Population pharmacokinetic analysis reveals no impact of aprepitant on the pharmacokinetics of ifosfamide, 2-dechloroifosfamide, and 3-dechloroifosfamide.

PURPOSE: Several case reports and retrospective series have clearly pointed to the role of aprepitant, an antiemetic drug, in the development of encephalopathy when used with ifosfamide. Described as an inhibitor of several CYP metabolic pathways, aprepitant is suspected of drug-drug-interaction on ifosfamide pharmacokinetics. The pharmacokinetics of ifosfamide and two of its metabolites (2-dechloroifosfamide and 3-dechloroifosfamide) was studied in patients with soft tissue sarcomas to evaluate the impact of aprepitant administration. METHODS: A population pharmacokinetic approach was applied to analyze data obtained in 42 patients at cycle 1 (without aprepitant) and cycle 2 (with aprepitant for 34 of them). RESULTS: A previously published pharmacokinetic model including a time-dependency process well fit the data. Aprepitant had no impact on ifosfamide or its two metabolite pharmacokinetic parameters. CONCLUSION: This study suggests that aprepitant does not lead to a significant modification of ifosfamide metabolization, even though other metabolites such as 4 hydroxyifosfamide and chloroacetaldehyde were not monitored in this study.

Pharmacokinetic parameters of ifosfamide in mouse pre-administered with grapefruit juice or naringin.

Grapefruit juice (GFJ) and naringin when consumed previously or together with medications may alter their bioavailavility and consequently the clinical effect. Ifosfamide (IF) is an antitumoral agent prescribed against various types of cancer. Nevertheless, there is no information regarding its interaction with the ingestion of GFJ or naringin. The aims of the present report were validating a method for the quantitation of IF in the plasma of mouse, and determine if mice pretreated with GFJ or naringin may modify the IF pharmacokinetics. Our HPLC results to quantify IF showed adequate intra and inter-day precision (RSD < 15%) and accuracy (RE < 15%) indicating reliability. Also, the administration of GFJ or naringin increased Cmax of IF 22.9% and 17.8%, respectively, and decreased Tmax of IF 19.2 and 53.8%, respectively. The concentration of IF was higher when GFJ (71.35 ± 3.5 µg/mL) was administered with respect to that obtained in the combination naringin with IF (64.12 ± µg/mL); however, the time required to reach such concentration was significantly lower when naringin was administered (p < 0.5). We concluded that pre-administering GFJ and naringin to mice increased the Tmax and decreased the Cmax of IF.

A pilot study of first-line olaratumab, doxorubicin and ifosfamide in patients with metastatic soft tissue sarcoma.

INTRODUCTION: Olaratumab (O) is a monoclonal antibody that specifically binds PDGFRα. The addition of O to doxorubicin (D) has been approved by the regulatory authorities for metastatic soft tissue sarcoma (MSTS). Since the combination of D + ifosfamide (I) is commonly used in MSTS and is associated with a higher response rate than D alone, it seems reasonable to combine O with the combination of D + I (ODI). We report our preliminary experience with O + D+I in MSTS. METHODS: Between 01/01/2015 and 30/05/2018, 15 patients (pts) with MSTS were treated with ODI as first-line therapy. The treatment protocol consisted of IV D 50 mg/m2 and I 5000 mg/m2, day 1 (3 pts), or D 37.5 mg/m2 and I 3000 mg/m2 days 1-2 (12 pts). O (15 mg/kg) was given IV on days 1, 8, and cycles were repeated every 21 days. RESULTS: With a median follow up of 16 months, 63 cycles of ODI were given. Objective response was achieved in 4 pts (27%) (CR in 3, PR in 1); 5 pts (33%) remained with stable disease for ≥ 5 mo. Median overall survival was 22 months. Major hematological toxicities (grade 3-4) included: neutropenia-7 pts (47%), and neutropenic fever-3 pts (20%). Non-hematological toxicities included grade 3 diarrheas in 2 pts (13%) after the second cycle. There was no treatment-related mortality. CONCLUSION: According to our preliminary experience, adding olaratumab to doxorubicin and ifosfamide is active and its safety profile is comparable to that of doxorubicin and ifosfamide alone in MSTS.

