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

Therapeutic drug monitoring of imatinib - how far are we in the leukemia setting?

INTRODUCTION

Tyrosine kinase inhibitors (TKIs) have revolutionized survival rates of chronic myeloid leukemia (CML) and Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) and replaced hematopoietic stem cell transplantation (hSCT) as the key treatment option for these patients. More recently, the so-called Philadelphia chromosome-like (Ph-like) ALL has similarly benefitted from TKIs. However, many patients shift from the first generation TKI, imatinib, due to treatment-related toxicities or lack of treatment efficacy. A more personalized approach to TKI treatment could counteract these challenges and potentially be more cost-effective. Therapeutic drug monitoring (TDM) has led to higher response rates and less treatment-related toxicity in adult CML but is rarely used in ALL or in childhood CML.

AREAS COVERED

This review summarizes different antileukemic treatment indications for TKIs with focus on imatinib and its pharmacokinetic/-dynamic properties as well as opportunities and pitfalls of TDM for imatinib treatment in relation to pharmacogenetics and co-medication for pediatric and adult Ph+/Ph-like leukemias.

EXPERT OPINION

TDM of imatinib adds value to standard monitoring of ABL-class leukemia by uncovering non-adherence and potentially mitigating adverse effects. Clinically implementable pharmacokinetic/-dynamic models adjusted for relevant pharmacogenetics could improve individual dosing. Prospective trials of TDM-based treatments, including both children and adults, are needed.

Quantitation of Venetoclax in Human Plasma by High-Performance Liquid Chromatography with Ultraviolet Detection

A simple, highly sensitive and specific method based on high-performance liquid chromatography (HPLC) with ultraviolet detection was developed for the measurement of venetoclax concentrations in plasma samples. The chromatographic method employed a mobile phase of acetonitrile: 0.5% KH2PO4 (pH 3.5) (80/20, v/v) on a CAPCELL PAK C18 UG120 column at a flow rate of 0.5 mL/min. The quantitative method was validated based on standards described in "Bioanalytical Method Validation: Guidance for Industry" published by the US Food and Drug Administration. The separation of venetoclax and the internal standard R051012 was satisfactory, and the chromatograms were free of interfering peaks from the biological matrix. The intra- and inter-day coefficients of variation for venetoclax assays were <12.9%, whereas intra- and inter-day accuracies were within 13.6%. Only 100 μL of human plasma was required to detect a lower limit of quantification of 10 ng/mL for venetoclax. The recoveries of venetoclax extracted with an Oasis HLB cartridge were between 81 and 85%. The developed HPLC method was successfully applied to the determination of venetoclax concentrations in plasma of acute myeloid leukemia patients taking venetoclax. The degree of drug interactions between venetoclax and CYP3A4 inhibitors can be determined by this HPLC assay.

Validation of Liquid Chromatography Coupled with Tandem Mass Spectrometry for the Determination of 12 Tyrosine Kinase Inhibitors (TKIs) and Their Application to Therapeutic Drug Monitoring in Adult and Pediatric Populations

Tyrosine kinase inhibitors (TKIs) are used as targeted cancer therapies in adults and have an off-label pediatric application for the treatment of Langerhans cell histiocytosis. A multitarget LC-MS/MS method was developed and validated for the determination of alectinib, alectinib-M4, binimetinib, cobimetinib, crizotinib, dabrafenib, encorafenib, imatinib, lorlatinib, osimertinib, AZ5104, and trametinib. A total of 150 µL of internal standard methanolic solution was added to 50 µL of plasma sample to precipitate proteins. After centrifugation, 10 µL of the supernatant was injected into the chromatographic system. The chromatographic separation was conducted on a Kinetex C18 Polar column with a gradient of 2 mM ammonium formate in 0.1% formic acid and acetonitrile over 5 min. Limits of detection and quantification, linearity, accuracy, precision, selectivity, carryover, matrix effect, recovery, and stability were evaluated and satisfied EMA guidelines on bioanalytical methods. This method has been successfully applied to the therapeutic drug monitoring (TDM) of adults with melanoma and lung cancer, as well as children with histiocytosis, to improve the pharmacokinetic data for these drugs, with the aim of enhancing the therapeutic management and follow-up of patients. Blood concentrations of trametinib and binimetinib were different in the two groups, highlighting the age-related inter-individual variability of these molecules and the need for TDM.

