular signalling pathways in tumour cells. This study looked at the impact of age and sex on the levels of imatinib, dasatinib, nilotinib, and ponatinib in plasma and cerebrospinal fluid samples of patients with chronic myeloid leukaemia. Imatinib and dasatinib were used to treat the majority of the enrolled patients, and most of them were paediatrics. A total of 82.4% of the patients were men; however, sex-related differences in the drugs' pharmacokinetics were not found. Age and imatinib plasma concentration were found to be inversely correlated. The dasatinib concentrations in plasma were found to be substantially lower than those found in cerebrospinal fluid, particularly in paediatrics. Analysing the obtained data, we can state that therapeutic drug monitoring is a useful method for adjusting a patient's treatment schedule that depends on drug concentrations in biological fluids. The use of therapeutic drug monitoring in conjunction with tyrosine kinase inhibitors for the treatment of chronic myeloid leukaemia is supported by a number of sources of evidence. As a result, as the research develops, the tyrosine kinase inhibitor therapeutic drug monitoring classification needs to be refined in terms of factors like sex and age.

Imatinib plasma levels in patients with gastrointestinal stromal tumour under routine clinical practice conditions.

Imatinib is the first therapeutic option for the treatment of unresectable or metastatic gastrointestinal stromal tumours. Previous studies have shown an improvement in patient survival rates following the use of imatinib. Nevertheless, adequate plasma concentrations of imatinib are necessary to achieve such improvement in survival and limit the toxicity of the drug. This study aims to analyse the influence of imatinib plasma concentrations on efficacy and safety in the treatment of gastrointestinal stromal tumour. This descriptive, multicentre study analysed plasma levels of imatinib in patients diagnosed with gastrointestinal stromal tumour in the period 2019-2020. An optimal therapeutic range of 750-1500 ng/mL was established for the patient stratification based on their minimum plasma concentrations measured at the steady state. This study included 11 patients with metastatic disease in total, among whom only 54.5% (n = 6) had a minimum plasma concentrations measured at the steady state value within the therapeutic range. A median progression-free survival of 7.0 months was recorded for those patients with minimum plasma concentrations measured at the steady state < 750 ng/mL, while that median progression-free survival value remained unachieved for the group with minimum plasma concentrations measured at the steady state > 750 ng/mL (p = 0.005). The toxicity rate was 25% and 14.3% for patients with minimum plasma concentrations measured at the steady state > 1500 ng/mL and minimum plasma concentrations measured at the steady state ≤1500 ng/mL, respectively (p = 0.66). The present study aims to describe the correlation between the toxicity and effectiveness of imatinib as a function of minimum plasma concentrations measured at the steady state under routine clinical practice conditions. The results described here show the usefulness of imatinib plasma concentrations monitoring as part of the standard daily routine in our hospitals.

Role of ADME gene polymorphisms on imatinib disposition: results from a population pharmacokinetic study in chronic myeloid leukaemia.

Imatinib is a substrate of CYP3A4, ABCB1 and ABCG2, and is known to have wide variability in pharmacokinetics (PK). At the same time, a clear relationship between drug levels and response also exists for imatinib in chronic myeloid leukaemia (CML). Therefore, pharmacogenetic-based dosing of imatinib is an attractive proposition. This study aims to characterize the population pharmacokinetics of imatinib in order to identify significant covariates including pharmacogenetic variants. Forty-nine patients with CML were enrolled in the study after being on imatinib for at least 4 consecutive weeks. Steady-state pharmacokinetic sampling was performed either in a sparse (4 samples each, n = 44) or intensive manner (9 samples each, n = 5). An additional pharmacogenetic sample was also collected from all patients. Plasma imatinib levels were estimated using a validated HPLC method. Pharmacogenetic variants were identified using the PharmacoScan array platform. Population pharmacokinetic analysis was carried out using NONMEM v7.2. Seven SNPs within CYP3A4, ABCB1 and ABCG2 genes were evaluated for covariate effect on the clearance of imatinib. Imatinib PK was well characterized using a one-compartment model with zero-order absorption. The clearance and volume of distribution were found to be 10.2 L/h and 389 L respectively. Only SNP rs1128503 of the ABCB1 gene had a small but insignificant effect on imatinib clearance, with a 25% reduction in clearance observed in patients carrying the polymorphism. Twenty-three out of forty-nine patients (47%) carried the polymorphic allele, of whom 17 were heterozygous and six were homozygous. Our study conclusively proves that genetic polymorphisms in the CYP3A4 and ABC family of transporters do not have any role in the personalized dosing of imatinib in CML.

