Anne-Charlotte Dubbelman

Pharmacokinetics of paclitaxel and metabolites in a randomized comparative study in platinum-pretreated ovarian cancer patients.

PURPOSE To investigate the pharmacokinetics and pharmacodynamics of paclitaxel in a randomized comparative study with four different treatment arms in patients with platinum-pretreated ovarian carcinoma. PATIENTS AND METHODS Eighteen patients were entered onto this study in which paclitaxel was administered at a high dose of 175 mg/m2 versus a low dose of 135 mg/m2 on a 3- or 24-hour infusion schedule. A solid-phase extraction technique for sample pretreatment followed by a reverse-phase high-performance liquid chromatographic (HPLC) assay was used for analysis of plasma. RESULTS Grade 3 neutropenia occurred in all four treatment arms. However, it was more severe on the 24-hour infusion schedule. Paclitaxel concentrations as low as 0.012 mumol/L were measured with the HPLC assay. With this low quantitation threshold, we found the plasma disappearance of paclitaxel to be triphasic, with half-lives t1/2(alpha), t1/2(beta), and t1/2(gamma) mean values for the different treatment arms of 0.19 hours (range, 0.01 to 0.4), 1.9 hours (range, 0.5 to 2.8), and 20.7 hours (range, 4 to 65), respectively. Eleven possible metabolites were found, of which three were identified as taxanes by on-line HPLC-photodiode array (PDA) detection. Investigation of pharmacodynamics shows no clear relationship between the pharmacokinetic parameters area under the plasma concentration time curve (AUC), area under the plasma concentration moment curve (AUMC), maximal plasma concentration (Cmax), clearance, and toxicity. However, a relationship was found between the duration of plasma concentrations above a threshold of 0.1 mumol/L with absolute neutrophil count (ANC) and white blood cell count (WBC). CONCLUSION Paclitaxel is metabolized, and putative metabolic products can be found in plasma of patients treated with the drug. Our results indicate that myelosuppression can be predicted by the measurement of the duration of plasma concentrations above the threshold of 0.1 mumol/L.

Phase I and pharmacological study of sequential intravenous topotecan and oral etoposide.

We performed a phase I and pharmacological study to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT) of a cytotoxic regimen of the novel topoisomerase I inhibitor topotecan in combination with the topoisomerase II inhibitor etoposide, and to investigate the clinical pharmacology of both compounds. Patients with advanced solid tumours were treated at 4-week intervals, receiving topotecan intravenously over 30 min on days 1-5 followed by etoposide given orally twice daily on days 6-12. Topotecan-etoposide dose levels were escalated from 0.5/20 to 1.0/20, 1.0/40, and 1.25/40 (mg m-2 day-1)/(mg bid). After encountering DLT, additional patients were treated at 3-week intervals with the topotecan dose decreased by one level to 1.0 mg m-2 and etoposide administration prolonged from 7 to 10 days to allow further dose intensification. Of 30 patients entered, 29 were assessable for toxicity in the first course and 24 for response. The DLT was neutropenia. At doses of topotecan-etoposide 1.25/40 (mg m-2)/(mg bid) two out of six patients developed neutropenia grade IV that lasted more than 7 days. Reduction of the treatment interval to 3 weeks and prolonging etoposide dosing to 10 days did not permit further dose intensification, as a time delay to retreatment owing to unrecovered bone marrow rapidly emerged as the DLT. Post-infusion total plasma levels of topotecan declined in a biphasic manner with a terminal half-life of 2.1 +/- 0.3 h. Total body clearance was 13.8 +/- 2.7 l h-1 m-2 with a steady-state volume of distribution of 36.7 +/- 6.2 l m-2. N-desmethyltopotecan, a metabolite of topotecan, was detectable in plasma and urine. Mean maximal concentrations ranged from 0.23 to 0.53 nmol l-1, and were reached at 3.4 +/- 1.0 h after infusion. Maximal etoposide plasma concentrations of 0.75 +/- 0.54 and 1.23 +/- 0.57 micromol l-1 were reached at 2.4 +/- 1.2 and 2.3 +/- 1.0 h after ingestion of 20 and 40 mg respectively. The topotecan area under the plasma concentration vs time curve (AUC) correlated with the percentage decrease in white blood cells (WBC) (r2 = 0.70) and absolute neutrophil count (ANC) (r2 = 0.65). A partial response was observed in a patient with metastatic ovarian carcinoma. A total of 64% of the patients had stable disease for at least 4 months. The recommended dose for use in phase II clinical trials is topotecan 1.0 mg m-2 on days 1-5 and etoposide 40 mg bid on days 6-12 every 4 weeks.

