Elucidation and Regulation of Tyrosine Kinase Inhibitor Resistance in Renal Cell Carcinoma Cells from the Perspective of Glutamine Metabolism.

Tyrosine kinase inhibitors (TKIs) play a crucial role in the treatment of advanced renal cell carcinoma (RCC). However, there is a lack of useful biomarkers for assessing treatment efficacy. Through urinary metabolite analysis, we identified the metabolites and pathways involved in TKI resistance and elucidated the mechanism of TKI resistance. To verify the involvement of the identified metabolites obtained from urine metabolite analysis, we established sunitinib-resistant RCC cells and elucidated the antitumor effects of controlling the identified metabolic pathways in sunitinib-resistant RCC cells. Through the analysis of VEGFR signaling, we aimed to explore the mechanisms underlying the antitumor effects of metabolic control. Glutamine metabolism has emerged as a significant pathway in urinary metabolite analyses. In vitro and in vivo studies have revealed the antitumor effects of sunitinib-resistant RCC cells via knockdown of glutamine transporters. Furthermore, this antitumor effect is mediated by the control of VEGFR signaling via PTEN. Our findings highlight the involvement of glutamine metabolism in the prognosis and sunitinib resistance in patients with advanced RCC. Additionally, the regulating glutamine metabolism resulted in antitumor effects through sunitinib re-sensitivity in sunitinib-resistant RCC. Our results are expected to contribute to the more effective utilization of TKIs with further improvements in prognosis through current drug therapies.

High throughput LC/ESI-MS/MS method for simultaneous analysis of 20 oral molecular-targeted anticancer drugs and the active metabolite of sunitinib in human plasma.

Many types of oral molecular-targeted anticancer drugs are clinically used in cancer genomic medicine. Combinations of multiple molecular-targeted anticancer drugs are also being investigated, expecting to prolong the survival of patients with cancer. Therapeutic drug monitoring of oral molecular-targeted drugs is important to ensure efficacy and safety. A liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been used for simultaneous determination of these drugs in human plasma. However, the sensitivity of mass spectrometers and differences in the therapeutic range of drugs have rendered the development of simultaneous LC/ESI-MS/MS methods difficult. In this study, a simultaneous quantitative method for 20 oral molecular-targeted anticancer drugs and the active metabolite of sunitinib was developed based on the results of linear range shifts of the calibration curves using four ion abundance adjustment techniques (collision energy defects, in-source collision-induced dissociation, secondary product ion selected reaction monitoring, and isotopologue selected reaction monitoring). The saturation of the detector for the seven analytes was resolved by incorporating optimal ion abundance adjustment techniques. Furthermore, the reproducibility of this method was confirmed in validation tests, and plasma from patients was measured by this method to demonstrate its usefulness in actual clinical practice. This analytical method is expected to make a substantial contribution to the promotion of personalized medicine in the future.

Predictive model for recurrence of renal cell carcinoma by comparing pre- and postoperative urinary metabolite concentrations.

To improve treatment outcomes in real practice, useful biomarkers are desired when predicting postoperative recurrence for renal cell carcinoma (RCC). We collected data from patients who underwent definitive surgery for RCC and for benign urological tumor at our department between November 2016 and December 2019. We evaluated the differences in pre- and postoperative urinary metabolites with our precise quantitative method and identified predictive factors for RCC recurrence. Additionally, to clarify the significance of metabolites, we measured the intracellular metabolite concentration of three RCC cell lines. Among the 56 patients with RCC, nine had a recurrence (16.0%). When comparing 27 patients with T1a RCC and 10 with benign tumor, a significant difference was observed between pre- and postoperative concentrations among 10 urinary metabolites. In these 10 metabolites, multiple logistic regression analysis identified five metabolites (lactic acid, glycine, 2-hydroxyglutarate, succinic acid, and kynurenic acid) as factors to build our recurrence prediction model. The values of area under the receiver operating characteristic curve, sensitivity, and specificity in this predictive model were 0.894%, 88.9%, and 88.0%, respectively. When stratified into low and high risk groups of recurrence based on this model, we found a significant drop of recurrence-free survival rates among the high risk group. In in vitro studies, intracellular metabolite concentrations of metastatic tumor cell lines were much higher than those of primary tumor cell lines. By using our quantitative evaluation of urinary metabolites, we could predict postoperative recurrence with high sensitivity and specificity. Urinary metabolites could be noninvasive biomarkers to improve patient outcome.

