In vitro pharmacodynamic evaluation of VP-16-213 and implications for chemotherapy

Intracerebroventricular drug administration

Among the various routes of drug administration, perhaps the least studied is intracerebroventricular (ICV) administration. This route has been shown to be particularly useful in administering to the central nervous system (CNS) drugs that do not cross the blood-brain barrier readily. As such, the ICV route is a valuable option for providing therapeutic CNS drug concentrations to treat patients with CNS infectious and neoplastic diseases. This route of drug administration also has the advantage of minimizing systemic toxicity.

Dose escalation study to evaluate safety, tolerability and efficacy of intravenous etoposide phosphate administration in 27 dogs with multicentric lymphoma

Comparative oncology has shown that naturally occurring canine cancers are of valuable and translatable interest for the understanding of human cancer biology and the characterization of new therapies. This work was part of a comparative oncology project assessing a new, clinical-stage topoisomerase II inhibitor and comparing it with etoposide in dogs with spontaneous lymphoma with the objective to translate findings from dogs to humans. Etoposide is a topoisomerase II inhibitor widely used in various humans' solid and hematopoietic cancer, but little data is available concerning its potential antitumor efficacy in dogs. Etoposide phosphate is a water-soluble prodrug of etoposide which is expected to be better tolerated in dogs. The objectives of this study were to assess the safety, the tolerability and the efficacy of intravenous etoposide phosphate in dogs with multicentric lymphoma. Seven dose levels were evaluated in a traditional 3+3 phase I design. Twenty-seven owned-dogs with high-grade multicentric lymphoma were enrolled and treated with three cycles of etoposide phosphate IV injections every 2 weeks. Adverse effects were graded according to the Veterinary Cooperative Oncology Group criteria. A complete end-staging was realized 45 days after inclusion. The maximal tolerated dose was 300 mg/m2. At this dose level, the overall response rate was 83.3% (n = 6, 3 PR and 2 CR). Only a moderate reversible gastrointestinal toxicity, no severe myelotoxicity and no hypersensitivity reaction were reported at this dose level. Beyond the characterization of etoposide clinical efficacy in dogs, this study underlined the clinical and therapeutic homologies between dog and human lymphomas.

Effectiveness of low-dose oral etoposide treatment in patients with recurrent and platinum-resistant epithelial ovarian cancer

The aim of this study was to evaluate the efficacy and toxicity profile of oral etoposide (50 mg/day, days 1-14, every 3 weeks) in recurrent platinum-resistant epithelial ovarian cancer (EOC). 52 recurrent platinum-resistant EOC patients followed up in four centres between April 2000 and December 2013 were analysed retrospectively. There was response in a total of 21 patients [partial response (PR) and stable disease (SD)], 12 of them used etoposide in second and third, and 9 of them used it in fourth- to fifth-lines of treatment. The overall response rate was 19.2% and clinical benefit rate was 40.4% [PR (19.2%), SD (21.2%)]. Median overall survival (OS) and progression-free survival (PFS) was 9.95 months (95%CI, 0.2-19.7 months) and 3.2 months (95%CI 2.6-3.8 months), respectively. Grade III-IV haematologic and non-haematologic adverse events were observed in 7 (13.4%) patients. We consider that oral etoposide (50 mg/day, days 1-14, every 3 weeks) is an effective treatment with a manageable adverse effect profile in recurrent platinum-resistant EOC patients. Impact statement What is already known on this subject: Oral etoposide is an effective option for recurrent EOC patients at a dose of 50-100 mg/m²/day (1-21 days, every 28 days) regimen. However, it has a high toxicity rate. What the results of this study add: Oral etoposide at a dose of 50 mg/kg (1-14 days, every 21 days) is an effective treatment with a manageable toxicity profile in platinum- resistant ovarian cancer patients when it is used as ≤4th-line palliative setting. What the implications are of these findings for clinical practice and/or further research: We need trials evaluating the effect of low-dose oral etoposide combination with bevacizumab or other chemotherapy agents (irinotecan and gemcitabine) in platinum-resistant EOC patients.

Oral etoposide in relapsed or refractory Ewing sarcoma: a monoinstitutional experience in children and adolescents

AIMS

To assess the efficacy and toxicity of low-dose oral etoposide (VP) 16 in relapsing/refractory Ewing sarcoma.

METHODS

The records of all patients treated at our department between 1989 and 2012 for relapsing/refractory Ewing sarcoma who received oral VP-16 were analyzed. The dose was 40 mg/m2 daily for 21 consecutive days in every 28. Response was assessed after 2/3 cycles according to Response Evaluation Criteria in Solid Tumors 1.0.

