Assay for etoposide in human serum using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

Target specific intracellular quantification of etoposide by quadrupole-time of flight based mass spectrometric method

Etoposide (ETP), a widely used chemotherapeutic agent has an intracellular target site of action. Unfortunately, the concentration of ETP in plasma does not properly reflect the concentration in its intracellular site of action. As per our knowledge, no reported bioanalytical method is available for intracellular quantification of ETP. In this research, we developed an LC-MS/MS method to quantitate ETP in intracellular compartments of MCF-7 cells. The Abcam nuclear extraction kit was used for extracting the nuclear and cytosolic protein from MCF-7 cells. The method showed excellent linearity in the 20-1000 ng/mL range. The intra and inter-day precision (%CV) including LLOQ were found to be in the range of 2.19-16.96% and 6.71-11.21%, respectively, with an accuracy of 86.87 to 110.37% and 93.03 to 100.50%, respectively. The concentration of ETP in nuclear and cytosolic fraction was successfully quantitated using the developed method. The developed method can be applied to understand the efficacy of different formulations based on the intracellular ETP concentration in vitro. It can be considered as a model method for quantification of other similar categories of drugs in their actual intracellular site of action after required optimization in the methodology.

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.

pH-responsive polymer-drug conjugates as multifunctional micelles for cancer-drug delivery

We developed a novel linear pH-sensitive conjugate methoxy poly(ethylene glycol)-4β-aminopodophyllotoxin (mPEG-NPOD-I) by a covalently linked 4β-aminopodophyllotoxin (NPOD) and PEG via imine bond, which was amphiphilic and self-assembled to micelles in an aqueous solution. The mPEG-NPOD-I micelles simultaneously served as an anticancer drug conjugate and as drug carriers. As a drug conjugate, mPEG-NPOD-I showed a significantly faster NPOD release at a mildly acidic pH of 5.0 and 4.0 than a physiological pH of 7.4. Notably, it was confirmed that this drug conjugate could efficiently deliver NPOD to the nuclei of the tumor cells and led to much more cytotoxic effects to A549, Hela, and HepG2 cancer cells than the parent NPOD. The half maximal inhibitory concentration (IC₅₀) of mPEG-NPOD-I was about one order magnitude lower than that of the NPOD. In vivo, mPEG-NPOD-I reduced the size of the tumors significantly, and the biodistribution studies indicated that this drug conjugate could selectively accumulate in tumor tissues. As drug carriers, the mPEG-NPOD-I micelles encapsulated hydrophobic PTX with drug-loading efficiencies of 57% and drug-loading content of 16%. The loaded PTX also showed pH-triggered fast release behavior, and good additive cytotoxicity effect was observed for the PEG-NPOD-I/PTX. We are convinced that these multifunctional drug conjugate micelles have tremendous potential for targeted cancer therapy.

Carbon nanotubes enhance the internalization of drugs by cancer cells and decrease their chemoresistance to cytostatics

Etoposide is a semisynthetic, chemotherapeutic drug widely recommended to treat an extensive range of human cancers. Our studies indicate that, while etoposide is capable of killing human cancer cells, exposure to single-walled carbon nanotubes (SWCNTs) and etoposide results in enhanced cell death that appears to be synergistic and not merely additive. In this study, we used high pressure liquid chromatography and mass spectrometry to quantify the internal effective dose of etoposide when the human pancreatic cancer cell (PANC-1) was exposed to the combination of these agents. Our results unequivocally indicate that SWCNTs improve etoposide uptake and increase its capacity to kill cancer cells. We suggest that a combination of SWCNTs and etoposide may prove to be a more efficient chemotherapeutic protocol, especially because of the potential to lower toxic drug doses to levels that may be useful in decreasing adverse side effects, as well as in lowering the probability of inducing chemoresistance in exposed cancer cells.

