A simple and sensitive assay for the quantitative analysis of paclitaxel and metabolites in human plasma using liquid chromatography/tandem mass spectrometry

The Quantification of Paclitaxel and Its Two Major Metabolites in Biological Samples by HPLC-MS/MS and Its Application in a Pharmacokinetic and Tumor Distribution Study in Xenograft Nude Mouse

A rapid and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the quantification of Paclitaxel (PTX), 6α-hydroxypaclitaxel (6α-OHP), and p-3'-hydroxypaclitaxel (3'-OHP) in mouse plasma and tumor tissue. The analytes were separated using a C18 column (50 × 2.1 mm, 1.8 μm), and a triple-quadrupole mass spectrometry device equipped with an electrospray ionization (ESI) source was applied for their detection. PTX, 6α-OHP, and 3'-OHP were extracted from the biological samples with the solid-phase extraction cartridge. The method was fully validated according to the FDA's guidance. The method was linear over the concentration ranges of 0.5~1000.0 ng/mL for PTX and 0.25~500.0 ng/mL for 6α-OHP and 3'-OHP. The precision, accuracy, extraction recovery, and matrix effects were within acceptable limits. The present method was successfully applied to the study of the pharmacokinetics and distribution of PTX, 6α-OHP, and 3'-OHP in the tumors of post xenograft nude mice intravenously injected with PTX solution.

Phase I study of continuous olaparib capsule dosing in combination with carboplatin and/or paclitaxel (Part 1)

Background The PARP inhibitor olaparib has shown acceptable toxicity at doses of up to 400 mg twice daily (bid; capsule formulation) with encouraging signs of antitumor activity. Based on its mode of action, olaparib may sensitize tumor cells to DNA-damaging agents. This Phase I trial (NCT00516724) evaluated the safety, pharmacokinetics (PK) and preliminary efficacy of olaparib combined with carboplatin and/or paclitaxel. Methods Patients with advanced solid tumors received olaparib (capsule bid) plus carboplatin (Part A), carboplatin and paclitaxel (Part B), or paclitaxel (Part C). In each part of the study, different drug doses were given to define the most appropriate dose/drug combination to use in further studies. Safety assessments included evaluation of dose-limiting toxicities (DLTs; cycle 1 only), adverse events (AEs) and physical examinations. PK assessments of olaparib, carboplatin and paclitaxel were performed. Tumor responses (RECIST) were assessed every two cycles. Results Fifty-seven patients received treatment. DLTs were reported in two patients (both receiving olaparib 100 mg bid and carboplatin AUC 4; Part A, cohort 2): grade 1 thrombocytopenia with grade 2 neutropenia lasting for 16 days, and grade 2 neutropenia lasting for 7 days. Non-hematologic AEs were predominantly grade 1-2 and included fatigue (70%) and nausea (40%). Bone marrow suppression, mainly neutropenia (51%) and thrombocytopenia (25%), frequently led to dose modifications. Conclusions Olaparib in combination with carboplatin and/or paclitaxel resulted in increased hematologic toxicities, making it challenging to establish a dosing regimen that could be tolerated for multiple cycles without dose modifications.

A new high-performance liquid chromatography-tandem mass spectrometry method for the determination of paclitaxel and 6α-hydroxy-paclitaxel in human plasma: Development, validation and application in a clinical pharmacokinetic study

