[Bayesian estimation of pharmacokinetic parameters of etoposide]

Studies of the relationships between the pharmacokinetics of a drug and its pharmacodynamics could significantly improve chemotherapy efficacy. However, despite their proven value, pharmacokinetic studies sometimes appear as cumbersome and difficult procedures. The bayesian approach associated with an optimal sampling time strategy (OST) allows the determination of the pharmacokinetic parameters of a drug with a smaller number of blood samples compared with that required by the classic maximum likelihood estimation (MLE). Therefore, the bayesian approach may lead to a less discomfort to the patients and less work for the medical staff. Such a method was developed to determine the individual pharmacokinetic parameters of etoposide (VP16). First, the statistical characteristics of the pharmacokinetic parameters were evaluated in 14 courses from 14 patients. Then, based on these results, a three-sample strategy was developed. Validation of this methodology was performed in 7 new patients and evaluated by computing bias and precision. The performance of the developed methodology shows that it could successfully be applied for the determination of VP16 pharmacokinetic parameters.

Clinical and pharmacokinetic study of oral etoposide in patients with AIDS-related Kaposi's sarcoma with no prior exposure to cytotoxic therapy

PURPOSE

In this phase II and pharmacokinetic study, chronic, low-dose, oral etoposide was evaluated for its efficacy in patients with AIDS-related Kaposi's sarcoma who were not previously exposed to cytotoxic therapy.

PATIENTS AND METHODS

Of 28 patients accrued for the study, 25 were assessable for toxicity and response. Twenty-four patients were male (homosexual or bisexual cases) and one patient was female (partner of a bisexual male). All patients were human immunodeficiency virus (HIV)-positive, New York University (NYU) disease stage IIB to IVB, and most exhibiting skin and lymph node and/or visceral disease. Median age was 33 years (range, 21 to 50), and median World Health Organization (WHO) performance status was 2 (range, 0 to 3). The patients received a mean number of six treatment courses (range, four to 27). Prior therapy included local/regional irradiation, immunotherapy (interferon-alpha), local resection, and/or cryotherapy. No prior cytotoxic therapy was allowed. Etoposide was administered at a schedule of 25 mg/m2 orally, twice a day for 7 days, every 2 weeks. Plasma concentrations of the drug were measured in six patients by a high-performance liquid chromatography (HPLC) method, after chloroform extraction using teniposide as internal standard.

RESULTS

The overall response rate was 32% (two complete and six partial responses), and the median progression-free survival was 8 weeks (range, 4 to 27). Five patients (20%) had stable disease, while 12 cases (48%) did not respond. Patients without a history of opportunistic infections seemed to respond better. The regimen was well tolerated. The main toxic effects consisted of mild to moderate nausea and vomiting in approximately half of the cases, and WHO grodes 3 to 4 leukopenia and thrombocytopenia in eight of 25 (36%) and five of 25 (20%) of cases, respectively. However, only two patients had to discontinue treatment because of prolonged and severe neutropenia. No toxic deaths were documented. The pharmacokinetic analyses revealed the achievement of potentially therapeutic and lowly myelosuppressive plasma etoposide concentrations (2.1 micrograms/mL; range, 1.3 to 2.6) for a significant period of time, ie, for approximately 4.6 hours postdosing.

CONCLUSION

At the schedule applied, etoposide shows significant objective antitumor activity in advanced AIDS-related Kaposi's sarcoma, and induces acceptable clinical toxicity. This apparent efficacy of the regimen could be a result of the prolonged maintenance of cytotoxic plasma concentrations of etoposide during each treatment course, and the absence of toxic peak levels of the drug. These results, together with the appreciable bioavailability of oral etoposide, make the regimen feasible for outpatient treatment of patients with advanced AIDS-related Kaposi's sarcoma. Further studies using the above-mentioned approach are warranted.

Pharmacology of 21-day oral etoposide given in combination with i.v. cisplatin in patients with extensive-stage small cell lung cancer: a cancer and leukemia group B study (CALGB 9062)

