Effect of Moderate Malnutrition on the Pharmacokinetics of Etoposide and Vincristine in Freshly Weaned Rats

BACKGROUND

Moderate malnutrition is a common problem in young children. It is observed that severe malnutrition affects the pharmacokinetics of chemotherapy drugs in pediatric cancer patients, but moderate malnutrition is not well studied in this context.

OBJECTIVES

In this study, we aimed to understand how moderate malnutrition affects the pharmacokinetics of two chemotherapy drugs, etoposide and vincristine, using a murine model of early age moderate malnutrition.

METHODS

We developed a murine model of moderate childhood malnutrition by subjecting freshly weaned Sprague-Dawley rats to 8% protein diet for 8 weeks. In two separate experiments, we administered etoposide and vincristine (N = 8 for etoposide and N = 12 for vincristine each in protein deficient and control groups) through tail vein injection for pharmacokinetics study.

RESULTS

We found ~ 60% increase in area under the concentration-time curve (AUC) of etoposide in malnourished animals as compared to well-nourished animals. Furthermore, clearance, volume of distribution, and half-life were decreased by ~ 37, 53, and 24%, respectively, in malnourished animals. Pharmacokinetic parameters of vincristine showed only marginal differences between well-nourished and malnourished groups.

CONCLUSIONS

Our results suggest that while moderate malnutrition significantly affects the pharmacokinetics of etoposide, pharmacokinetics of vincristine remain unchanged. Since chemotherapy drugs have a narrow therapeutic index, the difference in AUC observed in our study might explain the increased toxicity of etoposide in malnourished pediatric cancer patients. This brings forth a need for robust clinical studies to validate our findings and optimize dose for malnourished patients.

Comparison of ocular pharmacokinetics of etoposide and its nanoemulsion after subtenon administration in rabbits

Background Subtenon anticancer drugs are given as an adjunct to systemic chemotherapy for conditions like retinoblatoma. This study evaluated the ocular kinetics of nano-emulsion formulation of etoposide (NanoEt) and compared it with an equal dose of commercially available alcohol-based etoposide formulation in healthy rabbits. Methods A nanoemulsion formulation of NanoEt was developed and then evaluated for its ocular kinetics by subtenon administration in healthy rabbits. After the sterile subtenon administration of the drug, the eyes were enucleated after CO2 euthanasia at time intervals of 2 h, 6 h, 12 h, and 24 h, and ocular tissues, blood, and plasma were separated. The concentration of etoposide in the ocular tissues and blood was quantified using liquid chromatography tandem mass spectrometry (LC MS/MS). Results This study found that subtenon injection of NanoEt showed 24 times higher concentration in rabbit retina compared to an equal dose of conventional marketed formulation. Based on the ocular tissue bioavailability calculations (AUC0-24), the present study revealed that the formulation enhanced 90% ocular bioavailability of etoposide, when it was injected in the form of nano-emulsion in most of the tissues. Conclusions NanoEt has better bioavailability compared to the commercial alcohol-based formulation for subtenon injection. Low systemic exposure showed further advantage for its projected use in retinoblastoma (Rb) as an adjunct therapy. Further studies in Rb animal models are required to evaluate its safety and efficacy, for its clinical utility.

Deazaflavin Inhibitors of TDP2 with Cellular Activity Can Affect Etoposide Influx and/or Efflux

Tyrosyl DNA phosphodiesterase 2 (TDP2) facilitates the repair of topoisomerase II (TOP2)-linked DNA double-strand breaks and, as a consequence, is required for cellular resistance to TOP2 "poisons". Recently, a deazaflavin series of compounds were identified as potent inhibitors of TDP2, in vitro. Here, however, we show that while some deazaflavins can induce cellular sensitivity to the TOP2 poison etoposide, they do so independently of TDP2 status. Consistent with this, both the cellular level of etoposide-induced TOP2 cleavage complexes and the intracellular concentration of etoposide was increased by incubation with deazaflavin, suggesting an impact of these compounds on etoposide uptake/efflux. In addition, deazaflavin failed to increase the level of TOP2 cleavage complexes or sensitivity induced by m-AMSA, which is a different class of TOP2 poison to which TDP2-defective cells are also sensitive. In conclusion, while deazaflavins are potent inhibitors of TDP2 in vitro, their limited cell permeability and likely interference with etoposide influx/efflux limits their utility in cells.

Octreotide-Conjugated Core-Cross-Linked Micelles with pH/Redox Responsivity Loaded with Etoposide for Neuroendocrine Neoplasms Therapy and Bioimaging with Photoquenching Resistance

The study of multifunctional polymer micelles combined with chemotherapy due to reduced systemic toxicity and enhanced efficacy has attracted intensive attention. Herein, a multifunctional core-cross-linked hybrid micelle system based on mPEG- b-PGu(BA-TPE) and OCT-PEG- b-PGu(DA-TPE) with pH- and redox-triggered drug release and aggregation-induced emission (AIE) active imaging has been developed for active targeting of neuroendocrine neoplasms (NENs), especially neuroendocrine carcinomas (NECs) with poor prognosis. These micelles showed excellent biocompatibility and stability. After the formation of borate ester bonds, core-cross-linked micelles (CCLMs) showed enhanced emission properties. In addition, etoposide (ETO), one of the most important anticancer drugs of NECs, was loaded into the hydrophobic core of micelles by self-assembly with an average diameter of 274.6 nm and spherical morphology. Octreotide (OCT) conjugated onto the micelles enhanced cellular uptake by receptor-mediated endocytosis. ETO-loaded micelles demonstrated the dual-responsive triggered intracellular drug release and great tumor suppression ability in vitro. Compared with free ETO, ETO-loaded CCLMs exhibited a considerable antitumor effect and significantly reduced side effects. Considering the active tumor targeting, dual-responsive drug release and the AIE effect, the polymer micelle system will be a potential candidate for diagnosis and oncotherapy of NENs.

Drug Combination Synergy in Worm-like Polymeric Micelles Improves Treatment Outcome for Small Cell and Non-Small Cell Lung Cancer

Nanoparticle-based systems for concurrent delivery of multiple drugs can improve outcomes of cancer treatments, but face challenges because of differential solubility and fairly low threshold for incorporation of many drugs. Here we demonstrate that this approach can be used to greatly improve the treatment outcomes of etoposide (ETO) and platinum drug combination ("EP/PE") therapy that is the backbone for treatment of prevalent and deadly small cell lung cancer (SCLC). A polymeric micelle system based on amphiphilic block copolymer poly(2-oxazoline)s (POx) poly(2-methyl-2-oxazoline- block-2-butyl-2-oxazoline- block-2-methyl-2-oxazoline) (P(MeOx- b-BuOx- b-MeOx) is used along with an alkylated cisplatin prodrug to enable co-formulation of EP/PE in a single high-capacity vehicle. A broad range of drug mixing ratios and exceptionally high two-drug loading of over 50% wt. drug in dispersed phase is demonstrated. The highly loaded POx micelles have worm-like morphology, unprecedented for drug loaded polymeric micelles reported so far, which usually form spheres upon drug loading. The drugs co-loading in the micelles result in a slowed-down release, improved pharmacokinetics, and increased tumor distribution of both drugs. A superior antitumor activity of co-loaded EP/PE drug micelles compared to single drug micelles or their combination as well as free drug combination was demonstrated using several animal models of SCLC and non-small cell lung cancer.

Preparation and Evaluation of a Novel Class of Amphiphilic Amines as Antitumor Agents and Nanocarriers for Bioactive Molecules

Purpose

We describe a novel class of antitumor amphiphilic amines (RCn) based on a tricyclic amine hydrophilic head and a hydrophobic linear alkyl tail of variable length.

Methods

We tested the lead compound, RC16, for cytotoxicity and mechanism of cell death in several cancer cell lines, anti tumor efficacy in mouse tumor models, and ability to encapsulate chemotherapy drugs.

Results

These compounds displayed strong cytotoxic activity against cell lines derived from both pediatric and adult cancers. The IC50 of the lead compound, RC16, for normal cells including human keratinocytes, human fibroblasts and human umbilical vein endothelial cells was tenfold higher than for tumor cells. RC16 exhibited significant antitumor effects in vivo using several human xenografts and a metastatic model of murine neuroblastoma by both intravenous and oral administration routes. The amphiphilic character of RC16 triggered a spontaneous molecular self-assembling in water with formation of micelles allowing complexation of Doxorubicin, Etoposide and Paclitaxel. These micelles significantly improved the in vitro antitumor activity of these drugs as the enhancement of their aqueous solubility also improved their biologic availability.

Conclusions

RC16 and related amphiphilic amines may be useful as a novel cancer treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-016-1999-9) contains supplementary material, which is available to authorized users.