Development and validation of LC-MS/MS assays for the quantification of bendamustine and its metabolites in human plasma and urine.

A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assay is described for the quantification of the anti-cancer agent bendamustine and its phase I metabolites γ-hydroxy-bendamustine (M3) and N-des-methylbendamustine (M4) and for its product of two-fold hydrolysis, dihydroxy-bendamustine (HP2), in human plasma and urine. Like most alkylating nitrogen mustards, bendamustine is prone to chemical hydrolysis in aqueous solution. To minimize degradation of bendamustine, urine samples were stabilized by a 100-fold dilution with human plasma and then processed identically to plasma samples. Sample aliquots of 200 μL were mixed with an internal standard solution and acidified before separation of the analytes from the biomatrix with solid phase extraction. Dried and reconstituted extracts were injected on a Synergi Hydro RP column for the analysis of bendamustine, M3 and M4 or a Synergi Polar RP column for the analysis of HP2. Gradient elution was applied using 5mM ammonium formate with 0.1% formic acid in water and methanol as mobile phases. Analytes were ionized using an electrospray ionisation source in positive mode and detected with a triple quadrupole mass spectrometer. The quantifiable range for bendamustine, M3 and M4 was 0.5-500 ng/mL in plasma and 0.5-50 μg/mL in urine, and that for HP2 was 1-500 ng/mL in plasma and 0.1-50 μg/mL in urine. The assays were accurate and precise, with inter-assay and intra-assay accuracies within ± 20% of nominal and CV values below 20% at the lower limit of quantification and within ± 15% of nominal and below 15% at the other concentration levels tested. These methods were successfully applied to evaluate the pharmacokinetic profile of bendamustine and its metabolites in cancer patients treated with bendamustine.

Development and validation of LC–MS/MS assays for the quantification of E7080 and metabolites in various human biological matrices

To support clinical pharmacokinetic studies with the anticancer agent E7080 (lenvatinib), liquid chromatography tandem mass spectrometry (LC-MS/MS) methods were developed for the quantification of E7080 and four of its metabolites in human plasma, urine and faeces and of E7080 in whole blood. Cross-analyte interferences between metabolites and parent compound were expected and therefore accounted for early in the method development. Plasma, urine and faeces samples were extracted with acetonitrile. Chromatographic separation was achieved on a 50 mm × 2.1 mm I.D. XTerra MS C18 column, with a 0.2 mL/min flow and gradient elution starting with 100% formic acid in water, followed by an increasing percentage of acetonitrile. Whole blood samples were extracted with diethyl ether and extracts were injected on a 150 mm × 2.1mm I.D. Symmetry Shield RP8 column. Detection was performed using an API3000 triple quadrupole mass spectrometer, with a turbo ion spray interface, operating in positive ion mode. Using 250 μL of plasma, E7080 and its metabolites could be quantified between 0.25 and 50.0ng/mL. The quantifiable ranges of E7080 in whole blood, urine and faeces were 0.25-500 ng/mL, 1.00-500 ng/mL and 0.1-25μg/g, using sample volumes of 250 μL, 200 μL and 250 mg, respectively. Calibration curves in all matrices were linear with a correlation coefficient (r(2)) of 0.994 or better. At the lower limit of quantification, accuracies were within ±20% of the nominal concentration with CV values less than 20%. At the other concentrations the accuracies were within ±15% of the nominal concentration with CV values below 15%. The developed methods have successfully been applied in a mass balance study of E7080.