Clinical Importance of Plasma Drug Concentration of Oral Molecular Targeted Drugs for Renal Cell Carcinoma.

PURPOSE: Therapeutic drug monitoring (TDM) is widely used in clinical practice to maximize drug efficacy and minimize toxicities. Currently, it is also practiced in the use of oral molecular targeted drugs. The objective of this study was to assess the clinical importance of measuring the systemic concentration of oral molecular targeted drugs used to treat renal cell carcinoma (RCC). METHODS: The systemic concentrations of the oral molecular targeted drugs sorafenib, sunitinib, axitinib, pazopanib, and everolimus used for RCC were useful for therapeutic interventions, and clinical outcomes were evaluated retrospectively. RESULTS: The interventional use of systemic drug concentration was confirmed in 26 of 87, and their categories are presented. The systemic concentration of sunitinib was useful in dose reduction and/or discontinuation (n = 10), dose escalation (n = 3), and adherence monitoring (n = 2). Nine of the 10 patients whose dose was reduced showed reduced adverse event. Two patients who were intervened in adherence monitor showed improved adherence. For axitinib, dose reduction and/or discontinuation (n = 1) and dose escalation (n = 6) were confirmed. For pazopanib, dose reduction and/or discontinuation (n = 1) and drug interaction detection (n = 1) were confirmed, both of them were confirmed to have reduced adverse events. For everolimus, dose reduction and/or discontinuation (n = 1) and drug interaction detection (n = 1) were confirmed, a patient with reduced dose recovered from adverse events. Interventions for sorafenib were not identified. CONCLUSIONS: This study demonstrated that systemic concentrations of oral molecular targeted drugs for RCC were considered to be clinically useful for dose adjustment, monitoring of treatment adherence, and the detection of drug interactions. Moreover, this information could be successfully used to guide individualized therapy to maximize the antitumor effects of these drugs.

High-throughput liquid chromatography/electrospray ionization-tandem mass spectrometry method using in-source collision-induced dissociation for simultaneous quantification of imatinib, dasatinib, bosutinib, nilotinib, and ibrutinib in human plasma.

Recent studies have shown that therapeutic drug monitoring of tyrosine kinase inhibitors (TKIs) could improve treatment efficacy and safety. A simple analytical method using high-performance LC/electrospray ionization-tandem mass spectrometry has been developed and validated for simultaneous quantification of BCR-ABL and Bruton's TKIs used for chronic leukemia (imatinib, dasatinib, bosutinib, nilotinib, and ibrutinib) in human plasma. Although these structures and physical properties are similar, owing to their different linear ranges, simultaneously determining the plasma levels of these five TKIs by applying optimal MS parameters remains difficult. A quantitative range exceeding 60,000-fold was required, and the linear dynamic ranges of imatinib, bosutinib, and nilotinib were limited because of the presence of a saturated detection signal. In this study, we applied the in-source collision-induced dissociation technique to control the ion amounts in mass spectrometry. This new method allowed rapid determination within 5 min with simple pretreatment. The method was validated according to the US Food and Drug Administration guidelines. Moreover, all samples of patients with chronic leukemia were successfully measured and their values were within the linear range of measurement. Therefore, our high-throughput analytical system is useful to measure the plasma concentrations of imatinib, dasatinib, bosutinib, nilotinib, and ibrutinib in clinical practice.

Metabolomic Analysis to Elucidate Mechanisms of Sunitinib Resistance in Renal Cell Carcinoma.