Transdermal Delivery of Etoposide Phosphate I: In Vitro and In Vivo Evaluation

Cancer chemotherapy frequently requires long periods of multiple intravenous infusions that often results in patients opting out of treatment. The main purpose of this study was to investigate the feasibility of delivering one of these anticancer agents: etoposide phosphate (ETP) transdermally using iontophoresis and a combination of iontophoresis/microporation. The iontophoresis conditions for ETP were first optimized in vitro then tested in vivo in a rabbit model. Both ETP and its active form etoposide (VP) were quantified in dermis (via microdialysis sampling) and in plasma, with a specially developed high-performance liquid chromatography method. In vitro, the amount of total etoposide permeated and the steady state flux increased (p < 0.05) with increase in iontophoretic current densities (100-400 μA/cm(2)). At 300 μA/cm(2), microporation/iontophoresis further improved both parameters by 2- and 2.8-fold, respectively. In vivo, exposure increased proportionally to current density in plasma, whereas dermal concentration dropped significantly at the highest current density. Microporation led to a 50% increase in Cmax and AUClast values in both skin and plasma. In conclusion, a mild current density (300 μA/cm(2)) and a small surface area (10.1 cm(2)) achieved and maintained the minimum effective concentration for the entire duration of electrical current delivery; microporation further increased the plasma concentrations at the same current density.

pH sensitive nano layered double hydroxides reduce the hematotoxicity and enhance the anticancer efficacy of etoposide on non-small cell lung cancer

Etoposide (VP16), used for the treatment of many carcinomas, can cause leukopenia, thrombocytopenia and hair loss. To overcome the side effects and achieve target therapy, layered double hydroxides (LDHs), a pH sensitive layered double hydroxide nanohybrid, was used here as a nano-carrier. The functions of LDHs-VP16 on non-small cell lung cancer (NSCLC) were firstly explored both in vitro and in vivo. In A549 cell line, LDH-VP16 induced apoptosis 2.3-fold as that of plain VP16 by targeting to mitochondrial, stocking cells in G1 phase. The cellular uptake demonstrated the delivery of LDH for VP16 to pass through the membrane and accumulate in mitochondria. As a carrier, LDH greatly decreased the liver toxicity and hematotoxicity of VP16. The detected liver parameters, including glutamic-oxaloacetic transaminase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), were all turn back to normal range after the delivery of LDH, except ALP. In vivo, LDH-VP16 reduced A549 tumor growth significantly by 60.5%, whereas native VP16 exerted no significant anticancer activity. In LDH-VP16 treated mice, the AUC was increased by 6.26 folds as the native drug, and t1/2 of LDH-VP16 was prolonged from 6.68 to 98.78h. LDH-VP16 showed a targeting effect, which largely increase the concentration in tumor and lung. The phosphorylation antibody array and Western Blot of proteins from xenografts revealed that PI3K-AKT signaling was suppressed in the LDH-VP16 treated tumor, while in VP16 treated mice, ERBB signaling pathway was involved. These results suggested that LDH-VP16 diminishes hematotoxicity, targets NSCLC tumor, performs more effectively than VP16, and different signaling pathway is involved compared to VP16.

STATEMENT OF SIGNIFICANCE

This paper explored that nano-sized layered double hydroxide (LDH) could be used as a pH sensitive delivery system to overcome hematotoxicity and enhance the bioavailability and anticancer efficacy of etoposide (VP16) against non small cell lung cancer, which was not reported before, as the best of our knowledge. We found that the liver and hematotoxicity is nearly recovered after the loading of VP16 in pH sensitive LDH, which prongs the half time from 6.68h to 98h, helps target VP16 to tumor and lung, and protects white blood cells by its pH sensitive and nano-size property. LDH-VP16 achieve markedly performance on non-small cell lung cancer by targeting to mitochondria of A549 cells in vitro and effectively inhibiting the PI3K-AKT signaling pathway in vivo. The inhibition ratio of VP16 on A549 tumor growth is increased from less than 20% (no significance compared to control) to 60.5% after the delivery of LDH. This work provides a novel system for the safe and efficient use of etoposide on non-small cell lung cancer and explores the mechanism of the function of nano carrier in cancer therapy both in vitro and in vivo.

Dose schedule optimization and the pharmacokinetic driver of neutropenia

Toxicity often limits the utility of oncology drugs, and optimization of dose schedule represents one option for mitigation of this toxicity. Here we explore the schedule-dependency of neutropenia, a common dose-limiting toxicity. To this end, we analyze previously published mathematical models of neutropenia to identify a pharmacokinetic (PK) predictor of the neutrophil nadir, and confirm this PK predictor in an in vivo experimental system. Specifically, we find total AUC and Cmax are poor predictors of the neutrophil nadir, while a PK measure based on the moving average of the drug concentration correlates highly with neutropenia. Further, we confirm this PK parameter for its ability to predict neutropenia in vivo following treatment with different doses and schedules. This work represents an attempt at mechanistically deriving a fundamental understanding of the underlying pharmacokinetic drivers of neutropenia, and provides insights that can be leveraged in a translational setting during schedule selection.

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.

Selective induction of glutathione S-transferases in round spermatids from the Brown-Norway rat by the chemotherapeutic regimen for testicular cancer

Chemotherapeutic drugs can affect DNA in male germ cells, thereby impacting on the integrity of the genome transmitted to offspring. Drug metabolizing enzymes can protect cells from xenobiotic insult. We analyzed the expression pattern of such enzymes in isolated round spermatids from rats exposed to drugs used to treat testicular cancer: bleomycin, etoposide, and cisplatin (BEP). The number of isozymes expressed and the overall relative expression values were highest for the glutathione S-transferases (GSTs). Moreover, BEP treatment significantly increased the expression of 8 GSTs and 3 aldehyde dehydrogenases. Increased expression of GST isozymes was confirmed by qRT-PCR and Western blot analysis. Although Gst genes can be targets for epigenetic modifications, promoter DNA methylation was not affected by BEP treatment. As GSTs are involved in drug resistance mechanisms, we hypothesize that BEP induction of GST expression may lead to the survival of damaged germ cells and the production of abnormal sperm.

Effects of quercetin on the pharmacokinetics of Etoposide after oral or intravenous administration of etoposide in rats

Etoposide [4'-demethylepipodophyllotoxin-9-(4,6-O-ethylidene)-beta-D-glucopyranoside] is a substrate for P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A. This study was designed to investigate the effects of quercetin (3,5,7,3',4'-pentahydroxyflavanone), a P-gp and CYP3A inhibitor, on the pharmacokinetics of etoposide in rats. Etoposide was administered to rats orally (9 mg/kg) or i.v. (3 mg/kg) without or with quercetin (1, 5 or 15 mg/kg). The plasma concentration of etoposide was determined by high performance liquid chromatography (HPLC) equipped with a fluorescence detector. In the presence of quercetin, the pharmacokinetic parameters of etoposide were significantly altered in the oral group, but not in the i.v. group. The presence of quercetin significantly (5 mg/kg, p<0.05; 15 mg/kg, p<0.01) increased the area under the plasma concentration-time curve (AUC) of orally administered etoposide from 43.0 or 53.2% . The presence of 5 or 15 mg/kg of quercetin significantly (p<0.05) decreased the total body clearance (CL/F) of oral etoposide. Consequently, compared to the control group (8.87%), the presence of quercetin significantly (5 mg/kg, p<0.05; 15 mg/kg, p<0.01) increased the absolute bioavailability (AB) of etoposide to 12.7 or 13.6% . The enhanced oral bioavailability of etoposide by quercetin could mainly be due to inhibition of P-gp-mediated efflux and CYP3A-catalyzed metabolism in the intestine by quercetin. The dosage regimen of etoposide in cancer therapy should take drug interaction into consideration when etoposide is administered with quercetin or dietary supplements containing quercetin.

A tool for neutrophil guided dose adaptation in chemotherapy

Chemotherapy dosing in anticancer treatment is a balancing act between achieving concentrations that are effective towards the malignancy and that result in acceptable side-effects. Neutropenia is one major side-effect of many antitumor agents, and is related to an increased risk of infection. A model capable of describing the time-course of myelosuppression from administered drug could be used in individual dose selection. In this paper we describe the transfer of a previously developed semi-mechanistic model for myelosuppression from NONMEM to a dosing tool in MS Excel, with etoposide as an example. The tool proved capable to solve a differential equation system describing the pharmacokinetics and pharmacodynamics, with estimation performance comparable to NONMEM. In the dosing tool the user provides neutrophil measures from a previous treatment course and request for the dose that results in a desired nadir in the upcoming course through a Bayesian estimation procedure.

