Damien Montange

An APCI LC-MS/MS method for routine determination of capecitabine and its metabolites in human plasma

The anticancer drug capecitabine and its metabolites [including the active metabolite 5-fluorouracil (5-FU)] display high pharmacokinetic inter-patient variability. Such variability, which may lead to treatment failure or toxicity, could need drug concentration measurement to individualize dosing regimen. However, usual assay methods are often long and fastidious. A simultaneous and cost-effective method was thus developed for the determination of the concentrations of these compounds in human plasma. Compounds were extracted via a classic liquid-liquid extraction. Chromatographic analysis was performed on a C18 reverse phase column with detection by atmosphere pressure chemical ionization LC-MS/MS. Our method allows a good chromatographic separation of the compounds and was fully validated following Food and Drug Administration (FDA) recommendations (good selectivity, no carry-over, linearity of the calibration curves without weighting, deviations from nominal concentrations of standard samples lower than 15%, intra- and inter-assay precision and accuracy lower than 15%). Recovery and stability were also acceptable following the FDA guidelines. A matrix effect impairing the determination of 5-FU was avoided by using a stable isotopic derivative of 5-FU as internal standard. Interestingly, this method allows detection of TetraHydroUridine, an inhibitor of ex vivo degradation of metabolites, which is essential for the stability, the adequate conditioning of blood samples and for good laboratory practice, essential in routine determination. This method seems usable to routinely determine concentrations of capecitabine and its metabolites in blood and may be helpful in further studies aiming at performing therapeutic drug monitoring.

Impact of sunitinib pharmacokinetic monitoring in a patient with metastatic renal cell carcinoma undergoing hemodialysis

In clinical practice, physicians are confronted with the question of whether patients with terminal renal failure can be safely offered targeted drugs such as sunitinib. However, clinical trials leading to the approval have excluded these patients. We present the case of one patient requiring chronic hemodialysis and treated with escalating doses of sunitinib according to a pharmacological monitoring. The focus was on the clinical safety, pharmacokinetics assessment and the oncological outcome.

Influence of capecitabine absorption on its metabolites pharmacokinetics: a bioequivalence study

The clinical interest of capecitabine (Xeloda , Roche) administration lies in the areas of safety, quality of live, oral administration and shorter duration of hospitalisation [1, 2]. However, patients unable to swallow the tablets cannot benefit of this oral prodrug. To tackle this issue, we studied bioequivalence between crushed tablets and plain capecitabine tablets. Fourteen cancer patients were included in two arms of a randomised, single-centre intrapatient crossover phase I trial: regular commercial tablets on day 1 (1250 mg/m b.i.d.), then crushed regular commercial tablets on day 2 in the first arm and the opposite in the other arm. The administration of crushed tablets was carried out after dispersion in 40 ml of water. Eight pharmacokinetic samples were taken each morning during 6 h. Measurement of capecitabine and metabolites [5#DFCR (5#-deoxy-5-fluorocytidine), 5#-DFUR (5#-deoxy-5fluorouridine) and 5-fluorouracil (5-FU)] was carried out by HPLC with UV detection. Exposition was (AUC0–6) calculated by trapezoidal method, maximal concentration (Cmax), time to Cmax (Tmax) and apparent elimination constant (ke). Bioequivalence is defined as the relative 90% confidence interval (CI90) between 80% and 125% of the geometric mean as compared with the reference formulation [3]. A two-way analysis of variance with ‘sequence’, ‘period’, ‘treatment’ and ‘patients in treatment effects was applied to estimate the residual variance used for the calculation of CI90, whereas ke, and Tmax were compared using paired nonparametric comparisons (Wilcoxon test). High interindividual variability was observed with all compounds independent of the given galenic formulations (Figure 1). The administration of the crushed tablets resulted in statistically faster and more extensive absorption without modification of elimination process (ke) for all molecules. Interestingly, the study of individual pharmacokinetic profiles showed that the profiles of the metabolites, including 5-FU, followed that of capecitabine, indicating that its absorption is of great importance for the production and kinetics of these metabolites. Together with the variability of enzymes implied in 5-FU metabolism (thymidine synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase), this variability might suggest the potential need to perform therapeutic drug monitoring (TDM) in patients treated by capecitabine. For all compounds, bioequivalence was observed for area under the curve (AUC), but not for Cmax. For instance, the ratio between the AUC and the Cmax of the two formulations was, respectively, 101.1% (88.0% to 116.2) and 153.6% (1.093–2.159) for capecitabine and 94.6% (82.8% to 108.2) and 164.3% (119.1% to 226.7%) for 5-FU. The crushing of the regular tablets induced a faster and a more extensive absorption of capecitabine and, as previously mentioned, all metabolite pharmacokinetics are influenced by this absorption (Figure 1). Nevertheless, the AUC0–6 remained comparable and bioequivalence could be reached for this major parameter. We thus think that capecitabine crushed tablet-based treatments could be administered without dose adaptation allowing an extension of the use of capecitabine. Indeed, AUC is the main parameter used to assess and monitor toxicity, tumour response or survival [4]. Administration of crushed tablets of capecitabine can be suitable for patients unable to swallow tablets. Attention should be nevertheless paid regarding the potential need for TDM due letters to the editor Annals of Oncology

Intraperitoneal clearance as a potential biomarker of cisplatin after intraperitoneal perioperative chemotherapy: a population pharmacokinetic study