This was a pharmacological companion study to a randomized Phase III trial comparing 21-day oral versus 3-day i.v. etoposide in combination with i.v. cisplatin in patients with extensive-stage small cell lung cancer. Etoposide plasma concentrations were measured in patients randomized to the 21-day schedule and correlated with toxicity and tumor response. Patients were treated with etoposide (50 mg/m2/day) orally for 21 days and cisplatin (33 mg/m2/day) i.v. for 3 consecutive days every 28 days for 6 courses. Plasma samples before the daily etoposide dose (trough concentrations) and complete blood counts were obtained weekly during treatment. The average of three etoposide concentrations (EC) per course was calculated. Of 158 patients registered to this schedule of the study, 150 were eligible. In 106 patients, etoposide samples were obtained at least in the first course in which the mean EC was 0.39 microgram/ml (SD = 0.29). In 102 patients (missing albumin values in 4 of 106 patients), the concentration of etoposide not bound to protein (Efree) was estimated based on the following equation: percentage unbound = (1.4 x total bilirubin) - (6.8 x albumin) + 34.4. Regression analysis revealed that increasing age was correlated with higher EC (r = 0.27; two-tailed P < 0.01) and Efree (r = 0.31; two-tailed P < 0.01). Higher EC and Efree values were associated with lower WBC counts and absolute neutrophil counts after the first treatment course in 83 patients with nadir counts. Using multiple linear regression, a pharmacodynamic model was developed that included EC or Efree, age, and alkaline phosphatase. An interaction with bone marrow results at diagnosis was found, indicating a sharper decline in nadir counts with increasing EC or Efree when the marrow was involved with small cell lung cancer. This model explained 29% of the variation for WBC nadirs (P < 0.001) and 31% of the variation for absolute neutrophil count nadirs (P < 0. 001). Neither EC nor Efree showed a significant correlation with tumor response. A pharmacokinetic relationship between EC or Efree and age was found. A pharmacodynamic model could be developed for toxicity but not for tumor response.

Determination of a new podophyllotoxin derivative, TOP-53, and its metabolite in rat plasma and urine by high-performance liquid chromatography with electrochemical detection

A high-performance liquid chromatographic method was developed for the determination of a new podophyllotoxin derivative, TOP-53 (I), and TOP-53 glucuronide (II) as its major metabolite in rat plasma and urine. For the analysis of I, the sample was chromatographed on a reversed-phase C18 column with electrochemical detection after consecutive two-step liquid-liquid extractions. Compound II was determined as I after enzymatic hydrolysis of II. This method was validated sufficiently with respect to specificity, accuracy, and precision. The limits of quantitation for both I and II were 2 ng/ml in plasma and 10 ng/ml in urine. The method is thus useful for the pharmacokinetic study of I.

Phase I and pharmacokinetic study of etoposide phosphate by protracted venous infusion in patients with advanced cancer

PURPOSE

Etoposide has schedule-dependent cytotoxic activity, and clinical resistance may be overcome with prolonged low-dose therapy. Oral bioavailability is variable, and protracted intravenous administration is limited by water insolubility, which requires large infusion volumes. Etoposide phosphate (EP) is a water-soluble prodrug that is rapidly converted in vivo to etoposide, and may be administered in concentrated solution. A phase I study was conducted to determine the toxicity, pharmacokinetics, and pharmacodynamics of EP administered as a protracted venous infusion in the ambulatory setting.

METHODS

Twenty-three patients with advanced cancer were treated with a continuous infusion of EP using ambulatory pumps for 6 weeks followed by a 2-week rest. Cohorts were treated with EP at 10, 20, 25, and 30 mg/m2/d. Steady-state plasma etoposide levels (Css) and stability of EP in infusion pumps were measured using high performance liquid chromatography (HPLC).

RESULTS

Myelosuppression, mucositis, and fatigue were dose-limiting. The maximum-tolerated dose (MTD) of EP was 20 mg/m2/d. The mean Css (+/- SD) of etoposide were 0.67 +/- 0.25, 1.14 +/- 0.24, 1.38 +/- 0.64, and 2.19 +/- 0.52 microg/mL at daily EP doses of 10, 20, 25, and 30 mg/m2, respectively. Neutropenia correlated with Css (r = 0.65, P = .008). EP was stable in infusion pumps for at least 7 days. Partial responses were observed in patients with hepatoma and non-small-cell lung cancer (one each).

CONCLUSION

EP may be conveniently and safely administered as a low-volume protracted venous infusion in the ambulatory setting. Cytotoxic plasma concentrations of etoposide are obtained at the MTD. The pharmacodynamic relationships observed suggest the possibility of pharmacologically based dosing of EP.

Enhancement of etoposide (VP-16) cytotoxicity by enzymatic and photodynamically induced oxidative stress

The effects of glutathione (GSH) depletion by buthionine sulfoximane (BSO) or by photosensitization-induced oxidative stress using metallo-phthalocyanines (MePcS4) on etoposide (VP-16) cytotoxicity against K562 human leukemic cells were investigated. Both treatments enhanced VP-16 toxicity in a markedly synergistic way, as revealed by combination index analysis procedure. Synergistic drug interactions were accompanied by a supra-additive induction of DNA strand breaks. The proposed role of intracellular GSH in preventing metabolic transformations of VP-16 and thus decreasing its toxicity was confirmed by electron spin resonance (ESR) monitoring of the accumulation of the VP-16 phenoxyl radical in cell cytoplasm subjected to GSH depletion. Taken together the results emphasize the beneficial effect of GSH-related oxidative stress in enhancement of etoposide toxicity and possibly in its anticancer applications.