RESULTS

A total of 46 of 58 patients completed at least 2 cycles; 12 suspended the treatment earlier due to rapid disease progression. The patients' median age at diagnosis was 14 years and 25/58 had metastatic disease. All patients received intensive polychemotherapy including VP-16 IV as first- (n = 53) or second-line (n = 5) treatment; 21/58 had myeloablative regimens with peripheral blood stem cell rescue, and 1 underwent allogeneic stem cell transplantation. Oral VP-16 was prescribed as 2nd-, 3rd-, and 4th-line treatment for 19, 27, and 12 patients, respectively. The cycles administered totaled 241 (median 3, mean 4 per patient; range 1-14). A total of 46 of 58 patients were evaluable: 11 responded (9 partial remission, 1 very good partial remission, 1 complete remission) and 10 were stable, the response lasting a mean of 8 months. Hematologic toxicity G3/G4 (in 164/241 evaluable cycles) occurred in 15%, 16%, and 11% of cycles for leukocytes, hemoglobin, and platelets, respectively. There were 5 cases of pneumonia. Two patients developed secondary leukemia after receiving 12 and 14 cycles.

CONCLUSIONS

Low-dose oral VP-16 may be suitable in a palliative setting with an acceptable toxicity. The risk of secondary leukemia is in line with reports in the literature.

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.

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.

Oral etoposide for recurrent/progressive sarcomas of childhood

BACKGROUND

Etoposide (VP-16) is a topoisomerase II inhibitor that is effective in a broad spectrum of pediatric and adult malignancies. Chronic, low-dose, oral VP-16 has also been shown to be active in some recurrent malignancies mostly in adults. The aim of this prospective, single institution study is to assess the efficacy and toxicity of oral VP-16 in children with progressive or recurrent (P/R) sarcomas.

PROCEDURE

Twenty-one children (10 girls and 11 boys) with R/P sarcomas and a median age of 11 years (range 3-16 years) were enrolled in this study. The diagnosis was Ewing sarcoma family tumor (ESFT) in seven, osteosarcoma in eight, rhabdomyosarcoma in four, clear cell sarcoma of soft tissue in one, fibrosarcoma in one patient. Oral VP-16 was administered at a dose of 50 mg/m(2)/daily for 20 days. The next course was initiated after a 10 day rest. Response to oral VP-16 was assessed after two courses.

RESULTS

There was an objective response (one complete response [CR], two partial responses [PR]) in three patients (14%) by two courses of oral VP-16 alone. One of these patients with PR achieved CR by the use of radiotherapy (RT) and further oral VP-16. Two more patients (9.5%) achieved CR by RT and oral VP-16. Eight (38%) patients had disease stabilization for 2-15 months. Two patients (9.5%) are long-term survivors. They are alive with no evidence of disease (NED) 79 and 94 months from time of relapse/progressive disease (PD). A patient developed acute myeloid leukemia and died. There was no major acute toxicity related to oral VP-16 in a total of 126 courses.

CONCLUSIONS

Oral VP-16 therapy is simple, relatively nontoxic, and does not necessitate hospitalization. The cure rate is small. Given the risk of second malignancy, especially in children with previous exposure to topoisomerase II inhibitors and alkylating agents, this regimen may be used as a palliative treatment or in patients with poor prognosis.

Effect of isopropyl myristic acid ester on the physical characteristics and in vitro release of etoposide from PLGA microspheres

The purpose of this paper was to study the effect of the isopropyl myristic acid ester (IPM) on the physicochemical characteristics of etoposide-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres-specifically, the effects on the size and drug loading of the microspheres, the polymer matrix and surface morphology, and the release of etoposide from the microspheres. The experiment was structured to examine 2 IPM concentrations (25% and 50%) and 1 control (no IPM) at 2 different etoposide-loading percentages (10% and 5%). The microspheres were prepared using a single-emulsion solvent-extraction procedure. Samples from each batch of microspheres were then analyzed for size distribution, drug-loading efficiency, surface characteristics, in vitro release, and in vitro microsphere degradation. The incorporation of 50% IPM significantly increased (P <.05) the size of the microspheres when compared with the control and 25% IPM microspheres. However, incorporation of 25% or 50% IPM did not change (P >.05) the drug-loading efficiency in comparison with the microspheres prepared without IPM. The microspheres containing 50% IPM were shown to significantly increase (P <.05) the release of etoposide from the microspheres at both etoposide concentrations. The microspheres prepared incorporating 25% IPM and 5% etoposide increased the in vitro release (P <.05) in comparison with the microspheres prepared without IPM. The 5% etoposide-PLGA microspheres showed a smooth, nonporous surface that changed to a dimpled, nonporous surface after addition of 25% IPM. During the in vitro degradation study, the IPM-containing microspheres slowly became porous but retained their structural integrity throughout the experiment.