Development of simulated intestinal fluids containing nutrients as transport media in the Caco-2 cell culture model: Assessment of cell viability, monolayer integrity and transport of a poorly aqueous soluble drug and a substrate of efflux mechanisms

The purpose of this study was to identify simulated intestinal fluids (SIFs) containing nutrients compatible with the Caco-2 cell culture model and to examine the impact of the identified medium on the transport of a poorly aqueous soluble model compound, estradiol, and a substrate of efflux mechanisms, etoposide. Monolayer integrity was evaluated by transepithelial electrical resistance and cellular viability by release of lactate dehydrogenase to the apical compartment and cellular protein content. It was shown that the viability of Caco-2 cells was enhanced by use of the CO(2) independent nutritional medium, Leibovitz's L-15 compared to Hanks' balanced salt solution. SIF containing 5mM sodium taurocholate and 1.25 mM phosphatidylcholine or lysophosphatidylcholine in Leibovitz's L-15 induced less release of lactate dehydrogenase than the traditional transport medium, HBSS. Addition of lipolysis products, 0.5mM oleic acid and 0.25 mM monoolein, did only cause increase in lactate dehydrogenase in 3 of 12 comparisons. The presence of SIFs in the apical compartment was shown to decrease flux of estradiol due to incorporation of estradiol in micelles and hence a decreased fraction of free estradiol. Further, a concentration dependent increase in the apparent permeability of etoposide was observed from apical to basolateral compartment, which indicated that components in the SIFs affects efflux mechanisms.

Lipid nanocapsules for intracellular drug delivery of anticancer drugs

As non-phagocytic eukaryotic cells can internalize particles < 1 microm in size, small size (25 to 110 nm) lipid nanocapsules (LNC) are proposed for the intracellular drug delivery of anticancer drugs to cancer cells. LNC of different diameters were loaded with etoposide or paclitaxel and subsequently tested for drug release kinetics and their efficiency to reduce cancer cell growth in cell culture. Relative high drug loads could be achieved and sustained drug release can be provided over a period of several days (etoposide) up to a few weeks (paclitaxel). While particle size exhibited only minor influences on the release kinetics, higher initial drug load led to a distinctly lower burst release. In a cancer cell culture model, etoposide or paclitaxel LNC showed a 4-fold or 40-fold higher efficiency, respectively than the drug solution while blank LNC were found to be less toxic than the pure drug at equivalent concentrations. The uptake and intracellular accumulation of LNC was confirmed by confocal laser scanning microscopy after fluorescence labeling of the nanocarriers. This nanoparticulate system is able to achieve efficient intracellular drug concentrations and seems to be therefore a promising therapeutic approach in cancer treatment.

Continuous low-dose oral chemotherapy for adjuvant therapy of splenic hemangiosarcoma in dogs

BACKGROUND

Hemangiosarcoma (HSA) is a highly metastatic and often rapidly fatal tumor in dogs. At present, conventional adjuvant chemotherapy provides only a modest survival benefit for treated dogs. Continuous oral administration of low-dose chemotherapy (LDC) has been suggested as an alternative to conventional chemotherapy protocols. Therefore, we evaluated the safety and effectiveness of LDC using a combination of cyclophosphamide, etoposide, and piroxicam as adjuvant therapy for dogs with stage II HSA.

HYPOTHESIS

We hypothesized that oral adjuvant therapy with LDC could be safely administered to dogs with HSA and that survival times would be comparable to those attained with conventional doxorubicin (DOX) chemotherapy.

ANIMALS

Nine dogs with stage II splenic HSA were enrolled in the LDC study. Treatment outcomes were also evaluated retrospectively for 24 dogs with stage II splenic HSA treated with DOX chemotherapy.

METHODS

Nine dogs with stage II splenic HSA were treated with LDC over a 6-month period. Adverse effects and treatment outcomes were determined. The pharmacokinetics of orally administered etoposide were determined in 3 dogs. Overall survival times and disease-free intervals were compared between the 9 LDC-treated dogs and 24 DOX-treated dogs.

RESULTS

Dogs treated with LDC did not develop severe adverse effects, and long-term treatment over 6 months was well-tolerated. Oral administration of etoposide resulted in detectable plasma concentrations that peaked between 30 and 60 minutes after dosing. Both the median overall survival time and the median disease-free interval in dogs treated with LDC were 178 days. By comparison, the overall survival time and disease-free interval in dogs treated with DOX were 133 and 126 days, respectively.

CONCLUSIONS

Continuous orally administered LDC may be an effective alternative to conventional high-dose chemotherapy for adjuvant therapy of dogs with HSA.

Pharmacokinetics of doxorubicin and etoposide in a morbidly obese pediatric patient

This case report presents the pharmacokinetics of doxorubicin and etoposide in a 14-year-old morbidly obese (body mass index: 46.3 kg/m2) male patient with Hodgkin disease. Dosing based on an adjusted body surface area resulted in a dose reduction by approximately 25% as compared to dosing based on actual body surface area. Plasma clearance of doxorubicin as well as plasma clearance and elimination rate of etoposide for this patient was comparable to pharmacokinetic data from nonobese pediatric patients. The therapy was well tolerated without any specific toxicity and a complete response was obtained after 2 scheduled courses, with the patient in complete remission 25 months after end of treatment.

Dose finding study of oral PSC 833 combined with weekly intravenous etoposide in children with relapsed or refractory solid tumours

PSC 833 is an effective MDR1 reversal agent in vitro, including studies with paediatric cancer cell lines such as neuroblastoma and rhabdomyosarcoma. This study was performed to determine the safety profile, dose limiting toxicity (DLT) and maximum tolerated dose (MTD) in children with solid tumours and to determine the influence of PSC 833 on the pharmacokinetics of co-administered etoposide. Each patient received one cycle of intravenous etoposide (100 mg/m2 daily for 3 days on three consecutive weeks) to document baseline pharmacokinetics, and subsequently the same schedule using a dose of 50 mg/m2 was given combined with PSC 833 given orally every 6h at a starting dose of 4 mg/kg. Thirty two eligible patients (23 male, median age 8.3 years) were enrolled. Neuroblastoma and rhabdomyosarcoma were the common disease types. Brain tumours were excluded. DLT was defined as any non-haematological grade 3-4 toxicity (common toxicity criteria) and using a specific toxicity scale for cerebellar toxicity. The MDT was defined as the first dose below which 2 or more patients per dose level experienced DLT. Grade 1-2 ataxia occurred in cohorts 2 and 3 (4 and 5 mg/kg, respectively). Three patients developed grade 3 neurotoxicity in the 6 mg/kg cohort and this defined the MTD. Six responses were observed (2 CR, 4 PR). Pharmacokinetic studies indicated that the clearance of etoposide was reduced by approximately 50% when combined with PSC 833. It is concluded that the toxicity profile and MDT is similar in both children and adults, as is the effect on etoposide metabolism. The study demonstrated the feasibility and safety of carrying out a paediatric phase 1 trial across European boundaries and acts as a model for future cooperative studies in rare cancers among children.

[Preparation and in vitro and in vivo evaluation of etoposide submicro-emulsion for intravenous injection]

The aim of this thesis is to prepare etoposide submicro-emulsion (ESE) for intravenous injection and investigate its characteristics in vitro and in vivo. High-pressure homogenization was used to prepare ESE, using 10% (w/w) soybean oil and 10% (w/w) medium-chain triglyceride as mixed oil phase, and 1.8% (w/w) fabaceous lecithin as emulsifier. The pH was adjusted to 5.5 with 0.1 mol x L(-1) NaOH to keep the most stability of ESE. The particle size distribution and zeta potential were measured using photon correlation spectroscopy. Ultrafiltration was used to estimate the relative percentages of etoposide in each phase. Long-term storage test and accelerated isothermal test-Weibull distribution method were used to estimate the physical and chemical stability of ESE. Plasma pharmacokinetics in rats was monitored by high performance liquid chromatography by comparison with etoposide nonaqueous solution at the same time. The mean particle size, zeta potential and entrapment efficiency of ESE were (189.9 +/- 54.6) nm, - 32.6 mV and 91.7%, respectively. The emulsion was stable during 9 month storage at 4 degrees C. The shelf life (T0.9) of etoposide in lipid emulsion was estimated to be about 665 days at 4 degrees C. The drug concentration-time curves of ESE and solution were similar and could be described by two compartment model. The area under the curve of concentration versus time from zero to the last time point and the mean residence time of ESE and solution were (18.30 +/- 8.74) and (19.32 +/- 6.45) microg x h x mL(-1), and (1.46 +/- 0.32) and (1.71 +/- 0.52) h, respectively. Etoposide was incorporated in submicro-emulsion to improve its physical and chemical stability without addition of organic solvents with insignificant different characteristics in vivo when compared with solution.

Pharmacokinetic comparison of oral and intravenous etoposide in patients treated with the CHOEP-regimen for malignant lymphomas

BACKGROUND

The addition of etoposide to the CHOP protocol (CHOEP) has been shown to improve outcome in patients with aggressive non-Hodgkin's lymphoma. The intravenous administration of etoposide on three consecutive days represents a logistic problem and needs resources particular in the outpatient setting. This could be avoided by using etoposide capsules on days 2 and 3. However, the oral administration of cytotoxic agents is often affected by variable absorption and drug interactions.

