Pharmacokinetics Of Etoposide Research Articles

Efficacy, safety and pharmacokinetics of apatinib plus etoposide versus apatinib alone for platinum-resistant recurrent ovarian cancer: protocol of a multicenter, open-label, randomized phase 2 trial

Efficacy, safety and pharmacokinetics of apatinib plus etoposide versus apatinib alone for platinum-resistant recurrent ovarian cancer: protocol of a multicenter, open-label, randomized phase 2 trial

Effect of Moderate Malnutrition on thePharmacokinetics of Etoposide and Vincristine in Freshly Weaned Rats.

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. 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. We developed a murine model of moderate childhood malnutrition by subjecting freshly weaned Sprague-Dawley rats to 8% protein diet for 8weeks. 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. 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. 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.

Oral etoposide and zosuquidar bioavailability in rats: Effect of co-administration and in vitro-in vivo correlation of P-glycoprotein inhibition

P-glycoprotein inhibitors, like zosuquidar, have widely been used to study the role of P-glycoprotein in oral absorption. Still, systematic studies on the inhibitor dose-response relationship on intestinal drug permeation are lacking. In the present study, we investigated the effect of 0.79 nM-2.5 μM zosuquidar on etoposide permeability across Caco-2 cell monolayers. We also investigated etoposide pharmacokinetics after oral or IV administration to Sprague Dawley rats with co-administration of 0.063–63 mg/kg zosuquidar, as well as the pharmacokinetics of zosuquidar itself. Oral zosuquidar bioavailability was 2.6–4.2%, while oral etoposide bioavailability was 5.5 ± 0.9%, which increased with increasing zosuquidar doses to 35 ± 5%. The intestinal zosuquidar concentration required to induce a half-maximal increase in bioavailability was estimated to 180 μM. In contrast, the IC50 of zosuquidar on etoposide permeability in vitro was only 5–10 nM, and a substantial in vitro-in vivo discrepancy of at least four orders of magnitude was thereby identified. Overall, the present study provides valuable insights for future formulation development that applies fixed dose combinations of P-glycoprotein inhibitors to increase the absorption of poorly permeable P-glycoprotein substrate drugs.

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.

Population pharmacokinetics of carboplatin, etoposide and melphalan in children: a re-evaluation of paediatric dosing formulas for carboplatin in patients with normal or mild impairment of renal function.

Carboplatin dosage is calculated by using the estimated glomerular filtration rate (GFR) to achieve a target plasma area under the plasma concentration-time curve (AUC). The aims of the present study were to investigate factors that influence the pharmacokinetics of carboplatin in children with high-risk neuroblastoma, and whether target exposures for carboplatin were achieved using current treatment protocols. Data on children receiving high-dose carboplatin, etoposide and melphalan for neuroblastoma were obtained from two study sites [European International Society for Paediatric Oncology (SIOP) Neuroblastoma study, Children's Hospital at Westmead; n = 51]. A population pharmacokinetic model was built for carboplatin to evaluate various dosing formulas. The pharmacokinetics of etoposide and melphalan was also investigated. The final model was used to simulate whether target carboplatin AUC (16.4mg ml-1 ·min) would be achieved using the paediatric Newell formula, modified Calvert formula and weight-based dosing. Allometric weight was the only significant, independent covariate for the pharmacokinetic parameters of carboplatin, etoposide and melphalan. The paediatric Newell formula and modified Calvert formula were suitable for achieving the target AUC of carboplatin for children with a GFR <100ml min-1 1.73m-2 but not for those with a GFR ≥100ml min-1 1.73m-2 . A weight-based dosing regimen of 50mg kg-1 achieved the target AUC more consistently than the other formulas, regardless of renal function. GFR did not appear to influence the pharmacokinetics of carboplatin after adjusting pharmacokinetic parameters for weight. This model-based approach validates the use of weight-based dosing as an appropriate alternative for carboplatin in children with either mild renal impairment or normal renal function.

Pharmacokinetics and dose adjustment of etoposide administered in a medium-dose etoposide, cyclophosphamide and total body irradiation regimen before allogeneic hematopoietic stem cell transplantation.