Ten-day schedule oral etoposide therapy in advanced childhood malignancies

PURPOSE

The activity of etoposide (VP-16) has been demonstrated to be schedule-dependent. Several studies have been conducted on the efficacy and safety of different schedules of VP-16 both in adults and in children, but the optimal schedule has not been determined.

METHODS

In the current study, the feasibility and effectiveness of prolonged oral VP-16 in children with high-risk malignancies were evaluated. Between April 1995 and February 1999, 15 pretreated patients with high-risk tumors received oral VP-16. The schedule of therapy was oral VP-16 50 mg/m2/day for 10 consecutive days and 1-week interval between cycles. Therapy was stopped after 1 year of treatment or at time of progressive disease or possible surgery. All patients had received parenteral VP-16 in their earlier chemotherapy.

RESULTS

Twelve patients were evaluable for tumor response. After 2 to 4 months of treatment, one patient had complete remission (CR), two had partial response (PR), two had minor response (MR), two had mixed response (MxR), three had stable disease (SD), and two had progressive disease (PD). A useful palliative effect was noted in patients with stable disease. In three patients, oral VP-16 was administered for maintenance therapy. After an average follow-up of 27.5 months (range, 7-41 months), five patients are alive without disease (in three, total surgery was performed after VP-16 therapy) and three patients are alive with disease. Six patients died of progressive disease, and one died of promyelocytic leukemia. One patient had Grade 34 thrombocytopenia; in the remaining patients, no acute toxicity was observed during treatment.

CONCLUSIONS

This schedule of oral VP-16 produced CRs, PRs, and MRs in medulloblastoma, neuroblastoma, teratocarcinoma, and ependymoma. Stable disease was observed in three patients, one with an Askin tumor, one with medulloblastoma, and one with hepatoblastoma. Given the possible leukemogenic risk, this schedule should be used as a palliative form of therapy or in patients with poor prognosis..

Pharmacodynamic profile of prolonged etoposide administration in patients with small cell lung cancer and non-Hodgkin's lymphoma

STUDY OBJECTIVE

To determine whether therapeutic drug monitoring can enhance administration of etoposide in patients with drug-responsive neoplasms.

DESIGN

Prospective, open-label study.

SETTING

University-affiliated hospital and cancer center.

PATIENTS

Sixteen patients with small cell lung cancer or low-grade non-Hodgkin's lymphoma.

INTERVENTIONS

Patients were treated with etoposide, 25 mg/m2/day over 24 hours by continuous infusion for 35 days. Peripheral blood samples were collected twice a week to measure etoposide levels. Plasma was separated, frozen and stored at -20 degrees C until assayed.

MEASUREMENTS AND MAIN RESULTS

Steady-state plasma etoposide concentrations (ECpss) were determined and used to calculate total systemic clearance (Clsys). Despite differences in dosage and administration schedules, etoposide Clsys was similar to previous reports. In addition, a biexponential relationship between ECpss and absolute neutrophil count was demonstrated by nonlinear least squares estimation. Values generated from this equation indicated that ECpss above 1.5 microg/ml was strongly associated with grade III-IV leukocyte toxicity. Although less precise, there may also be a correlation between ECpss and antitumor activity.

CONCLUSION

Based on these findings, we propose a pharmacodynamic construct that uses measurements of both pharmacokinetic (ECpss, Clsys) and pharmacodynamic (hematologic toxicity, tumor response) parameters for patients with etoposide-sensitive tumors. Therapeutic drug monitoring may be able to mitigate hematologic toxicity.

Etoposide: four decades of development of a topoisomerase II inhibitor

Podophyllin-containing materials have been used as folk medicines for centuries. In the 1950s, scientists began a search to identify a more effective podophyllotoxin derivative. These efforts eventually resulted in the development of a new class of antineoplastic agents which target the DNA unwinding enzyme, topoisomerase II. The history of the development of one of the first identified topoisomerase II inhibitors, etoposide, is reviewed in this paper. Critical developments in etoposide's mechanism of action, pharmacology and administration schedule are summarised. The clinical benefits of the recently marketed etoposide prodrug, etoposide phosphate (Etopophos) are also detailed. The current status of other clinically approved anticancer agents which target topoisomerase II is briefly reviewed.