PATIENTS AND METHODS

We investigated the pharmacokinetic equivalency of oral and intravenous etoposide in ten patients (male, n=7; female, n=3; median age 56 years) with aggressive lymphomas. Treatment consisted of standard CHOP plus etoposide 100 mg/m2 given intravenously on day 1, and 200 mg/m2 orally on days 3 and 4. Samples from blood and urine were taken on days 1 (i.v. study) and 3 (p.o. study) before and after etoposide administration. Etoposide levels were determined by high-performance liquid chromatography (HPLC), and pharmacokinetic parameters were calculated with the TOPFIT computer program.

RESULTS

Mean peak plasma level after intravenous etoposide was significantly higher compared to oral administration (16.3+/-3.7 vs. 12.0+/-4.2 microg/ml; P=0.015). The mean bioavailability of oral etoposide was 58+/-15% with an interpatient variability of 26%. Significant differences of bioavailability of oral etoposide between the used dose levels (350, 400 and 450 mg) were not observed. Mean AUC after a 100 mg/m2 intravenous and a 200 mg/m2 oral dose of etoposide were 74.0+/-18.3 and 84.9+/-29.6 microg h/ml (P=0.481). Interpatient variability of AUC was 25% for the intravenous route and 35% after oral intake. Urinary etoposide excretion as percentage of administered dose was 39.4+/-10.6% after intravenous infusion versus 35.4+/-9.4% after oral intake (P=0.422). Renal clearance was also very similar with intravenous and oral route (18.5+/-7.4 vs. 16.7+/-6.6 ml/min; P=0.546).

CONCLUSION

The equivalency of AUC after 200 mg/m2 of oral and 100 mg/m2 of intravenous etoposide support the use of the oral preparation in patients treated with the CHOEP regimen, which makes the chemotherapy more convenient for the patients and help to reduce costs.

Thanatop: A Novel 5-Nitrofuran that Is a Highly Active, Cell-Permeable Inhibitor of Topoisomerase II

A series of nitrofuran-based compounds were identified as inhibitors of estrogen signaling in a cell-based, high-throughput screen of a diverse library of small molecules. These highly related compounds were subsequently found to inhibit topoisomerase II in vitro at concentrations similar to that required for the inhibition of estrogen signaling in cells. The most potent nitrofuran discovered is approximately 10-fold more active than etoposide phosphate, a topoisomerase II inhibitor in clinical use. The nitrofurans also inhibit topoisomerase I activity, with approximately 20-fold less activity. Moreover, the nitrofurans, in contrast to etoposide, induce a profound cell cycle arrest in the G(0)-G(1) phase of the cell cycle, do not induce double-stranded DNA breaks, are not substrates for multidrug resistance protein-1 export from the cell, and are amenable to synthetic development. In addition, the nitrofurans synergize with etoposide phosphate in cell killing. Clonogenic assays done on a panel of human tumors maintained ex vivo in nude mice show that the most active compound identified in the screen is selective against tumors compared with normal hematopoietic stem cells. However, this compound had only moderate activity in a mouse xenograft model. This novel class of topoisomerase II inhibitor may provide additional chemotherapeutic strategies for the development of cytotoxic agents with proven clinical utility.

Pharmacokinetic modulation of oral etoposide by ketoconazole in patients with advanced cancer

PURPOSE

Etoposide is a widely used cytotoxic drug that is commercially available in both intravenous and oral formulations. High interpatient pharmacokinetic variability has been associated with oral etoposide administration. Various strategies used in the past to reduce such variability have not been successful. Hence, this study was designed to evaluate if pharmacokinetic modulation of oral etoposide with ketoconazole could lead to a favorable alteration of etoposide pharmacokinetics, and to assess the feasibility and safety of this approach.

METHODS

Thirty-two patients were treated with ketoconazole 200 mg daily with an escalating dose of oral etoposide starting at a dose of 50 mg every other day. Pharmacokinetic samples were obtained during the first treatment cycle after the administration of an oral etoposide and ketoconazole dose. Additional baseline pharmacokinetic studies of etoposide alone were performed 4 days prior to the first treatment cycle.

RESULTS

Dose limiting toxicities were neutropenia and fatigue. Ketoconazole increased the area under the plasma concentration-time curve (AUC) of oral etoposide by a median of 20% (p < 0.005). Ketoconazole did not reduce the interpatient variability in etoposide pharmacokinetics. Pretreatment bilirubin levels correlated with etoposide clearance (Spearman's r = -0.48, p = 0.008). The maximum tolerated dose was etoposide administered at 50 mg daily and ketoconazole 200 mg qd for 3 of 5 weeks.

CONCLUSIONS

Ketoconazole reduces the apparent clearance of oral etoposide, does not alter its toxicity profile and does not reduce interpatient pharmacokinetic variability. Other methods to reduce the pharmacokinetic variability of oral etoposide are needed.

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.

Etoposide pharmacokinetics in children treated for acute myeloid leukemia

We studied the pharmacokinetics of etoposide in 45 children treated for newly diagnosed acute myeloid leukemia. Etoposide, 100 mg/m body surface area/24 h, was administered by 96-h continuous intravenous infusion. Concomitantly, the children received cytarabine 200 mg/m/24 h by intravenous infusion and 6-thioguanine 100 mg/m twice daily orally. Median total body clearance in children 0.5-1.8 (n=4) and 2.3-17.7 years old (n=36) without Down's syndrome was 17.1 and 17.6 ml/min/m, respectively (P=0.96). Five children with Down's syndrome had a median clearance of 13.6 ml/min/m (P=0.067 compared with non-Down's syndrome children). Eighteen of the children received a second identical treatment course 3-4 weeks later; there was a significant correlation between individual clearance values (rho=0.56; P=0.017). We found no significant correlation between etoposide pharmacokinetics and the remission rate or the relapse rate. In conclusion, our findings indicate that special dose-calculation guidelines for infants above 3 months old are not substantiated by age-dependent pharmacokinetics of etoposide. Down's syndrome children might be candidates for dose reduction if our data are confirmed in larger numbers of patients. Low course-to-course variability indicates that pharmacokinetically guided dosing of etoposide might be clinically relevant, if larger studies can demonstrate that this approach decreases toxicity or increases response rates.

Evaluation in melanoma-bearing mice of an etoposide derivative associated to a cholesterol-rich nano-emulsion

A cholesterol-rich nano-emulsion (LDE) may be used as a vehicle to target antineoplastic drugs against cancer cells. The association of an etoposide derivative to LDE is stable and retains the cytotoxic activity of etoposide. We have evaluated the toxicity and antitumoral action of this new preparation in-vivo. Melanoma-bearing mice and control mice were administered LDE-etoposide oleate or commercial etoposide, either with or without radioactive labelling. The maximum tolerated dose (MTD), tissue distribution, plasma decay curves, pharmacokinetic parameters and antitumoral activity were determined. Association to LDE drastically reduced the drug toxicity, since MTD was approximately five-fold greater than in commercial etoposide. LDE-etoposide oleate was concentrated four-fold in the tumour compared with the normal adjacent tissues, was removed faster from plasma in tumour-bearing mice than in controls, and remained in the bloodstream longer than commercial etoposide. The tumour growth inhibition rate and survival were greater in animals treated with LDE-etoposide oleate compared with commercial etoposide. However, increasing the dose from 17 to 85 microM kg(-1) did not result in further improvement of the antitumour action. The incorporation of etoposide oleate to LDE resulted in markedly reduced toxicity and superior antitumoral activity. LDE-etoposide oleate is a promising new weapon for cancer treatment.

Oral etoposide in elderly patients with advanced non small cell lung cancer: a clinical and pharmacological study

Seventeen elderly patients with advanced progressive non small cell lung cancer (NSCLC) were treated with oral etoposide at the daily dose of 100 mg for 14 days every 3-4 weeks with pharmacokinetic monitoring. One partial response and 6 stabilizations were documented with a median overall duration of 13 weeks (range 8-32). The median survival was 24 weeks with an apparent advantage for non-progressive patients (40 weeks vs. 18 weeks). The treatment was well tolerated especially by those patients without concomitant illness, suggesting the crucial role of a careful selection of the geriatric population. Toxicity was not related to the etoposide plasma level, but was clearly dependent on comorbidity. A geriatric assessment rather than chronological age therefore appears to be more reliable in the selection of elderly patients for clinical trials. The easy self-management, favorable toxicity profile and synergy with other compounds makes oral etoposide suitable for further clinical-pharmacological studies in elderly patients.

Sequential oral 9-nitrocamptothecin and etoposide: a pharmacodynamic- and pharmacokinetic-based phase I trial

PURPOSE

Resistance to topoisomerase (topo) I inhibitors has been related to down-regulation of nuclear target enzyme, whereas sensitization to topo II inhibitors may result from induction of topo II by topo I inhibitors. Here, we evaluated a sequence-specific administration of a topo I inhibitor followed by a topo II inhibitor.