Paclitaxel belongs to the taxanes family and it is used, alone or in multidrug regimens, for the therapy of several solid tumours, such as breast-, lung-, head and neck-, and ovarian cancer. Standard dosing of chemotherapy does not take into account the many inter-patient differences that make drug exposure highly variable, thus leading to the insurgence of severe toxicity. This is particularly true for paclitaxel considering that a relationship between haematological toxicity and plasma exposure was found. Therefore, in order to treat patients with the correct dose of paclitaxel, improving the overall benefit–risk ratio, Therapeutic Drug Monitoring is necessary. In order to quantify paclitaxel and its main metabolite, 6α-hydroxy-paclitaxel, in patients’ plasma, we developed a new, sensitive and specific HPLC–MS/MS method applicable to all paclitaxel dosages used in clinical routine. The developed method used a small volume of plasma sample and is based on quick protein precipitation. The chromatographic separation of the analytes was achieved with a SunFire^™ C18 column (3.5 μM, 92 Å, 2,1 x 150 mm); the mobile phases were 0.1% formic acid/bidistilled water and 0.1% formic acid/acetonitrile. The electrospray ionization source worked in positive ion mode and the mass spectrometer operated in selected reaction monitoring mode. Our bioanalytical method was successfully validated according to the FDA-EMA guidelines on bioanalytical method validation. The calibration curves resulted linear (R² ≥0.9948) over the concentration ranges (1–10000 ng/mL for paclitaxel and 1–1000 ng/mL for 6α-hydroxy-paclitaxel) and were characterized by a good accuracy and precision. The intra- and inter-day precision and accuracy were determined on three quality control concentrations for paclitaxel and 6α-hydroxy-paclitaxel and resulted respectively <9.9% and within 91.1–114.8%. In addition, to further verify the assay reproducibility, we tested this method by re-analysing the incurred samples. This bioanalytical method was employed with success to a genotype-guided phase Ib study of weekly paclitaxel in ovarian cancer patients treated with a wide range of drug’s dosages.

Mass spectrometry in the pharmacokinetic studies of anticancer natural products

In the history of medicine, nature has represented the main source of medical products. Indeed, the therapeutic use of plants certainly goes back to the Sumerian and Hippocrates and nowadays nature still represents the major source for new drugs discovery. Moreover, in the cancer treatment, drugs are either natural compounds or have been developed from naturally occurring parent compounds firstly isolated from plants and microbes from terrestrial and marine environment. A critical element of an anticancer drug is represented by its severe toxicities and, after administration, the drug concentrations have to remain in an appropriate range to be effective. Anyway, the drug dosage defined during the clinical studies could be inappropriate for an individual patient due to differences in drug absorption, metabolism and excretion. For this reason, personalized medicine, based on therapeutic drug monitoring (TDM), represents one of most important challenges in cancer therapy. Mass spectrometry sensitivity, specificity and fastness lead to elect this technique as the Golden Standard for pharmacokinetics and drug metabolism studies therefore for TDM. This review focuses on the mass spectrometry-based methods developed for pharmacokinetic quantification in human plasma of anticancer drugs derived from natural sources and already used in clinical practice. Particular emphasis was placed both on the pre-analytical and analytical steps, such as: sample preparation procedures, sample size required by the analysis and the limit of quantification of drugs and metabolites to give some insights on the clinical practice applicability. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:213-251, 2017.

Incorporation of concentration data below the limit of quantification in population pharmacokinetic analyses

Handling of data below the lower limit of quantification (LLOQ), below the limit of quantification (BLOQ) in population pharmacokinetic (PopPK) analyses is important for reducing bias and imprecision in parameter estimation. We aimed to evaluate whether using the concentration data below the LLOQ has superior performance over several established methods. The performance of this approach (“All data”) was evaluated and compared to other methods: “Discard,” “LLOQ/2,” and “LIKE” (likelihood-based). An analytical and residual error model was constructed on the basis of in-house analytical method validations and analyses from literature, with additional included variability to account for model misspecification. Simulation analyses were performed for various levels of BLOQ, several structural PopPK models, and additional influences. Performance was evaluated by relative root mean squared error (RMSE), and run success for the various BLOQ approaches. Performance was also evaluated for a real PopPK data set. For all PopPK models and levels of censoring, RMSE values were lowest using “All data.” Performance of the “LIKE” method was better than the “LLOQ/2” or “Discard” method. Differences between all methods were small at the lowest level of BLOQ censoring. “LIKE” method resulted in low successful minimization (<50%) and covariance step success (<30%), although estimates were obtained in most runs (∼90%). For the real PK data set (7.4% BLOQ), similar parameter estimates were obtained using all methods. Incorporation of BLOQ concentrations showed superior performance in terms of bias and precision over established BLOQ methods, and shown to be feasible in a real PopPK analysis.