A phase II study of carboplatin and prolonged administration of oral etoposide in patients with small-cell lung cancer

Prolonged oral administration of etoposide may have a theoretical advantage over intravenous infusion, and carboplatin has a more favorable toxicity profile than cisplatin. A combination of carboplatin 300 mg/m2 and oral etoposide 40 mg/m2/day for 21 days was assessed in 74 (42 limited, 32 extensive disease) previously untreated patients with small-cell lung cancer. Response rate was 69% (CR 19%, PR 50%,) for limited disease and 72% (CR 9%, PR 63%) for extensive disease. Median response duration and overall survival was 6.6 and 10.1 months for limited disease, and 5.3 and 9.1 months for extensive disease, respectively. One-year and two-year survival was 36 and 10% for limited disease and 31 and 2% for extensive disease, respectively. The major toxicity was hematological with grade 4 or greater neutropenia in 36% and grade 4 thrombocytopenia in 16%, and one patient died of neutropenic fever. Non-hematologic toxicities were mild and grade 3 emesis was observed in 5% of patients. Carboplatin combined with 21-day oral etoposide showed only modest activity against small-cell lung cancer with high toxicity and did not merit further evaluation.

Phase II study of 21 day schedule oral etoposide in children. New Agents Group of the United Kingdom Children's Cancer Study Group (UKCCSG)

We report a multicentre phase II study of orally administered prolonged schedule etoposide in children with refractory or relapsed malignancy. 83 children were entered into the study. The largest diagnostic groups were neuroblastoma (n = 20), rhabdomyosarcoma/soft tissue sarcoma (n = 16) and brain tumours (n = 16). Etoposide was administered twice daily at a dose of 50 mg/m2/day for 21 days using the intravenous preparation given orally. Disease reassessment was performed after the second course. Etoposide plasma concentrations were measured by HPLC, 2 and 6 h after administration of therapy on days 7 and 14 in 15 patients. 61 patients completed two courses and were evaluable for response. There was 1 complete response (CR), 5 partial responses (PR) 22 stable disease (SD) and 33 progressive disease (PD). Of the 6 with responses, 3 had a diagnosis of medulloblastoma/cerebral primitive neuroectodermal tumour. 24 of 26 patients with SD/PR/CR received further courses with excellent palliative effect. The main toxicity observed was myelosuppression, with 8% and 7% of evaluable courses complicated by grade III-IV neutropenia and thrombocytopenia, respectively. Severe infection (grade III-IV) was rare, complicating only 2/94 evaluable courses. Plasma etoposide median concentrations at 2 h after administration on day 7 of course 1 were 1.5 (range 0.6-2.4) micrograms/ml. Total course 1 area under the etoposide plasma concentration versus time curve (AUC) values were estimated using a limited sampling model. Grade > or = 2 leucopenia was only observed in patients with a day 72 h etoposide concentration of > 2 micrograms/ml or a course 1 AUC of > 35 mg/ml.min. It is concluded that given at a dose of 50 mg/m2/day in two doses for 21 day courses, oral etoposide is well tolerated in children. A correlation between drug concentrations and toxicity was observed. Overall, a low response rate was seen (approximately 10%), but disease stabilisation appears to occur, and useful palliative effect was frequently noted. The response in brain tumours was more encouraging (3/14 PR) and this group requires further evaluation.

Long-lasting complete remission after prolonged administration of etoposide in a child with a second recurrence of alveolar rhabdomyosarcoma

The authors report a case of alveolar rhabdomyosarcoma (RMS) of the thigh complicated by two successive distant relapses shortly after radio- and chemotherapy, treated with etoposide, and resulting in complete long-lasting remission. The schedule of etoposide was 100 mg/ m2/d intravenously for three days weekly for 3 weeks, with an interval of 1 week between courses. This was administered for 11 months. The child is alive without disease and off therapy 20 months after completion of etoposide treatment. Preclinical studies and experience in adults have suggested that the cytotoxic effects of etoposide show a marked dependence on schedule. A divided dose regimen of single-agent etoposide has previously been shown to have activity in relapsed rhabdomyosarcoma, but the outcome or the duration of complete response has not yet been fully evaluated. In out poor-prognosis case, the prolonged administration of etoposide achieved a long-lasting complete response.

Etoposide for the treatment of paediatric tumours: what is the best way to give it?

Etoposide is one of the most important drugs available for the treatment of paediatric malignancies. Although there is evidence of schedule dependency for etoposide therapy in adults with small-cell lung cancer, the relevance of this observation to childhood cancers is uncertain. Prolonged parenteral or oral etoposide therapy has not yet shown a clear-cut advantage over intermittent treatment, and there are still no data to show that the administration of etoposide as a short intravenous (i.v.) daily infusion for 5 days does not represent acceptable therapy for primary disease. The pharmacokinetic variability seen with etoposide argues strongly for the use of pharmacologically guided dosing, and the introduction of etoposide phosphate will simplify both parenteral etoposide administration and the future evaluation of alternative etoposide schedules. Although the impact of molecular and cellular pharmacological investigations on the clinical use of etoposide has yet to be felt, the tools to perform these studies are now available and prospective trials can be designed. Such studies, performed in the setting of a pharmacologically guided trial to ensure control over pharmacokinetic variability, should identify the best way of treating children with etoposide.