Phase I study of sequentially administered topoisomerase I inhibitor (irinotecan) and topoisomerase II inhibitor (etoposide) for metastatic non-small-cell lung cancer

We conducted a phase I study of irinotecan (CPT-11) and etoposide (VP-16) given sequentially to untreated patients with metastatic non-small-cell lung cancer. Arm A: CPT-11 was given over 90 min on days 1-3 and VP-16 was given over 60 min on days 4-6. Arm B: VP-16 was given on days 1-3 and CPT-11 on days 4-6. G-CSF was given to all patients daily on days 7-17. Twenty-seven patients were entered randomly at the two arms. The major dose-limiting toxicities in arms A and B were granulocytopenia and diarrhoea. Transient elevations of transaminases and bilirubin were observed in both arms. The degree of the toxicities did not differ between the two arms. The maximum tolerated doses (MTDs) were 60 mg m-2 CPT-11 and 60 mg m-2 VP-16 in both arms. Of the 13 patients who received more than two cycles, two out of five achieved partial response (PR) at the first level of arm A and one out of four achieved PR at the second level of arm B. We conclude that these schedules of sequential CPT-11 and VP-16 administration were inappropriate because of severe toxicities.

Topoisomerase II inhibitors fail to induce chromosome-type aberrations in etoposide-resistant cells: evidence for essential contribution of the cleavable complex formation to the induction of chromosome-type aberrations

The induction of chromosome-type aberrations is mediated by stabilization of the DNA-topoisomerase II (topo-II) complex, the cleavable complex (CC), induced by topo-II inhibitors. In the present study, in order to confirm the critical contribution of topo-II in producing chromosome-type aberrations, the inducibility of chromosome-type aberrations by topo-II inhibitors was compared between human epidermoid cancer KB cells and their mutant cells (KB/ VP-2 cells) which were resistant to etoposide (VP-16) and which have reduced levels of topo-II and its gene expression. KB/VP-2 cells were resistant to the cytotoxicity of topo-II inhibitors and most resistant to etoposide. In KB cells treated with etoposide which had accumulated CC, chromosome-type aberrations but not chromatid-type aberrations were efficiently induced, as has already been reported in Chinese hamster fibroblasts. In contrast, in KB/VP-2 cells with no accumulation of CC, etoposide induced mainly chromatid-type aberrations, with a few chromosome-type aberrations. Unlike etoposide, however, adriamycin, which was known to accumulate CC in Chinese hamster fibroblastic cells, neither induced chromosome-type aberrations nor accumulated CC in either KB or KB/VP-2 cells. No difference in cell incorporation of [3H]etoposide between the two cell lines was observed. These findings indicate that CC formation contributes to the induction of chromosome-type aberrations, although the reason why adriamycin could not accumulate CC in KB cells is not clear. This may suggest a mechanism for resistance to topo-II inhibitors in cancer chemotherapy.

Randomized comparison of etoposide pharmacokinetics after oral etoposide phosphate and oral etoposide

Etoposide phosphate is a water-soluble prodrug of etoposide. The plasma pharmacokinetics of etoposide following oral administration of etoposide phosphate or oral etoposide were compared. Seventeen patients with solid tumours were enrolled to receive oral etoposide phosphate 125 mg m(-2) on days 1-5 every 3 weeks, with escalation to 175 mg m(-2) from course 3 when possible. Patients were randomized to receive oral etoposide phosphate or oral etoposide on day 1 of course 1 and the alternative compound on day 1 of course 2. Fifteen patients received two or more courses and were evaluable for pharmacokinetic comparisons. The median AUC(inf) (area under the concentration vs time curve from zero to infinity) of etoposide was 77.7 mg l(-1) h after etoposide phosphate (95% CI 61.3-100.5) and 62.0 mg l(-1) h after oral etoposide (95% CI 52.2-76.9). The difference in favour of etoposide phosphate was borderline significant: median 9.9 mg l(-1) h (95% CI 0.1-32.8 mg l(-1) h; P = 0.05). However, the inter-patient variability of etoposide AUC(inf) was not improved (coefficients of variation 42.3% and 48.4%). Etoposide phosphate was undetectable in plasma after oral administration. Toxicities of oral etoposide phosphate were not different from those known for etoposide. In conclusion, oral etoposide phosphate does not offer a clinically relevant benefit over oral etoposide.