Radiosynthesis, molecular modeling studies and biological evaluation of 99mTc-Ifosfamide complex as a novel probe for solid tumor imaging.

PURPOSE: Ifosfamide as a chemotherapeutic drug is used for the treatment of different cancer types. The purpose of this study is the preparation of 99mTc-ifosfamide complex to be evaluated as a potential candidate for tumor imaging. MATERIALS AND METHODS: The radiolabeling of ifosfamide with technetium-99m was carried out by mixing 4mg ifosfamide and 5 µg of SnCl2.2H2O with 400 MBq Na99mTcO4 at pH 9 for 30 min at room temperature. Computer simulation studies were performed using Accelrys Discovery Studio 2.5 operating system to illustrate the interaction of ifosfamide and 99mTc-ifosfamide complexes with DNA. The in-vivo biodistribution of 99mTc-ifosfamide was studied in tumor-bearing Albino mice. RESULTS: A new 99mTc-ifosfamide complex was synthesized with a good radiochemical yield of 90.3 ± 2.1% under the optimized conditions and exhibited in-vitro stability up to 2 h. Biodistribution studies showed good uptake in tumor site and high uptake in tumor site with T/NT ∼3 after 60 min post-injection. Besides, the molecular docking study confirmed that the complexation of ifosfamide with technetium-99m does not abolish its binding to the target receptor. CONCLUSION: These promising results afford a new radiopharmaceutical that could be used as a potential tumor imaging.

Poly-isoprenylated ifosfamide analogs: Preactivated antitumor agents as free formulation or nanoassemblies.

Oxazaphosphorines including cyclophosphamide, trofosfamide and ifosfamide (IFO) belong to the alkylating agent class and are indicated in the treatment of numerous cancers. However, IFO is subject to limiting side-effects in high-dose protocols. To circumvent IFO drawbacks in clinical practices, preactivated IFO analogs were designed to by-pass the toxic metabolic pathway. Among these IFO analogs, some of them showed the ability to self-assemble due to the use of a poly-isoprenyloxy chain as preactivating moiety. We present here, the in vitro activity of the nanoassembly formulations of preactivated IFO derivatives with a C-4 geranyloxy, farnesyloxy and squalenoxy substituent on a large panel of tumor cell lines. The chemical and colloidal stabilities of the geranyloxy-IFO (G-IFO), farnesyloxy-IFO (F-IFO) and squalenoxy-IFO (SQ-IFO) NAs were further evaluated in comparison to their free formulation. Finally, pharmacokinetic parameters and maximal tolerated dose of the most potent preactivated IFO analog (G-IFO) were determined and compared to IFO, paving the way to in vivo studies.

Evaluation of a method for calculating carboplatin dosage in DeVIC ± R therapy (combination therapy of dexamethasone, etoposide, ifosfamide and carboplatin with or without rituximab) as a salvage therapy in patients with relapsed or refractory non-Hodgkin lymphoma.

PURPOSE: Several studies have evaluated the utility of extrapolating the Calvert formula in calculating carboplatin (CBDCA) dosages in solid tumours; however, data regarding haematological cancers are less. Therefore, we conducted a preliminary study of the utility of extrapolating the Calvert formula in calculating CBDCA dosages for DeVIC ± R therapy. METHODS: A retrospective study on 57 non-Hodgkin lymphoma patients who had received DeVIC ± R therapy was conducted. The area under the curve (AUC) of CBDCA was back-calculated from actual dosages using the Calvert formula. Patients were divided into two groups according to an AUC ≥ 4 or an AUC < 4, respectively. The Revised Response Criteria of the International Working Group and CTCAE version 4.0 were used for assessing the treatment efficacy and adverse events, respectively. RESULTS: The use of AUC instead of body surface area had greater utility in calculating CBDCA dosage, with a response rate of greater than 50 % in patients receiving DeVIC ± R therapy with an AUC ≥ 4 for CBDCA. The response rate of the AUC ≥ 4 group was significantly higher than that of the AUC < 4 group. Decreased platelet and neutrophil counts of grade ≥3 occurred at higher rates in the AUC ≥ 4 group. CONCLUSION: The extrapolation of the Calvert formula has utility in calculating the CBDCA dosage for DeVIC ± R therapy, and therapeutic efficacy was increased by maintaining the AUC of CBDCA at ≥4.