EXPERIMENTAL DESIGN

Twenty-five patients with advanced or metastatic malignancies were treated with increasing doses (0.75, 1.0, 1.25, 1.5, 1.75, or 2.0 mg/m(2)) of 9-nitrocamptothecin (9-NC) on days 1 to 3, followed by etoposide (100 or 150 mg/d) on days 4 and 5. At the maximally tolerated dose, 20 additional patients were enrolled. The median age was 60 years (range, 40-84 years). Endpoints included pharmacokinetic analyses of 9-NC and etoposide, and treatment-induced modulations of topo I and II expression in peripheral blood mononuclear cells.

RESULTS

Neutropenia, thrombocytopenia, nausea, vomiting, diarrhea, and fatigue were dose-limiting toxicities and occurred in six patients. Despite a median number of four prior regimens (range 1-12), 2 (4%) patients had an objective response and 13 (29%) patients had stable disease. In contrast to the expected modulation in topo I and IIalpha levels, we observed a decrease in topo IIalpha levels, whereas topo I levels were not significantly altered by 9-NC treatment.

CONCLUSIONS

Sequence-specific administration of 9-NC and etoposide is tolerable and active. However, peripheral blood mononuclear cells may not be a predictive biological surrogate for drug-induced modulation of topo levels in tumor tissues and should be further explored in larger studies.

Enhanced delivery of etoposide to Dalton's lymphoma in mice through polysorbate 20 micelles

The study evaluates the possibility of enhancing uptake of etoposide (topoisomerase II inhibitor) by tumor when delivered through polysorbate 20 micelles. The micelle formation was ascertained by determining the critical micellar concentration (CMC) with a du Nouy ring tensiometer and by size measurement using dynamic light scattering. Addition of 5% ethanol decreased the CMC of Polysorbate 20 (from 5.0 x 10(-5) to 4.54 x 10(-5) mol L(-1)). Etoposide (ET) and etoposide loaded polysorbate 20 micelles (EPM) were radiolabeled with 99mTc by the reduction method using stannous chloride. Labeling parameters were optimized to obtain high labeling efficiency. The diethylenetriaminepentaacetic acid and cysteine challenge tests showed very low transchelation of 99mTc-ET and 99mTc-EPM complexes indicating their in vitro stability. The complexes also exhibited serum stability assessed by ascending thin layer chromatography. Subcutaneous injection of EPM resulted in significantly higher tumor uptake ( 100 folds compared to ET 6 h post injection) (p < 0.001) and prolonged tumor retention. Tumor uptake was also confirmed by gamma imaging studies. EPM exhibited relatively high brain concentrations ( 7 fold 24 h post injection) compared to ET, suggesting the potential use of EPM in the treatment of brain malignancies.

Transport of hydroxyzine and triprolidine across bovine olfactory mucosa: role of passive diffusion in the direct nose-to-brain uptake of small molecules

Hydroxyzine and triprolidine have both been reported to reach the CNS following nasal administration. The objective of this study was to investigate their in vitro permeation across bovine olfactory mucosa in order to further characterize the biological and physicochemical parameters that influence direct nose-to-brain transport. In vitro experiments were conducted using Sweetana-Grass (Navicyte) vertical diffusion cells to evaluate the effect of directionality, donor concentration and pH on the permeation of hydroxyzine and triprolidine across excised bovine olfactory mucosa. These studies demonstrated that the Jm-s (mucosal-submucosal flux) and Js-m (submucosal-mucosal flux) of hydroxyzine and triprolidine across the olfactory mucosa were linearly dependent upon the donor concentration without any evidence of saturable transport. Hydroxyzine inhibited the efflux of P-gp substrates like etoposide and chlorpheniramine across the olfactory mucosa. Both hydroxyzine and triprolidine reduced the net flux (Js-m-Jm-s) of etoposide with IC50 values of 39.2 and 130.6 microM, respectively. The lipophilicty of these compounds, coupled with their ability to inhibit P-gp, enable them to freely permeate across the olfactory mucosa. Despite the presence of a number of protective barriers such as efflux transporters and metabolizing enzymes in the olfactory system, lipophilic compounds such as hydroxyzine and triprolidine can access the CNS primarily by passive diffusion when administered via the nasal cavity.

Tumoricidal effects of etoposide incorporated into solid lipid nanoparticles after intraperitoneal administration in Dalton's lymphoma bearing mice

The tumoricidal effects of etoposide incorporated into lipid nanoparticles after single-dose administration were investigated in Dalton's lymphoma ascites bearing mice. Etoposide and its nanoparticle formulations were administered intraperitoneally, and the cell cycle perturbation, cytogenetic damage, cell death (apoptosis), tumor regression, and animal survival were investigated as parameters of response with time. The tumor burden of mice treated with etoposide and its nanoparticle formulations decreased significantly (P < .001) compared with the initial up to 4 to 6 days, followed by an increase at later time intervals. Of the 3 different formulations, the survival time of mice was higher when treated with etoposide-loaded tripalmitin (ETP) nanoparticles, followed by etoposide-loaded glycerol monostearate (EGMS) (27.3%) and etoposide-loaded glycerol distearate (EGDS) (27.3%) compared with free etoposide. Cell cycle analysis revealed the hypodiploid peak (sub G0/G1 cell population) as well as G2 arrest in mice treated with etoposide and its nanoparticle formulations. The frequency of dead cells treated with the nanoparticle formulations remained high even after 8 days of treatment compared with free etoposide. The mice treated with nanoparticle formulations exhibited hypodiploid peaks and reduced S phase even 8 days after treatment, whereas the free etoposide-treated mice showed decrease in apoptosis after 3 days of treatment. The apoptotic frequency in cells 17 days after treatment was in the order of ETP > EGMS > EGDS > etoposide. The experimental results indicated that among the 3 nanoparticle formulations studied, the ETP nanoparticles showed greater and prolonged apoptotic induction properties, resulting in the higher increase in survival time of tumor bearing mice.

Pharmacokinetics and tissue distribution of etoposide delivered in long circulating parenteral emulsion

PURPOSE

The aim of the study is to ascertain the influence of pegylation of parenteral emulsion (PE) on their long circulating property.

METHODS

Etoposide encapsulated parenteral emulsion (EPE) was prepared using soybean oil, egg lecithin and cholesterol. Etoposide encapsulated long circulating parenteral emulsion (PEG-EPE) was prepared using PEG (2000)-DSPE as a stealth agent. The effect of monovalent and divalent electrolytes on the stability of EP was assessed by measuring the fixed aqueous layer thickness (FALT) and flocculation rate. Pharmacokinetics and tissue distribution pattern of PE following i.v. (bolus) were assessed in Wistar rats and Swiss albino mice.

RESULTS

FALT of PEG-EPE was larger than that of EPE. In case of PEG-EPE, as the concentration of pegylated lipid (PEG) increased from 0.15 to 0.45% w/v the flocculation rate decreased asymptomatically in the presence of monovalent and divalent electrolytes. The increased circulation time of PEG-EPE (0.3%) after intravenous injection to rats confirms the presence of FALT around globules. PEG-EPE showed improved pharmacokinetic parameters with 5.5 times higher AUC than etoposide commercial formulation (ETP). Tissue distribution results show that etoposide levels in all tissues except in brain and heart were lower in case of PEG-EPE than ETP. The percentage of tumor growth suppression rate (%T/C) in Lewis lung carcinoma bearing mice was 63.23, 62.83 and 33.78% in EPE, PEG-EPE and ETP treated mice, respectively. The improved activity of PEG-EPE is due to enhanced permeability and retention effect (EPR).

CONCLUSION

Encapsulation of etoposide in PEG-coated PE produced improved pharmacokinetic profile than that of EPE and ETP.

Biliary excretion of etoposide in children with cancer

PURPOSE

Two children with soft tissue sarcomas receiving etoposide as part of their standard clinical treatment had external biliary drainage due to obstruction of the bile duct. These unusual cases provided an opportunity to investigate the biliary clearance of etoposide by determining etoposide concentrations in bile and plasma samples obtained during chemotherapy.

PATIENTS AND METHODS

Etoposide was administered to patient 1 at a dose of 150 mg/m(2), as a 4 h infusion, on each of three days of treatment. Patient 2 received a daily etoposide dose of 800 mg/m(2) as a 24 h continuous infusion, also over a 3-day treatment period. Bile and plasma samples were obtained at regular intervals from both patients and etoposide levels quantified by LC/MS analysis.

RESULTS AND DISCUSSION

Biliary etoposide clearance was approximately equal to the flow of bile, with an average clearance of 0.32 ml/min determined in patient 1. Less than 2% of the etoposide dose administered was excreted in the bile in either patient studied, indicating that biliary clearance of etoposide is relatively minor. These results suggest that etoposide dose adjustment is unnecessary in patients with biliary obstruction.