Quantification of docetaxel and its metabolites in human plasma by liquid chromatography/tandem mass spectrometry

RATIONALE During drug development accurate quantification of metabolites in biological samples using mass spectrometry is often hampered by the lack of metabolites of chemically pure quality. However, quantification of metabolites can be useful for assessment and interpretation of (pre)clinical data. We now describe an approach to quantify docetaxel metabolites in human plasma by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using docetaxel calibration standards. METHODS Metabolites (M1/M3, M2 and M4) were generated using microsomal incubations. Retention times of docetaxel and its metabolites were assessed using an LC/UV assay and peak identification was performed by LC/MS(n). Samples containing isolated metabolites from human faeces were quantified by LC/UV and used as references for spiking human plasma samples. LC/MS/MS was applied to sensitively quantify docetaxel and its metabolites in human plasma using docetaxel calibration standards in a range of 0.25-500 ng/mL. RESULTS Because ionisation of docetaxel and its metabolites differed, correction factors were established to quantify the metabolites using docetaxel calibration samples. During method validation, accuracy and precision of the metabolites were within ±7.7% and ≤17.6%, respectively, and within ±14.3% and ≤10.1%, respectively, for docetaxel. Metabolites were found to be unstable in human plasma at ambient temperature. After storage up to 1 year at -20 °C, recovered metabolite concentrations were within ±25%. CONCLUSIONS Development and validation of an LC/MS/MS assay for the quantification of docetaxel and its metabolites M1/M3, M2 and M4 using docetaxel calibration standards is described. The same approach may be used for quantification of metabolites of other drugs by LC/MS/MS when chemically pure reference substances are unavailable.

Systematic evaluation of commercially available ultra-high performance liquid chromatography columns for drug metabolite profiling: optimization of chromatographic peak capacity.

The present study investigated the practical use of modern ultra-high performance liquid chromatography (UHPLC) separation techniques for drug metabolite profiling, aiming to develop a widely applicable, high-throughput, easy-to-use chromatographic method, with a high chromatographic resolution to accommodate simultaneous qualitative and quantitative analysis of small-molecule drugs and metabolites in biological matrices. To this end, first the UHPLC system volume and variance were evaluated. Then, a mixture of 17 drugs and various metabolites (molecular mass of 151-749Da, logP of -1.04 to 6.7), was injected on six sub-2μm particle columns. Five newest generation core shell technology columns were compared and tested against one column packed with porous particles. Two aqueous (pH 2.7 and 6.8) and two organic mobile phases were evaluated, first with the same flow and temperature and subsequently at each columns individual limit of temperature and pressure. The results demonstrated that pre-column dead volume had negligible influence on the peak capacity and shape. In contrast, a decrease in post-column volume of 57% resulted in a substantial (47%) increase in median peak capacity and significantly improved peak shape. When the various combinations of stationary and mobile phases were used at the same flow rate (0.5mL/min) and temperature (45°C), limited differences were observed between the median peak capacities, with a maximum of 26%. At higher flow though (up to 0.9mL/min), a maximum difference of almost 40% in median peak capacity was found between columns. The finally selected combination of solid-core particle column and mobile phase composition was chosen for its selectivity, peak capacity, wide applicability and peak shape. The developed method was applied to rat hepatocyte samples incubated with the drug buspirone and demonstrated to provide a similar chromatographic resolution, but a 6 times higher signal-to-noise ratio than a more traditional UHPLC metabolite profiling method using a fully porous particle packed column, within one third of the analysis time. In conclusion, a widely applicable, selective and fast chromatographic method was developed that can be applied to perform drug metabolite profiling in the timeframe of a quantitative analysis. It is envisioned that this method will in future be used for simultaneous qualitative and quantitative analysis and can therefore be considered a first important step in the Quan/Qual workflow.