Trabectedin for the treatment of soft tissue sarcomas.

INTRODUCTION: Trabectedin, a marine-derived DNA-binding antineoplastic agent, has been registered by the EMA and recently also by the FDA for the treatment of patients with advanced soft-tissue sarcoma (STS), a rare and heterogeneous disease. AREAS COVERED: The antitumor activity of trabectedin is related both to direct effects on cancer cells, such as growth inhibition, cell death and differentiation, and indirect effects related to its anti-inflammatory and anti-angiogenic properties. Furthermore, trabectedin is the first compound that targets an oncogenic transcription factor with high selectivity in mixoid liposarcomas. This peculiar mechanism of action is the basis of its clinical development. The clinical pharmacology of trabectedin, the subsequent phase I, II and III trials are summarized and put into perspectives in this review. EXPERT OPINION: Trabectedin is a relevant pleiotropic antitumoral agent within the complex scenario of the management of STS. It can be used in advanced STS, either after failure of anthracyclines and ifosfamide or in patients unfit for these drugs, especially when reaching a high-tumor control and a long-term benefit is a priority. Toxicity profile is acceptable and manageable with no reported cumulative toxicities. Therefore, trabectedin has become one relevant therapeutic option in metastatic STS, especially in selected histologies.

Ecotoxicity and genotoxicity of cyclophosphamide, ifosfamide, their metabolites/transformation products and their mixtures.

Cyclophosphamide (CP) and ifosfamide (IF) are commonly used cytostatic drugs that repress cell division by interaction with DNA. The present study investigates the ecotoxicity and genotoxicity of CP, IF, their human metabolites/transformation products (TPs) carboxy-cyclophosphamide (CPCOOH), keto-cyclophosphamide (ketoCP) and N-dechloroethyl-cyclophosphamide (NdCP) as individual compounds and as mixture. The two parent compounds (CP and IF), at concentrations up to 320 mg L(-1), were non-toxic towards the alga Pseudokirchneriella subcapitata and cyanobacterium Synecococcus leopoliensis. Further ecotoxicity studies of metabolites/TPs and a mixture of parent compounds and metabolites/TPs performed in cyanobacteria S. leopoliensis, showed that only CPCOOH (EC50 = 17.1 mg L(-1)) was toxic. The measured toxicity (EC50 = 11.5 mg L(-1)) of the mixture was lower from the toxicity predicted by concentration addition model (EC50 = 21.1 mg L(-1)) indicating potentiating effects of the CPCOOH toxicity. The SOS/umuC assay with Salmonella typhimurium revealed genotoxic activity of CP, CPCOOH and the mixture in the presence of S9 metabolic activation. Only CPCOOH was genotoxic also in the absence of metabolic activation indicating that this compound is a direct acting genotoxin. This finding is of particular importance as in the environment such compounds can directly affect DNA of non-target organisms and also explains toxicity of CPCOOH against cyanobacteria S. leopoliensis. The degradation study with UV irradiation of samples containing CP and IF showed efficient degradation of both compounds and remained non-toxic towards S. leopoliensis, suggesting that no stable TPs with adverse effects were formed. To our knowledge, this is the first study describing the ecotoxicity and genotoxicity of the commonly used cytostatics CP and IF, their known metabolites/TPs and their mixture. The results indicate the importance of toxicological evaluation and monitoring of drug metabolites as they may be for certain aquatic species more hazardous than parent compounds.