Metabolomics analysis possibly identifies new therapeutic targets in treatment resistance by measuring changes in metabolites accompanying cancer progression. We previously conducted a global metabolomics (G-Met) study of renal cell carcinoma (RCC) and identified metabolites that may be involved in sunitinib resistance in RCC. Here, we aimed to elucidate possible mechanisms of sunitinib resistance in RCC through intracellular metabolites. We established sunitinib-resistant and control RCC cell lines from tumor tissues of RCC cell (786-O)-injected mice. We also quantified characteristic metabolites identified in our G-Met study to compare intracellular metabolism between the two cell lines using liquid chromatography-mass spectrometry. The established sunitinib-resistant RCC cell line demonstrated significantly desuppressed protein kinase B (Akt) and mesenchymal-to-epithelial transition (MET) phosphorylation compared with the control RCC cell line under sunitinib exposure. Among identified metabolites, glutamine, glutamic acid, and α-KG (involved in glutamine uptake into the tricarboxylic acid (TCA) cycle for energy metabolism); fructose 6-phosphate, D-sedoheptulose 7-phosphate, and glucose 1-phosphate (involved in increased glycolysis and its intermediate metabolites); and glutathione and myoinositol (antioxidant effects) were significantly increased in the sunitinib-resistant RCC cell line. Particularly, glutamine transporter (SLC1A5) expression was significantly increased in sunitinib-resistant RCC cells compared with control cells. In this study, we demonstrated energy metabolism with glutamine uptake and glycolysis upregulation, as well as antioxidant activity, was also associated with sunitinib resistance in RCC cells.

Importance of Therapeutic Drug Monitoring to Detect Drug Interaction between Pazopanib and Warfarin: A Case Report.

Pazopanib is an orally available multi-tyrosine kinase inhibitor and has been used to treat renal cell carcinoma (RCC). Here, we report the case of a patient with RCC with an increased prothrombin time- international normalized ratio (PT-INR) due to pazopanib therapy. In addition, we have reported the change in the blood levels of pazopanib. A 75-year-old man underwent a left nephrectomy for RCC. Four years later, his cancer recurred and pazopanib therapy was initiated. He was also taking warfarin for atrial fibrillation and his PT-INR was constant at approximately 2. His warfarin dose was reduced from 3.5 mg/day to 3.0 mg/day on day 10 because his PT-INR increased from 2.19 to 3.07 compared to that before starting pazopanib. On day 28, his PT-INR further increased to 4.34, and his aspartate aminotransferase, alanine transaminase, and alkaline phosphatase levels increased. The target concentration of pazopanib was 20.5 to 50.3 µg/mL, but his blood concentrations were 92.1 µg/mL on day 6 and 93.7 µg/mL on day 13. Therefore, both pazopanib and warfarin were discontinued. One week later, his laboratory tests recovered, and hence, warfarin treatment was resumed. However, pazopanib therapy was terminated due to concerns about liver dysfunction. His hepatic dysfunction and increased PT-INR were considered to be due to pazopanib treatment. Pazopanib has been reported to have no effect on the pharmacokinetics of warfarin in clinical patients. In this case, blood levels of pazopanib were abnormally high, possibly causing liver dysfunction and drug interactions, leading to his PT-INR prolongation. TDM monitoring, in addition to the recommended monitoring for pazopanib hepatotoxicity, may help identify patients at risk for drug interactions. For patients receiving concomitant pazopanib and warfarin, close monitoring of PT-INR is warranted.

Accurate quantification of urinary metabolites for predictive models manifest clinicopathology of renal cell carcinoma.