Conversion of the prodrug etoposide phosphate to etoposide in gastric juice and bile

Etoposide phosphate is a water-soluble prodrug of etoposide. It was expected that this prodrug could be used to overcome the solubility limitations and erratic bioavailability of oral etoposide. To investigate the possibility of prodrug conversion to etoposide within the gastrointestinal lumen, etoposide phosphate was dissolved in water and incubated with human gastric juice or human bile in vitro. Samples were collected during 150 min and analysed for etoposide concentration with high-performance liquid chromatography. Conversion of prodrug to etoposide during incubation with gastric juice was negligible. There was significant conversion during incubation with bile at pH 7-8. The percentage of prodrug converted to etoposide at pH 8 after 60 min was 78 +/- 18% (mean +/- S.D.) for a 0.1 mg ml-1 prodrug solution and 36 +/- 26% for 0.5 mg ml-1. At pH 7, after 60 min 22% of prodrug was converted to etoposide when incubated at 0.1 mg ml-1 and 10% at 0.5 mg ml-1. No conversion was found after inactivation of alkaline phosphate (AP) by overnight heating of bile at 65 degrees C or by the addition of disodium edetate to the bile. In conclusion, because of AP in bile, variable conversion of etoposide phosphate to etoposide can be expected within the intestinal lumen after oral administration. This could have important pharmacokinetic consequences.

Pharmacokinetics of carboplatin and etoposide in a haemodialysis patient with Merkel-cell carcinoma

We present a Merkel-cell carcinoma patient with chronic renal failure requiring haemodialysis and evaluate the pharmacokinetics of carboplatin and etoposide during haemodialysis. The area under the concentration-time curve of carboplatin was increased by prolonging the interval between administration and haemodialysis. However, that of etoposide was not changed. Carboplatin showed good membrane permeability in haemodialysis, while etoposide showed no permeability. In conclusion, the pharmacokinetics of carboplatin could be controlled by haemodialysis and the interval between chemotherapy and haemodialysis. However, the pharmacokinetics of etoposide were not affected.

A pharmacodynamic evaluation of hematologic toxicity observed with etoposide phosphate in the treatment of cancer patients

The pharmacodynamics of etoposide phosphate (Etopophos; Bristol-Myers Squibb Company, Princeton, NJ), a water-soluble prodrug of etoposide, was evaluated in 39 patients with solid tumors after a 30-minute intravenous infusion of escalating doses (equivalent to 50 to 175 mg/m2 of etoposide) on a day 1, 3, and 5 schedule of treatment. Serial blood samples were collected at predose and throughout the 32 hours following day 1 of treatment to determine the area under the plasma concentration-time curve (AUC) of etoposide phosphate and etoposide. Hematology profiles and serum chemistries were determined at predose and twice weekly for approximately 3 weeks after each treatment cycle. Both linear and nonlinear pharmacodynamic models were used to evaluate the relationship between hematologic toxicity and etoposide AUC and patient factors (age, gender, performance status, prior radiation therapy, prior chemotherapy, baseline albumin, bilirubin, alkaline phosphatase, creatinine, leukocyte count, granulocyte count). Etoposide phosphate was converted rapidly to etoposide in vivo. The ratio of the etoposide phosphate AUC to that of etoposide was < or = 1.2% indicating that etoposide was the main species in the systemic circulation. Myelosuppression was the dose-limiting toxicity, and significant decreases in white blood cell and granulocyte counts were noted. Hematologic toxicity was best described by a stepwise linear regression model consisting of etoposide AUC, serum albumin, and bilirubin. In summary, hematologic toxicity produced by the intravenous administration of etoposide phosphate correlates significantly with etoposide AUC and patient factors (baseline serum albumin and bilirubin) in cancer patients.