Validation of high-performance liquid chromatography–tandem mass spectrometry assays for the quantification of eribulin (E7389) in various biological matrices

This paper presents specific and sensitive high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) assays for the quantification of the novel anticancer agent eribulin in human plasma, whole blood, urine and faeces. These assays, developed to support clinical pharmacological studies with the drug, quantify eribulin concentration ranges of 0.2-100ng/mL for plasma, 0.5-100 ng/mL for whole blood and urine and 0.1-25 μg/g for faeces, using sample volumes of 500 μL or 250 μg (faeces). Samples were prepared with liquid-liquid extraction, separated on a C18 column with gradient elution and analysed with a triple quadrupole MS, in positive ion mode. A structural analogue of eribulin was used as internal standard for the quantification. The assays were linear with correlation coefficients (r(2)) of 0.99 and better, whereby the deviation from nominal concentrations ranged from -8.2 to 8.9% with CV values of maximally 14.2%. Stability assessments demonstrated that eribulin is stable at -20°C in plasma, whole blood, urine and faeces for at least 38, 4, 10.5 and 5 months, respectively. In conclusion, the validation results show that the assays are specific and accurate and can therefore adequately be applied to support clinical studies of eribulin.

Bioanalytical aspects of clinical mass balance studies in oncology

Clinical mass balance studies aim to investigate the absorption, distribution, metabolism and excretion (ADME) of a(n) (often radiolabeled) drug, following a single administration to humans. They are perfectly suited to determine the disposition and major metabolic pathways of a drug, the exposure to the parent drug and its metabolites, and the rate and route of elimination. A mass balance study, however, poses interesting challenges to the analysis of parent drug and metabolites in different biological matrices. Using recent clinical mass balance studies in oncology as an example, this review focuses on the aspects of mass balance studies, from bioanalytical assay development, analysis of clinical samples to reporting of study results. Along the way, it discusses bioanalytical problems and practical solutions.

Pharmacokinetics of Etoposide after Oral and Intravenous Administration in Patients with Gastric Carcinoma

SummaryThe effects of the primary tumour in situ or of gastrectomy on the bioavailability and other pharmacokinetic parameters of etoposide, after oral administration of commercially available etoposide (Vepesid®, Bristol-Myers Squibb) capsules, were studied in 8 patients with histologically proven gastric carcinoma. The dose of etoposide was 50mg. The oral bioavailability was found to be 56 ± 14%, which was similar to values reported in other studies in patients without malignancies of the gastrointestinal tract. After intravenous and oral administration, the apparent volumes of distribution were 21.5 ± 10.4 and 27.7 ± 11.1 L/m2, respectively, the mean residence times were 9.0 ± 2.6 and 10.2 ± 2.7 hours, respectively, and the elimination half-lives were 11.8 ± 5.9 and 7.8 ± 1.7 hours, respectively. These pharmacokinetic parameters were not significantly different after intravenous and oral administration. The plasma clearance of etoposide was 21.6 ± 3.2 ml/min/m2. The bioavailability of etoposide was not significantly altered (p > 0.05) by reversing the sequence of administration, nor were the apparent volume of distribution, the mean residence time or the terminal half-life of etoposide in plasma. Although the number of patients was small, it can be concluded that the pharmacokinetic parameters of etoposide are not altered in the presence of gastric cancer or gastrectomy.

LIMITED SAMPLING MODELS FOR THE PHARMACOKINETICS OF DOCETAXEL

SummaryLimited sampling models for estimation of the docetaxel area under the plasma concentration versus time curve (AUC) and the duration above a threshold concentration of 100 µg/L (T > 100) from a limited number of plasma concentration determinations are desired for population kinetic studies. We have developed and validated models using 24 pharmacokinetic curves of patients participating in a phase II study of docetaxel (100 mg/m2) administered as a 1-hour infusion. Two models were selected as optimal: