Trastuzumab induced in vivo tissue remodelling associated in vitro with inhibition of the active forms of AKT and PTEN and RhoB induction in an ovarian carcinoma model.

BACKGROUND: The incidence of ovarian cancer has been increasing worldwide and it is currently the leading cause of death from gynaecological malignancy. Unlike breast cancer, the prognostic role of the human epidermal growth factor receptor-2 (HER-2) in ovarian carcinoma remains controversial. METHODS: The aim of this preclinical study was to further characterise the biological, molecular and cellular effects of trastuzumab (Herceptin) using NIH-OVCAR-3 and derived cell lines both in vitro and in vivo. RESULTS: In vitro assessments have shown that trastuzumab treatment inhibited total and phosphorylated HER-2. This was associated with inhibition of the phosphorylated form of phosphatase and tensin homologue (PTEN), mitogen-activated protein kinase and AKT, and the total level of p27(kip). Inhibition of PTEN is associated with phosphorylated MEK1/2 upregulation, suggesting a specific inhibition of the protein phosphatase function of PTEN. Moreover, trastuzumab induced the upregulation of RhoB. These molecular modifications promote inhibition of cell migration and potentially restoration of tumour cell contact inhibition. RhoB induction in NIH-OVCAR-3 control cell lines mimics the molecular and cellular trastuzumab long-time exposition effects. RhoB inhibition in NIH-OVCAR-3 long-time exposed to trastuzumab cell line reverses the cellular and molecular effects observed in this model. In vivo examinations have shown that these changes are also associated with the restoration of structural, morphological and normal functions of the peritoneum of an ovarian carcinoma mouse model. CONCLUSION: These results provide an indication of the mechanisms underlying the anti-tumour activity of trastuzumab that strongly implicate RhoB in an ovarian carcinoma model that does not show HER-2 amplification or overexpression. These findings highlight that trastuzumab effects involve a possible cross-talk between RhoB and PTEN in the early stages of tumour re-growth in a model of micrometastatic ovarian cancer.

Prediction of carboplatin clearance from standard morphological and biological patient characteristics.

BACKGROUND: Hematologic toxicity of an antineoplastic drug, carboplatin, is largely dependent on its pharmacokinetics. Its therapeutic efficacy may be related to plasma drug exposure. Dosage adjustment based on isotopic determination of glomerular filtration rate has been proposed, but its ambulatory use is not yet conceivable. The dosage adjustment based on a patient's creatinine clearance relies on accurate measurement of urine volume per unit time and can be done with ease. PURPOSE: A population pharmacokinetics study was undertaken to determine a relationship between carboplatin clearance and patient characteristics. A predictive formula was derived that was then prospectively evaluated, and its outcome was compared with that obtained by other methods available to predict carboplatin clearance. METHODS: Plasma carboplatin pharmacokinetics determined as ultrafilterable platinum in 70 patients (age range, 23-84 years) treated with different combination regimens that included carboplatin at doses ranging from 184 mg to 950 mg (1-hour intravenous infusion) for various tumor types. Data were analyzed using the nonlinear mixed effects model (NONMEM). The data from 34 patients (46 cycles) were utilized to derive the most predictive formula. The reliability of the formula was subsequently evaluated by analyzing the data obtained from 36 other patients (49 cycles). RESULTS: Carboplatin clearance (mL/min) was found to be best predicted by the following formula: 0.134.weight + [218.weight.(1-0.00457.age).(1-0.314.sex)]creatinine expressed in micromolar concentration (with weight in kg, age in years, and sex = 0 if male and sex = 1 if female). Prospectively, this formula predicted the carboplatin clearance with good precision (median absolute percent error of 10% [range, 0% to 30%]) and minimal bias (median percent error of 2% [range, -25% to 30%]). This method of prediction was as accurate as the one derived from the measurement of glomerular filtration rate following the injection of 51 chromium-EDTA. CONCLUSION: This formula for the determination of carboplatin clearance can permit individualized determination of carboplatin dosage in adults by simply multiplying the calculated carboplatin clearance by the area under the curve for the desired dosage administration.

Kinetics of the in vivo interconversion of the carboxylate and lactone forms of irinotecan (CPT-11) and of its metabolite SN-38 in patients.

The kinetics of the in vivo interconversion of the carboxylate and lactone forms of the prodrug irinotecan, 7-ethyl-10-[4-(1-piperidino)-1- piperidino]carbonyloxycamptothecin (CPT-11), and its active metabolite SN-38 were studied in five patients using a HPLC method that allows the simultaneous determination of all four compounds and detects any hydrolysis of lactones due to inadequate sample handling and storage. The apparent conversion of CPT-11 lactone to the carboxylate in vivo was rapid with a mean half-life of 9.5 min; the carboxylate became the predominant form of plasma CPT-11 soon after the end of the infusion. The ratio of the area under the plasma concentration-time curves of the lactone to total CPT-11 was 36.8 +/- 3.5% (SD). In contrast, SN-38 was present predominantly as the lactone at all times and with little interpatient variability (lactone/total area under the plasma concentration-time curve ratio, 64.0 +/- 3.4%). This may explain in part the promising activity of CPT-11 because CPT derivatives are active against their target, topoisomerase I, only in their lactone form.

Plasma and cellular pharmacokinetics of mitoxantrone in high-dose chemotherapeutic regimen for refractory lymphomas.

We have studied the plasma and peripheral leukocyte pharmacokinetics of mitoxantrone associated, in a high-dose regimen, with cyclophosphamide, carmustine, and etoposide in patients with refractory lymphoma undergoing autologous bone marrow transplantation. Nineteen patients with refractory lymphoma were involved in a clinical trial with escalated doses (15-90 mg/m2) of mitoxantrone administered by 30-min i.v. infusion 8 days before an autologous bone marrow transfusion. Mitoxantrone was measured by high-performance liquid chromatography in plasma and peripheral lymphocytes. The plasma pharmacokinetics of mitoxantrone was linear between 15 and 90 mg/m2: total body clearance (19.3 +/- 6.2 liter/h/m2) and volume of distribution at steady state (486 +/- 254 liter/m2) were not altered by increasing the dose. The exposure of bone marrow transplant to the plasma residual concentration of mitoxantrone was correlated with the limiting hematological toxicity of the regimen (P < 0.001). At all times, the mitoxantrone concentration in peripheral cells was much higher than in plasma and was retained at a constantly high concentration level. Whereas cellular versus plasma maximum concentration ratio was near 1, the area under the concentration +/- time curve ratio reached 100, suggesting a long elimination half-life from cells. Plasma and cellular pharmacokinetics data of mitoxantrone reinforce the idea that this drug is a good candidate for high-dose chemotherapy regimen.

Cardiotoxicity of high-dose continuous infusion fluorouracil: a prospective clinical study.

PURPOSE: A prospective clinical study was performed to determine the incidence of high-dose continuous intravenous infusion fluorouracil (5FU-CIV) cardiotoxicity. PATIENTS AND METHODS: Three hundred sixty-seven patients who were given first-cycle high-dose 5FU-CIV were monitored for cardiac function by clinical examination, ECG, and laboratory tests. 5FU-CIV was administered during a 96- or 120-hour period at doses that ranged from 600 to 1,000 mg/m2/d. Associated drugs included cisplatin (56%), mitomycin (12.5%), folinic acid (leucovorin) (7%), and others (14%). Thirty-nine patients (10.5%) received 5FU as a single agent. RESULTS: 5FU-induced cardiac events occurred in 28 patients (7.6%; 95% confidence interval, 4.9% to 10.3%). Nine of them had a history of cardiac disease. Primary tumors included head and neck (n = 13), gastrointestinal (n = 6), breast (n = 3), and others (n = 6). The mean onset time of cardiac symptoms was 3 days (range, 2 to 5). Inaugural symptoms included angina pectoris (n = 18), hypotension (n = 6), hypertension (n = 5), malaise (n = 4), dyspnea (n = 2), arrhythmia (n = 1), or sudden death (n = 1). At 5FU discontinuation, six patients' cardiac symptoms returned to baseline, but 21 patients experienced unstable angina (n = 8), hypotension/cardiovascular collapse (n = 11), pulmonary edema (n = 1), or sudden death (n = 4). The lethality rate was 2.2% (five sudden deaths plus three irreversible collapses). ECG showed repolarization changes (ST segment deviation; T-wave inversion) in 65% and/or diffuse microvoltage in 22% of the patients who presented with cardiac events. Echocardiography showed partial or global hypokinesia in nine of the 16 patients who were examined, and one case of prolonged akinesia. Cardiac enzymes rarely showed an increase (n = 2). In severe but reversible cases, clinical, ECG, and echographic parameters returned to baseline status within 48 hours after the drug discontinuation. A fluorine 19 nuclear magnetic resonance (19F NMR) analysis of urine was performed on 14 patients; six had cardiac symptoms and eight did not. Fluoroacetate (FAC), a known cardiotoxic compound, was detected in all cases. CONCLUSION: In our study, the incidence of high-dose 5FU-CVI cardiotoxicity was 7.6%. The hypothesis of a toxic cardiomyopathic process requires further confirmation.

Pharmacokinetics and pharmacodynamics of irinotecan during a phase II clinical trial in colorectal cancer. Pharmacology and Molecular Mechanisms Group of the European Organization for Research and Treatment of Cancer.