Effects of gender, age, and race on the pharmacokinetics of etoposide after intravenous administration of etoposide phosphate in cancer patients

The influence of gender, age, and race on the pharmacokinetics of etoposide and on the extent of conversion of etoposide phosphate (Etopophos; Bristol-Myers Squibb Company, Princeton, NJ) to etoposide are summarized. Included in the integrated statistical analyses were 192 patients from six phase I/II studies (102 men and 90 women, 128 aged < or = 65 years and 64 aged > 65 years; 134 were white, 18 were other races, and race was not recorded for 40). The dose of etoposide phosphate ranged from 25 to 200 mg/m2 of etoposide equivalents and was administered as 5-(bolus) to 210-minute intravenous infusions. Total body clearance of etoposide was comparable between men and women. However, significantly lower steady-state volumes of distribution and shorter half-lives were observed in women relative to men. Patients who were older than 65 years had significantly lower etoposide total body clearance and longer half-lives than younger patients. The gender- and age-related differences observed in the pharmacokinetic parameters of etoposide were significant but generally of a small magnitude (< or = 13%), indicating no need for dose adjustment in these patient populations. There were no significant race-related differences in the pharmacokinetic parameters of etoposide. All patients showed rapid conversion of etoposide phosphate to etoposide. The individual area under the plasma concentration-time curve ratio of etoposide phosphate/etoposide was < or = 0.0324, indicating that etoposide was the major circulating moiety after infusion of etoposide phosphate. Significant gender-, age-, or race-related differences in the area under the plasma concentration-time curve ratios were not observed. An evaluation of the area under the plasma concentration-time curve ratios with respect to infusion time suggested that the conversion of etoposide phosphate to etoposide was independent of infusion time.

Etoposide phosphate infusion with therapeutic drug monitoring in combination with carboplatin dosed by area under the curve: a cancer research campaign phase I/II committee study

The area under the plasma concentration-time curve (AUC) following an intravenous dose of etoposide varies considerably among patients, which in part contributes to the unpredictability of toxicity and response seen in individual patients. This study evaluated the utility of therapeutic drug monitoring of etoposide in reducing the interpatient variability of etoposide steady-state concentrations during prolonged infusion. The etoposide prodrug etoposide phosphate (Etopophos; Bristol-Myers Squibb Company, Princeton, NJ) was administered by infusion using an adaptive dosing strategy. It was given in combination with carboplatin, which was dosed on an AUC basis. Patients with histologically or cytologically proven small cell lung cancer were treated with etoposide phosphate by continuous 120-hour infusion and carboplatin at a dose calculated by the Calvert formula to give an AUC of 5 mg/ mL.min. Blood samples were taken on days 2 through 5 of each treatment cycle, and high-performance liquid chromatography was used to measure the plasma etoposide concentration. The resultant concentrations were compared with target concentrations of 1 or 2 micrograms/mL and these data were used to calculate the rate of infusion for the following 24 hours. In the first cohort, the target etoposide concentration was 1 microgram/mL, and this was achieved (mean +/- SD = 1.05 +/- 0.24 micrograms/mL) by infusing etoposide phosphate doses of 21 to 109 mg (15 to 68 mg/m2) per day. In the second cohort, the target concentration of 2.0 micrograms/mL was achieved (mean +/- SD = 2.05 +/- 0.31 micrograms/mL) with infused etoposide phosphate doses of 69 to 193 mg (41 to 114 mg/m2) per day. This technique reduced the variation in plasma levels and resulted in predictable hematologic toxicity. Cumulative hematologic toxicity necessitated an extension of the treatment cycle from 3 to 4 weeks, however. Of six evaluable patients, two had a complete response and one had a partial response. Therapeutic drug monitoring was shown to reduce the interpatient variation in the plasma etoposide concentration by half and shows promise for individualizing treatment with combination chemotherapy. Exploiting the known relationships between the pharmacokinetics and pharmacodynamics of these two drugs by using therapeutic drug monitoring may lead to better therapeutic safety and efficacy.

Pharmacodynamic modeling of prolonged administration of etoposide

PURPOSE

A refined pharmacodynamic model for toxicity is necessary for successful adaptive control of the administration of an anticancer drug to avoid toxicity. We sought to establish a pharmacodynamic model of leukopenia in a 14-day administration of etoposide.

METHODS

Pharmacokinetic data of 32 patients treated with etoposide infused over 14 days in a phase I study (20 patients) or in an adaptive control study (12 patients) were used to develop a model for the prediction of a leukocyte nadir count. The concentrations of both estimated unbound and total etoposide at steady state, as well as patient demographic factors, were included in linear and nonlinear models. The unbound fraction of etoposide was estimated using an equation based on serum albumin and total bilirubin. The efficacy of the models was evaluated in terms of correlation coefficient (r), mean predictive error (MPE) and root mean square error (RMSE).

RESULTS

For both total and unbound drug concentration, a nonlinear model predicted leukopenia more precisely and with less bias than a linear model, and unbound drug explained more variability of leukopenia than total drug concentration in both linear and nonlinear models. The best model was a nonlinear model with three variables of unbound concentration, pretreatment leukocyte count and prior treatment (r = 0.76, MPE +/- SEM = 0.07 +/- 0.17 x 10(3)/microl, RMSE = 0.95 x 10(3) microl), which was better than the best linear model.