Validation and Comparison of Two Analytical Methods for Imatinib Therapeutic Drug Monitoring

Our objective was to validate and compare the automated and chromatography methods for determining imatinib levels in plasma, in terms of linearity, precision, accuracy and specificity, for therapeutic drug monitoring. Imatinib patterns were prepared in human plasma and were analysed by both methods to determine the calibration curve of each method. The methods were validated for linearity, extraction recovery, intra- and inter-day precision (relative standard deviation, RSD%), accuracy, and specificity of imatinib analysis. Method comparison study was carried out using the imatinib concentrations determined in the 25 patient samples by Deming regression and Bland–Altman analysis. The calibration curve of the automated and chromatography methods were linear over the range 500–2750 ng/ml (r = 0.996) and 500–3000 ng/ml (r = 0.999), respectively. Intra- and inter-day precision showed that not all the CV values of the drug were below 15% for the automated method, recommended by the EMA and the FDA. In contrast, all CV values for precision of the chromatography method are below 6.0%. Average recovery percentage is 94.4% and 100.8 for the automated and chromatography methods, respectively. Agreement between the two methods was illustrated using Bland–Altman plot with a mean difference (Immunoassay—UPLC-UV) of 191.28 ng/ml and a 95% confidence interval of − 201.41 to 583.97 ng/ml. Deming regression analysis showed that the correlation coefficient for the automated method versus the chromatography method was 0.927 The chromatographic technique was the better option for therapeutic drug monitoring of imatinib in clinical practice in patients with Chronic Myeloid Leukemia (CML).

Feasibility of Extrapolating Randomly Taken Plasma Samples to Trough Levels for Therapeutic Drug Monitoring Purposes of Small Molecule Kinase Inhibitors.

Small molecule kinase inhibitors (SMKIs) are widely used in oncology. Therapeutic drug monitoring (TDM) for SMKIs could reduce underexposure or overexposure. However, logistical issues such as timing of blood withdrawals hamper its implementation into clinical practice. Extrapolating a random concentration to a trough concentration using the elimination half-life could be a simple and easy way to overcome this problem. In our study plasma concentrations observed during 24 h blood sampling were used for extrapolation to trough levels. The objective was to demonstrate that extrapolation of randomly taken blood samples will lead to equivalent estimated trough samples compared to measured Cmin values. In total 2241 blood samples were analyzed. The estimated Ctrough levels of afatinib and sunitinib fulfilled the equivalence criteria if the samples were drawn after Tmax. The calculated Ctrough levels of erlotinib, imatinib and sorafenib met the equivalence criteria if they were taken, respectively, 12 h, 3 h and 10 h after drug intake. For regorafenib extrapolation was not feasible. In conclusion, extrapolation of randomly taken drug concentrations to a trough concentration using the mean elimination half-life is feasible for multiple SMKIs. Therefore, this simple method could positively contribute to the implementation of TDM in oncology.

Plasma imatinib levels and ABCB1 polymorphism influences early molecular response and failure-free survival in newly diagnosed chronic phase CML patients

Achieving early molecular response (EMR) has been shown to be associated with better event free survival in patients with chronic phase chronic myeloid leukemia (CP-CML) on Imatinib therapy. We prospectively evaluated the factors influencing the 2-year failure free survival (FFS) and EMR to imatinib therapy in these patients including day29 plasma Imatinib levels, genetic variants and the gene expression of target genes in imatinib transport and biotransformation. Patients with low and intermediate Sokal score had better 2-year FFS compared to those with high Sokal Score (p = 0.02). Patients carrying ABCB1-C1236T variants had high day29 plasma imatinib levels (P = 0.005), increased EMR at 3 months (P = 0.044) and a better 2 year FFS (P = 0.003) when compared to those with wild type genotype. This translates to patients with lower ABCB1 mRNA expression having a significantly higher intracellular imatinib levels (P = 0.029). Higher day29 plasma imatinib levels was found to be strongly associated with patients achieving EMR at 3 months (P = 0.022), MMR at 12 months (P = 0.041) which essentially resulted in better 2-year FFS (p = 0.05). Also, patients who achieved EMR at 3 months, 6 months and MMR at 12 months had better FFS when compared to those who did not. This study suggests the incorporation of these variables in to the imatinib dosing algorithm as predictive biomarkers of response to Imatinib therapy.