BackgroundWe investigated the pharmacokinetics of etoposide (ETP) to reduce the inter-individual variations of ETP concentrations in patients with acute leukemia who underwent allogeneic hematopoietic stem cell transplantation. We also carried out an in vivo study using rats to verify the dose adjustment.MethodsThis study included 20 adult patients. ETP was administered intravenously at a dose of 15 mg/kg once daily for 2 days (total dose: 30 mg/kg) combined with standard conditioning of cyclophosphamide and total body irradiation. In an in vivo study using rats, ETP was administered intravenously at a dose of 15 mg/kg or an adjusted dose. The ETP plasma concentration was determined by using HPLC. The pharmacokinetic parameters were estimated by using a 1-compartment model.ResultsThe peak concentration (Cmax) of ETP and the area under the plasma concentration-time curve (AUC) of ETP differed greatly among patients (range of Cmax, 51.8 - 116.5 μg/mL; range of AUC, 870 - 2015 μg · h/mL). A significant relationship was found between Cmax and AUC (R = 0.85, P < 0.05). Distribution volume (Vd) was suggested to be one of the factors of inter-individual variation in plasma concentration of ETP in patients (range of Vd, 0.13 - 0.27 L/kg), and correlated with Alb and body weight (R = 0.56, P < 0.05; R = 0.40, P < 0.05 respectively). We predicted Vd of rats by body weight of rats (with normal albumin levels and renal function), and the dose of ETP was adjusted using predicted Vd. In the dose adjustment group, the target plasma ETP concentration was achieved and the variation of plasma ETP concentration was decreased.ConclusionThe results suggested that inter-individual variation of plasma concentration of ETP could be reduced by predicting Vd. Prediction of Vd is effective for reducing individual variation of ETP concentration and might enable a good therapeutic effect to be achieved.

Pharmacokinetics of Chemotherapeutic Drugs in Pediatric Patients With Down Syndrome and Leukemia.

Children with Down syndrome (DS) have a 10- to 30-fold increased risk of developing acute myeloid leukemia or acute lymphoblastic leukemia. Patients with DS and leukemia are treated with the same chemotherapeutic agents as patients without DS. Treatment regimens for pediatric leukemia comprise multiple cytotoxic drugs including methotrexate, doxorubicin, vincristine, cytarabine, and etoposide. There have been reports of increased toxicity, as well as altered therapeutic outcomes in pediatric patients with DS and leukemia. This review is focused on the pharmacokinetics of cytotoxic drugs in pediatric patients with leukemia and DS. The available literature suggests that methotrexate and thioguanine display altered pharmacokinetic parameters in pediatric patients with DS. It has been hypothesized that the variable pharmacokinetics of these drugs may contribute to the increased incidence of treatment-related toxicities seen in DS. Data from a small number of studies suggest that the pharmacokinetics of vincristine, etoposide, doxorubicin, and busulfan are similar between patients with and without DS. Definitive conclusions regarding the pharmacokinetics of cytotoxic drugs in pediatric patients with leukemia and DS are difficult to reach due to limitations in the available studies.

Etoposide pharmacokinetics impact the outcomes of lymphoma patients treated with BEAM regimen and ASCT: a multicenter study of the LYmphoma Study Association (LYSA).

Relationships between pharmacokinetic (PK) parameters of etoposide and toxicity survivals were reported in cancer patients treated at standard doses. The clinical impact of PK variations of etoposide high doses has never been explored in lymphoma patients. The primary objective of LYMPK study was to prospectively assess the impact of etoposide PK parameters on outcomes in lymphoma patients receiving high-dose chemotherapy regimen (carmustine, cytarabine, etoposide and melphalan) followed by autologous stem cell transplant (ASCT). Individual etoposide PK parameters were estimated with a previously reported bi-compartment model using NONMEM(®) program. The impact of PK parameters on toxicity and survival was assessed using univariate/multivariate analyses. A total of 91 patients with malignant lymphoma [non-Hodgkin's lymphoma (NHL): 79; Hodgkin's lymphoma: 12] at first line (n = 49) or relapse (n = 42) were enrolled in five centers. Large inter-individual variabilities in individual PK values were found for the same administration doses. In NHL patients, cumulative higher trough concentrations over the eight administrations of the first cycle (TotC min, categorized by the median 58.71 mg/L) had significant prognostic value regarding the 5-year progression-free survival (PFS: 73.6 vs 46.5 %, P = 0.015) and 5-year overall survival (OS: 74.0 vs 52.2 %, P = 0.034). Using a Cox model analysis, integrating disease settings (first line vs recurrent disease), simplified IPI and other prognostic factors, TotC min was the only significant independent prognostic factor influencing PFS, disease-specific survival and OS. This prospective study suggests survival of NHL patients treated with BEAM regimen and ASCT might be improved by increasing etoposide administration dose, or plasma concentration-based adjustment.