CONCLUSIONS

The nonlinear model using unbound etoposide concentration explained the interpatient variability of leukocyte nadir count to a fairly large extent. Although the model provided useful information on the pharmacodynamics of etoposide, it was still imprecise and a more refined model is necessary for application to an adaptive control study.

Phase I study of high-dose etoposide phosphate in man

Etoposide is a widely used cytotoxic agent with a broad spectrum of activity in human malignancies. This agent has been incorporated into many transplant regimens although toxicity occurs because of its poor water solubility and toxic excipients. Etoposide phosphate, a water soluble prodrug of etoposide, has been studied at conventional dosages in man and shown to have advantages over the parent compound. We have extended our previous experience with this new agent to evaluate the levels needed in transplantation protocols. This phase I study of intravenous high-dose etoposide phosphate over 2 h on days 1 and 2 was designed to determine whether or not dose linearity between the amount of etoposide phosphate administered to patients and generation of etoposide in vivo as seen with conventional dosages of this agent would be present at transplant-dose levels. In addition, the toxicities of these dose levels with the short infusion schedule were defined. A conservative dose escalation scheme was chosen based upon prior knowledge of etoposide. Thirty-one patients (19 male, 12 female) with CALGB performance status 0-1 with a variety of solid tumors entered this study. The patients were treated with dose levels of etoposide phosphate given as the etoposide-equivalent doses of 250, 500, 750, 1000, 1200, 1400, and 1600 mg/m2/day in 250-400 ml of normal saline given as an intravenous infusion over 2 h on days 1 and 2 every 28 days. After the maximal tolerated dose level was determined on this schedule, additional patients received etoposide phosphate as a 4 h infusion on both days in an attempt to reduce toxicities. G-CSF (5 micrograms/kg/day) was administered subcutaneously to all patients from day 3 until the WBC > or = 10000/microliters. Nonhematologic toxicity was considered to be dose limiting. Serial plasma samples for pharmacokinetics were obtained from patients on day 1 of cycle 1. For the 2 h infusion, the maximum tolerated dose of etoposide phosphate was 1000 mg/m2/day x 2 with dose limiting mucositis. In the small number of patients studied, the maximum tolerated dose was reached for the 4 h infusion at 1400 mg/m2/day of drug, again due to mucositis. Other toxicities, despite the rapid infusion schedule, were modest with transient mild headache being most common. At the highest doses etoposide phosphate was efficiently and rapidly dephosphorylated to etoposide. Etoposide generated by dephosphorylation of etoposide phosphate had plasma disposition curves characteristic of etoposide administered parenterally. One partial response occurred in a patient with small cell lung cancer. Etoposide phosphate can be rapidly infused in modest fluid volumes at dosages required for transplantation protocols with minimal acute side-effects. On a 2 h schedule, mucositis becomes the dose limiting nonhematologic toxicity. Mucositis seems to correlate with peak dose levels of the drug rather than total drug administered. On a 4 h infusion schedule given sequentially for 2 days, the maximum tolerated dosage could be increased 40% compared to the 2 h schedule. The relative ease of administration and the rapid conversion of this prodrug into etoposide should make it useful in high-dose therapy settings.

Microdialysis assessment of microfibrous collagen containing a P-glycoprotein-mediated transport inhibitor, cyclosporine A, for local delivery of etoposide

PURPOSE

This study was designed to assess a local drug delivery system of an anticancer agent, etoposide (VP-16), using microfibrous collagen as a drug carrier. For this objective, the microdialysis method was utilized to investigate the local pharmacokinetics of VP-16.

METHODS

Microfibrous collagen sheets (CS) containing 20 mg/kg of VP-16 with and without 40 mg/kg of cyclosporine A (CyA) were prepared and applied on the liver surface of rats. VP-16 concentrations in the liver extracellular fluid (ECF) were monitored by a microdialysis method.

RESULTS

The local application of CS containing VP-16 resulted in a relatively long maintenance of drug concentrations in the liver ECF with very low concentrations in plasma. The inclusion of CyA in the CS resulted in 2-fold and 3-fold increases of the AUC and MRT values of VP-16 in the liver ECF, respectively. The liver ECF-to-plasma AUC ratios of VP-16 were 32-39 and 0.17 with local CS application and iv administration, respectively, indicating a remarkable advantage of the local drug delivery system. A pharmacokinetic interaction experiment suggested that the observed increase of the liver ECF concentrations of VP-16 with CyA resulted from inhibition of the biliary excretion of VP-16 by CyA.