Decorated graphene oxide with gold nanoparticles as a sensitive modified carbon paste electrode for simultaneous determination of tyrosine and uric acid

It is presented here as a simple, selective, rapid, low-cost, with a wide linear range method to simultaneously determine tyrosine and uric acid using a modified carbon paste electrode decorated with graphene oxide and gold nanoparticles (GO/AuNPs/MCPE). In order to characterize and evaluate the morphology and constituents of the nanostructures, X-ray diffraction spectroscopy, Transmission electron microscopes, Dynamic light scattering, Zeta potential, electrochemical impedance spectroscopy, and Voltammetry were employed. The current response on the surface of the modified electrode had a dynamic linear range relationship in the concentrations of 0.14-340.00 µmol L-1 and 0.06-141.00 µmol L-1 for tyrosine and uric acid, respectively, and the method detection limit (MDL) was 0.0060 µmol L-1 and 0.0037 µmol L-1, respectively. This modified electrode provided high stability, sensitivity, and acceptable reproducibility for voltammetric measurements of tyrosine and uric acid simultaneously in a biological matrix.

Validation of an LC-MS/MS assay for rapid and simultaneous quantification of 21 kinase inhibitors in human plasma and serum for therapeutic drug monitoring

Kinase inhibitors have revolutionized cancer treatment in the past 25 years and currently form the cornerstone of many treatments. Due to the increasing evidence for therapeutic drug monitoring (TDM) of kinase inhibitors, the need is growing for new assays to rapidly evaluate kinase inhibitor plasma concentrations. In this study, we developed an LC-MS/MS assay for the rapid and simultaneous quantification of 21 kinase inhibitors. First, a literature search was conducted to ensure that the linear ranges of the analytes were in line with the reported therapeutic windows and/or TDM reference values. Subsequently, the assay was validated according to FDA and EMA guidelines for linearity, selectivity, carry-over, accuracy, precision, dilution integrity, matrix effect, recovery, and stability. The assay was fast, with a short run-time of 2 min per sample. Sample pre-treatment consisted of protein precipitation with methanol enriched with stable isotope-labeled internal standards (SIL-IS), and the mixture was vortexed and centrifuged before sample injection. Separation was achieved using a C18 column (3 μm,50 × 2.1 mm) with a gradient of two mobile phases (ammonium formate buffer pH 3.5 and acetonitrile). Analyte detection was conducted in positive ionization mode using selected reaction monitoring. The assay was accurate and precise in plasma as well as in serum. Extraction recovery ranged between 95.0% and 106.0%, and the matrix effect was 95.7%-105.2%. The stability of the analytes varied at room temperature and in refrigerated conditions. However, all drugs were found to be stable for 7 days in the autosampler. The clinical applicability of the analytical method (486 analyzed samples between 1 July 2022-1 July 2023) as well as external quality control testing results were evaluated. Taken together, the results demonstrate that the analytical method was validated and applicable for routine analyses in clinical practice.

Therapeutic Drug Monitoring (TDM) Implementation in Public Hospitals in Greece in 2003 and 2021: A Comparative Analysis of TDM Evolution over the Years