Simultaneous quantification of preactivated ifosfamide derivatives and of 4-hydroxyifosfamide by high performance liquid chromatography-tandem mass spectrometry in mouse plasma and its application to a pharmacokinetic study.

The antitumor drug, ifosfamide (IFO), requires activation by cytochrome P450 (CYP) to form the active metabolite, 4-hydroxyisfosfamide (4-OHIFO), leading to toxic by-products at high dose. In order to overcome these drawbacks, preactivated ifosfamide derivatives (RXIFO) were designed to release 4-OHIFO without CYP involvement. A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the simultaneous quantification of 4-OHIFO, IFO and four derivatives RXIFO in mouse plasma using multiple reaction monitoring. Because of its instability in plasma, 4-OHIFO was immediately converted to the semi-carbazone derivative, 4-OHIFO-SCZ. For the six analytes, the calibration curves were linear from 20 to 5000ng/mL in 50µL plasma and the lower limit of quantitation was determined at 20ng/mL with accuracies within ±10% of nominal and precisions less than 12%. Their recoveries ranged from 62 to 96% by using liquid-liquid extraction. With an improved assay sensitivity compared to analogues, the derivative 4-OHIFO-SCZ was stable in plasma at 4°C for 24h and at -20°C for three months. For all compounds, the assay was validated with accuracies within ±13% and precisions less than 15%. This method was applied to a comparative pharmacokinetic study of 4-OHIFO from IFO and three derivatives RXIFO in mice. This active metabolite was produced by some of the novel conjugates with good pharmacokinetic properties.

Hydroxylation and N-dechloroethylation of Ifosfamide and deuterated Ifosfamide by the human cytochrome p450s and their commonly occurring polymorphisms.

The hydroxylation and N-dechloroethylation of deuterated ifosfamide (d4IFO) and ifosfamide (IFO) by several human P450s have been determined and compared. d4IFO was synthesized with deuterium at the alpha and alpha' carbons to decrease the rate of N-dechloroethylation and thereby enhance hydroxylation of the drug at the 4' position. The purpose was to decrease the toxic and increase the efficacious metabolites of IFO. For all of the P450s tested, hydroxylation of d4IFO was improved and dechloroethylation was reduced as compared with nondeuterated IFO. Although the differences were not statistically significant, the trend favoring the 4'-hydroxylation pathway was noteworthy. CYP3A5 and CYP2C19 were the most efficient enzymes for catalyzing IFO hydroxylation. The importance of these enzymes in IFO metabolism has not been reported previously and warrants further investigation. The catalytic ability of the common polymorphisms of CYP2B6 and CYP2C9 for both reactions were tested with IFO and d4IFO. It was determined that the commonly expressed polymorphisms CYP2B6*4 and CYP2B6*6 had reduced catalytic ability for IFO compared with CYP2B6*1, whereas CYP2B6*7 and CYP2B6*9 had enhanced catalytic ability. As with the wild-type enzymes, d4IFO was more readily hydroxylated by the polymorphic variants than IFO, and d4IFO was not dechloroethylated by any of the polymorphic forms. We also assessed the use of specific inhibitors of P450 to favor hydroxylation in human liver microsomes. We were unable to separate the pathways with these experiments, suggesting that multiple P450s are responsible for catalyzing both metabolic pathways for IFO, which is not observed with the closely related drug cyclophosphamide.

Pazopanib exposure decreases as a result of an ifosfamide-dependent drug-drug interaction: results of a phase I study.