Quantification of taxanes in biological matrices: a review of bioanalytical assays and recommendations for development of new assays

Since the isolation of paclitaxel and its approval for the treatment of breast cancer, various taxanes and taxane formulations have been developed. To date, almost 100 bioanalytical assays have been published with the method development and optimization often extensively discussed by the authors. This Review presents an overview of assays published between January 1970 and September 2013 that described method development and validation of assays used to quantify taxanes in biological matrices such as plasma, urine, feces and tissue samples. For liquid chromatography assays, sample pretreatment, chromatographic separation and assay performance are compared. Since this Review discusses the limitations of previously developed liquid chromatography assays and gives recommendations for future assay development, it can be used as a reference for future development of liquid chromatography assays for the quantification of taxanes in various biological matrices to support preclinical and clinical studies.

A rapid analytical method for the quantification of paclitaxel in rat plasma and brain tissue by high-performance liquid chromatography and tandem mass spectrometry

RATIONALE

Paclitaxel, an antitumor agent for the treatment of several types of cancers, has recently been reported to cause impaired cognitive function and neuropathic pain in humans. To assess the effects of paclitaxel on the central nervous system, a sensitive and accurate method is required to quantify paclitaxel concentrations in plasma and brain tissue obtained from rodents receiving paclitaxel.

METHODS

The biological samples were prepared by liquid-liquid extraction and separated by a 3.5 min reversed-phase liquid chromatography (RPLC) method using a BDS Hypersil C8 column under isocratic conditions. Paclitaxel was quantified using multiple reaction monitoring (MRM) with a triple quadrupole tandem mass spectrometer working in the positive electrospray ionization (ESI+) mode. A stable isotope labeled analogue of paclitaxel was used as the internal standard (IS).

RESULTS

The method was validated to be precise and accurate within the dynamic range of 0.5-100 ng/mL based on 100 μL plasma and 1.5-300 ng/g based on 33 mg of brain tissue in homogenate. This method was applied to samples from 2 mg/kg intravenously dosed rats. The plasma concentrations were observed to be 26.62 ± 8.93 ng/mL and brain concentrations 11.08 ± 4.18 ng/g when measured 4 h post-dose.

CONCLUSIONS

This rapid LC/MS/MS method was validated to be sensitive, specific, precise and accurate for the quantification of paclitaxel in rat plasma and brain tissue homogenate. Application of the method to study samples provided sufficient proof of blood-brain barrier penetration of paclitaxel, allowing further investigation of its influence on the central nervous system.

Competitive mass spectrometry binding assay for characterization of three binding sites of tubulin

Tubulin is an attractive and established target for anticancer therapy. To date, the only method to determine the binding of inhibitor to tubulin has been competitive radioligand binding assays. We developed a non-radioactive mass spectrometry (MS) binding assay to study the tubulin binding of colchicine, vinblastine and paclitaxel and to identify which of these three binding sites that a novel inhibitor binds. The method involves a very simple step of separating the unbound ligand from macromolecules using ultrafiltration. The unbound ligand in the filtrate can be accurately determined using highly sensitive and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) method using multiple reaction monitoring (MRM) mode. The assay was validated using podophyllotoxin, vincristine and docetaxel, drugs that compete to the colchicine-, vinblastine- and paclitaxel-binding sites in tubulin, respectively. This competitive binding assay allowed the reliable detection of interactions of these drugs with three binding sites on tubulin. This method was subsequently applied to determine the tubulin-binding site of 4-substituted methoxylbenzoyl-aryl-thiazoles (SMART-H), a potent antitubulin agent developed in our laboratory. The results indicated that SMART-H specifically and reversibly bound only to the colchicine-binding site, but not to vinblastine- or paclitaxel sites. This new non-radioligand binding method to determine the binding site on tubulin will function as a useful tool to study the binding sites of tubulin inhibitors.

Pharmacokinetic/pharmacodynamic modeling and simulation of neutropenia during phase I development of liposome-entrapped paclitaxel

PURPOSE

To evaluate the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), and pharmacokinetics of liposome-entrapped paclitaxel easy-to-use (LEP-ETU) and to characterize the relationship between LEP-ETU concentrations and the time course of neutropenia in cancer patients.