Clinical pharmacology of etoposide in children undergoing autologous stem cell transplantation for various solid tumours

1. The population pharmacokinetics of high-dose etoposide was studied in a group of young children and adolescents. 2. Twenty-six children and adolescent were administered high-dose etoposide as a continuous infusion over 24 h. Etoposide plasma concentration-time data was modelled using NONMEM® 7. The effect of age, weight, serum creatinine (SCr), and gender on pharmacokinetic parameters (CL and V(d)) were determined by a nonlinear mixed effect model. 3. The pharmacokinetics of etoposide based on BSA dosing was best described with a 1-compartment structural model which was parameterised in terms of clearance (CL) and volume of distribution (V(d)). An exponential error model was used to explain intersubject variability and a proportional error model was used to describe residual or intrapatient variability. The final model parameter estimates for the typical (normalised to 70 kg) values of CL and V(d) were 2.31 L/hr and 17.5 L, respectively. The CL and V(d) allometrically increased with weight with the power of 3/4 and 1, respectively. After accounting for weight dependence using the allometric scaling, age, serum creatinine, and gender did not have any influence on model parameters. 4. The results of this children and adolescent population pharmacokinetic study indicates that etoposide pharmacokinetics were influenced by body weight on an allometric basis. The pharmacokinetic parameters CL and V(d) increased with increasing weight similar to BSA.

A validated stability-indicating LC method for estimation of etoposide in bulk and optimized self-nano emulsifying formulation: Kinetics and stability effects

The present investigation was aimed to establish a validated stability-indicating liquid chromatographic method for the estimation of etoposide (ETP) in bulk drug and self-nano emulsifying formulation. ETP was successfully separated from the degradation products formed under stress conditions on LiChrospher 100 C18 reverse-phase column (a 250 mm × 4.6 mm i.d., 5-μm particle size) using 55:45 (v/v) acetonitrile-phosphate buffer saline (pH 4.5) as the mobile phase, at a flow rate of 1.0 mL min(-1) and detection at 283 nm. The response was a linear function of analyte concentration (R(2) > 0.9997) over the concentration range of 0.05-50 μg mL(-1). The method was validated for precision, accuracy, robustness, sensitivity and specificity. The % recovery of ETP at three different levels (50%, 100% and 150%) ranged between 93.84% and 100.06% in optimized self-nano emulsifying formulation, Etosid® soft-gelatin capsule and Fytosid® injection. First-order degradation kinetics of ETP were observed under acidic and alkaline conditions. The method was also applied for the stability assessment of self-nano emulsifying formulation under accelerated conditions, the formulation was found to be stable at all storage conditions with the shelf-life of 2.37 years at 25 °C. The method holds promise for routine quality control of ETP in bulk, pharmaceutical formulations as well as in stability-indicating studies.

Electrochemical Study of the Antineoplastic Agent Etoposide at Carbon Paste Electrode and Its Determination in Spiked Human Serum by Differential Pulse Voltammetry

The electrochemical oxidation of the antineoplastic agent etoposide was studied at carbon paste electrode in Britton-Robinson buffer solutions over the pH range 2.0-10.0 using cyclic, linear sweep and differential pulse voltammetry. Oxidation of the drug was effected in a single reversible, diffusion-controlled step within the pH range 2.0-4.0, a second oxidation process was produced above pH 4.0. Using differential pulse voltammetry (DPV), the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 3.0 at 0.500 V (vs. Ag/AgCl) on carbon paste electrode. This process could be used to determine etoposide concentrations in the range 2.5 x 10(-7) to 2.5 x 10(-5) M with a detection limit of 1.0 x 10(-7) M. The method was successfully applied to the determination of the drug in spiked human serum.