BACKGROUND: The vascular endothelial growth factor receptor (VEGFR) pathway plays a pivotal role in solid malignancies and is probably involved in chemotherapy resistance. Pazopanib, inhibitor of, among other receptors, VEGFR1-3, has activity as single agent and is attractive to enhance anti-tumour activity of chemotherapy. We conducted a dose-finding and pharmacokinetic (PK)/pharmacodynamics study of pazopanib combined with two different schedules of ifosfamide. METHODS: In a 3+3+3 design, patients with advanced solid tumours received escalating doses of oral pazopanib combined with ifosfamide either given 3 days continuously or given 3-h bolus infusion daily for 3 days (9 g m(-2) per cycle, every 3 weeks). Pharmacokinetic data of ifosfamide and pazopanib were obtained. Plasma levels of placental-derived growth factor (PlGF), vascular endothelial growth factor-A (VEGF-A), soluble VEGFR2 (sVEGFR2) and circulating endothelial cells were monitored as biomarkers. RESULTS: Sixty-one patients were included. Pazopanib with continuous ifosfamide infusion appeared to be safe up to 1000 mg per day, while combination with bolus infusion ifosfamide turned out to be too toxic based on a variety of adverse events. Ifosfamide-dependent decline in pazopanib exposure was observed. Increases in PlGF and VEGF-A with concurrent decline in sVEGFR2 levels, consistent with pazopanib-mediated VEGFR2 inhibition, were observed after addition of ifosfamide. CONCLUSION: Continuous as opposed to bolus infusion ifosfamide can safely be combined with pazopanib. Ifosfamide co-administration results in lower exposure to pazopanib, not hindering biological effects of pazopanib. Recommended dose of pazopanib for further studies combined with 3 days continuous ifosfamide (9 g m(-2) per cycle, every 3 weeks) is 800 mg daily.

Use of precision-cut renal cortical slices in nephrotoxicity studies.

1.Unlike cell lines and primary cells in culture, precision-cut tissue slices remain metabolically differentiated for at least 24-48 h and allow to study the effect of xenobiotics during short-term and long-term incubations. 2.In this article, we illustrate the use of such an experimental model to study the nephrotoxic effects of (i) chloroacetaldehyde, a metabolite of the anticancer drug ifosfamide, (ii) of cobalt chloride, a potential leakage product of the cobalt-containing nanoparticles, and (iii) of valproate, a widely used antiepileptic drug. 3.Since all the latter test compounds, like many toxic compounds, negatively interact with cellular metabolic pathways, we also illustrate our biochemical toxicology approach in which we used not only enzymatic but also carbon 13 NMR measurements and mathematical modelling of metabolic pathways. 4.This original approach, which can be applied to any tissue, allows to predict the nephrotoxic effects of milligram amounts of test compounds very early during the research and development processes of drugs and chemicals. This approach, combined with the use of cells that retain their in vivo metabolic properties and, therefore, are predictive, reduces the risk, the time and cost of such processes.

N-acetylcysteine as a novel prophylactic treatment for ifosfamide-induced nephrotoxicity in children: translational pharmacokinetics.

Ifosfamide (IFO), which is used in the treatment of pediatric solid tumors, causes high rates of nephrotoxicity. N-acetylcysteine (NAC), an antidote for acetaminophen overdose, has been shown to prevent IFO-induced renal cell death and nephrotoxicity in both LLCPK-1 cells and a rat model. To facilitate the use of NAC in preventing IFO-induced nephrotoxicity in children, the authors compared the systemic exposure to NAC in children treated for acetaminophen overdose to the systemic exposure of the therapeutically effective rat model. The mean systemic exposure in the rat model was 18.72 mM·h (range, 9.92-30.02 mM·h), compared to the mean systemic exposure found in treated children (14.48 mM·h; range, 6.22-32.96 mM·h). They also report 2 pediatric cases in which NAC-attenuated acute renal failure associated with IFO when given concurrently with their chemotherapy treatment. Systemic exposure to NAC measured in 1 of these cases was comparable to that in the children treated for acetaminophen overdose. These results corroborate NAC's potential to protect against IFO-induced nephrotoxicity in children when used in its clinically approved dose schedule and supports a clinical trial in children.

Doxorubicin and ifosfamide for high-grade sarcoma during pregnancy.