Characterization of human NSCLC cell line with innate etoposide-resistance mediated by cytoplasmic localization of topoisomerase II alpha

Topoisomerase (topo) II alpha is a target for many chemotherapeutic agents in clinical use. In tumor cells resistant to topo II poisons, there have been descriptions of quantitative and qualitative alterations involved in this enzyme. More recently, the cytoplasmic localization of topo II alpha has been described as a mechanism to confer drug resistance. Here, we report the characterization of a human non-small-cell lung cancer cell line, INER-37, which shows an innate resistance to etoposide. In this cell line, etoposide resistance was directly associated with the expression of topo II alpha resident mainly in the cytoplasmic region. At the molecular level, INER-37 cells carry on a heterozygous gene deletion, transcribing two different topo II alpha mRNAs: 4.8 kb and 2.0 kb. The bigger 4.8 kb mRNA (missing 1.3 kb of 3' mRNA and including the untranslated region) is translated into a truncated cytoplasmic protein of approximately 160 kDa. The protein truncation affects at least 96 amino acids in the COOH-terminal region where the more proximal bipartite nuclear localization signal is located. The INER-37 cell line is the first cancer cell line reported with an innate mutation affecting the 3'-end region of the topo II alpha gene that confers a cytoplasmic localization of the enzyme and therefore an increased resistance to etoposide.

The Systemic Absorption of Etoposide after Intravaginal Administration in Patients with Cervical Intraepithelial Lesions Associated with Human Papillomavirus Infection

PURPOSE

The purpose of this study was to determine the systemic absorption and the release of etoposide in cervical tissue administered via a vaginal ovule to women diagnosed with cervical intraepithelial lesions associated with human papillomavirus (HPV).

METHODS

Fifteen women with low- and high-grade intraepithelial neoplasia confirmed by colposcopic test received a 50-mg intravaginal etoposide dose three times a week for 3 weeks. At the end of the study period, paralleled with the last ovule administered, blood samples were collected over a period of 24 h, and in situ cervical samples were obtained at 3 and 10 h after drug administration. Etoposide concentrations were determined in plasma and in in situ cervical samples using the high-performance liquid chromatography method with electrochemical detection.

RESULTS

Pharmacokinetic analyses of plasma data indicated low or lack of systemic exposure of etoposide after the vaginal administration. Nevertheless, high concentrations of etoposide were found in all in situ cervical samples, indicating that etoposide could be released from its pharmaceutical formulation.

CONCLUSIONS

The results of the study suggest that the etoposide administered as intravaginal ovule is safe and tolerable and apparently could be a suitable option in patients with cervical intraepithelial neoplasia. Clinical results and the true impact on HPV infection and evolution of dysplasia need to be confirmed.

Development of an on-line extraction turbulent flow chromatography tandem mass spectrometry method for cassette analysis of Caco-2 cell based bi-directional assay samples

Caco-2 cells are frequently used for screening compounds for their permeability characteristics and P-glycoprotein (P-gp) interaction potential. Bi-directional permeability studies performed on Caco-2 cells followed by analysis by HPLC-UV or LC-MS method constitutes the "method of choice" for the functional assessment of efflux characteristics of a test compound. A high throughput LC-MS/MS method has been developed using on-line extraction turbulent flow chromatography coupled to tandem mass spectrometric detection to analyze multiple compounds present in Hanks balanced salt solution in a single analytical run. All standard curves (P-gp substrates: quinidine, etoposide, rhodamine 123, dexamethasone, and verapamil and non-substrates: metoprolol, sulfasalazine, propranolol, nadolol, and furosemide) were prepared in a cassette mode (ten-in-one) while Caco-2 cell incubations were performed both in discreet mode and in cassette mode. The standard curve range for most compounds was 10-2500 nM with regression coefficients (R(2)) greater than 0.99 for all compounds. The applicability and reliability of the analysis method was evaluated by successful demonstration of efflux ratio greater than 1 for the P-gp substrates studied in the Caco-2 cell model. The use of cassette mode analysis through selected reaction monitoring mass spectrometry presents an attractive option to increase the throughput, sensitivity, selectivity, and efficiency of the model over discreet mode UV detection.

Topotecan Combination Chemotherapy in Two New Rodent Models of Retinoblastoma

Chemotherapy combined with laser therapy and cryotherapy has improved the ocular salvage rate for children with bilateral retinoblastoma. However, children with late-stage disease often experience recurrence shortly after treatment. To improve the vision salvage rate in advanced bilateral retinoblastoma, we have developed and characterized two new rodent models of retinoblastoma for screening chemotherapeutic drug combinations. The first model is an orthotopic xenograft model in which green fluorescent protein- or luciferase-labeled human retinoblastoma cells are injected into the eyes of newborn rats. The second model uses a replication-incompetent retrovirus (LIA-E(E1A)) encoding the E1A oncogene. Clonal, focal tumors arise from mouse retinal progenitor cells when LIA-E(E1A) is injected into the eyes of newborn p53-/- mice. Using these two models combined with pharmacokinetic studies and cell culture experiments, we have tested the efficacy of topotecan combined with carboplatin and of topotecan combined with vincristine for the treatment of retinoblastoma. The combination of topotecan and carboplatin most effectively halted retinoblastoma progression in our rodent models and was superior to the current triple drug therapy using vincristine, carboplatin, and etoposide. Vincristine had the lowest LC50 in culture but did not reduce tumor growth in our preclinical retinoblastoma models. Taken together, these data suggest that topotecan may be a suitable replacement for etoposide in combination chemotherapy for the treatment of retinoblastoma.

A phase I trial defining the maximum tolerated systemic exposure of topotecan in combination with Carboplatin and Etoposide in extensive stage small cell lung cancer

PURPOSE

Topotecan is active in relapsed small cell lung cancer; thus, its addition to the standard carboplatin-etoposide regimen may improve outcomes in extensive-stage small cell lung cancer (ES-SCLC) patients. Significant interpatient variability in the topotecan systemic exposure results when it is dosed based on body surface area (mg/m2). The purpose of this Phase I trial was to determine the maximally tolerated systemic exposure (MTSE) of topotecan in combination with carboplatin and etoposide.

METHODS

Thirty-four chemotherapy-naïve ES-SCLC patients received topotecan in combination with carboplatin AUC 5 mg/mL*min and oral etoposide 100 mg/m2/day. Topotecan was administered as a 30-minute infusion either on Days 1-5 or Days 1-3 and the dosage was individualized to attain a topotecan lactone AUC range (ng/mL*hr) in successive patient cohorts from 7 to 23; 24 to 36; 37 to 53; 54 to 66.

RESULTS

The majority (67 percent) of the measured topotecan AUCs were within target range. Overall, 8 of 34 patients experienced Cycle 1 dose-limiting toxicity (DLT), either neutropenia or thrombocytopenia. Carboplatin administration prior to topotecan resulted in 2 of 6 patients having Cycle 1 DLT. When the administration sequence was changed (topotecan, carboplatin, etoposide), Cycle 1 hematologic toxicity decreased; however, the maximum topotecan lactone AUC of 24-36 ng/mL*hr (median dose 0.82 mg/m2) had significant cumulative hematologic toxicity. The number of topotecan doses were reduced from 5 to 3, which resulted in a maximum topotecan lactone AUC of 37 to 53 ng/mL*hr with only 1 of 6 patients having Cycle 1 DLT. Overall response rate was 71 percent with median survival of 10.8 months.

CONCLUSION

It is feasible to target topotecan lactone AUC in adult ES-SCLC patients. However, this triplet regimen resulted in considerable hematologic toxicity and has a median survival comparable to carboplatin-etoposide. Alternative, less toxic regimens should be investigated for improving survival in ES-SCLC.

Human splicing factor SPF45 (RBM17) confers broad multidrug resistance to anticancer drugs when overexpressed--a phenotype partially reversed by selective estrogen receptor modulators

The splicing factor SPF45 (RBM17) is frequently overexpressed in many solid tumors, and stable expression in HeLa cells confers resistance to doxorubicin and vincristine. In this study, we characterized stable transfectants of A2780 ovarian carcinoma cells. In a 3-day cytotoxicity assay, human SPF45 overexpression conferred 3- to 21-fold resistance to carboplatin, vinorelbine, doxorubicin, etoposide, mitoxantrone, and vincristine. In addition, resistance to gemcitabine and pemetrexed was observed at the highest drug concentrations tested. Knockdown of SPF45 in parental A2780 cells using a hammerhead ribozyme sensitized A2780 cells to etoposide by approximately 5-fold relative to a catalytically inactive ribozyme control and untransfected cells, suggesting a role for SPF45 in intrinsic resistance to some drugs. A2780-SPF45 cells accumulated similar levels of doxorubicin as vector-transfected and parental A2780 cells, indicating that drug resistance is not due to differences in drug accumulation. Efforts to identify small molecules that could block SPF45-mediated drug resistance revealed that the selective estrogen receptor (ER) modulators tamoxifen and LY117018 (a raloxifene analogue) partially reversed SPF45-mediated drug resistance to mitoxantrone in A2780-SPF45 cells from 21-fold to 8- and 5-fold, respectively, but did not significantly affect the mitoxantrone sensitivity of vector control cells. Quantitative PCR showed that ERbeta but not ERalpha was expressed in A2780 transfectants. Coimmunoprecipitation experiments suggest that SPF45 and ERbeta physically interact in vivo. Thus, SPF45-mediated drug resistance in A2780 cells may result in part from effects of SPF45 on the transcription or alternate splicing of ERbeta-regulated genes.