Therapeutic drug monitoring of etoposide in a 14-day infusion for non-small-cell lung cancer

We investigated whether a constant plasma concentration could be obtained by the individualized administration of low-dose, prolonged-infusional etoposide. Etoposide was infused for 14 days at 40 mg/m2/day initially in patients with inoperable non-small-cell lung cancer. The infusion rate was modified based upon the etoposide concentration at 24 h following the initiation of the infusion (C24) to achieve a target concentration of 1.5 microgram/ml. We postulated that severe toxicities could be avoided by maintaining the steady-state concentration at less than 2 microgram/ml, while antitumor activity could be expected if the steady-state concentration was maintained at more than 1 microgram/ml. In a total of 21 courses in 12 patients, the mean etoposide dose was 35+/-6 mg/m2 daily. The C24 was 1.8+/-0.4 microgram/ml and ranged from 1.1 to 2.9 microgram/ml. Following dose modification, the mean concentration from 96 to 336 h (C mean) was 1.6+/-0.2 microgram/ml and ranged from 1.2 to 2.0 microgram/ml. The toxicities were well-tolerated except for one patient with WHO grade 4 leukopenia and neutropenia who developed infectious complications. There were no treatment-related deaths. Following dose modification, the inter-patient variability was decreased successfully. Although this pharmacologically-guided method needs to be validated using more patients, it could be used for therapeutic drug monitoring.

The importance of drug scheduling in cancer chemotherapy: etoposide as an example

Etoposide is a drug whose antineoplastic activity is dependent on the schedule of drug administration. This article reviews the rationale for a prolonged schedule of etoposide administration and the therapeutic results of use of such a schedule in the treatment of cancer. The pharmacology of etoposide is also reviewed, with particular attention paid to the pharmacokinetics of oral etoposide and etoposide plasma concentrations associated with cytotoxicity.

Exposure and schedule dependency of etoposide in neuroblastoma and leukaemia cells in vitro

Using an in vitro clonogenic assay system, we examined the relationship between concentration, duration and schedule of exposure to etoposide and cytotoxicity in three cell lines. Two cell lines (SK-N-SH and IMR32) were derived from human neuroblastomas, and one (L1210) was the original murine leukaemia cell line used to define schedule dependency of etoposide in vivo. Cytotoxicity was found to be determined by the product of concentration and duration of exposure over a 120-fold range of durations and a 100-fold range of concentrations. No difference in cytotoxicity was seen following equivalent exposure either continuously or in two separate intervals. In one cell line, exposure to etoposide when at confluence led to a highly resistant subpopulation comprising 10-15% of the entire cell number. This did not seem to be associated with any difference in the rate of etoposide efflux from cells preloaded with 3H-etoposide. We conclude that etoposide does not show schedule dependency in vitro, but cytotoxicity is related to total exposure to etoposide. The schedule dependency seen in vivo may possibly arise from host pharmacokinetic factors.

Etoposide-induced cell cycle delay and arrest-dependent modulation of DNA topoisomerase II in small-cell lung cancer cells

As an approach to the rational design of combination chemotherapy involving the anti-cancer DNA topoisomerase II poison etoposide (VP-16), we have studied the dynamic changes occurring in small-cell lung cancer (SCLC) cell populations during protracted VP-16 exposure. Cytometric methods were used to analyse changes in target enzyme availability and cell cycle progression in a SCLC cell line, mutant for the tumour-suppressor gene p53 and defective in the ability to arrest at the G1/S phase boundary. At concentrations up to 0.25 microM VP-16, cells became arrested in G2 by 24 h exposure, whereas at concentrations 0.25-2 microM G2 arrest was preceded by a dose-dependent early S-phase delay, confirmed by bromodeoxyuridine incorporation. Recovery potential was determined by stathmokinetic analysis and was studied further in aphidicolin-synchronised cultures released from G1/S and subsequently exposed to VP-16 in early S-phase. Cells not experiencing a VP-16-induced S-phase delay entered G2 delay dependent upon the continued presence of VP-16. These cells could progress to mitosis during a 6-24 h period after drug removal. Cells experiencing an early S-phase delay remained in long-term G2 arrest with greatly reducing ability to enter mitosis up to 24 h after removal of VP-16. Irreversible G2 arrest was delimited by the induction of significant levels of DNA cleavage or fragmentation, not associated with overt apoptosis, in the majority of cells. Western blotting of whole-cell preparations showed increases in topoisomerase II levels (up to 4-fold) attributable to cell cycle redistribution, while nuclei from cells recovering from S-phase delay showed enhanced immunoreactivity with an anti-topoisomerase II alpha antibody. The results imply that traverse of G1/S and early S-phase in the presence of a specific topoisomerase II poison gives rise to progressive low-level trapping of topoisomerase II alpha, enhanced topoisomerase II alpha availability and the subsequent irreversible arrest in G2 of cells showing limited DNA fragmentation. We suggest that protracted, low-dose chemotherapeutic regimens incorporating VP-16 are preferentially active towards cells attempting G1/S transition and have the potential for increasing the subsequent action of other topoisomerase II-targeted agents through target enzyme modulation. Combination modalities which prevent such dynamic changes occurring would act to reduce the effectiveness of the VP-16 component.

