Detailed study of imatinib metabolization using high-resolution mass spectrometry

Physiologically based pharmacokinetic modeling of imatinib and N-desmethyl imatinib for drug-drug interaction predictions

The first-generation tyrosine kinase inhibitor imatinib has revolutionized the development of targeted cancer therapy and remains among the frontline treatments, for example, against chronic myeloid leukemia. As a substrate of cytochrome P450 (CYP) 2C8, CYP3A4, and various transporters, imatinib is highly susceptible to drug-drug interactions (DDIs) when co-administered with corresponding perpetrator drugs. Additionally, imatinib and its main metabolite N-desmethyl imatinib (NDMI) act as inhibitors of CYP2C8, CYP2D6, and CYP3A4 affecting their own metabolism as well as the exposure of co-medications. This work presents the development of a parent-metabolite whole-body physiologically based pharmacokinetic (PBPK) model for imatinib and NDMI used for the investigation and prediction of different DDI scenarios centered around imatinib as both a victim and perpetrator drug. Model development was performed in PK-Sim® using a total of 60 plasma concentration-time profiles of imatinib and NDMI in healthy subjects and cancer patients. Metabolism of both compounds was integrated via CYP2C8 and CYP3A4, with imatinib additionally transported via P-glycoprotein. The subsequently developed DDI network demonstrated good predictive performance. DDIs involving imatinib and NDMI were simulated with perpetrator drugs rifampicin, ketoconazole, and gemfibrozil as well as victim drugs simvastatin and metoprolol. Overall, 12/12 predicted DDI area under the curve determined between first and last plasma concentration measurements (AUClast) ratios and 12/12 predicted DDI maximum plasma concentration (Cmax) ratios were within twofold of the respective observed ratios. Potential applications of the final model include model-informed drug development or the support of model-informed precision dosing.

A novel workflow utilizing open-source software tools in the environmental fate studies: The example of imatinib biotransformation

The aim of this study is to utilize novel and powerful workflows with publicly available tools to efficiently process data and facilitate rapid acquisition of knowledge on environmental fate studies. Taking imatinib (IMA) as an example, we developed an efficient workflow to describe IMA biodegradation with activated sludge (AS) from wastewater treatment plants (WWTP). IMA is a cytostatic pharmaceutical; a selective tyrosine kinase inhibitor used to treat chronic myeloid leukemia. Its reported ecotoxic, endocrine and genotoxic effects imply high risk for aquatic wildlife and human health, however its fate in the environment is not yet well known. The study was conducted in a batch biotransformation setup, at two AS concentration levels and in presence and absence of carbon source. Degradation profiles and formation of IMA transformation products (TPs) were investigated using UHPLC-QqOrbitrap-MS/MS which showed that IMA is readily biodegradable. TPs were determined using multivariate statistical analysis. Eight TPs were determined and tentatively identified, six of them for first time. Hydrolysis of amide bond, oxidation, demethylation, deamination, acetylation and succinylation are proposed as major biodegradation pathways. TP235, the product of amide bond hydrolysis, was detected and quantified in actual wastewaters, at levels around 1 ng/L. This calls for more studies on the environmental fate of IMA in order to properly asses the environmental risk and hazard associated to IMA and its TPs.

A Study of the Identification, Fragmentation Mode and Metabolic Pathways of Imatinib in Rats Using UHPLC-Q-TOF-MS/MS

In this study, The metabolites, metabolic pathways, and metabolic fragmentation mode of a tyrosine kinase inhibitor- (TKI-) imatinib in rats were investigated. The samples for analysis were pretreated via solid-phase extraction, and the metabolism of imatinib in rats was studied using ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS/MS). Eighteen imatinib metabolites were identified in rat plasma, 21 in bile, 18 in urine, and 12 in feces. Twenty-seven of the above compounds were confirmed as metabolites of imatinib and 9 of them were newly discovered for the first time. Oxidation, hydroxylation, dealkylation, and catalytic dehydrogenation are the main metabolic pathways in phase I. For phase II, the main metabolic pathways were N-acetylation, methylation, cysteine, and glucuronidation binding. The fragment ions of imatinib and its metabolites were confirmed to be produced by the cleavage of the C-N bond at the amide bond. The newly discovered metabolite of imatinib was identified by UHPLC-Q-TOF-MS/MS. The metabolic pathway of imatinib and its fragmentation pattern were summarized. These results could be helpful to study the safety of imatinib for clinical use.

Detection of Imatinib Based on Electrochemical Sensor Constructed Using Biosynthesized Graphene-Silver Nanocomposite

The establishment of a monitoring technique for imatinib is necessary in clinical and environmental toxicology. Leaf extracts of Lycoris longituba were used as reducing agent for the one-step synthesis of reduced graphene oxide-Ag nanocomposites. This nanocomposite was characterized by TEM, FTIR, XRD, and other instruments. Then, the graphene/Ag nanocomposite was used as a modifier to be cemented on the surface of the glassy carbon electrode. This electrode exhibited excellent electrochemical sensing performance. Under the optimal conditions, the proposed electrode could detect imatinib at 10 nM−0.28 mM with a low limit of detection. This electrochemical sensor also has excellent anti-interference performance and reproducibility.

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.

Novel sulphur-containing imatinib metabolites found by untargeted LC-HRMS analysis

Untargeted metabolite profiling using high-resolution mass spectrometry coupled with liquid chromatography (LC-HRMS), followed by data analysis with the Compound Discoverer 2.0™ software, was used to study the metabolism of imatinib in humans with chronic myeloid leukemia. Plasma samples from control (drug-free) and patient (treated with imatinib) groups were analyzed in full-scan mode and the unknown ions occurring only in the patient group were then, as potential imatinib metabolites, subjected to multi-stage fragmentation in order to elucidate their structure. The application of an untargeted approach, as described in this study, enabled the detection of 24 novel structurally unexpected metabolites. Several sulphur-containing compounds, probably originating after the reaction of reactive intermediates of imatinib with endogenous glutathione, were found and annotated as cysteine and cystine adducts. In the proposed mechanism, the cysteine adducts were formed after the rearrangement of piperazine moiety to imidazoline. On the contrary, in vivo S-N exchange occurred in the case of the cystine adducts. In addition, N-O exchange was observed in the collision cell in the course of the fragmentation of the cystine adducts. The presence of sulphur in the cysteine and cystine conjugates was proved by means of ultra-high resolution measurements using Orbitrap Elite. The detection of metabolites derived from glutathione might improve knowledge about the disposition of imatinib towards bioactivation and help to improve understanding of the mechanism of its hepatotoxicity or nephrotoxicity in humans.