Pharmacokinetically guided phase I trial of topotecan and etoposide phosphate in recurrent ovarian cancer

A pharmacokinetically guided phase I study of topotecan and etoposide phosphate was conducted in recurrent ovarian cancer. The scheduling of the topoisomerase I and II inhibitors was determined using in vitro activity data. All patients had recurrent disease following prior platinum-containing chemotherapy. Patients had a World Health Organisation performance status of 0–2 and adequate bone marrow, renal and hepatic function. Treatment was with topotecan intravenously for 5 days followed immediately by a 5-day intravenous infusion of etoposide phosphate (EP), with pharmacokinetically guided dose adjustment. Plasma etoposide levels were measured on days 2 and 4 of the infusion. A total of 21 patients entered the study. In all, 48% were platinum resistant and 71% had received prior paclitaxel. The main toxicities were haematological, short lived and reversible. A total of 29% of patients experienced grade 4 thrombocytopenia and 66% grade 4 neutropenia after the first cycle. Neutropenia and thrombocytopenia was dose limiting. The maximum-tolerated dose was topotecan 0.85 mg m⁻² day⁻¹ days 1–5 followed immediately by a 5-day infusion of EP at a plasma concentration of 1 μg ml⁻¹. The response rate (RR) was 28% in 18 evaluable patients. There was marked interpatient variability in topoisomerase IIα levels measured from peripheral lymphocytes, with no observed increase following topotecan. This regimen of topotecan followed by EP demonstrated good activity in recurrent ovarian cancer and was noncrossresistant with paclitaxel. Both the toxicity and RR was higher than would be expected from the single agent data, in keeping with synergy of action.

NHS76/PEP2, a fully human vasopermeability-enhancing agent to increase the uptake and efficacy of cancer chemotherapy

PURPOSE

Previously, we have shown that the attachment of interleukin 2 (IL-2) to a tumor-targeting antibody can produce a 4-fold enhancement in the uptake of antibodies and drugs in tumors. More recently, we discovered that a 37-amino-acid linear sequence of IL-2 designated vasopermeability-enhancing peptide (PEP), contained the vasopermeability activity of IL-2, and could be used after linkage to tumor-targeting antibodies to produce the same enhancement of drugs and antibodies in tumors. We now describe the generation of a fully human antibody fusion protein, designated NHS76/PEP(2), which can be used in patients to enhance the therapeutic potential of chemotherapy.

METHODS

NHS76/PEP(2) was expressed in NS0 cells using the glutamine synthetase gene amplification system. To show its clinical potential as a pretreatment to chemotherapy, NHS76/PEP(2) was given i.v. 2 hours before the injection of suboptimal doses of etoposide, doxorubicin, Taxol, Taxotere, 5-fluorouracil, or vinblastine in mice bearing established solid tumors. Results were recorded by measuring tumor volumes thrice per week.

RESULTS

Compared with drug treatment alone, NHS76/PEP(2) pretreatment substantially improved the effectiveness of chemotherapeutic agents in solid tumor models. Tumor suppression was most pronounced in those groups of mice bearing tumors known to be sensitive to the specific drug under study. However, in certain instances, tumors previously known to be resistant to specific single chemotherapeutic agents were shown to respond by the addition of NHS76/PEP(2) pretreatment.

CONCLUSIONS

NHS76/PEP(2) seems an excellent candidate to improve the value of standard chemotherapy drug treatment by virtue of its ability to increase the uptake of drugs in solid tumors selectively.

Influence of administration route on tumor uptake and biodistribution of etoposide loaded solid lipid nanoparticles in Dalton's lymphoma tumor bearing mice

The study evaluates the capability of tripalmitin nanoparticles in enhancing the tumor uptake of etoposide, and the influence of administration route on the biodistribution and tumor uptake of etoposide loaded tripalmitin (ETPL) nanoparticles in Dalton's lymphoma tumor bearing mice. ETPL nanoparticles were prepared by melt-emulsification and high pressure homogenization followed by the spray drying of nanodispersion. Characterization of the nanoparticles was done by particle size analysis, zeta potential measurement and scanning electron microscopy. The size of ETPL nanoparticles was 387 nm and possessed negative charge. Etoposide and ETPL nanoparticles were radiolabeled with 99mTc with high labeling efficiency. The labeled complexes showed good in vitro stability in the presence of DTPA/cysteine and serum stability. Etoposide and ETPL nanoparticles were injected by subcutaneous, intravenous or intraperitoneal routes and their biodistribution and tumor uptake were determined. Subcutaneous injection reduced the distribution of ETPL nanoparticles to all the tissues studied whereas after intraperitoneal injection, the distribution of ETPL nanoparticles to tissues was higher than free etoposide. The intravenous injection resulted in lower concentrations of ETPL nanoparticles in the organs of RES compared to free etoposide. ETPL nanoparticles experienced significantly high brain distribution after intraperitoneal injection indicating its potential use in targeting etoposide to brain tumors. After subcutaneous injection, the tissue distribution of ETPL nanoparticles increased with time indicating their accumulation at the injection site for a longer time. The tumor uptake of both etoposide and ETPL nanoparticles was significantly high after subcutaneous injection (P<0.001) compared to the other routes of administration. The tumor concentration of ETPL nanoparticles after subcutaneous injection was 59 folds higher than that obtained after intravenous and 8 folds higher than after intraperitoneal route at 24 h post-injection. The tumor concentration of ETPL nanoparticles increased with time after subcutaneous injection indicating the slower and progressive penetration from the injection site into the tumor. The study signifies the advantage of incorporating etoposide into tripalmitin nanoparticles in controlling its biodistribution and enhancing the tumor uptake by several folds. The study also reveals that, of the three routes investigated, subcutaneous injection is the route of preference for facilitating high tumor uptake and retention and is likely to have greater antitumor effect resulting in tumor regression.

Plasma kinetics and uptake by the tumor of a cholesterol-rich microemulsion (LDE) associated to etoposide oleate in patients with ovarian carcinoma

OBJECTIVES

Previously, we reported that etoposide oleate associated to a cholesterol-rich microemulsion (LDE) is taken up by malignant cells overexpressing low-density lipoprotein (LDL) receptors. The association is stable, preserves antiproliferative activity of the drug, and reduces toxicity to animals. Here, we determined in patients the plasma kinetics of LDE-etoposide oleate and verified whether the complex concentrates in ovarian carcinomas.

METHODS

[(3)H]-etoposide oleate associated to LDE labeled with [(14)C]-cholesteryl oleate was intravenously injected into four ovarian carcinoma patients (50 +/- 8.7 years) 24 h before surgery. Blood samples were collected over a 24-h period to determine the radioactivity plasma decay curves, and the plasma fractional clearance rate (FCR) was calculated by compartmental analysis. Specimens of tumors and normal ovaries excised during the surgery were collected for lipid extraction and radioactive counting.

RESULTS

FCRs of LDE label and of the drug were similar (0.0985 and 0.1722, respectively, P = 0.2422). [(14)C]-LDE uptake was 4.9 times and [(3)H]-etoposide oleate uptake was 4.1 times greater in the ovarian tumors than in the contralateral normal ovaries (LDE uptake, in cpm/g = 560 +/- 171 and 146 +/- 59; etoposide oleate uptake = 346 +/- 75 and 103 +/- 56, respectively).

CONCLUSIONS

Most of the drug is retained in the microemulsion particles until its removal from the circulation and internalization by the cells. In addition, LDE-etoposide oleate has the ability to concentrate in malignant ovarian tissues. Therefore, the complex may be used to direct and concentrate etoposide oleate in ovarian carcinomas.

The extent of chromosomal aberrations induced by chemotherapy in non-human primates depends on the schedule of administration

We utilized a non-human primate model, the rhesus monkey (Macaca mulatta), to quantitate the extent of chromosomal damage in bone marrow cells following chemotherapy. Thiotepa, etoposide, and paclitaxel were chosen as the chemotherapy agents due to their distinct mechanisms of action. Chromosomal aberrations were quantitated using traditional Giemsa stain. We sought to evaluate the extent to which genotoxicity was dependent on the schedule of administration by giving chemotherapy as either a bolus or a 96 h continuous infusion. Neutropenia and areas under the concentration curve (AUCs) were monitored to ensure comparable cytotoxicity and dose administered. At least 100 metaphases were scored in each marrow sample by an investigator unaware of the treatment history of the animals. All three drugs produced a statistically significant higher percentage of abnormal metaphases following bolus chemotherapy (p<0.0001, p=0.0015 and p<0.0001 for thiotepa, etoposide and paclitaxel, respectively). We conclude that infusional administration of thiotepa, etoposide and paclitaxel is less genotoxic to normal bone marrow cells than is bolus administration. These results suggest infusional regimens may be considered where there are concerns about long-term genotoxic sequelae, including secondary cancer, teratogenicity, or possibly the development of drug resistance. We believe this approach provides a reproducible model in which drugs and eventually, regimens can be compared.