Clinical and In Vitro Studies on Impact of High-Dose Etoposide Pharmacokinetics Prior Allogeneic Hematopoietic Stem Cell Transplantation for Childhood Acute Lymphoblastic Leukemia on the Risk of Post-Transplant Leukemia Relapse

The impact of etoposide (VP-16) plasma concentrations on the day of allogeneic hematopoietic stem cell transplantation (allo-HSCT) on leukemia-free survival in children with acute lymphoblastic leukemia (ALL) was studied. In addition, the in vitro effects of VP-16 on the lymphocytes proliferation, cytotoxic activity and on Th1/Th2 cytokine responses were assessed. In 31 children undergoing allo-HSCT, VP-16 plasma concentrations were determined up to 120 h after the infusion using the HPLC–UV method. For mentioned in vitro studies, VP-16 plasma concentrations observed on allo-HSCT day were used. In 84 % of children, VP-16 plasma concentrations (0.1–1.5 μg/mL) were quantifiable 72 h after the end of the drug infusion, i.e. when allo-HSCT should be performed. In 20 (65 %) children allo-HSCT was performed 4 days after the end of the drug infusion, and VP-16 was still detectable (0.1–0.9 μg/mL) in plasma of 12 (39 %) of them. Post-transplant ALL relapse occurred in four children, in all of them VP-16 was detectable in plasma (0.1–0.8 μg/mL) on allo-HSCT day, while there was no relapse in children with undetectable VP-16. In in vitro studies, VP-16 demonstrated impact on the proliferation activity of stimulated lymphocytes depending on its concentration and exposition time. The presence of VP-16 in plasma on allo-HSCT day may demonstrate an adverse effect on graft-versus-leukemia (GvL) reaction and increase the risk of post-transplant ALL relapse. Therefore, if 72 h after VP-16 administration its plasma concentration is still above 0.1 μg/mL then the postponement of transplantation for next 24 h should be considered to protect GvL effector cells from transplant material.

Pharmacokinetics and Tolerability of Etoposide in Newly Diagnosed Lymphoma Patients with Hepatic Impairment

Background: The addition of etoposide to chemotherapy regimens (e.g.- CHOEP and EPOCH) may be beneficial for the treatment of aggressive lymphomas. Previous studies have shown decreased clearance of etoposide in hepatic impairment leading to a dose reduction or removal of drug. Total clearance of etoposide does not change significantly in patients with elevated bilirubin. However, free (or unbound) etoposide levels are a more accurate measurement of drug clearance (Stewart el al. Changes in the Clearance of Total and Unbound Etoposide in Patients with Liver Dysfunction. J Clin Oncol. 1990 Nov;8(11):1874-9.). No studies have analyzed etoposide pharmacokinetics and clinical toxicity in lymphoma patients with hepatic impairment.Methods: Patients with newly diagnosed aggressive lymphoma received 1 to 8 cycles of DA-EPOCH +/-R at the NCI. Of 56 pts studied, 48 had normal and 8 had elevated bilirubin (median 3.4mg/dL, range 1.4-22.5mg/dL). All patients received full dose etoposide at 200mg/m2 over 96-hours on cycle 1. Blood samples were collected at 0, 22 and 96 hours after infusion began.Results: There was no significant difference between free etoposide clearance (Cl) and the free etoposide concentration (Css) in patients with elevated versus normal bilirubin (see table below). In all patients, irrespective of bilirubin, there was no significant correlation between free etoposide Cl, free etoposide Css and creatinine clearance (CrCl) or age. Neutropenia and thrombocytopenia was higher in patients with elevated bilirubin. Complete response (CR) was achieved in 75% (6/8) versus 85% (41/48) and PR in 0% (0/8) vs 4% (2/48) of patients with elevated vs normal bilirubin.Conclusions: Etoposide pharmacokinetics were not altered in patients with abnormal versus normal hepatic function. Although there was an increase in hematologic toxicities, there was no difference in Css or Cl of etoposide. Importantly, there were no significant differences in febrile neutropenia or grade 3/4 toxicities. The toxicity difference is likely attributed to other drugs. Response rates were similar between the 2 groups. Our results do not support the empiric dose reduction of etoposide in patients with aggressive lymphomas receiving potentially curative treatment.TableResultsElevated BilirubinNormal Bilirubinp-valueMedian age (yrs)39 (17-59)54 (20-75)0.15 IPI (int hi/hi risk)75% (6/8)23% (11/48)0.0070ANC nadir < 500/mm3 (C1)100% (8/8) 54% (26/48)0.017PLT nadir < 25x103/mm3 (C1)38% (3/8)4% (2/48)0.017Febrile Neutropenia (C1)13% (1/8)13% (6/48)1.00G3/4 GI and neuro tox (C1)38% (3/8)13% (6/48)0.11Median free etoposide clearance on C1 (ml/min/m2)724 (438-1413)663 (199-1148)0.40Median free etoposide concentration on C1 (μM)0.082 (0.044-0.135)0.089 (0.052-0.298)0.44 DisclosuresNo relevant conflicts of interest to declare.