Therapeutic drug monitoring (TDM) is the clinical practice of measuring drug concentrations. TDM can be used to determine treatment efficacy and to prevent the occurrence or reduce the risk of drug-induced side effects, being, thus, a tool of personalized medicine. Drugs for which TDM is applied should have a narrow therapeutic range and exhibit both significant pharmacokinetic variability and a predefined target concentration range. The aim of our study was to assess the current status of TDM in Greek public hospitals and estimate its progress over the last 20 years. All Greek public hospitals were contacted to provide data and details on the clinical uptake of TDM in Greece for the years 2003 and 2021 through a structured questionnaire. Data from 113 out of 132 Greek hospitals were collected in 2003, whereas for 2021, we have collected data from 98 out of 122 hospitals. Among these, in 2003 and 2021, 64 and 51 hospitals, respectively, performed TDM. Antiepileptics and antibiotics were the most common drug categories monitored in both years. The total number of drug measurement assays decreased from 2003 to 2021 (153,313 ± 7794 vs. 90,065 ± 5698; p = 0.043). In direct comparisons between hospitals where TDM was performed both in 2003 and 2021 (n = 35), the mean number of measurements was found to decrease for most drugs, including carbamazepine (198.8 ± 46.6 vs. 46.6 ± 10.1, p < 0.001), phenytoin (253.6 ± 59 vs. 120 ± 34.3; p = 0.001), amikacin (147.3 ± 65.2 vs. 91.1 ± 71.4; p = 0.033), digoxin (783.2 ± 226.70 vs. 165.9 ± 28.9; p < 0.001), and theophylline (71.5 ± 28.7 vs. 11.9 ± 6.4; p = 0.004). Only for vancomycin, a significant increase in measurements was recorded (206.1 ± 96.1 vs. 789.1 ± 282.8; p = 0.012). In conclusion, our findings show that TDM clinical implementation is losing ground in Greek hospitals. Efforts and initiatives to reverse this trend are urgently needed.

Therapeutic Drug Monitoring in Oncohematological Patients: A Fast and Accurate HPLC-UV Method for the Quantification of Nilotinib in Human Plasma and Its Clinical Application

Nilotinib, a second-generation tyrosine kinase inhibitor, has demonstrated clinical activity in chronic myeloid leukemia. As an exposure–response relationship has been observed for nilotinib, its therapeutic drug monitoring could be a valuable tool in clinical practice. Therefore, the aim of this study was to develop and validate a selective and precise high performance liquid chromatography–ultraviolet method for the measurement of nilotinib in plasma from patients with cancer. After protein precipitation extraction with acetonitrile, nilotinib and rilpivirine were separated using isocratic elution on a Tracer Excel 120 ODS C18 column using a mobile phase consisting of a mixture of potassium dihydrogen phosphate-buffered solution (pH 5.5; 0.037 M)–methanol–acetonitrile (45:45:10, v/v/v), pumped at a flow rate of 1.7 mL·min−1. A wavelength of 254 nm was selected for the quantification of the analyte and the internal standard (IS). The technique was validated following the guidelines for the validation of analytical methods of regulatory agencies (Food and Drug Administration (FDA) and the European Medicines Agency (EMA)). Linearity was established in a concentration range between 125 and 7000 ng/mL. The detection limit was 90 ng/mL, and the lower limit of quantification was 125 ng/mL. For all concentrations in the calibration curve, the intraday and interday coefficients of variation were less than 4.1%. Median recovery of nilotinib from plasma was ≥65.1% (±21.4%). The method described is sensitive, selective, reproducible, and rapid, and can be used for the accurate determination of nilotinib in human plasma for pharmacokinetics studies and for therapeutic drug monitoring (TDM) of nilotinib in routine clinical practice.

Development and Validation of a Simple Method for Simultaneously Measuring the Concentrations of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Blood Spot (DBS): A Pilot Study to Obtain Candidate Conversion Equations for Predicting Plasma Concentration Based on DBS Concentration

BACKGROUND

Dried blood spots (DBSs) are promising candidates for therapeutic drug monitoring. In this study, a simple method for the simultaneous measurement of tyrosine kinase inhibitors (TKIs), including bosutinib, dasatinib, ibrutinib, imatinib, nilotinib, and ponatinib, using DBS was developed and validated. The prediction of the plasma concentration of TKIs based on the TKI concentrations in the DBS was assessed using the developed measurement method.

METHODS

DBS was prepared using venous blood on Whatman 903 cards. One whole DBS sample containing the equivalent of 40 μL of blood was used for the analysis. The analytical method was validated according to the relevant guidelines. For clinical validation, 96 clinical samples were analyzed. The regression equation was derived from a weighted Deming regression analysis, and correction factors for calculating the estimated plasma concentrations (EPCs) of the analytes from their concentrations in the DBS and the predictive performance of EPC were evaluated using 2 conversion equations.