Background:Intraperitoneal (IP) perioperative chemotherapy with cisplatin is an interesting option in ovarian cancer treatment. A combination of cisplatin with IP epinephrine (already shown to improve IP and decrease systemic platinum (Pt) exposure) was evaluated using a population pharmacokinetic analysis.Methods:Data from 55 patients treated with cisplatin-based IP perioperative chemotherapy with (n=26) or without (n=29) epinephrine were analysed using NONMEM.Results:Epinephrine halves clearance between peritoneum and serum (IPCL) and increases the Pt central volume of distribution, IP exposure and penetration in tissue. IPCL has a better predictive value than any other parameter with respect to renal toxicity.Conclusion:This confirms that IPCL could be useful in assessing renal toxicity. As IPCL is also linked to tissue penetration and IP exposure, it may be proposed as biomarker. In addition to a Bayesian estimation, we propose a single-sample calculation-way to assess it. Prospective studies are needed to validate IPCL as a biomarker in this context.

Duration: escalation study of oral etoposide with carboplatin in patients with varied solid tumors.

Prolonged fractionated oral administration of etoposide may present a theoretical advantage over intravenous administration of the bolus. This phase I trial was carried out to determine the recommended duration of oral etoposide in combination with a fixed dose of carboplatin. Nineteen patients with varied solid tumors, who were not candidates for standard chemotherapy, were administered an escalating duration (6, 9 or 12 consecutive days) of oral etoposide (a 25 mg capsule three times daily) combined with carboplatin AUC5 administered on day 1, by a 30 min intravenous infusion, to define the maximum tolerated dose on the basis of the acute toxicities that were reported. Etoposide was started on day 2; the cycles repeated every 28 days until disease progression or toxicity. Pharmacokinetics was carried out during the two first cycles. The maximum tolerated dose was determined to be the 12-day treatment level, with two cases of grade 4 neutropenia, grade 3 anemia and thrombocytopenia. As no severe toxicity occurred with the 9-day treatment level and in an attempt to explore an optimal combination, a new 10-day treatment plan was studied in three patients. As one patient presented dose-limiting toxicity at that level, five additional patients were included to establish the recommended regimen. Nonhematological toxicities among all patients were moderate, consisting of grade 2 nausea and asthenia. No treatment-related death occurred. Objective responses were observed in four patients and stabilization in three patients. Pharmacokinetics highlighted no interaction between etoposide and carboplatin. Fractionated oral etoposide (3×25 mg/day) for 10 days in combination with carboplatin AUC 5 presents acceptable toxicity and efficacy. The main toxicity remains hematological.

A simple and fast HPLC-MS/MS method for simultaneous determination of direct oral anticoagulants apixaban, dabigatran, rivaroxaban in human plasma

Direct Oral Anticoagulants (DOACs) available for the treatment and prevention of thromboembolic diseases include dabigatran, a direct thrombin (IIa) inhibitor, and apixaban, edoxaban and rivaroxaban, which are direct inhibitors of Stuart factor (Xa). DOACs have a different pharmacokinetic and pharmacodynamics profiles, with less probable drug-drug interactions than vitamin K antagonists. They do not require systematic therapeutic monitoring except in specific clinical situations such as emergency procedures or drug non-compliance. Furthermore, anticoagulant effects of DOACs could be impacted by renal impairment, drug-drug interactions, food interactions, or pharmacogenetic variability. In this context, we developed a method for simultaneous determination of dabigatran, rivaroxaban and apixaban in human plasma using high performance liquid chromatography coupled with a mass spectrometry assay and applied it to 26 patient samples. Our method presents a total run time of 5 min and extends from 25 to 1000 μg/L for apixaban and dabigatran; and from 5 to 1000 μg/L for rivaroxaban. Intra- and inter-assay accuracy were between -22.3 and 25.4%; and - 23.7 and 3.8%, respectively. Precision at low and high concentrations were below 17.5%. Frozen samples were stable up to 3 months. No significant cross-contamination was observed. In conclusion, our assay can be used during clinical studies and in daily routine practice for the management of specific clinical situations at reasonable cost.

A simple and fast LC-MS/MS method with a very high sensitivity for the measurement of raltitrexed in human plasma

Raltitrexed is a thymidylate synthase inhibitor that can be administered safely to patients with cardiovascular disease or dihydropyrimidine dehydrogenase deficiency, as opposed to 5FU. The recommended dose of 3mg/m2 every 3 weeks often leads to toxicity. Interestingly, the 2mg/m2 every 2 weeks dose appears to be less toxic. A pharmacokinetic trial was then performed by our team to investigate such phenomenon. However, there are currently, two main methods for RTX measurement described in the literature: a radioimmunoassay (RIA) and chromatographic-based methods with either UV or mass spectrometry detections. The RIA methods: display a low limit of quantification (below 1μg/L), but also a low extent of linearity for the calibration curve. The chromatographic-based methods: include high level of calibrators, but have poor sensitivity (>2μg/mL). If a high sensitivity is essential to satisfactorily describe the elimination of RTX, high concentrations in the calibration curve are also needed to avoid bias linked to the dilutions of the samples. A new LC-MS/MS method was then developed that allows to simultaneously measure very low (0.1μg/L) and very high (3000μg/L) concentrations in the same run. Moreover, the extraction steps are very simple and fast with mainly a precipitation and a filtration steps. This method was validated following the EMA recommendations. In view of the extent of the calibration curve, the carry-over effect was more deeply investigated. With this method, it was possible to measure RTX in samples taken 3 weeks after the administration. Taken together, this method allows to simply and quickly measure RTX in plasma of patients.