P67 * DEFINING A TARGET INTRA-CEREBROSPINAL FLUID STEADY STATE ETOPOSIDE CONCENTRATION [CSF ETOPOSIDE] FOR PHASE I STUDY IN CHILDREN WITH LEPTOMENINGEAL METASTASIS (LM): INTREPID, A FIRST IN MAN STUDY

INTRODUCTION: Continuous intra-CSF etoposide infusion may optimise etoposide pharmacokinetics by bypassing the blood-brain-barrier and compensating for CSF bulk flow removal, at < 1/340th dose of standard regimens. A 3 + 3 phase I study is proposed, escalating target [CSF etoposide] and infusion durations of intra-CSF etoposide in children with LM. We justify target [CSF etoposide] and infusion durations based upon previously reported clinical and our own preclinical studies. METHOD: AUC24 values were calculated from Fleischhack report of 24 patients receiving intra-ventricular etoposide at 0.25 mg/12h, 0.5 mg/24h or 1 mg/24h, for 5 days, q 2-4 wks (n = 119 cycles), no dose limiting toxicity was reported. The AUC24 values derived from these clinical studies were compared to etoposide cytotoxicity data in human tumour and neural stem cell 3D co-cultures. AUC values were selected to derive target [CSF etoposide], levels 1 & 2 for infusion durations of 7, 10 and 14 days: AUC24= [CSF etoposide] x time (h). RESULTS: Based upon 0.25 mg/12h dose level, the AUC24 25 µg x h/ml (level 1) predicted [CSF etoposide] 1 µg/ml over 24 hours and an AUC7day of 175 µg x h/ml. The cytotoxicity assay [etoposide] of 0.8-1.2 µg/ml resulted in 22% neural stem cell and 8% tumour cell viability, illustrating differential toxicity. Level 1[CSF etoposide] was selected as 0.8 µg/ml as equivalent of AUC24 20, for 7 days (AUC7day 140). Level 2 [CSF etoposide] of 1.2 µg/ml was selected, (AUC7day 210, AUC10days 300; AUC14day 420). CONCLUSION: Target [CSF etoposide] will be 0.8 µg/ml (level 1) to 1.2 µg/ml (level 2), with infusion durations of 7, 10 or 14 day.

Investigating the pharmacokinetics and dosing of anticancer drugs in infants and young children.

10033 Background: Dosing regimens for anticancer drugs administered to infants and young children frequently differ between tumour types and protocols, with dosing based on body weight commonly implicated. We have recently highlighted a reduced exposure to 13-cis-retinoic acid in neuroblastoma patients &lt;12kg dosed on body weight (Clin Cancer Res19:469-79,2013). Given the toxicity observed with many chemotherapeutics, it is appropriate to establish a pharmacological basis for dose adjustments implemented in younger patients. Methods: The pharmacokinetics of cyclophosphamide (CPA), actinomycin D (Act D), carboplatin and etoposide were investigated in children aged 0-6, 6-12 and 12-24 months. CPA was administered i.v. at a dose of 100-1,500 mg/m2, with infusion times up to 1.5h, Act D as a bolus i.v. infusion of 0.4-1.5mg/m2, carboplatin as an i.v. dose of 3.8-30mg/kg over 1-4h and etoposide as an i.v. dose of 3.5-14mg/kg over 1-6h. Eighty-six children were studied at 14 centres, with PK sampling carried out over 24h for CPA and Act D, 3h for carboplatin and up to 6h for etoposide. Plasma concentrations of CPA, Act D and etoposide were determined by LC-MS analysis, with carboplatin concentrations determined in plasma ultrafiltrate by AAS. PK parameters were calculated using WinNonlin or previously used PK models as appropriate. Results: Clearance values normalized to body weight ranged from 0.5-7.7 ml/min/kg for CPA, 1.7-17.4 for Act D, 1.6-10.5 for carboplatin and 0.2-1.7 for etoposide. No significant differences in normalized clearance were observed between the defined age cohorts of 0-6, 6-12 and 12-24 months and the data do not indicate clear differences in drug handling in infants and young children. However, when normalized clearance values were compared to data from older children, a greater degree of inter-patient variation was observed in patients &lt;2 years than in children &gt;2 years for all drugs. Conclusions: While normalized clearance values for the drugs studied do not support reduced dosing approaches, data suggest that individual drug clearance values may be more difficult to predict in younger patients. Further studies involving additional anticancer drugs may allow more rationale approaches to dosing. Clinical trial information: NCT00897871.