RESULTS

This method was successfully validated. Hematocrit had no significant effect on the method's accuracy or precision. Ibrutinib was stable in the DBS for up to 8 weeks at room temperature, whereas all BCR-ABL TKIs were stable for 12 weeks. All BCR-ABL TKIs exhibited similar predictive performance for EPCs using both calculation methods. Good agreement between EPCs and the measured plasma concentrations of bosutinib, imatinib, and ponatinib was observed with both conversion equations. However, Bland-Altman analysis showed that blood sampling time affected the EPC accuracy for dasatinib and nilotinib.

CONCLUSIONS

A simple method for the simultaneous determination of BCR-ABL and Bruton TKI concentrations in DBS was developed and validated. Owing to the small clinical sample size, further clinical validation is needed to determine the predictive performance of EPCs for the 6 TKIs.

Simultaneous quantification of dasatinib, nilotinib, bosutinib, and ponatinib using high-performance liquid chromatography-Photodiode array detection

Background

Dasatinib, nilotinib, and bosutinib, second‐generation tyrosine kinase inhibitors (TKIs), and ponatinib, a third‐generation TKI, are approved pharmaceuticals used in the treatment of chronic myeloid leukemia (CML). Although liquid chromatography‐tandem mass spectrometry assays for simultaneous quantification of the four TKIs in human serum have been reported in the literature, a high‐performance liquid chromatography (HPLC) assay that simultaneously quantifies these compounds has not yet been developed. This study aims to establish and validate an efficient HPLC analytical method using a photodiode array (PDA) detector for the simultaneous quantification of the four TKIs.

Methods

Calibration standards were prepared by serial dilution of serum samples containing the four TKIs, followed by solid‐phase extraction. The four TKIs were eluted in order within 10 min using a binary HPLC gradient system.

Results

The calibration ranges were 2–500 ng/ml for dasatinib, 100–5000 ng/ml for nilotinib, and 10–500 ng/ml for bosutinib and ponatinib. Intra‐day and inter‐day precision and accuracy values were found to be in accordance with the U.S. Food and Drug Administration guidelines. The recovery rates were 92.9%–96.0%, 80.7%–86.1%, 91.6%–99.0%, and 86.4%–92.6% for dasatinib, nilotinib, bosutinib, and ponatinib, respectively.

Conclusion

To the best of our knowledge, this is the first report of an HPLC‐PDA analytical method that allows efficient simultaneous quantification of the four TKIs in the serum of patients with CML. We believe that the method developed herein can improve the efficiency of therapeutic drug monitoring in patients with CML in clinical practice.

Therapeutic Drug Monitoring and Individualized Medicine of Dasatinib: Focus on Clinical Pharmacokinetics and Pharmacodynamics

Dasatinib is an oral second-generation tyrosine kinase inhibitor known to be used widely in Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). Notably, although a high pharmacokinetic variability in patients and an increased risk of pleural effusion are attendant, fixed dosing remains standard practice. Retrospective studies have suggested that dasatinib exposure may be associated with treatment response (efficacy/safety). Therapeutic drug monitoring (TDM) is gradually becoming a practical tool to achieve the goal of individualized medicine for patients receiving targeted drugs. With the help of TDM, these patients who maintain response while have minimum adverse events may achieve long-term survival. This review summaries current knowledge of the clinical pharmacokinetics variation, exposure-response relationships and analytical method for individualized dosing of dasatinib, in particular with respect to therapeutic drug monitoring. In addition, it highlights the emerging insights into several controversial issues in TDM of dasatinib, with the aim of presenting up-to-date evidence for clinical decision-making and insights for future studies.

Simultaneous Quantification of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Plasma Spots and Its Application to Clinical Sample Analysis

BACKGROUND

Recent reports highlight the importance of therapeutic drug monitoring (TDM) of BCR-ABL and Bruton tyrosine kinase inhibitors (TKIs); thus, large-scale studies are needed to determine the target concentrations of these drugs. TDM using dried plasma spots (DPS) instead of conventional plasma samples is a promising approach. This study aimed to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of BCR-ABL and Bruton TKIs for further TDM studies.

METHODS

A 20-μL aliquot of plasma was spotted onto a filter paper and dried completely. Analytes were extracted from 2 DPS using 250 μL of solvent. After cleanup by supported liquid extraction, the sample was analyzed by LC-MS/MS. Applicability of the method was examined using samples of patients' DPS transported by regular mail as a proof-of-concept study. The constant bias and proportional error between plasma and DPS concentrations were assessed by Passing-Bablok regression analysis, and systematic errors were evaluated by Bland-Altman analysis.

RESULTS

The method was successfully validated over the following calibration ranges: 1-200 ng/mL for dasatinib and ponatinib, 2-400 ng/mL for ibrutinib, 5-1000 ng/mL for bosutinib, and 20-4000 ng/mL for imatinib and nilotinib. TKI concentrations were successfully determined for 93 of 96 DPS from clinical samples. No constant bias between plasma and DPS concentrations was observed for bosutinib, dasatinib, nilotinib, and ponatinib, whereas there were proportional errors between the plasma and DPS concentrations of nilotinib and ponatinib. Bland-Altman plots revealed that significant systematic errors existed between both methods for bosutinib, nilotinib, and ponatinib.

CONCLUSIONS

An LC-MS/MS method for the simultaneous quantification of 6 TKIs in DPS was developed and validated. Further large-scale studies should be conducted to assess the consistency of concentration measurements obtained from plasma and DPS.

Resonance Rayleigh scattering technique-using erythrosine B, as novel spectrofluorimetric method for determination of anticancer agent nilotinib: Application for capsules and human plasma

A exceedingly touchy resonance Rayleigh scattering (RRS) strategy for the assurance of nilotinib (NILO) was introduced. In the pH 3.4 acetate buffer solution, NILO reacted with erythrosine B to produce an ion-association complex, which increased the RRS intensity of the studied system. The enhanced RRS intensity (ΔI) was linearly proportional to the concentration of NILO, the linear range of the method was 0.1-1.0 µg/mL and the detection limit (DL) was 0.025 µg/mL. In like manner, this test was connected to distinguish the concentration of NILO in capsules and human plasma with palatable comes about.

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.

Solid phase extraction-based magnetic carbon nitride/metal organic framework composite with high performance liquid chromatography for the determination of tyrosine kinase inhibitors in urine samples

In this study, a novel solid phase extraction method was constructed to detect three tyrosine kinase inhibitors (TKIs) in urine with a high-performance liquid chromatography-diode array detector. The sorbent MCN/BIF-20 was constructed by magnetic g-C₃N₄ (MCN) and boron imidazole framework-20 (BIF-20) and was characterized by multiple techniques. The experimental results of the adsorption isotherm and adsorption kinetics indicated that the composites had good adsorption of TKIs (148.33 mg g^-1, 283.25 mg g^-1, 188.17 mg g^-1). The reason for the good adsorption property of the complex material was revealed by comparison with each single material. The analytical method was built by a single factor experiment, and was evaluated as a suitable method to detect TKIs in urine by its good accuracy (90.35-98.69%), precision (<3.9%), appropriate detection limits (2.2-3.4 ng mL^-1), and linear ranges (12.5-500 ng mL^-1) with convenient determination coefficients (>0.9997). The performance of the MCN/BIF-20 composite did not decrease dramatically in 3 cycles. These analytical results demonstrated that g-C₃N₄ and BIFs had a bright prospect in sample pretreatment, and the proposed approach based on MCN/BIF-20 was applicable for analysis of TKIs in urine.

Targeted Strategy to Analyze Antiepileptic Drugs in Human Serum by LC-MS/MS and LC-Ion Mobility-MS

Routine small-molecule analysis is challenging owing to the need for high selectivity and/or low limits of quantification. This work reports a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify 14 antiepileptic drugs (AEDs) in human serum. For the optimized LC-MS/MS method described herein, we applied the guidelines outlined in the Clinical and Laboratory Standards Institute (CLSI) LC-MS C62-A document and the U.S. Food and Drug Administration (FDA) Bioanalytical Method Validation Guidance for Industry to evaluate the quality of the assay. In these studies, AED linearity, analyte recovery, matrix effects, precision, and accuracy were assessed. Using liquid chromatography-drift tube ion mobility-mass spectrometry (LC-DTIM-MS), a qualitative method was also used to increase confidence in AED identification using accurate mass and collision cross section (CCS) measurements. The LC-DTIM-MS method was also used to assess the ability of drift tube CCS measurements to aid in the separation and identification of AED structural isomers and other AEDs. These data show that another dimension of information, namely CCS measurements, provides an orthogonal dimension of structural information needed for AED analysis. Multiplexed AED measurements using LC-MS/MS and LC-DTIM-MS have the potential to enable better optimization of dosing owing to the high precision capabilities available in these types of analytical studies. Taken together, these data also show the ability to increase confidence in small-molecule identification and quantification using these analytical technologies.