EXPERIMENTAL DESIGN

LEP-ETU was administered to 88 patients and 63 were evaluable for pharmacokinetic/pharmacodynamic (PK/PD) analysis following 1.5- and 3-h infusions every 3 weeks (q3w; dose range, 135-375 mg/m(2)). MTD was identified using a 3 + 3, up-and-down dose-finding algorithm. PK/PD modeling was done to describe the temporal relationship between paclitaxel concentrations and neutrophil count. Simulations assessed the influence of dose and schedule on neutropenia severity to help guide dose selection.

RESULTS

The MTD of LEP-ETU was identified as 325 mg/m(2). DLTs occurring at 375 mg/m(2) consisted of febrile neutropenia and neuropathy. The C(max) and area under the plasma concentration-time curve of LEP-ETU were less than proportional with increasing dose. The PK/PD model showed that LEP-ETU inhibition of neutrophil proliferation was 9.1% per 10 mug/mL of total paclitaxel concentration. The incidence of grade 4 neutropenia increased from 33% to 42% across the dose range of 275 to 325 mg/m(2) q3w. For a dose of 110 mg/m(2) given weekly, grade 4 neutropenia was estimated to be 16% compared with 42% for the same total dose administered q3w.

CONCLUSIONS

LEP-ETU can be administered safely at higher doses than Taxol. Modeling and simulation studies predict that 325 mg/m(2) LEP-ETU q3w provides acceptable neutropenic events relative to those observed at 175 mg/m(2) Taxol q3w. A 275 mg/m(2) dose may offer an improved therapeutic index.

A sensitive assay for the quantitative analysis of vinorelbine in mouse and human EDTA plasma by high-performance liquid chromatography coupled with electrospray tandem mass spectrometry

A sensitive, specific and fast high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) assay for the determination of vinorelbine in mouse and human plasma is presented. A 200 microL aliquot was extracted with solid-phase extraction (SPE) using Bond-Elut C(2) cartridges. Dried extracts were reconstituted in 100 microL 1 mM ammonium acetate pH 10.5-acetonitrile-methanol (21:9:70, v/v/v) containing the internal standard vintriptol (100 ng/mL) and 10 microL volumes were injected onto the HPLC system. Separation was achieved on a 50 mm x 2.0 mm i.d. Gemini C(18) column using isocratic elution with 1 mM ammonium acetate pH 10.5-acetonitrile-methanol (21:9:70, v/v/v) at a flow rate of 0.4 mL/min. HPLC run time was only 5 min. Detection was performed using positive ion electrospray ionization followed by tandem mass spectrometry (ESI-MS/MS). The assay quantifies vinorelbine from 0.1 to 100 ng/mL using human plasma sample volumes of 200 microL. With this method vinorelbine can be measured in mouse plasma samples when these samples are diluted eight times in control human plasma. Calibration samples prepared in control human plasma can be used for the quantification of the drug. The lower limit of quantification in mouse plasma is 0.8 ng/mL. This assay is used to support preclinical and clinical pharmacologic studies with vinorelbine.

Novel paclitaxel formulations for oral application: a phase I pharmacokinetic study in patients with solid tumours

PURPOSE

To explore the pharmacokinetics (PKs) of paclitaxel and two major metabolites after three single oral administrations of a novel drinking solution and two capsule formulations in combination with cyclosporin A (CsA) in patients with advanced cancer. Moreover, the tolerability and safety of the formulations was studied. In addition, single nucleotide polymorphisms in the multidrug resistance (MDR1) gene were determined.

PATIENTS AND METHODS

Ten patients were enrolled and randomized to receive CsA 10 mg/kg followed by oral paclitaxel 180 mg given as (1) drinking solution (formulation 1), (2) capsule formulation 2B, and (3) capsule formulation 2C on day 1, 8, or 15.