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 0.2ng/mL for IM, 0.4ng/mL for NDI, and 4ng/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 (<15min), this method can be useful in the determination of imatinib levels in blood.

Efficacy and Safety of Generic Imatinib in Chronic Phase of Chronic Myeloid Leukemia (CP-CML): Experience from a Multi-Center in China

Background: Imatinib is the first TKI that was officially approved by the Food and Drug Administration (FDA) for the treatment of patients (pts) with CP-CML and it is the most commonly used treatment in CML pts on the international scene. Generic imatinib was offered and accessible as frontline treatment of CML in china in June 2013, which predictably lowered the cost of CML therapy. However the statistics regarding their effectiveness and tolerability in greater proportion of the population of CML pts are not available. (ClinicalTrials. gov number, NCT02317159.) Aim: To evaluate the efficacy and safety of generic imatinib in the treatment of pts that were newly diagnosed with CP-CML. Methods: In this multi-center, prospective open-label study, 75 pts with CP-CML were enrolled to receive generic imatinib mesylate capsules at a dose of 400 mg once daily. The primary end point was major molecular response (MMR) by 12 months. Imatinib plasma level and adverse events (AEs) were assessed. Results: The Median age at diagnosis was 46 years (range 19-75 years), and 50 pts (66.7%) were male. The median follow-up was 22.1 (range0.5-24) months. 35 pts (44%), 26 pts (34.7%) and 12 pts (16%) were in low, intermediate and high risk group, respectively, according to Sokal prognostic score (Not available in 2 pts). By 12 months, the cumulative rate of MMR (BCR-ABL1IS ≤0.1%) was 42.7% (32/75), and the cumulative rate of complete cytogenic response (CCyR) was74.7% (56/75). Complete hematologic response (CHR), CCyR, MMR rate at 3 months,6 months and 12 months were shown in Table 1. For pts who presented with BCR-ABL1 IS≤ 10% at 3 months, had better response as compared with those with BCR/ABL1IS&gt; 10% (Table 2). The estimated progression-free survival at 12 months was 94.7%. Imatinib plasma levels at 29 days on imatinib were variable in individual, with 1522.9±775.3 ng/mL for median level (rang 394.4 to3891 ng/mL). Although those numerical values showed difference, no statistically significant correlations were found between imatinib plasma level and CCyR or MMR(P=0.902;P=0.349). The incidents and profile of AEs were similar to those reported previously. Conclusion: This study confirmed that generic imatinib produced in China is effective and well-tolerated in Chinese CP-CML pts. The outcome of generic imatinib in the treatment of CP-CML is similar to brand imatinib reported in the literatures. The introduction of generic imatinib at a reduced and affordable cost may strikingly impact the cost of care for CML and improve the clinical outcomes of CML in China. Disclosures No relevant conflicts of interest to declare.

Discontinuation of Tyrosine Kinase Inhibitor in Children with Chronic Myeloid Leukemia (JPLSG STKI-14 study)

Kada: Bayer Yakuhin: Other: personal fees for a member of independent data monitoring committee of clinical trials, outside of the submitted work.. Imai:Juno Therapeutics: Patents & Royalties.

Analysis of correlation between plasma trough level and response of generic imatinib in the treatment of Chinese patients with chronic myeloid leukemia

目的评价我国慢性髓性白血病慢性期（CML-CP）患者接受国产伊马替尼（商品名：格尼可）治疗后伊马替尼及其代谢物血浆谷浓度水平与疗效的关系。方法以2012年10月11日至2013年5月8日入组编号为YMTN1.0临床研究的21例接受国产伊马替尼治疗的CML-CP患者为研究对象，评价其血浆药物谷浓度与疗效、年龄、体重、体表面积的关系。伊马替尼及其代谢物浓度检测采用高效液相色谱-串联质谱法。结果①伊马替尼及其代谢物血浆谷浓度分别为（1 185.07±417.91）µg/L和（251.53±76.50）µg/L。②伊马替尼及其代谢物血浆谷浓度与患者年龄、体重和体表面积均无明显相关性（P值均>0.05）。③伊马替尼稳态血浆谷浓度高于1 000 µg/L的患者其完全及主要分子学反应率显著高于未达1 000 µg/L的患者（42%对0，P<0.01）。结论接受国产伊马替尼治疗的CML-CP患者中，伊马替尼及其代谢产物稳态血浆谷浓度存在较大个体差异，伊马替尼血浆谷浓度与患者获得分子学疗效有一定的相关性。