Schedule-dependent topoisomerase II-inhibiting drugs

A number of topoisomerase II-acting drugs have been described, but few demonstrate schedule-dependent anti-tumour activity. The activity of the epipodophyllotoxins etoposide and teniposide and the acridine dye derivative amsacrine is clearly schedule-dependent, and this related not only to the observation that the activity of topoisomerase II varies throughout the cell cycle but also to the finding that these drugs are rapidly cleared from the cell following exposure, permitting DNA repair. Etoposide has been most clearly shown to be schedule dependent in clinical studies. The response rates of patients with small-cell lung cancer receiving a 24-h infusion was only 10% as compared with 89% when the same dose was given over 5 days. Pharmacokinetic studies performed in these patients demonstrated that although the total systemic exposure (area under the plasma concentration-time curve, AUC) was the same in both arms of the study, the duration of exposure to low levels of drug (> 1 microgram/ml) was doubled in the 5-day arm. Haematological toxicity was the same in both arms of the study, as was the duration of exposure to higher plasma levels (> 5 micrograms/ml), suggesting that this toxicity may be associated with higher plasma concentrations, whereas anti-tumour activity is related to prolonged exposure to low levels of drug. This was confirmed in a subsequent study, where prolongation of treatment to 8 days compared to 5 days resulted in a similar exposure to low plasma concentrations and no difference in response rates or survival. Haematological toxicity in this study was worse in the 5-day arm, which also had an increase exposure to high levels of drug (> 5 micrograms/ml). More recently, interest has focused on even more prolonged etoposide administration, typically involving small daily doses repeated for 14-21 days. Although this schedule shows high activity in relapsed small-cell lung cancer and lymphoma, it is associated with significant toxicity (around one-third of patients experience grade III/IV leukopenia or neutropenia), which may be related to the observation that the etoposide dose delivered per course in these studies is higher than that obtained with standard dosing over 3-5 days. Further randomised studies are required to determine the optimal dose and schedule of etoposide.

Use of etoposide in patients with organ dysfunction: pharmacokinetic and pharmacodynamic considerations

Etoposide is a podophyllotoxin deriverative with activity against a wide variety of malignancies. It is also used in many clinical conditions in which renal or hepatic function is impaired. To establish a basis for making initial dose adjustments in patients with renal or hepatic dysfunction, the clinical pharmacology (e.g., absorption, distribution, protein binding, metabolism, and elimination) of etoposide is presented. Studies of the use of etoposide in patients with renal or hepatic dysfunction are summarized. The importance of protein binding to etoposide disposition, especially in patients with hepatic dysfunction is discussed. Pharmacodynamics refers to the relationship between drug concentration at the site of action (receptor) and pharmacologic response (toxicity or efficacy). The pharmacodynamics of etoposide has been studied in only a few patients with renal and (or) hepatic dysfunction and must be studied in larger populations before definitive dosing guidelines can be recommended. However, some general initial dosing recommendations for the use of etoposide in patients with renal and hepatic dysfunction are presented.

A limited sampling method for estimation of the etoposide area under the curve

A limited sampling method for estimation of the etoposide area under the curve (AUC) is presented. The method was developed and validated in 23 patients (42 pharmacokinetic studies) with small-cell lung cancer (SCLC), limited disease. The patients received 100 mg/m2 etoposide as a 90-min intravenous infusion in combination with carboplatin, allowing for etoposide dose modification at a following course (25% increase or decrease) due to high or low nadir values for leukocytes or thrombocytes. Of the 42 pharmacokinetic studies, 27 were used in the model development and 15 were used in the model validation. Single regression analyses of the AUC versus the fitted concentrations for the model data set were performed at several time points. The analyses demonstrated high and essentially identical correlation coefficients in the interval between 2 and 21 h, with a maximal value of 0.96 being recorded at 4 h. Multiple regression analysis was then performed using fitted concentrations corresponding to 0.08-21 h. The best model for one sample was AUC = 1.01 x (dose level divided by 100 mg/m2) + 799 x C4 h, that for two samples was AUC = 1.43 x (dose level divided by 100 mg/m2) + 544 x C4 h + 1756 x C21 h, and that for three samples was AUC = 0.07 x (dose level divided by 100 mg/m2) + 110 x C5 min + 474 x C4 h + 1759 x C21 h. Not unexpectedly, the model validation revealed that the one-sample model was less precise than the two- or three-sample model [percentage of root mean squared error (RMSE%) = 11.6%, 7.1%, and 5.4%, respectively]. All models proved to be unbiased in the validation [percentage of mean predictive error (MPE%) +/- SE = 4.2% +/- 11.0%, 7.9% +/- 6.1%, and 6.3% +/- 5.3%, respectively]. The models were subsequently validated in 14 pharmacokinetic studies of patients with metastatic germ-cell tumours who were receiving combination chemotherapy with cisplatin and bleomycin plus 100 mg/m2 etoposide as a 90-min infusion. The RMSE% was 13.4%, 10.8%, and 9.0% and the MPE% +/- SE was -1.0% +/- 11.9%, 1.7% +/- 10.5%, and 2.7% +/- 7.9% for the one-, two-, and three-sample models, respectively. The limited sampling methods presented herein may prove to be a most valuable tool for therapeutic drug monitoring in regimens in which etoposide is given in combination with carboplatin or with cisplatin and bleomycin.