RESULTS

The median C (max) of paclitaxel was 0.42 (0.23-0.96), 0.48 (0.08-0.59), and 0.39 (0.11-1.03) microg/ml and the area under the plasma concentration-time curve was 2.83 (1.69-5.12), 2.01 (1.57-3.04), and 2.67 (1.05-3.61) mug h/ml following administration of formulations 1, 2B, and 2C, respectively. The novel formulations were tolerated after single oral dose without causing relevant gastrointestinal or haematological toxicity.

CONCLUSIONS

The PK and metabolism of paclitaxel were comparable between the oral formulations co-administered with CsA.

Multidrug resistance protein 2 is an important determinant of paclitaxel pharmacokinetics

PURPOSE

P-glycoprotein (P-gp; ABCB1) efficiently transports lipophilic amphipathic drugs, including the widely used anticancer drug paclitaxel (Taxol). We found previously that human multidrug resistance protein 2 (MRP2; ABCC2) also transports paclitaxel in vitro, and although we expected that paclitaxel pharmacokinetics would be dominated by P-gp, the effect of Mrp2 was tested in vivo.

EXPERIMENTAL DESIGN

We generated and characterized Mdr1a/1b/Mrp2(-/-) mice, allowing assessment of the distinct roles of Mrp2 and Mdr1a/1b P-gp in paclitaxel pharmacokinetics.

RESULTS

Surprisingly, the effect of Mrp2 on i.v. administration of paclitaxel was as great as that of P-gp. The area under plasma concentration-time curve (AUC)i.v. in both Mrp2(-/-) and Mdr1a/1b(-/-) mice was 1.3-fold higher than in wild-type mice, and in Mdr1a/1b/Mrp2(-/-) mice, a 1.7-fold increase was found. In spite of this similar effect, Mrp2 and P-gp had mostly complementary functions in paclitaxel elimination. Mrp2 dominated the hepatobiliary excretion, which was reduced by 80% in Mrp2(-/-) mice. In contrast, P-gp dominated the direct intestinal excretion, with a minor role for Mrp2. The AUCoral of paclitaxel was 8.5-fold increased by Mdr1a/1b deficiency but not affected by Mrp2 deficiency. However, in the absence of Mdr1a/1b P-gp, additional Mrp2 deficiency increased the AUCoral another 1.7-fold.

CONCLUSIONS

Thus far, Mrp2 was thought to mainly affect organic anionic drugs in vivo. Our data show that Mrp2 can also be a major determinant of the pharmacokinetic behavior of highly lipophilic anticancer drugs, even in the presence of other efficient transporters. Variation in MRP2 activity might thus directly affect the effective exposure to paclitaxel, on i.v. administration, but also on oral administration, especially when P-gp activity is inhibited.

A novel self-microemulsifying formulation of paclitaxel for oral administration to patients with advanced cancer

To explore the parmacokinetics, safety and tolerability of paclitaxel after oral administration of SMEOF#3, a novel Self-Microemulsifying Oily Formulation, in combination with cyclosporin A (CsA) in patients with advanced cancer. Seven patients were enrolled and randomly assigned to receive oral paclitaxel (SMEOF#3) 160 mg+CsA 700 mg on day 1, followed by oral paclitaxel (Taxol®) 160 mg+CsA 700 mg on day 8 (group I) or vice versa (group II). Patients received paclitaxel (Taxol®) 160 mg as 3-h infusion on day 15. The median (range) area under the plasma concentration–time curve of paclitaxel was 2.06 (1.15–3.47) μg h ml⁻¹ and 1.97 (0.58–3.22) μg h ml⁻¹ after oral administration of SMEOF#3 and Taxol®, respectively, and 4.69 (3.90–6.09) μg h ml⁻¹ after intravenous Taxol®. Oral SMEOF#3 resulted in a lower median T_max of 2.0 (0.5–2.0) h than orally applied Taxol® (T_max=4.0 (0.8–6.1) h, P=0.02). The median apparent bioavailability of paclitaxel was 40 (19–83)% and 55 (9–70)% for the oral SMEOF#3 and oral Taxol® formulation, respectively. Oral paclitaxel administered as SMEOF#3 or Taxol® was safe and well tolerated by the patients. Remarkably, the SMEOF#3 formulation resulted in a significantly lower T_max than orally applied Taxol®, probably due to the excipients in the SMEOF#3 formulation resulting in a higher absorption rate of paclitaxel.