Pharmacokinetics of dasatinib in a hemodialysis patient with chronic myeloid leukemia and chronic kidney disease

Until now, no studies have addressed the use of dasatinib in hemodialysis patients. Herein, we report the case of a 73-year-old hemodialysis patient with chronic myeloid leukemia (CML) who was treated with dasatinib. For 5 years prior, the patient had received nilotinib for the treatment of CML. Regular hemodialysis was initiated due to progression of hypertensive nephrosclerosis, whereupon nilotinib was discontinued and the patient began receiving 100 mg dose of dasatinib once daily. On dialysis days, dasatinib was administered immediately after completion of dialysis. Four months after starting dasatinib, we performed a pharmacokinetic study. The plasma concentrations of dasatinib before, immediately, and 2 h after the completion of hemodialysis were 7.4, 6.1, and 59.5 ng/mL, respectively. Ultrasound cardiography revealed a gradual decline in ejection fraction during dasatinib therapy. Because the patient's dasatinib trough concentration was higher (6.1 ng/mL) than the target level (1.5 ng/mL), we suspected the development of dasatinib-related heart dysfunction; thus, dasatinib was discontinued 6 months after its initiation. We concluded that hemodialysis patients are potentially vulnerable to the cardiotoxic effects of dasatinib; monitoring of cardiac function and plasma drug concentration may thus be useful in assessing their condition.

Simultaneous electrochemical detection of levodapa, paracetamol and l-tyrosine based on multi-walled carbon nanotubes

A novel electrochemical sensor for the simultaneous detection of levodopa, paracetamol and l-tyrosine was developed based on multi-walled carbon nanotubes. The sensor has the merits of wide linear range, good selectivity and good reproducibility.

Bioanalytical LC-MS/MS validation of therapeutic drug monitoring assays in oncology

Therapeutic drug monitoring (TDM) has shown to benefit patients treated with drugs of many drug classes, among which is oncology. With an increasing demand for drug monitoring, new assays have to be developed and validated. Guidelines for bioanalytical validation issued by the European Medicines Agency and US Food and Drug Administration are applicable for clinical trials and toxicokinetic studies and demand fully validated bioanalytical methods to yield reliable results. However, for TDM assays a limited validation approach is suggested based on the intended use of these methods. This review presents an overview of publications that describe method validation of assays specifically designed for TDM. In addition to evaluating current practice, we provide recommendations that could serve as a guide for future validations of TDM assays.

[Personalized medicine for oral molecular-targeted anticancer drugs]

Therapeutic drug monitoring (TDM) is carried out by evaluating drug plasma (or serum) concentrations in response to individual optimal treatments by dose adjustment to improve efficacy or avoid side effects. Many molecular-targeted anticancer drugs show exposure-efficacy and exposure-toxicity relationships. Therefore, plasma concentrations of anticancer drugs can be used as biomarkers. However, to carry out TDM, therapeutic target ranges indicating exposure-response (efficacy/toxicity) relationships must be determined. In Japan, treatment fees for managing the TDM of imatinib and sunitinib have been assessed since 2012 and 2018, respectively. In therapy for imatinib or sunitinib using TDM, reduced toxicity, discontinuation rates, and costs for treatments as well as improved clinical efficacy have been noted. To establish the use of TDM in clinical practice, it is necessary to determine target plasma concentrations (minimum effective concentration or minimum toxic concentration) of many molecular-targeted anticancer drugs by retrospective and prospective clinical trials. In these clinical trials, analytical methods with high precision are needed. By carrying out TDM, we may determine the optimal anticancer therapy for patients as precision medicine after the start of therapy.