A phase I and pharmacologic study of idarubicin, cytarabine, etoposide, and the multidrug resistance protein (MDR1/Pgp) inhibitor PSC-833 in patients with refractory leukemia

This study was conducted to define the maximum tolerated dose (MTD), dose limiting toxicity (DLT), and pharmacokinetics of idarubicin when administered with and without the P-glycoprotein inhibitor PSC-833 in combination with cytarabine, and etoposide. Fifteen patients with relapsed and refractory acute leukemia were enrolled and received cytarabine as a 7-day continuous infusion, with etoposide and idarubicin administered for any three consecutive days during the cytarabine infusion. Two hours prior to the second dose of idarubicin, PSC-833 administration was initiated. The pharmacokinetics of idarubicin alone and with PSC-833 was assessed at three idarubicin dose levels (6, 8 and 10 mg/m(2)). The MTD of idarubicin in this combination was 8 mg/(m(2) day) with a DLT of oral mucositis. The complete remission rate (on an intent-to-treat basis) for this regimen was 33%, with a median duration of 6 months. The clearance of idarubicin was 140 +/- 200 and 181 +/- 94.3 l/h for idarubicin alone and with PSC-833, respectively. The volume of distribution of the central compartment was 423 +/- 443 and 337 +/- 394 l for idarubicin alone and in combination with PSC-833, respectively. This combination including PSC-833 was well tolerated. Although a pharmacokinetic interaction might have been expected, PSC-833 did not significantly alter the disposition of idarubicin.

Pharmacokinetics and Tissue Distribution of Etoposide Delivered in Parenteral Emulsion

Etoposide was incorporated in an injectable parenteral emulsion, in an attempt to alter its pharmacokinetics and improve anticancer activity. Parenteral emulsion of etoposide (EPE), which remained stable over 6 months' storage, was prepared (under optimal experimental conditions) using soybean oil and phosphatidylcholine as emulsifier. The particle size distribution and zeta potential were measured using photon correlation spectroscopy. The pharmacokinetics and tissue distribution of EPE and commercial etoposide injectable solution (ETP) were studied in Swiss albino mice. The antitumor activity was performed on BDF1 mice bearing Lewis lung carcinoma. The particle size distribution with polydispersity indices, zeta potential, entrapment efficacy, and assay of EPE were found to be 218.7 +/- 4.7 (0.14 +/- 0.0) nm, -53.5 +/- 0.2 mV, 75 +/- 2.1%, and 0.85 +/- 0.1 mg/mL, respectively. The EPE was stable for >6 months and drug leaching was 5.8 +/- 1.5%. The pharmacokinetics and tissue distribution of EPE was significantly different than that of ETP. The EPE showed high AUC(0-alpha), MRT (mean residence time), and lower clearance than that of ETP. It was found that etoposide concentration was higher in liver, spleen, and lung after ETP administration when compared with EPE; however, in heart and brain, etoposide was more after EPE than that of ETP. The EPE showed lower reticuloendothelial system (liver and spleen) tissue uptake. The anticancer activity of EPE was higher in Lewis lung carcinoma-bearing mice. On the fifteenth day of transplantation, the percentage of tumor growth suppression rate was 63.23% in EPE-treated mice and 33.78% in ETP-treated mice.

MRP2 (ABCC2) transports taxanes and confers paclitaxel resistance and both processes are stimulated by probenecid

ATP binding cassette (ABC) multidrug transporters such as P-glycoprotein (P-gp, ABCB1) and BCRP (ABCG2) confer resistance against anticancer drugs and can limit their oral availability, thus contributing to failure of chemotherapy. Like P-gp and BCRP, another ABC transporter, MRP2 (ABCC2), is found in apical membranes of pharmacologically important epithelial barriers and in a variety of tumors. MRP2 transports several anticancer drugs and might thus have a similar impact on chemotherapy as P-gp and BCRP. We here show that human MRP2 transduced into epithelial MDCKII cells efficiently transported the taxane anticancer drugs paclitaxel and docetaxel and that this transport could be substantially stimulated with the drug probenecid, a representative of a range of MRP2-stimulating drugs. Transport of 2 previously identified MRP2 substrates, etoposide and vinblastine, was likewise stimulated by probenecid. MRP2 further conferred substantial resistance against paclitaxel toxicity, and this resistance was 2.7-fold stimulated by probenecid. Our data indicate that MRP2 function might affect chemotherapy with taxanes, potentially influencing both tumor resistance and taxane pharmacokinetics. Moreover, coadministration of probenecid and other MRP2-stimulating drugs might lead to unforeseen drug-drug interactions by stimulating MRP2 function, potentially leading to suboptimal levels of taxanes and other anticancer drugs in plasma and tumor.

Resistance to topoisomerase II inhibitors in human glioma cell lines overexpressing multidrug resistant associated protein (MRP) 2

For understanding of the resistance to topoisomerase II inhibitors, 50 sublines were isolated as single clones from parental glioma cell lines by exposure to VP-16 or m-AMSA. The quantitative aspects of topoisomerase II alpha,multi drug resistant gene (MDR)-1, breast cancer resistance protein (BCRP), and multidrug resistant associated protein (MRP) 1-5 were studied by Northern blotting in 50 resistant cell lines. By understanding the function of MRP2, we picked up three drug resistant sublines (T98G-ml, T98G-m2, and gli36-VP1) that overexpressed MRP2, but did not overexpress MDR-1 or MRP1-5 except 2. Moreover, in the results of northern blot analysis of mRNA for topoisomerase II alpha identical results are observed in parental cell lines and their resistant cell lines, suggesting that alterations in topoisomerase II do not account for the resistance in these cells. To determine whether the cellular sensitivity to anticancer agents was closely associated with the cellular levels of MRP2, we established cell lines with the same levels of MRP2 as their parental cells by introducing the MRP2 antisense expression plasmid into resistant cells. Etoposide (VP-16) accumulation and efflux studies were carried out in the parental cell lines and their drug resistant cell lines. Decreases in the HS-VP-16 accumulation and increases in the efflux were observed in these drug resistant cell lines. In the cytotoxicity assay, these drug resistant cell lines were resistant to multiple topoisomerase II inhibitors with little cross resistance to vincristine, and display efflux of VP-16. We found that the resistant cells transfected with MRP2 antisense cDNA displayed increased cellular levels of VP-16 and enhanced sensitivities to topoisomerase II inhibitors. In this study on the T98G-ml, T98G-m2, and gli36-VP1 cell lines, we showed a high correlation between MRP2 mRNA and VP-16 efflux, suggesting that MRP2 could be a new transporter for topoisomerase II inhibitors.

Plasma etoposide catechol increases in pediatric patients undergoing multiple-day chemotherapy with etoposide

PURPOSE

The purpose of this research was to determine inter- and intrapatient differences in the pharmacokinetic profiles of etoposide and its genotoxic catechol metabolite during conventional multiple-day dosing of etoposide in pediatric patients.

EXPERIMENTAL DESIGN

Seven pediatric patients with various malignancies received etoposide at a dose of 100 mg/m(2) i.v. over 1 h daily for 5 days. Blood samples were taken at selected time points on days 1 and 5. Plasma and protein-free plasma concentrations of etoposide and etoposide catechol were determined using a validated liquid chromatography/tandem mass spectrometry assay. Pharmacokinetic parameters of both etoposide and etoposide catechol were calculated using the WinSAAM modeling program developed at NIH.

RESULTS

The mean maximum concentration (C(max)) for total (0.262 +/- 0.107 micro g/ml) and free catechol (0.0186 +/- 0.0082 micro g/ml) on day 5 were higher than the mean C(max) for total (0.114 +/- 0.028 micro g/ml) and free catechol (0.0120 +/- 0.0091 micro g/ml) on day 1. The mean area under the plasma concentration-time curve (AUC)(24h) for total (105.4 +/- 49.1 micro g.min/ml) and free catechol (4.89 +/- 2.23 micro g x min/ml) on day 5 were much greater (P < 0.05) than those for total (55.9 +/- 16.1 micro g x min/ml) and free catechol (3.04 +/- 1.04 micro g x min/ml) on day 1. In contrast, the AUC(24h) for etoposide was slightly lower on day 5 than on day 1.

CONCLUSIONS

The C(max) and AUC(24h) for etoposide catechol were significantly higher on day 5 than on day 1. This suggests that metabolism of etoposide to its catechol metabolite increases in pediatric patients receiving multiple-day bolus etoposide infusions. These findings may be relevant to future reduction of the risk of leukemia as a treatment complication, because etoposide and etoposide catechol are both genotoxins.