Using surgically resected tissue, we identified characteristic metabolites related to the diagnosis and malignant status of clear cell renal cell carcinoma (ccRCC). Specifically, we quantified these metabolites in urine samples to evaluate their potential as clinically useful noninvasive biomarkers of ccRCC. Between January 2016 and August 2018, we collected urine samples from 87 patients who had pathologically diagnosed ccRCC and from 60 controls who were patients with benign urological conditions. Metabolite concentrations in urine samples were investigated using liquid chromatography-mass spectrometry with an internal standard and adjustment based on urinary creatinine levels. We analyzed the association between metabolite concentration and predictability of diagnosis and of malignant status by multiple logistic regression and receiver operating characteristic (ROC) curves to establish ccRCC predictive models. Of the 47 metabolites identified in our previous study, we quantified 33 metabolites in the urine samples. Multiple logistic regression analysis revealed 5 metabolites (l-glutamic acid, lactate, d-sedoheptulose 7-phosphate, 2-hydroxyglutarate, and myoinositol) for a diagnostic predictive model and 4 metabolites (l-kynurenine, l-glutamine, fructose 6-phosphate, and butyrylcarnitine) for a predictive model for clinical stage III/IV. The sensitivity and specificity of the diagnostic predictive model were 93.1% and 95.0%, respectively, yielding an area under the ROC curve (AUC) of 0.966. The sensitivity and specificity of the predictive model for clinical stage were 88.5% and 75.4%, respectively, with an AUC of 0.837. In conclusion, quantitative analysis of urinary metabolites yielded predictive models for diagnosis and malignant status of ccRCC. Urinary metabolites have the potential to be clinically useful noninvasive biomarkers of ccRCC to improve patient outcomes.

Development of a precise quantitative method for monitoring sirolimus in whole blood using LC/ESI-MS/MS.

Sirolimus is used on patients after solid organ transplantation and on lymphangioleiomyomatosis (LAM) patients, and therapeutic drug monitoring is required in clinical practice. We have previously reported an accurate method for quantitative determination of sirolimus, but its sample preparation step was complicated. In this study, we developed a modified liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method for sirolimus quantification. A supported liquid extraction cartridge was used to purify sirolimus from whole blood and ion suppression was mostly prevented. The validation results met the acceptance criteria. This method was compared with the antigen conjugated magnetic immunoassay (ACMIA) and our previously reported method, using whole blood samples from LAM patients. Comparison of the Bland-Altman plots of the currently developed method and the previous method revealed no significant difference between the two methods (mean bias, -2.02%; 95% CI, -7.81-3.78). The values obtained using ACMIA were significantly higher than those obtained using the current method by 13.87% (95% CI, 6.49-21.25) owing to cross-reactivity. The degrees of cross reactivities in LAM patients and in organ transplant patients were similar, and our LC/ESI-MS/MS method precisely measured the blood concentrations of sirolimus.

[Toward Personalized Cancer Therapy with Oral Molecular-targeted Agents].

Oral molecular-targeted agents are used clinically for the treatment of various types of cancer. However, even when treatment is started at the dosage indicated in the medical package insert, we have experienced many cases in which treatment had to be stopped early owing to the occurrence of serious side effects or an insufficient therapeutic effect. In recent years, a wide range of studies has been conducted on the therapeutic drug monitoring (TDM) of oral molecular-targeted therapeutic agents to prevent serious side effects and maximize the therapeutic effect. In Japan, the TDM of imatinib has been covered by insurance since 2012, and the TDM of sunitinib has been covered since 2018. In contrast, tyrosine kinase inhibitors may have severe side effects, but their TDM is not covered by medical insurance. We aimed to identify a safe, highly effective chemotherapy regimen based on scientific evidence gathered from Japanese patients. We examined the relationship between the plasma concentration of drugs and clinical findings, such as side effects and treatment effects, at our hospital. In this symposium review, we introduce our results based on the treatment of patients with renal cell carcinoma.

Estimation of Blood Sirolimus Concentration Based on Tacrolimus Concentration/Dose Normalized by Body Weight Ratio in Lung Transplant Patients.