Oral treatment with etoposide in small cell lung cancer – dilemmas and solutions

BackgroundEtoposide is a chemotherapeutic agent, widely used for the treatment of various malignancies, including small cell lung cancer (SCLC), an aggressive disease with poor prognosis. Oral etoposide administration exhibits advantages for the quality of life of the patient as well as economic benefits. However, widespread use of oral etoposide is limited by incomplete and variable bioavailability. Variability in bioavailability was observed both within and between patients. This suggests that some patients may experience suboptimal tumor cytotoxicity, whereas other patients may be at risk for excess toxicity.ConclusionsThe article highlights dilemmas as well as solutions regarding oral treatment with etoposide by presenting and analyzing relevant literature data. Numerous studies have shown that bioavailability of etoposide is influenced by genetic, physiological and environmental factors. Several strategies were explored to improve bioavailability and to reduce pharmacokinetic variability of oral etoposide, including desired and undesired drug interactions (e.g. with ketoconazole), development of suitable drug delivery systems, use of more water-soluble prodrug of etoposide, and influence on gastric emptying. In addition to genotype-based dose administration, etoposide is suitable for pharmacokinetically guided dosing, which enables dose adjustments in individual patient.Further, it is established that oral and intravenous schedules of etoposide in SCLC patients do not result in significant differences in treatment outcome, while results of toxicity are inconclusive. To conclude, the main message of the article is that better prediction of the pharmacokinetics of oral etoposide may encourage its wider use in routine clinical practice.

Enhanced tumor uptake, biodistribution and pharmacokinetics of etoposide loaded nanoparticles in Dalton′s lymphoma tumor bearing mice

Background:Nanotechnology plays a remarkable role in the field of the treatment of Lymphomas associated with tumor.Objective:The purpose of this study is to determine and to compare the tumor uptake, biodistribution and pharmacokinetics of radiolabeled etoposide and etoposide loaded nanoparticles in Dalton's Lymphoma tumor bearing mice and healthy mice.Materials and Methods:Etoposide loaded nanoparticles were prepared by nanoprecipitation technique using the poly (lactic-co-glycolic) acid (PLGA) in the presence of Pluronic F 68 (F 68) as a stabilizer and characterized by particle size analyzer, zeta potential and transmission electron microscope. Etoposide and etoposide loaded nanoparticles were labeled with Technetium-99m (Tc-99m) by the direct method and various quality control tests were carried out. The labeling parameters like labeling efficiency, stability, etc., were optimized to get high labeling efficiency as well as stability of the labeled formulations. Tc-99m labeled formulations were administered intravenously in Balb C mice and their biodistribution and pharmacokinetics were determined.Results:Mean size of the etoposide loaded PLGA nanoparticles was found to be 105.1 nm. The concentration of both free etoposide and nanoparticles increased with time and showed higher tumor concentrations of both free etoposide and nanoparticles increased with time and showed higher retention, indicating their applicability in effective and prolonged tumor therapy. Nuclear scintigraphic images confirm the presence of labeled complexes at the site of tumor for 24 h at higher concentration than in the normal muscles.Conclusion:This study indicated higher tumor affinity and targeting properties of etoposide loaded nanoparticles than free etoposide.