CONCLUSIONS

We found that the local delivery of the CS containing CyA on the liver surface is advantageous in terms of the extent and duration of liver ECF drug concentrations, when CyA was included in the CS. The effect of CyA was probably derived from the inhibition of P-glycoprotein-mediated biliary excretion of VP-16 by CyA. The usefulness of the microdialysis technique for the assessment of the local drug delivery system was also demonstrated.

Etoposide phosphate, the water soluble prodrug of etoposide

Etoposide (Vepesid) is a widely used drug in a variety of neoplasms. To improve the pharmaceutical characteristics of etoposide, etoposide phosphate (Etopophos, Bristol-Myers Squibb) has been developed as a prodrug. Etoposide phosphate is the phosphate ester derivative of etoposide. In comparison to the parent compound, etoposide phosphate is highly soluble in water and can be readily formulated for intravenous use, resulting in higher clinical application. This paper presents information on the pharmaceutical properties and the current status of etoposide phosphate in clinical trials.

Activity of menogaril against various malignant lymphoma cell lines and a human lymphoma xenograft in mice

Menogaril is an antitumor agent different from other anthracyclines in that it is active after oral administration; therefore, extravasation is not a side effect. In this basic study, we examined the antitumor activity of menogaril against malignant lymphoma. We compared its activity towards experimental malignant lymphoma with that of Adriamycin, epirubicin, pirarubicin, vincristine, and etoposide, treating mice with each drug at the dose schedule usually used for patients. Menogaril rapidly penetrated lymphoma cells and remained there at least 3 hours after the drug was washed out. Menogaril cleaved more double-stranded DNA in lymphoma cells than Adriamycin, epirubicin, pirarubicin, or etoposide. Menogaril had stronger antitumor activity against experimental malignant lymphoma in mice than Adriamycin, epirubicin, vincristine, and etoposide. Menogaril significantly lengthened the life span of mice bearing one of three lymphoma cell lines resistant to cisplatin, vincristine, or cyclophosphamide. Menogaril had stronger antitumor activity against the human malignant lymphoma xenograft LM-3 than Adriamycin. The strength of the cytotoxic activity of Menogaril might arise from its ready penetration into cells and its cleavage of double-stranded DNA. Therefore, Menogaril might become a useful drug for the treatment of patients with malignant lymphoma by oral administration; 7 days of administration was effective in the in vivo experiments.

[Drug distribution of pelvic intraarterial infusion chemotherapy by bilateral internal iliac arterial catheter placement with coil occlusion of superior, inferior gluteal and obturator arteries]

The anticancer drug distribution in pelvic arterial infusion chemotherapy with bilateral internal iliac arterial catheter placement with coil occlusion of the superior, inferior and obturator arteries was indirectly evaluated by serially performed DSA, CTA and RI on 18 patients with pelvic malignancies. The distribution was judged to be Excellent (E), defined as uniform distribution in the entire lesion alone, in 9 of 18 patients (50%) evaluated prior to the start of the arterial infusion (AI), and as Good (G), defined as uniform distribution in the entire lesion and partly on an unaffected portion, in 9 (50%). Of the 11 patients evaluated after 7 times AI, E was found in 3 patients (27%), G in 7 (64%) and Fair (F), defined as distribution with a defect in the lesion, in one patient (9%). Of the 11 patients evaluated after 14 AI, E was found in 5 (45%), G in 4 (36%) and F in 2 (18%). Of the 7 patients evaluated after 21 AI, E was found in 2 (29%), G in 4 (57%) and F in one (14%). G was found in 2 of 2 patients (100%) evaluated after 28 AI. These results suggest that this method can maintain a favorable anticancer drug distribution even after multiple sessions of AI.

Phase I and pharmacologic study of 7- and 21-day continuous etoposide infusion in patients with advanced cancer

PURPOSE

This phase I study was undertaken to evaluate the safety and tolerability of prolonged infusional etoposide, and to evaluate its pharmacokinetic/pharmacodynamic profile in patients with advanced cancer.

METHODS

A group of 17 patients received a 7-day infusion of etoposide (schedule A) every 21 days at doses from 30 to 75 mg/m2 per day, and a second group of 37 patients a 21-day infusion (schedule B) every 28 days at doses from 18 to 40 mg/m2 per day. Patients had a median Karnofsky performance status (PS) of 80%, and 34 patients had no prior chemotherapy. Etoposide concentrations at steady state (Css) and other pharmacokinetic parameters (plasma clearance, CLp; area under the curve, AUC) were determined during the first treatment cycle. Correlation coefficients were calculated to measure the relationship between variables.