BACKGROUND: Sirolimus and tacrolimus require accurate drug dosing based on their target blood levels to produce better clinical outcomes, specifically, the avoidance of drug-induced adverse effects and the maintenance of efficacy. However, because the ideal dose of sirolimus and the schedule for measuring its blood levels are unclear in lung transplant patients, an index is required for estimating sirolimus blood concentrations. The aim of this work is to study the correlation between the trough concentration/dose normalized by body weight (C0/D) ratios of sirolimus and tacrolimus in lung transplant patients. METHODS: Thirteen lymphangiomyomatosis patients who underwent lung transplantation and were treated with sirolimus and tacrolimus from February 2015 to July 2018 were divided into 2 groups, one receiving twice-daily (TD, n = 6) and the other once-daily (OD, n = 7) tacrolimus formulations. The correlation between the C0/D ratio of sirolimus and patient background was evaluated using Spearman's rank correlation coefficient. Correlations between sirolimus and tacrolimus C0/D ratios or doses were analyzed by single regression analysis. RESULTS: Significant correlations were found between the C0/D ratios of sirolimus and tacrolimus. The regression equations from the initial data of TD and OD groups at steady state were y = 1.880x + 32.636 (adjusted R = 0.743, P = 0.017) and y = 1.684x + 38.816 (adjusted R = 0.919, P < 0.001), respectively. In addition, the regression equations from all data of TD and OD groups were y = 1.883x + 4.170 (adjusted R = 0.546, P < 0.001) and y = 1.950x + 43.188 (adjusted R = 0.898, P < 0.001), respectively. A significant correlation between the dosage of sirolimus and tacrolimus was observed only in the OD group, with relatively low accuracy. CONCLUSIONS: Blood sirolimus concentrations can be estimated using the C0/D ratio of tacrolimus, suggesting that the C0/D ratio of tacrolimus is an index of required sirolimus dosage and the frequency of blood sirolimus concentration measurements.

Long-term relationship between everolimus blood concentration and clinical outcomes in Japanese patients with metastatic renal cell carcinoma: a prospective study.

BACKGROUND: Everolimus is an oral inhibitor of mammalian target of rapamycin, approved for metastatic renal cell carcinoma (mRCC). Recently, personalized medicine through therapeutic drug monitoring (TDM) is recommended in cancer therapy. In this study, the relationship between everolimus blood concentration and clinical outcomes on a long-term were evaluated in Japanese patients with mRCC. METHODS: Patients with mRCC were enrolled following treatment with everolimus at Tohoku University Hospital between April 2012 and December 2016. The relationship between everolimus trough blood concentration on day 8 of everolimus therapy and just before discontinuation or dose reduction, and their adverse events were evaluated. Patients were divided into two groups based on the median of everolimus blood concentration on day 8 of treatment, and the profiles of adverse events, and efficacy [time to treatment failure (TTF) and progression-free survival (PFS)] were evaluated. RESULTS: The median (range) everolimus blood concentrations on day 8 after starting everolimus administration and just before discontinuation or dose reduction were 15.3 (8.1-28.0) ng/mL and 14.8 (6.4-58.4) ng/mL, respectively, with no significant difference between these values (P = 0.3594). Patients (n = 6) with discontinuation or dose reduction following adverse events in everolimus therapy had significantly higher blood concentrations than patients (n = 4) with dose maintenance on both day 8 (median, 18.0 vs 8.2 ng/mL; P = 0.0139) and just before discontinuation or dose reduction (median, 22.9 vs 9.7 ng/mL; P = 0.0142). Median TTF and PFS of the total patients (n = 10) were 96 days (95% confidence interval [CI], 26-288) and 235 days (95% CI, 28-291), respectively. Subgroup analysis showed that TTF of the patients with > 15.3 ng/mL (n = 5) was not significantly different from that of the patients with ≤15.3 ng/mL (n = 5; P = 0.5622). Similarly, PFS of the patients with > 15.3 ng/mL was not significantly different from that of the patients with ≤15.3 ng/mL (P = 0.3436). CONCLUSIONS: This study demonstrated the long-term relationship between everolimus blood level and clinical outcomes and adverse events in Japanese patients with mRCC. Thus, TDM in everolimus therapy could be a useful tool for the early prediction of adverse events for Japanese patients with mRCC.

Value of global metabolomics in association with diagnosis and clinicopathological factors of renal cell carcinoma.