270O - Imatinib induced toxicity and its influence on cytogenetic and molecular response in newly diagnosed patients with chronic myeloid leukemia

BackgroundIncidence of imatinib-induced toxicity and its influence on clinical outcomes in Indian patients with CML is not well-studied. We investigated the influence of imatinib-induced toxicity on therapeutic outcomes in newly diagnosed patients with CML. We also studied the effect of drug levels on imatinib-induced hematological toxicity. MethodsTwo hundred and fifty newly diagnosed patients with chronic-phase CML, started on imatinib therapy, were enrolled and followed-up for 24 months. Toxicity due to imatinib were assessed and graded as per CTCAE. Cytogenetic and molecular responses were assessed by conventional bone-marrow cytogenetics and qRTPCR using international scale, respectively, based on which patients were categorized as imatinib responders and non-responders. Imatinib trough levels were measured using LC-MS/MS. Multivariate analysis was done to find the influence of various covariates on imatinib response. ResultsA total of 719 adverse reactions due to imatinib occurred among 250 enrolled patients. Hematological toxicity was the most common imatinib-induced toxicity and its incidence was significantly higher in non-responders than responders (65% vs. 35%; P < 0.001). Patients with thrombocytopenia [RR = 1.768; 95%CI (1.357, 2.302); P < 0.001] and neutropenia [RR = 1.654; 95%CI (1.322, 2.070); P < 0.001] were at high risk of imatinib failure. Patients without any hematological toxicity were at lower risk for failure of imatinib therapy [RR = 0.520; 95%CI (0.388, 0.698); P < 0.001]. Although patients with hematological toxicity had higher imatinib levels than those without (2039.1±1361.6 vs. 1833.8±1335.3 ng/mL), the difference was not statistically significant [mean difference 205.2; 95% CI (590.4, -180); P = 0.295]. Hematological toxicity requiring dose interruption or reduction emerged as an independent factor predicting cytogenetic and molecular response to imatinib in multivariate analysis. ConclusionsImatinib induced hematological toxicities significantly influence cytogenetic and molecular response in patients with CML. Active monitoring and prompt management of imatinib induced adverse events is indispensable to achieve optimal therapeutic outcomes. Clinical trial identificationNot Applicable. Editorial acknowledgementNot Applicable. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.

Association of Hepatic Nuclear Factor 4 Alpha Gene Polymorphisms With Free Imatinib Plasma Levels and Adverse Reactions in Chinese Gastrointestinal Stromal Tumor Patients.

As the first-line treatment of gastrointestinal stromal tumor (GIST), the pharmacokinetic and pharmacodynamic of imatinib (IM) were characterized by marked interindividual variability. Pharmacogenetics of IM involved metabolic enzymes and transporters have been extensively reported, but the results remained inconsistent. This study investigated the effect of genetic variants in hepatocyte nuclear factor 4 alpha (HNF4α, encoded by gene NR2A1), a pivotal transcriptional regulator of drug disposition genes, on dose-adjusted IM-free plasma levels and related adverse reactions in Chinese GIST patients. Five common polymorphisms of NR2A1 (rs3818247, rs1884613, rs2071197, rs2425640, and rs736824) were genotyped in 70 Chinese GIST patients who had been administered IM 300-600 mg/d. The free IM trough plasma levels were determined based on a method of ultrafiltration coupled with high performance liquid chromatography-tandem mass spectrometry. There were wide interpatient variations in free plasma levels of IM (range, 9.50-67.50 ng/mL), in which significant sex differences were observed (P < 0.01). The dose-adjusted IM-free plasma levels showed a significant negative correlation with body surface area (r = -0.302, P = 0.012). Although there were no significant effects of NR2A1 polymorphisms on dose-adjusted IM-free plasma levels among the study population, polymorphism in rs736824 was found to be significantly associated with dose-adjusted IM-free plasma levels in male subjects (P = 0.031). For the IM-related adverse reaction, polymorphisms in rs3818247 were found to be significantly associated with periorbital edema (P = 0.032). In addition, no significant correlations were found between IM-free plasma levels and IM-related adverse reactions, except for the correlation of IM-free plasma levels with periorbital edema among male patients (P = 0.013). The research demonstrated that NR2A1 polymorphisms may act as contributors of IM pharmacokinetics and responses in Chinese GIST patients. This represents an attractive opportunity for IM therapy optimization, worth testing in clinical trials.