RESULTS

Myelosuppression was the major toxicity, and was associated with three deaths. The maximum tolerated dose due to neutropenia was 75 mg/m2 per day for schedule A and 40 mg/m2 per day for schedule B. There was significant interpatient pharmacokinetic variability in both infusional schedules. Even though etoposide dose levels did not significantly correlate with plasma levels, the Css was > or = 1 microgram/ml in the majority of the patients. A significant correlation between AUC and neutrophil absolute decrease was noted only in schedule B (r = 0.56, P = 0.003). There were several marginal relationships in schedule B: PS versus Css (r = 0.31, P = 0.058), PS versus AUC (r = -0.38; P = 0.058) and age versus CLp (r = -0.31, P = 0.057).

CONCLUSION

Overall, significant correlations were found for several hematologic variables and etoposide dose levels, but not with the Css values. One major problem with the application of pharmacodynamic models to predict hematologic toxicity in clinical practice is the presence of significant interpatient variability.

Bioequivalence assessment of etoposide phosphate and etoposide using pharmacodynamic and traditional pharmacokinetic parameters

The bioequivalence of etoposide phosphate, a prodrug of etoposide, to etoposide was assessed in a randomized, crossover study in 29 patients with histologically established solid tumors that had failed conventional treatment. Cohorts of patients received one treatment course each of etoposide and etoposide phosphate which consisted of a 100 mg/m2 per day etoposide equivalent dose infused i.v. over 1 hr on a Day 1 to 5 schedule of treatment. The second course was administered 21 days later or on recovery of blood cell counts. Plasma and urine samples were collected over 24 hr on Day 1 of each course and assayed for etoposide content by a validated HPLC/UV method. Resulting data were subjected to noncompartmental pharmacokinetic analysis. Hematology profiles were obtained by collecting blood samples prior to the first course and twice a week after each course. The pharmacodynamics and pharmacokinetics of etoposide were virtually identical after the two treatments. The point estimates (90% confidence intervals) for nadir WBC, granulocytes, hemoglobin, and platelets expressed as % decrease from the baseline, and for the pharmacokinetic parameters, Cmax, and AUC0 infinity, after intravenous etoposide phosphate relative to etoposide were 100% (96%, 105%), 97% (91%, 103%), 95% (82%, 109%), 95% (84%, 106%), 107% (101%, 113%), and 113% (107%, 119%), respectively. Therefore, etoposide phosphate is bioequivalent to etoposide based on pharmacokinetic and pharmacodynamic assessments.

[Biliary and pancreatic excretion of etoposide]

Although biliary excretion of Etoposide is thought to be one of the main excretory routes, less investigation has been performed in human because of the clinical difficulties of bile collection. In the present study, the biliary and pancreatic excretion of Etoposide was examined through the hepaticus- or pancreaticus drainage in two pancreatoduodenectomized patients. The drug (95 mg) was infused for 30 min. Blood, bile and pancreatic juice were taken consecutively during and after infusion. Etoposide in the samples was measured as an unchanged type by HPLC. Etoposide was detected in the bile at the same level or more of the blood, their correlation being significant during the observation period. Recovery of the unchanged drug from the hepatic bile in the present series was 2.7-3.0% during the period of 3.5 hrs. And total recovery was estimated as 3.5-4.0% from AUC of the further extended concentration curve. Pancreatic excretion of Etoposide was minimum, its ratio with blood concentration being 2-3%. Recovery for 3.5 hrs. was less than 0.02%. From the data obtained, the biliary excretion of Etoposide was discussed together with its metabolites.

[Chemotherapy for two patients with non-Hodgkin's lymphoma in hemodialysis]

There are few reports on chemotherapy of non-Hodgkin's lymphoma (NHL) in patients with chronic renal failure. Two long-term hemodialysis patients were treated for NHL with modified CHOP therapy. The plasma pharmacokinetics of adriamycin (ADR) and etoposide (VP-16) were investigated in these patients. In the first case, NHL was diagnosed in a 37-year-old male (diffuse pleomorphic, T cell type, stage I E). After 4 courses of chemotherapy, he achieved complete remission. The second case, was a 56-year-old male who was admitted to our hospital with melena and abdominal pain. A diagnosis of NHL (diffuse mixed, B cell type, stage III E) was made. Complete remission was achieved with 2 courses of chemotherapy. Levels of hematological and neurological toxicity were moderately severe but tolerable. Pharmacokinetics of ADR and VP-16 in these patients were similar to those in patients with normal renal function. These results suggested that ADR and VP-16 were effective drugs for hemodialysis patients with NHL.