Effects of morin on the pharmacokinetics of etoposide in rats

This study investigated the effects of orally administered morin, an inhibitor of CYP isozyme and P-glycoprotein (P-gp), on the pharmacokinetics of intravenous and orally administered etoposide in rats. It was reported that etoposide is a substrate for P-gp and metabolized mainly via CYP3A4 and to a lesser degree via CYP1A2 and 2E1. Etoposide was administered through intravenous (2 mg/kg) or oral (6 mg/kg) routes to rats with or without orally administered morin (5 or 15 mg/kg), which was administered 30 min before etoposide. The pharmacokinetic parameters of etoposide intravenously administered were not significantly different from other groups, suggesting that CYP 3A-mediated metabolism and the P-gp mediated efflux of etoposide in the liver and kidney seemed not to be markedly inhibited by orally administered morin. However, orally administered morin (15 mg/kg) significantly increased the AUC (45.8%), C(max) (32.0%) and the absolute bioavailability (35.9%) of orally administered etoposide compared with the control, which could be mainly due to inhibition of CYP isoenzyme and P-gp in the intestine by morin. The dosage regimen of etoposide should be taken into consideration for toxic reactions when combined with morin or dietary supplements containing morin in patients.

Quantification of Etoposide and Etoposide Phosphate in Human Plasma by Micellar Electrokinetic Chromatography and Near-Field Thermal Lens Detection

A method employing micellar electrokinetic chromatography in combination with near-field thermal lens detection (NF-TLD) was developed for the rapid simultaneous determination of etoposide phosphate and etoposide in human blood plasma, taking teniposide as internal standard. The method developed allows the baseline separation of the solutes of interest from each other and from potential interfering matrix constituents within 4 min. The NF-TLD device employed permits detection of solutes absorbing electromagnetic radiation at lambda = 257 nm in fused-silica capillaries with 75-microm i.d. via the near-field thermal lens effect with LODs of 100 microg L(-1) for etoposide phosphate and 170 microg L(-1) for etoposide. Comparison of the performance of this detector to the performance of a commercial absorption spectrometric detector working at lambda = 257 nm showed a substantial improvement in detection limits (up to 60-fold improvement) for the near-field thermal lens detector.

Mitoxantrone, etoposide, and cytarabine with or without valspodar in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome: a phase III trial (E2995)

PURPOSE

To determine whether adding the multidrug resistance gene-1 (MDR-1) modulator valspodar (PSC 833; Novartis Pharmaceuticals, Hanover, NJ) to chemotherapy provided clinical benefit to patients with poor-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS).

PATIENTS AND METHODS

A phase III randomized study was performed using valspodar plus mitoxantrone, etoposide, and cytarabine (PSC-MEC; n=66) versus MEC (n=63) to treat patients with relapsed or refractory AML and high-risk MDS.

RESULTS

For the PSC-MEC versus MEC arms, complete response (CR) was achieved in 17% versus 25% of patients, respectively (P=not significant). For patients who had not received prior intensive chemotherapy (ie, with secondary AML or high-risk MDS), the CR rate was increased--35% versus 15% for the remaining patients (P=.018); CR rates did not differ between treatment arms. The median disease-free survival in those achieving CR was similar in the two arms (10 versus 9.3 months) as was the patients' overall survival (4.6 versus 5.4 months). The CR rates in MDR+ (69% of patients) versus MDR- patients were similar for those receiving either chemotherapy regimen (16% versus 24%). The CR rate for unfavorable cytogenetic patients (45% of patients) was 13% compared to the remainder, 28% (P=.09). Population pharmacokinetic analysis demonstrated that the clearances of mitoxantrone and etoposide were decreased by 59% and 50%, respectively, supporting the empiric dose reductions in the PSC-MEC arm designed in anticipation of drug interactions between valspodar and the chemotherapeutic agents.

CONCLUSION

CR rates and overall survival were not improved by using PSC-MEC compared to MEC chemotherapy alone in patients with poor-risk AML or high-risk MDS.