PURPOSE: Doxorubicin and ifosfamide are highly active drugs for the treatment of high-grade sarcomas, but little is known on the optimal management of young patients who develop such malignancies during pregnancy. METHODS: We report on a single-institution series of patients (n = 9) with high-grade sarcoma diagnosed during the third trimester of pregnancy. Neoadjuvant chemotherapy combining doxorubicin (50 mg/m(2) day 1) and ifosfamide (2.5 g/m(2) days 1-2) with standard mesna rescue every 3 weeks was administered during the third trimester of pregnancy in five patients. RESULTS: We observed a favourable outcome for both the mother and the offspring in all cases. Maternal and neonatal pharmacokinetic data for ifosfamide were obtained from one patient and did not evidence a transplacental transfer of this drug. The use of other active drugs (cisplatin, etoposide, dactinomycin and cyclophosphamide) in sarcoma during pregnancy is discussed on the basis of a comprehensive review of the English literature. CONCLUSIONS: In view of this single-centre experience, we suggest that the treatment of high-grade sarcoma during the third trimester of pregnancy should include an adapted regimen tailored to the pharmacological specificities of the pregnant patients.

Xenobiotic metabolomics: major impact on the metabolome.

Xenobiotics are encountered by humans on a daily basis and include drugs, environmental pollutants, cosmetics, and even components of the diet. These chemicals undergo metabolism and detoxication to produce numerous metabolites, some of which have the potential to cause unintended effects such as toxicity. They can also block the action of enzymes or receptors used for endogenous metabolism or affect the efficacy and/or bioavailability of a coadministered drug. Therefore, it is essential to determine the full metabolic effects that these chemicals have on the body. Metabolomics, the comprehensive analysis of small molecules in a biofluid, can reveal biologically relevant perturbations that result from xenobiotic exposure. This review discusses the impact that genetic, environmental, and gut microflora variation has on the metabolome, and how these variables may interact, positively and negatively, with xenobiotic metabolism.

Anticancer activity of stabilized palifosfamide in vivo: schedule effects, oral bioavailability, and enhanced activity with docetaxel and doxorubicin.

Palifosfamide, the DNA-alkylating metabolite of ifosfamide (IFOS), has been synthesized as a stabilized tris or lysine salt and found to have preclinical and clinical antitumor activity. Stabilized palifosfamide overcomes limitations of IFOS because of patient-to-patient variability in response resulting from variable prodrug activation, resistance and toxicities of metabolic byproducts, acrolein and chloroacetaldehyde. Palifosfamide represents an effective alternative to IFOS and other DNA-alkylating prodrugs. The antitumor activities of stabilized palifosfamide were investigated in vivo. Dose response, route and schedule of administration, and interaction with docetaxel or doxorubicin were investigated in NCr-nu/nu mice bearing established orthotopic mammary MX-1 tumor xenografts. Oral activity was investigated in P388-1 leukemia in CD2F1 mice. Oral and intraperitoneal bioavailabilities were compared in Sprague-Dawley rats. Stabilized palifosfamide administered by optimized regimens suppressed MX-1 tumor growth (P<0.05) by greater than 80% with 17% complete antitumor responses and up to three-fold increase in time to three tumor doublings over controls. Median survival in the P388-1 (P<0.001) model was increased by 9 days over controls. Oral bioavailability in rats was 48-73% of parenteral administration, and antitumor activity in mice was equivalent by both routes. Treatment with palifosfamide-tris combined with docetaxel or doxorubicin at optimal regimens resulted in complete tumor regression in 62-75% of mice. These studies support investigation of stabilized palifosfamide in human cancers by parenteral or oral administration as a single agent and in combination with other approved drugs. The potential for clinical translation of the cooperative interaction of palifosfamide-tris with doxorubicin by intravenous administration is supported by results from a recent randomized Phase-II study in unresectable or metastatic soft-tissue sarcoma.

Surface-modified solid lipid nanoparticulate formulation for ifosfamide: development and characterization.