Effects of morin on the pharmacokinetics of etoposide in 7,12-dimethylbenz[a]anthracene-induced mammary tumors in female Sprague-Dawley rats

Etoposide, used for the treatment of breast cancer, is mainly metabolized via hepatic cytochrome P450 (CYP) 3A4 in humans and is also a substrate for p-glycoprotein (P-gp). Morin is known to be able to modulate the activities of metabolic enzymes including CYPs and can act as a potent P-gp inhibitor. The purpose of this study was to investigate the effects of morin on the pharmacokinetics of etoposide in rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors. Etoposide was administered intravenously (2mg/kg) and orally (10 mg/kg) in control and DMBA rats without (DMBA-WOM) and with (DMBA-WM) morin (15mg/kg). Protein and mRNA expression of CYP3A and P-gp was analyzed, and the tissue distribution of etoposide was also measured. Both protein and mRNA expression of CYP3A and P-gp was inhibited by morin in the liver, intestine and breast tumors of DMBA-WM rats. After both intravenous and oral administration of etoposide in DMBA-WM rats, the total area under the plasma concentration-time curve from time zero to infinity (AUC) of etoposide was significantly greater, and the time-averaged total body clearance (CL) of etoposide was significantly slower than those in control and DMBA-WOM rats. The amount of etoposide recovered from each tissue was significantly higher in DMBA-WM rats, especially in the breast tumor, liver and large intestine. No significant differences between control and DMBA-WOM rats were observed. Taken together, greater AUC and slower CL of etoposide in DMBA-WM rats could possibly be due to the inhibition of hepatic CYP3A (intravenous) and mainly due to the inhibition of intestinal CYP3A and P-gp (oral) by morin.

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 Vd) 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 (Vd). 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 Vd were 2.31 L/hr and 17.5 L, respectively. The CL and Vd 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 Vd increased with increasing weight similar to BSA.

Population pharmacokinetics of cytarabine, etoposide, and daunorubicin in the treatment for acute myeloid leukemia

Interpatient variability in the pharmacokinetics (PK) of cytarabine, etoposide, and daunorubicin following body surface area-adjusted doses calls for studies that point to other covariates to explain this variability. The purpose of this study was to investigate such relationships and give insights into the PK of this combination treatment. A prospective population PK study of twenty-three patients with acute myeloid leukemia was undertaken. Plasma concentrations of patients were determined by high-pressure liquid chromatography. PK models were developed with NONMEM; for daunorubicin, PK information from a prior study was utilized. Baseline white blood cell count (bWBC) influenced the PK for all drugs. A small, statistically insignificant improvement in model fit was achieved when a relationship between bWBC and daunorubicin central volume of distribution was included. The volume increased 1.9% for each increase in bWBC by 1 × 10(6) cells/mL. The clearances of etoposide and cytarabine were significantly increased and decreased, respectively, by increased bWBC. Tenfold changes in bWBC were needed for these relationships to have potential clinical relevance. A decrease in creatinine clearance of 60 mL/min resulted in a decrease in etoposide clearance of 32%. Population-based models characterized the PK for all three drugs. bWBC was a significant covariate for etoposide and cytarabine and showed a trend for daunorubicin. Linking the significant bWBC relationships and the relationship between kidney function and etoposide clearance to clinical end points would support dose individualization. Patients with above-normal creatinine clearances and high bWBC may receive sub-optimal treatment due to elevated etoposide clearances.

Cysteine effects on the pharmacokinetics of etoposide in protein–calorie malnutrition rats: increased gastrointestinal absorption by cysteine

Protein–calorie malnutrition (PCM) occurs frequently in advanced cancer patients and has a profound impact on the toxicity of many drugs. Thus, the pharmacokinetics of etoposide were evaluated in control, control with cysteine (CC), PCM, and PCM with cysteine (PCMC) rats.Etoposide was administered intravenously (2 mg/kg) or orally (10 mg/kg). Changes in hepatic and intestinal cytochrome P450s (CYPs) and effects of cysteine on intestinal P-glycoprotein (P-gp)-mediated efflux were also measured.In PCM rats, the CLNR (AUC0–∞) of intravenous etoposide was significantly slower (greater) than that in controls, because of the significant decrease in the hepatic CYP3A subfamily and P-gp. In PCMC rats, the slowed CLNR of etoposide in PCM rats was restored to the control level by cysteine treatment. PCMC rats showed a significantly greater AUC0–6 h of oral etoposide than PCM rats, primarily because of the increased gastrointestinal absorption of etoposide as a result of the inhibition of intestinal P-gp by cysteine.The gastrointestinal absorption of an oral anticancer drug, which is a substrate of P-gp, may be improved by co-administration of cysteine in advanced cancer patients if the present rat data can be extrapolated to patients.