A pharmacokinetic and safety study of a novel polymeric paclitaxel formulation for oral application

PURPOSE

To investigate the pharmacokinetics, safety, and tolerability of a new oral formulation of paclitaxel containing the polymer polyvinyl acetate phthalate in patients with advanced solid tumors.

PATIENTS AND METHODS

A total of six patients received oral paclitaxel as single agent given as a single dose of 100 mg on day 1, oral paclitaxel 100 mg in combination with cyclosporin A (CsA) 10 mg/kg both given as a single dose on day 8, and i.v. paclitaxel (Taxol) 100 mg as a 3-h infusion on day 15.

RESULTS

The AUC (mean +/- standard deviation) values of paclitaxel after oral administration without CsA and with CsA were 476 +/- 254 and 967 +/- 779 ng/ml h, respectively. T (max) was 4.0 +/- 0.9 h after oral paclitaxel without CsA, and 6.0 +/- 3.1 h after oral paclitaxel with CsA. The mean AUC after oral administration as single agent was 13% of the AUC after i.v. administration of paclitaxel, and increased to 26% after co-administration with CsA. No haematological toxicities were observed, and only mild (CTC-grade 1 and 2) non-hematological toxicities occurred after oral intake of paclitaxel with or without CsA.

CONCLUSION

The AUC of the new polymeric paclitaxel formulation increased a factor 2 in combination with CsA, which confirms that CsA co-administration can also improve exposure to paclitaxel after oral administration of a polymeric formulation. Because of the delayed release of paclitaxel from this formulation, we hypothesize that a split-dose regimen of CsA where it is administered before and after paclitaxel administration will further increase the systemic exposure to paclitaxel up to therapeutic levels. The formulation was well tolerated at the dose of 100 mg without induction of severe toxicities.

A simple and sensitive assay for the quantitative analysis of rivastigmine and its metabolite NAP 226-90 in human EDTA plasma using coupled liquid chromatography and tandem mass spectrometry

A sensitive and specific high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) assay for the determination of rivastigmine and its major metabolite NAP 226-90 is presented. A 100 microL plasma aliquot was spiked with a structural analogue of rivastigmine as internal standard (PKF214-976-AE-1) and proteins were precipitated by adding 200 microL of methanol. After centrifugation a volume of 100 microL of the clear supernatant was mixed with 100 microL of methanol/water (30:70, v/v) and volumes of 25 microL were injected onto the HPLC system. Separation was acquired on a 150 x 2.0 mm i.d. Gemini C18 column using a gradient system with 10 mM ammonium hydroxide and methanol. Detection was performed by using a turboionspray interface and positive ion multiple reaction monitoring by tandem mass spectrometry. The assay quantifies rivastigmine from 0.25 to 50 ng/mL and its metabolite NAP 226-90 from 0.50 to 25 ng/mL, using human plasma samples of 100 microL. Validation results demonstrate that rivastigmine and metabolite concentrations can be accurately and precisely quantified in human EDTA plasma. This assay is now used to support clinical pharmacologic studies with rivastigmine.

Determination of paclitaxel in human plasma following the administration of Genaxol or Genetaxyl by liquid chromatography/tandem mass spectrometry

A sensitive and specific assay for paclitaxel in plasma has been developed to overcome limitations in previously published assays, using liquid chromatography with tandem mass spectrometric detection. Plasma samples (100 microL) were subjected to liquid-liquid extraction with 1-chlorobutane/acetonitrile (4:1, v/v), with [(2)H(5)]paclitaxel employed as the internal standard. Chromatography was carried out with a Waters SymmetryShield C8 column (50 x 2.1 mm, 3.5 microm). The total run time, including equilibration, was 8 min, using a gradient of acetonitrile and 10 mM ammonium formate, pH 4.0. The assay is accurate and precise over the range of 2-2500 ng/mL and has been successfully applied to study the clinical pharmacokinetics of two formulations of paclitaxel, Genaxol and Genetaxyl, given orally and intravenously.