24-hour plasma etoposide profile after oral and intravenous administration in children

Pharmacokinetic profiles of oral and intravenous etoposide have been compared in 9 children receiving the drug either as a single agent or in combination chemotherapy. The plasma etoposide levels were estimated using a competitive coated antigen ELISA technique. The median bioavailability was 48% and beyond 30 min after either oral or intravenous injection there was little difference in the plasma profile. The duration of plasma concentrations above 1, 5 and 10 micrograms/ml following either route were compared. It is concluded that unless the height of initial peak concentration is of therapeutic value the oral route should be comparable in children provided that twice the intravenous dose is administered. The short elimination half-life results in low plasma levels beyond 12 h and suggests that a twice daily regimen may be preferable.

A phase II trial of cisplatin and prolonged administration of oral etoposide in extensive-stage small cell lung cancer

Etoposide is a schedule-dependent agent with greater activity against small cell lung cancer (SCLC) when a given dose is administered over several days compared with a 1-day administration of the same dose. In an attempt to capitalize on the schedule dependency of etoposide, 22 previously untreated extensive-stage SCLC patients were given cisplatin (100 mg/m2 on day 1) plus 21 days of low-dose, oral etoposide (50 mg/m2/d). Chemotherapy was repeated every 28 days for four cycles. Complete blood counts were monitored weekly, and etoposide was discontinued if either the leukocyte or platelet count dropped below 2000/microliters or 75,000/microliters, respectively. All 22 patients were evaluable for response; 18 had either a complete (9%) or partial response (73%), an overall response rate of 82% (95% confidence interval, 62% to 93%). The median response duration was 7 months, and the median survival was 9.9 months (range, 1 to 17+ months). Sixteen (73%) patients received all planned cycles of etoposide. In Cycle 1 of chemotherapy, the median leukocyte nadir was 2700/microliters (range, 100 to 6300/microliters), and median platelet nadir was 180,000/microliters (range, 51,000 to 397,000/microliters). Life-threatening leukopenia (less than 1000/microliters) was rare (3 of 74 cycles). There were three treatment-related deaths, only one of which was associated with neutropenia. One patient had mild renal insufficiency that resolved after discontinuation of therapy. Alopecia was observed in all patients, but other nonhematologic toxicities were uncommon. A randomized study is necessary to determine if this schedule of cisplatin and etoposide administration is superior to more standard methods. However, these data do not indicate a major survival benefit will be derived from increasing the duration of etoposide administration when used in combination with cisplatin given every 28 days.

Current status of etoposide in the management of small cell lung cancer

Etoposide is a schedule-dependent drug with excellent activity against small cell lung cancer (SCLC). Single-agent etoposide achieves overall response rates ranging from 15% to 84%, depending on the schedule of drug administration and the characteristics of the treated population. The route of etoposide administration (intravenous versus oral) has little impact on response rate, provided appropriate dose adjustments are made for oral therapy. In combination with other active agents, etoposide has proven particularly effective in the management of SCLC. Etoposide can be substituted for doxorubicin or vincristine in the cyclophosphamide, doxorubicin, and vincristine (CAV) regimen without loss of efficacy. The etoposide and cisplatin (EP) combination is thought to be synergistic and has proven to be an effective salvage regimen for CAV failures. A regimen that alternates CAV and EP has been found by some investigators to be modestly more effective against SCLC than CAV alone; however, EP alone may be as useful as an alternating regimen. Most studies to date have demonstrated that EP induction is at least as effective as any other standard induction regimen. However, EP has the potential advantage of being more easily integrated with thoracic radiation therapy (RT). This is particularly important in limited-disease patients: two recent pilot studies employing EP induction with hyperfractionated thoracic RT yielded 2-year survival rates of greater than 50%. These promising results are being evaluated further in an ongoing Phase III trial in the United States. The available data indicate that etoposide is one of the most active agents against SCLC and therefore should be included as a component of induction therapy in all patients. New schedules of etoposide administration warrant further study.