Effects of oral curcumin on the pharmacokinetics of intravenous and oral etoposide in rats: possible role of intestinal CYP3A and P‐gp inhibition by curcumin

This study aimed to investigate the effects of oral curcumin on the pharmacokinetics of intravenous and oral etoposide in rats. Intravenous (6 mg/kg) or oral (2 mg/kg) etoposide was administered to rats in the absence and the presence of oral curcumin (0.4, 2 or 8 mg/kg). The effects of curcumin on the P-glycoprotein (P-gp) and CYP3A4 activity was also evaluated. Curcumin inhibited CYP3A4 enzyme activity with a 50% inhibition concentration (IC(50) ) of 2.7 µM. In addition, curcumin (10 µm) significantly enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp. Compared with the control group (given etoposide alone), curcumin (2 or 8 mg/kg) increased significantly the oral bioavailability (AUC and C(max) ) of etoposide. Consequently, the extent of absolute oral bioavailability (F) of etoposide with curcumin was significantly enhanced compared with that in the control group. In contrast, curcumin did not affect the pharmacokinetics of etoposide after intravenous administration. Therefore, the enhanced oral bioavailability of etoposide in the presence of curcumin might be due mainly to inhibition of the P-gp efflux pump in the small intestine and possibly by reduced first-pass metabolism of etoposide in the small intestine by inhibition of CYP3A activity in rats. The combined use of curcumin may be helpful to improve the F of etoposide in chemotherapeutic applications.

Abstract 5461: Effects of morin on the pharmacokinetics of etoposide in rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors

Abstract Etoposide, used for the treatment of breast cancer, is mainly metabolized via hepatic cytochrome P450 (CYP) 3A4 in humans and rats and it has been reported that protein expression of CYP3A4 was significantly lower in breast cancer. Etoposide is also a substrate for P-glycoprotein (P-gp). Morin could modulate the activities of metabolic enzymes including CYPs and could be a potent P-gp inhibitor. The purpose of this study was to investigate the effects of morin on the pharmacokinetics of etoposide in 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor rats (DMBA rats) as an animal model of human breast cancer. Etoposide was administered intravenously (2 mg/kg) and orally (10 mg/kg) in control and DMBA rats without (DMBA-WOM) and with (DMBA-WM) oral morin (15 mg/kg). Protein and mRNA expression of CYP3A4 and P-gp were measured using immunoblot analysis and quantitative real-time PCR. After intravenous administration of etoposide in control and DMBA-WOM rats, the area under the plasma concentration-time at time zero to infinity (AUC), total body (CL) and non-renal clearance (CLNR) were comparable but in DMBA-WM rats, AUC was significantly greater (by 49.9∼64.8%), terminal half-life was significantly longer (by 54.4∼157%) and CL and CLNR were significantly slower (by 34.1∼36.1%) than those of control and DMBA-WOM rats. This suggests that DMBA did not affect considerably the hepatic metabolism of etoposide in rats. The mRNA expression of CYP3A4 was lower (by 58.4%) in DMBA rats compared to control rats but the protein expression of hepatic CYP3A subfamily in DMBA rats was comparable to control rats. The greater AUC in DMBA-WM rats could be due to slower CL and this could mainly be due to the slower CLNR than control rats, since renal clearances (CLRs) were comparable among three groups of rats. Therefore, in DMBA-WM rats, the greater AUC and slower CLNR of etoposide could be due to the inhibition of P-gp by morin. The mRNA expression of MDR1 was lower (by 30.4%) in DMBA-WM rats compared to control rats. Thus, the amount (concentration) of etoposide taken into the liver could be somewhat greater than the amount for saturation in hepatic metabolism of etoposide. After oral administration of etoposide in control and DMBA-WOM rats, AUCs were also comparable, suggesting that the effect of DMBA on the intestinal metabolism of etoposide did not seem to be considerable. However, AUC of etoposide in DMBA-WM rats was greater (by 62.5∼80.5%) than those in control and DMBA-WOM rats and this could be due to the inhibition of P-gp by morin; 34.4% lower in mRNA expression of MDR1 by morin. Taken together, the greater AUCs of etoposide in DMBA-WM rats after both intravenous and oral administration of etoposide could possibly be due to the inhibition of P-gp by morin. Supported by National Research Foundation of Korea grant R-2009-006-6765. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5461. doi:10.1158/1538-7445.AM2011-5461