AIMS: The present research focuses on the development of the surface modified solid lipid nanoparticulate (SLN) system for enhancing the stability and sustaining the release of a model hydrophilic drug ifosfamide. MATERIALS & METHODS: SLNs consisting of glyceryl monooleate (GMO) and chitosan were prepared by double emulsion technique, crosslinked with sodium tripolyphosphate, followed by lyophilization under two different vacuum conditions. The physicochemical characterization of SLNs included evaluation of surface morphology, particle size and surface charge, moisture content and physical state of the drug in the delivery system. The in vitro drug release and the stability were evaluated using high-performance liquid chromatography and liquid chromatography/mass spectrometry, respectively. Cellular permeability and subcellular localization studies were performed using Caco-2 cells. RESULTS: Different chamber pressures during lyophilization produced SLNs with different morphologies and moisture contents. SLNs demonstrated high encapsulation efficiency, sustained release, and enhanced stability of ifosfamide with a high cellular uptake and permeability for Caco-2 cells. CONCLUSION: GMO and chitosan SLNs could be successfully used for enhancing the stability, sustaining the release, enhancing the targeting and permeability characteristics of ifosfamide.

Investigation into modification of mass transfer kinetics by acrolein in a renal biochip.

In this study we present a method for investigating the effect of acrolein, a nephrotoxic and urotoxic metabolite of the anticancerous prodrugs ifosfamide and cyclophosphamide, in a blood-renal barrier biochip. The real time monitoring of mass transfers of caffeine, vitamin B12 and albumin in the biochip was performed thanks to an in vitro dialysis method. The diffusion coefficients of the solutes and their dialysance from the apical to the basolateral compartments were found to be molecular weight and cell-membrane dependent, thus demonstrating the cell-barrier functionality. The toxicity induced by the acrolein led to modifications to mass transfer properties which appeared to be acrolein dose, time and solute molecular weight dependent. Solute mass transfer across the cell layer increased with acrolein concentrations. The sensitivity of this analysis method contributes to identify the mass transfer properties and to monitor the modification to the renal parameter when submitted to toxic cell compounds. The results provide the foundation for exploring kidney behavior in response to drugs thanks to a blood-tissue barrier model using a technique based on in vitro dialysis and real time analysis.

Mass spectrometry imaging with high resolution in mass and space (HR(2) MSI) for reliable investigation of drug compound distributions on the cellular level.

Mass spectrometry (MS) imaging is a versatile method to analyze the spatial distribution of analytes in tissue sections. It provides unique features for the analysis of drug compounds in pharmacokinetic studies such as label-free detection and differentiation of compounds and metabolites. We have recently introduced a MS imaging method that combines high mass resolution and high spatial resolution in a single experiment, hence termed HR(2) MS imaging. In the present study, we applied this method to analyze the spatial distribution of the anti-cancer drugs imatinib and ifosfamide in individual mouse organs. The whole kidney of an animal dosed with imatinib was measured at 35 µm spatial resolution. Imatinib showed a well-defined distribution in the outer stripe of the outer medulla. This area was analyzed in more detail at 10 µm step size, which constitutes a tenfold increase in effective spatial resolution compared to previous studies of drug compounds. In parallel, ion images of phospholipids and heme were used to characterize the histological features of the tissue section and showed excellent agreement with histological staining of the kidney after MS imaging. Ifosfamide was analyzed in mouse kidney at 20 µm step size and was found to be accumulated in the inner medulla region. The identity of imatinib and ifosfamide was confirmed by on-tissue MS/MS measurements. All measurements including mass spectra from 10 µm pixels featured accurate mass (≤2 ppm root mean square) and mass resolving power of R = 30,000. Selected ion images were generated with a bin size of ∆m/z = 0.01 ensuring highly specific information. The ability of the method to cover larger areas was demonstrated by imaging a compound in the intestinal tract of a rat whole-body tissue section at 200 µm step size. The described method represents a major improvement in terms of spatial resolution and specificity for the analysis of drug compounds in tissue sections.