Clinical pharmacodynamics of continuous-infusion etoposide

Continuous-infusion etoposide was given to 15 patients with newly diagnosed small-cell lung cancer (extensive disease) and 10 patients with various refractory malignancies. The untreated patients with lung cancer received 200 mg/m2 etoposide over 24 h in combination with 100 mg/m2 cisplatin, and the pretreated patients received 400 mg/m2 etoposide over 36 h as monotherapy. Pharmacokinetic studies of etoposide were carried out in all patients. High-performance liquid chromatography (HPLC) was used to measure etoposide. All patients had normal hepatic and renal function tests and were followed weekly for hematologic toxicity after therapy. In all, 14 untreated and 9 pretreated patients were evaluable. Biostatistical analysis was done to correlate pharmacokinetic results to hematologic effects. Pearson correlation coefficients were calculated for continuous variables (i.e., blood counts), and Spearman correlation coefficients were calculated for ranked variables (i.e., toxicity grades). The values for the area under the plasma concentration vs time curve (AUC) and systemic clearance varied widely among patients. However, the AUC and clearance were significantly correlated (P less than 0.05) with the WBC and platelet nadirs and the decrease in hemoglobin. The grade of leukopenia and total grade of hematologic toxicity were also correlated with AUC and clearance. Because the interpatient variability in etoposide pharmacokinetics correlates with the variable degree of hematologic toxicity, pharmacokinetic drug monitoring is suggested.

Five-day continuous infusion of cisplatin and etoposide in non-small cell lung cancer. A phase II trial

Cisplatin (CDDP) and etoposide are synergistic in vitro: the aim of this study was to evaluate the efficacy of a continuous infusion (C.I.) of these 2 drugs in inoperable non-small cell lung cancer. Patients were to receive 3 courses of CDDP 20 mg/m2/d in 1 l saline x 5d and etoposide 50 mg/m2/d in 21 saline x 5d--both in C.I.--every 3-4 weeks. Thirty patients have entered the study. Four were inevaluable for response. One patient got complete remission, 15 partial remission, 8 no change and 2 progressive disease. The response rate was 53.3% overall (95% confidence interval: 35-71%), and 61.5% for 26 assessable patients. Toxicity appeared to be acceptable despite 52% transient neutropenia--one patient died during aplasia--and 78% grade 1 to 3 nausea or vomiting. Treatment was stopped in only one case, and modified in 6 others. The high response rate that we observed, supports the idea of potentiation of the antineoplastic effect of CDDP and etoposide by C.I., in non-small cell lung cancer. These results must be confirmed in larger series before definitive conclusions can be drawn.

Infusion of high doses of undiluted etoposide through central venous catheters during preparation for bone marrow transplantation

We employed a new method to administer etoposide in high doses to 51 patients undergoing autologous bone marrow transplantation. Undiluted etoposide (20 mg/ml) was sterilely drawn into Luer-Lok plastic syringes, connected to IV extension tubing, and infused intravenously by a syringe pump over 3-4 hours. Patients received etoposide at doses ranging from 400 to 1600 mg/m2 per day (median dose: 800 mg). Total actual etoposide doses infused during the transplant period ranged from 2200 to 9000 mg. The infusion rate range was 4.1-13.4 mg/min. No episodes of hypotension, bronchospasm, or hemorrhagic cystitis were noted during or within 3 days of the etoposide infusion. In addition, no cracking of the infusion apparatus was observed in any of the 148 separate infusions. Serum bicarbonate concentrations fell significantly in 6 patients who received the higher etoposide doses. This procedure is superior to the standard method of etoposide drug delivery, since large doses of etoposide may be given without the concomitant administration of large volumes of fluid over short periods of time.

Clinical pharmacology of cancer chemotherapy in children

The pharmacokinetics of most anticancer drugs are highly variable in children, and are commonly different when children are compared to adults. Several recent studies have demonstrated that variability in systemic exposure due to interpatient pharmacokinetic variability, may be related to the probability of oncolytic effects or toxicity for some anticancer drugs. This review has exemplified differences in the clinical pharmacology of several anticancer drugs, when children are compared to adults. Such age-related differences in the pharmacokinetics and pharmacodynamics of these drugs, together with biologic differences between pediatric and adult cancers, provide the rationale for systematically conducting pediatric phase I through IV studies of anticancer drugs and denote the risks of relying on adult trials to identify new therapeutic strategies for childhood cancers.