Renal cell carcinoma (RCC) is a malignant tumor that currently lacks clinically useful biomarkers indicative of early diagnosis or disease status. RCC has commonly been diagnosed based on imaging results. Metabolomics offers a potential technology for discovering biomarkers and therapeutic targets by comprehensive screening of metabolites from patients with various cancers. We aimed to identify metabolites associated with early diagnosis and clinicopathological factors in RCC using global metabolomics (G-Met). Tumor and nontumor tissues were sampled from 20 cases of surgically resected clear cell RCC. G-Met was performed by liquid chromatography mass spectrometry and important metabolites specific to RCC were analyzed by multivariate statistical analysis for cancer diagnostic ability based on area under the curve (AUC) and clinicopathological factors (tumor volume, pathological T stage, Fuhrman grade, presence of coagulation necrosis and distant metastasis). We identified 58 metabolites showing significantly increased levels in tumor tissues, 34 of which showed potential early diagnostic ability (AUC >0.8), but 24 did not discriminate between tumor and nontumor tissues (AUC ≤0.8). We recognized 6 pathways from 9 metabolites with AUC >0.8 and 7 pathways from 10 metabolites with AUC ≤0.8 about malignant status. Clinicopathological factors involving malignant status correlated significantly with metabolites showing AUC ≤0.8 (p = 0.0279). The tricarboxylic acid cycle (TCA) cycle, TCA cycle intermediates, nucleotide sugar pathway and inositol pathway were characteristic pathways for the malignant status of RCC. In conclusion, our study found that metabolites and their pathways allowed discrimination between early diagnosis and malignant status in RCC according to our G-Met protocol.

Relationships between sunitinib plasma concentration and clinical outcomes in Japanese patients with metastatic renal cell carcinoma.

BACKGROUND: The aim was to investigate the relationships between total sunitinib plasma concentrations (sunitinib plus its active metabolite; N-desethyl sunitinib) and clinical outcomes in Japanese patients with metastatic renal cell carcinoma (mRCC). METHODS: Twenty patients with mRCC were enrolled following treatment with sunitinib. To assess safety, the total sunitinib concentration range up to discontinuation of treatment and dosage reduction associated with adverse events within 6 weeks from initiating administration were analyzed. The longest administered sunitinib dosage was defined as the maintenance dose, and the relationship between total sunitinib concentration at the maintenance dosage and sunitinib efficacy was investigated. RESULTS: Total sunitinib concentration was significantly higher in patients who discontinued treatment or had dosage reduction due to adverse events within 6 weeks after initiation of sunitinib than in patients who continued treatment with the initial dosage. The time to treatment failure, progression-free survival, and overall survival were better in patients with total sunitinib concentrations < 50 ng/mL than in those with concentrations ≥ 50 ng/mL. CONCLUSIONS: The present study demonstrated that the effective range of total sunitinib concentration in Japanese patients with mRCC was lower than 50-100 ng/mL which was previously reported. These results indicate that therapeutic drug monitoring could maintain the therapeutic effect of sunitinib while minimizing adverse events by personalizing sunitinib dosages for Japanese patients with mRCC.

Simultaneous analysis of oral anticancer drugs for renal cell carcinoma in human plasma using liquid chromatography/electrospray ionization tandem mass spectrometry.

An analytical method using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry has been developed and validated for simultaneous measurement of four tyrosine kinase inhibitors used for renal cell carcinoma and their metabolites in human plasma. Despite their similar structures, it is difficult to measure plasma levels of these compounds simultaneously using optimal MS parameters for each compound because a quantitative range exceeding 50,000-fold is required. To overcome this problem, we used a linear range shift technique using in-source collision-induced dissociation. Linearity ranges of sorafenib, sorafenib N-oxide, sunitinib, N-desethyl sunitinib, axitinib and pazopanib were 100-10,000, 10-1,000, 1-100, 1-100, 1-100 and 500-50,000 ng/mL, respectively. The intra- and inter-day precision and accuracy were high, and coefficients of variation and relative error were <10.3% and within ±11.8%, respectively. The matrix effects of all analytes ranged from 87.7 to 114.8%. Extraction recoveries and overall recoveries showed small extraction loss (<15.0%) for all analytes. Moreover, all cancer patient samples used in this study were successfully quantified and fell within the linear range of measurement. Therefore, this novel analytical system using in-source collision-induced dissociation has sufficient performance to measure plasma concentrations of these four tyrosine kinase inhibitors and their metabolites for therapeutic drug monitoring.