High-performance liquid chromatographic methods for the determination of topoisomerase II inhibitors

Various methods for separating eleven different types of topoisomerase II (TOPO-2) inhibitors, including epipodophyllotoxins, anthracyclines, anthracenediones, anthrapyrazoles, anthracenebishydrazones, indole derivatives, aminoacridines, benzisoquinolinediones, isoflavones, bisdioxopiperazines and thiobarbituric acids, are summarized. Proper sample preparation and storage is critical to the successful analysis of some TOPO-2 inhibitors due to difficulties associated with adsorption, instability and complex biological components. Solid-phase and liquid-liquid extractions are widely used to separate TOPO-2 inhibitors from biological samples, although simple deproteinization followed by direct analysis of the supernatant is preferable to extraction based on its speed and simplicity. High-performance liquid chromatography (HPLC) is the favored method for the bioanalysis of TOPO-2 inhibitors. UV or diode array detection is generally employed for early pharmacokinetic studies, while fluorescence or electrochemical detection is used more frequently for analytes with fluorescent or oxidative-reductive properties. For analyses requiring highly sensitive and/or specific detection, electrospray mass spectrometry (ESI-MS or ESI-MS-MS) provides a suitable alternative. A comprehensive compilation of the HPLC techniques currently used to separate TOPO-2 inhibitors will aid the future development of analytical methods for new TOPO-2 inhibitors.

Analytical approaches for traditional chinese medicines exhibiting antineoplastic activity

Traditional Chinese medicines have attracted great interest in recent researchers as alternative antineoplastic therapies. This review focuses on analytical approaches to various aspects of the antineoplastic ingredients of traditional Chinese medicines. Emphasis will be put on the processes of biological sample extraction, separation, clean-up steps and the detection. The problems of the extraction solvent selection and different types of column chromatography are also discussed. The instruments considered are gas chromatography, capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) connected with various detectors (ultraviolet, fluorescence, electrochemistry, mass, etc.). In addition, determinations of antineoplastic herbal ingredients, including camptothecin, taxol (paclitaxel), vinblastine. vincristine, podophyllotoxin, colchicine, and their related compounds, such as irinotecan, SN-38, topotecan, 9-aminocamptothecin, docetaxel (taxotere) and etoposide, are briefly summarized. These drugs are structurally based on the herbal ingredients, and some of them are in trials for clinical use. Evaluation of potential antineoplastic herbal ingredients, such as harringtonine, berberine, emodin, genistein, berbamine, daphnoretin, and irisquinone, are currently investigated in laboratories. Other folk medicines are excluded from this paper because their antineoplastic ingredients are unknown.

Simultaneous determination of etoposide and its catechol metabolite in the plasma of pediatric patients by liquid chromatography/tandem mass spectrometry

The anticancer drug etoposide is associated with leukemias with MLL gene translocations and other translocations as a treatment complication. The genotype of cytochrome P450 3A4 (CYP3A4), which converts etoposide to its catechol metabolite, influences the risk. In order to perform pharmacokinetic studies aimed at further elucidation of the translocation mechanism, we have developed and validated a liquid chromatography/electrospray/tandem mass spectrometry assay for the simultaneous analysis of etoposide and its catechol metabolite in human plasma. The etoposide analog teniposide was used as the internal standard. Liquid chromatography was performed on a YMC ODS-AQ column. Simultaneous determination of etoposide and its catechol metabolite was achieved using a small volume of plasma, so that the method is suitable for pediatric patients. The limits of detection were 200 ng ml(-1) etoposide and 10 ng ml(-1) catechol metabolite in human plasma and 25 ng ml(-1) etoposide and 2.5 ng ml(-1) catechol metabolite in protein-free plasma, respectively. Acceptable precision and accuracy were obtained for concentrations in the calibration curve ranges 0.2--100 microg ml(-1) etoposide and 10--5000 ng ml(-1) catechol metabolite in human plasma. Acceptable precision and accuracy for protein-free human plasma in the range 25--15 000 ng ml(-1) etoposide and 2.5--1500 ng ml(-1) etoposide catechol were also achieved. This method was selective and sensitive enough for the simultaneous quantitation of etoposide and its catechol as a total and protein-free fraction in small plasma volumes from pediatric cancer patients receiving etoposide chemotherapy. A pharmacokinetic model has been developed for future studies in large populations.