Switching to nilotinib is associated with deeper molecular responses in chronic myeloid leukemia chronic phase with major molecular responses to imatinib: STAT1 trial in Japan

The purpose of this clinical trial was to evaluate the efficacy of 2-year consolidation therapy using nilotinib (NIL) for achieving a molecular response (MR^4.5, BCR-ABL1^IS ≤ 0.0032% on the International Scale) in patients with chronic myeloid leukemia in the chronic phase (CML-CP) who had achieved a major molecular response (MMR, BCR-ABL1^IS ≤ 0.1%) with imatinib (IM). We recruited 76 Japanese patients for this trial. Nilotinib 300 mg, twice daily, was administered for 2 years, and 74 patients were evaluated in the study. The median age was 55.0 years. The median duration of IM treatment was 69.0 months. All patients showed MMR at the time of entry into the study; the median time to MMR on IM therapy was 20.4 months. The proportion of patients who achieved MR^4.5 increased over time. The rates of MR^4.5 in the 74 evaluable patients were 27.0% [90% confidence interval (CI) (18.7-36.8%)] and 44.6% [90% CI (34.7-54.8%)] at 12 and 24 months, respectively. The frequency of ABCG2 421C/A + A/A was an independent predictive biomarker for achieving a 24-month MR^4.5. Switching to NIL led to safer, deeper molecular responses in patients with MMR on long-term IM therapy for future treatment-free remission.

Correlation of plasma concentration and adverse effects of bosutinib: standard dose or dose-escalation regimens of bosutinib treatment for patients with chronic myeloid leukemia

Purpose

To investigate the exposure-toxicity relationship of bosutinib and to identify the target trough plasma concentration (C₀).

Methods

The toxicity and C₀ of bosutinib in Japanese chronic myeloid leukemia (CML) patients were monitored every 2 weeks for the first 3 months of treatment, and subsequently once a month during the 6 months after beginning 500 mg/day of standard dose (SD group, n = 10) or beginning 100 mg/day and increased by 100 mg every 2 weeks of dose escalation (DE group, n = 15).

Results

Nine of 10 patients (90%) in the SD group were not able to continue bosutinib therapy without interruption due to adverse events, compared to 2 patients (13.5%) in the DE group. The total duration of treatment interruption was 35 and 14 days in the SD and DE groups, respectively. The median time until liver dysfunction or diarrhea was day 28 and day 1 in the SD group, and day 53.5 and day 19 in the DE group, respectively. The cumulative dose of bosutinib was comparable between the SD and DE groups (51,700 vs. 53,550 mg, respectively). At 6 months, the median C₀ was 63.7 ng/mL and 63.0 ng/mL in the SD and DE groups, respectively. Liver dysfunction (all grades) and diarrhea (> grade 2) were prevalent in quartile 4 of C₀ (> 91.0 ng/mL), as calculated by the total C₀ distribution.

Conclusions

The DE regimen was better suited to avoid treatment interruption. The daily dose of bosutinib might be adjusted based on target C₀ to avoid adverse events by therapeutic drug monitoring in general practice.

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.

High-throughput determination of vancomycin in human plasma by a cost-effective system of two-dimensional liquid chromatography

Therapeutic drug monitoring (TDM) is one of the most important services of clinical laboratories. Two main techniques are commonly used: the immunoassay and chromatography method. We have developed a cost-effective system of two-dimensional liquid chromatography with ultraviolet detection (2D-LC-UV) for high-throughput determination of vancomycin in human plasma that combines the automation and low start-up costs of the immunoassay with the high selectivity and sensitivity of the liquid chromatography coupled with mass spectrometric detection without incurring their disadvantages, achieving high cost-effectiveness. This 2D-LC system offers a large volume injection to provide sufficient sensitivity and uses simulated gradient peak compression technology to control peak broadening and to improve peak shape. A middle column was added to reduce the analysis cycle time and make it suitable for high-throughput routine clinical assays. The analysis cycle time was 4min and the peak width was 0.8min. Compared with other chromatographic methods that have been developed, the analysis cycle time and peak width for vancomycin was reduced significantly. The lower limit of quantification was 0.20μg/mL for vancomycin, which is the same as certain LC-MS/MS methods that have been recently developed and validated. The method is rapid, automated, and low-cost and has high selectivity and sensitivity for the quantification of vancomycin in human plasma, thus making it well-suited for use in hospital clinical laboratories.

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.