Development of a Liquid Chromatography-Tandem Mass Spectrometric Method for Quantification of Mycophenolic Acid and Its Glucuronides in Dried Blood Spot Samples.

BACKGROUND: Personalized immunosuppressive therapy, including accurate drug dosing based on the drug blood level, leads to better clinical outcomes, specifically regarding avoidance of drug-induced adverse effects and maintenance of efficacy. Mycophenolic acid (MPA) is used as an immunosuppressant in transplantation of various solid organs. The aim of this study was to develop a method for quantification of MPA and its metabolites, mycophenolic acid 7-O-glucuronide (MPAG) and mycophenolic acid acyl glucuronide, in dried blood spot (DBS) samples, using liquid chromatography/electrospray ionization/tandem mass spectrometry. METHODS: For sample preparation, a microwave-drying approach was used to deactivate enzymes and reduce drying time. Blood volume was calculated in a DBS disk of 3 mm diameter. Concentrations of analytes in plasma from patients receiving mycophenolate mofetil were compared with DBS samples after hematocrit correction. RESULTS: The method yielded good recoveries of all 3 analytes (90.3%-104.2%). Blood volume in the disk was calculated as 3.0 ± 0.2 µL. Linearity over concentration ranges of 0.1-30 mcg/mL MPA, 0.1-200 mcg/mL MPAG, and 0.125-10 mcg/mL mycophenolic acid acyl glucuronide was obtained with r ≥0.999. Intraday and interday variations were less than 14.6%, and accuracy was within ±11.9%. Passing-Bablok analysis showed no significant differences between plasma concentrations and DBS concentrations after hematocrit correction of MPA and MPAG. CONCLUSIONS: We developed and validated a liquid chromatography/electrospray ionization-tandem mass spectrometry method for analysis of MPA in DBS samples. The method is useful for monitoring the MPA blood level.

Severe toxicity induced by accumulation of active sunitinib metabolite in a Japanese patient with renal cell carcinoma: a case report.

BACKGROUND: Sunitinib is a multi-targeted tyrosine kinase inhibitor that is approved for treatment of renal cell carcinoma as an oral anticancer drug. Therapeutic drug monitoring of total sunitinib (sunitinib and N-desethyl sunitinib) is used in our hospital to improve therapeutic efficacy, while preventing adverse effects. Here, we report the first case of a patient with metastatic renal cell carcinoma undergoing hemodialysis and presenting severe adverse events induced by the accumulation of N-desethyl sunitinib. CASE PRESENTATION: A 60-year-old Japanese man was diagnosed with metastatic renal cell carcinoma requiring hemodialysis. On day 26 of the first cycle of sunitinib therapy, our patient presented grade 3 thrombocytopenia and leukopenia, which required interruption of therapy although the plasma levels of total sunitinib in the patient were less than the effective concentration of 50 ng/mL. The elimination half-life of sunitinib was normal at 50.8 hours, but that of N-desethyl sunitinib was an extended 211.4 hours. Moreover, the N-desethyl sunitinib/sunitinib trough level ratio was higher than 1.0. We attribute our patient's severe adverse events to the excessive accumulation of N-desethyl sunitinib owing to its delayed excretion. Although the reason for the delayed excretion of N-desethyl sunitinib in this patient was unknown, it may have been caused by genetic polymorphisms related to the pharmacokinetics of sunitinib rather than the hemodialysis. In this case, the patient was homozygous for the ABCG2 421C allele, but was capable of potentially harboring polymorphisms in other genes, such as ABCB1, an efflux pump of sunitinib. In addition, even though there is no clear evidence, urinary excretion of the metabolic products of N-desethyl sunitinib could be inhibited by the interaction of transporters such as the organic ion transporter. CONCLUSIONS: The monitoring of not only total sunitinib concentration but also N-desethyl sunitinib concentration and their elimination half-lives during sunitinib therapy is recommended to avoid critical adverse events.