DEVELOPMENT OF QUANTITATIVE PROTOCOL FOR IMATINIB IN HUMAN SERUM BY LIQUID CHROMATOGRAPHY TANDEM MASS SPECTROMETRY FOR THERAPEUTIC DRUG MONITORING

Estimation of therapeutic levels of Imatinib and its correlation with clinical response has become important to monitor response of this drug in chronic myeloid leukemia (CML) patients. Various attempts have been made to develop quantitative protocols for imatinib in human serum using different analytical tools. A simple, sensitive and specific quantitative method was developed in the present study for monitoring of imatinib levels in human serum by applying high performance liquid chromatography (HPLC) and QQQ tandem mass spectrometry. An efficient simple sample extraction method was developed using solid phase extraction (SPE) method for extraction of imatinib in human serum with a recovery of around 80-85%. The developed method was successfully tested on 30 human serum samples who have been receiving imatinib for CML.&#x0D; Keywords: Imatinib, LCMS, MRM, methanol, serum

Determination of serum imatinib and its' metabolite in patients chronic myeloid leukemia

IntroductionImatinib has favorable pharmacokinetic properties, but primary and secondary resistance mechanisms may cause a decrease in clinical response over time. There is a positive correlation between serum imatinib concentrations and treatment response. Our aim was to develop a method for the measurement of imatinib and its' active metabolite N-desmethyl imatinib. MethodsSerum imatinib and N-desmethyl imatinib levels were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and validation studies were carried out according to CLSI (The Clinical & Laboratory Standards Institute) protocols. Serum samples were collected from 40 patients with chronic myeloid leukemia (CML) and analyzed with LC-MS/MS and ultra high-performance liquid chromatography (UHPLC) methods. ResultsThe linearity range and correlation coefficient were 12.2–12,500 ng/mL and 0.9987 for LC-MS/MS method, respectively. Limit of quantitation was determined as 24.4 ng/mL. The retention times of imatinib and N-desmethyl imatinib were 1.66 and 1.60 min, respectively. There was no statistically significant difference between the results of both methods. DiscussionThis LC-MS/MS method is cost-effective and has adavantages such as using low serum volumes, requiring simple pretreatment steps (only protein precipitation) and reduced turnaround times for analysis.

Quantitative Mass Spectrometry Imaging Reveals Mutation Status-independent Lack of Imatinib in Liver Metastases of Gastrointestinal Stromal Tumors

Mass spectrometry imaging (MSI) is an enabling technology for label-free drug disposition studies at high spatial resolution in life science- and pharmaceutical research. We present the first extensive clinical matrix-assisted laser desorption/ionization (MALDI) quantitative mass spectrometry imaging (qMSI) study of drug uptake and distribution in clinical specimen, analyzing 56 specimens of tumor and corresponding non-tumor tissues from 27 imatinib-treated patients with the biopsy-proven rare disease gastrointestinal stromal tumors (GIST). For validation, we compared MALDI-TOF-qMSI with conventional UPLC-ESI-QTOF-MS-based quantification from tissue extracts and with ultra-high resolution MALDI-FTICR-qMSI. We introduced a novel generalized nonlinear calibration model of drug quantities based on computational evaluation of drug-containing areas that enabled better data fitting and assessment of the inherent method nonlinearities. Imatinib tissue spatial maps revealed striking inefficiency in drug penetration into GIST liver metastases even though the corresponding healthy liver tissues in the vicinity showed abundant imatinib levels beyond the limit of quantification (LOQ), thus providing evidence for secondary drug resistance independent of mutation status. Taken together, these findings underscore the important application of MALDI-qMSI in studying the spatial distribution of molecularly targeted therapeutics in oncology, namely to serve as orthogonal post-surgical approach to evaluate the contribution of anticancer drug disposition to resistance against treatment.