[A Case of Renal Cell Carcinoma with High Everolimus Blood Concentrations and Hyperglycemia Due to Everolimus-Induced Hepatic Dysfunction].

We report the case of a patient who had renal cell carcinoma with high everolimus blood concentrations and hyperglycemia due to everolimus-induced hepatic dysfunction. A 74-year-old man who underwent right nephrectomy for renal cell carcinoma was administered everolimus for multiple lung metastases. Everolimus caused grade 3 hepatic dysfunction and hyperglycemia; hence, high blood levels of everolimus were observed. Although the patient was re-administrated everolimus after recovering from hepatic dysfunction, hepatic function test values worsened again. Everolimus was discontinued before its blood concentration increased, and the patient was switched to axitinib treatment. Therefore, the measurement of everolimus blood level is considered useful for the management of adverse events in renal cell carcinoma.

Pemirolast potently attenuates paclitaxel hypersensitivity reactions through inhibition of the release of sensory neuropeptides in rats.

The effects of anti-allergic agents on the hypersensitivity reactions to paclitaxel, an anti-cancer agent, were examined in rats. Intravenous injection of paclitaxel (15 mg/kg) caused a marked extravasation of plasma protein in lungs and a transient decrease in arterial partial oxygen pressure (PaO(2)). The paclitaxel-induced protein extravasation was inhibited by low doses (0.1-1 mg/kg) of pemirolast or high doses (30-100 mg/kg) of cromoglycate. However, ketotifen was not effective. The decrease in PaO(2) induced by paclitaxel was also significantly reversed by pemirolast. On the other hand, the paclitaxel-induced plasma extravasation was not attenuated by a histamine H(1) blocker diphenhydramine or an H(2) blocker famotidine, but was significantly reduced by a neurokinin NK(1) antagonist LY303870 (0.5 mg/kg) and an NK(2) antagonist SR48968 (1 mg/kg). The concentrations of proteins and sensory peptides such as substance P, neurokinin A and calcitonin gene-related peptide but not histamine in the rat bronchoalveolar lavage fluid were elevated by paclitaxel injection. Both cromoglycate and pemirolast reduced the paclitaxel-induced rise in proteins and sensory peptides. Therefore, we demonstrated for the first time that sensory nerve peptides are involved in paclitaxel hypersensitivity and that an anti-allergic agent pemirolast attenuates the paclitaxel response by inhibiting the release of sensory nerve peptides.

Role of sensory nerve peptides rather than mast cell histamine in paclitaxel hypersensitivity.

Paclitaxel is one of the most extensively used anticancer agents, however, its use is often limited by severe hypersensitivity reactions, including respiratory distress, bronchospasm, and hypotension, which can occur despite premedication with dexamethasone and histamine H1 and H2 antagonists. The present study was designed to determine the mechanisms of paclitaxel hypersensitivity. In rats, paclitaxel (15 mg/kg, intravenously) caused a marked increase in pulmonary vascular permeability and edema. PaO2 decreased, whereas PaCO2 increased, transiently after paclitaxel injection. The paclitaxel-induced pulmonary vascular hyperpermeability was blocked by dexamethasone but not by histamine H1 or H2 antagonists. Paclitaxel increased the vascular permeability in lungs of mast cell-deficient rats Ws/Ws(-/-) to almost the similar extent as that elicited in wild-type rats. On the other hand, the paclitaxel-induced pulmonary vascular hyperpermeability was reversed by sensory denervation with capsaicin or pretreatment with LY303870 and SR48968, NK1 and NK2 antagonists, respectively. Consistent with these findings, a marked elevation of sensory neuropeptides such as substance P, neurokinin A, and calcitonin gene-related peptide was observed in rat bronchoalveolar lavage fluid after paclitaxel injection. These findings suggest that sensory nerves rather than mast cells are implicated in the etiology of paclitaxel hypersensitivity.