PURPOSE: A pharmacokinetic study was performed during a phase II clinical trial of irinotecan (CPT-11) to confirm the pharmacokinetic profile of this drug and its metabolite and to investigate interpatient and intrapatient pharmacokinetic variations and pharmacokinetic-pharmacodynamic relationships. PATIENTS AND METHODS: Twenty-six men and 21 women (mean age, 61 years) with metastatic colorectal cancer, performance status less than 3 (World Health Organization [WHO] scale), and normal renal and hepatic function were administered CPT-11 (350 mg/m2) by 30-minute intravenous (IV) infusion every 21 days. CPT-11 and its metabolites SN-38 and SN-38 glucuronide (SN-38G) were determined by high-performance liquid chromatography (HPLC) using fluorimetric detection. RESULTS: The mean CPT-11 clearance and area under the concentration-time curve (AUC) were 15.2 L/h. m2 and 24,769ng. h/mL, respectively. The large difference in SN-38 and SN-38G AUCs (559 v 2,283 ng. h/mL) was suggestive of extensive glucuronidation of SN-38. Interindividual variation in the metabolic ratio ([AUCSN-38 + AUCSN-38Gl/AUCCPT-11) was marked (coefficient of variation [CV] = 51.6%] compared with intrapatient variation in this variable (CV = 32.6%). A significant relationship existed between percentage reduction in neutrophil count and the AUC of CPT-11 (r = .597, P < .001) and SN-38 (r = .559, P < .001). No relationship was identified between any pharmacokinetic parameter and delayed diarrhea or therapeutic outcome. CONCLUSION: Interindividual variations in the metabolic ratio suggest interpatient variation in carboxylesterase activity. Furthermore, glucuronidation of SN-38 may also be in part responsible for the large interpatient variability in the total SN-38 AUC. Conversely, low intrapatient variation of this parameter was observed in this study, which indicates a lack of autoinduction of the carboxylesterase system. The relationship between neutropenia and both CPT-11 and SN-38 pharmacokinetic parameters confirms the results of previous studies.

Escalating dose of mitoxantrone with high-dose cyclophosphamide, carmustine, and etoposide in patients with refractory lymphoma undergoing autologous bone marrow transplantation.

PURPOSE: We conducted a dose-finding study of mitoxantrone (MITO) in combination with high-dose cyclophosphamide, carmustine (BCNU), and etoposide (CBV) in refractory lymphoma undergoing autologous bone marrow transplantation (ABMT). The objective were to determine the following: (1) the maximum-tolerated dose of MITO, (2) the extramedullary toxicity of this regimen, (3) its antitumor activity, and (4) the pharmacokinetic characteristics of MITO at each dose level. PATIENTS AND METHODS: Escalating doses of MITO (15 to 90 mg/m2, single bolus infusion on day -8) followed by CBV were administered to 20 patients (mean age, 38.5 years) with refractory lymphoma. MITO concentrations were determined by high-performance liquid chromatography (HPLC). RESULTS: No toxic death occurred. The maximum-tolerated dose appears to be 75 mg/m2. Two of five patients treated with 90 mg/m2 developed severe organ toxicity, versus zero of 15 treated with doses up to 75 mg/m2. Duration of neutropenia was longer for patients treated with 90 mg/m2 (31.7 days) than for patients treated with doses up to 75 mg/m2 (22.1 days) (P < .05). A linear relationship was observed between administered dose of MITO and (1) plasma peak value, (2) area under the curve (AUC), and (3) plasma concentration on the day of marrow infusion (day 0). Hematologic toxicity was related to the terminal half-life (T1/2) of MITO, and day-0 plasma concentration. A high complete response (CR) rate was observed (60%), and eight of 11 (73%) patients treated with MITO > or = 60 mg/m2 achieved a CR. CONCLUSION: MITO (up to 75 mg/m2) and CBV can be administered with acceptable toxicity and a promising CR rate in this poor-risk population, justifying further phase II studies.

Phase I study of cinchonine, a multidrug resistance reversing agent, combined with the CHVP regimen in relapsed and refractory lymphoproliferative syndromes.

Overexpression of P-glycoprotein (P-gp) in cancer cells reduces intracellular accumulation of various anticancer drugs including anthracyclines and vinca alkaloids. This multidrug resistance (MDR) phenotype can be reversed in vitro by a number of non-cytotoxic drugs. We have identified the quinine's isomer cinchonine as a potent MDR reversing agent, both in vitro and in animal models. Here, we report an open phase I dose escalation trial in patients with refractory or relapsed malignant lymphoid diseases. Cinchonine dihydrochloride was administered by continuous i.v. infusion for 48 h and escalated over five dose levels ranging from 15 to 35 mg/kg/d. Cinchonine infusion started 24 h before i.v. doxorubicin (25 mg/m2), vinblastine (6 mg/m2), cyclophosphamide (600 mg/m2) and methylprednisolone (1 mg/kg/d) (CHVP regimen) and lasted for 24 h after chemotherapy infusion. Thirty-four patients received 87 cycles of CHVP/cinchonine. The MTD of cinchonine administered by continuous i.v. infusion was 30 mg/kg/d. Prolonged cardiac repolarization was the main dose-limiting toxicity. No ventricular arrhythmia including 'torsade de pointes' was observed. An MDR reversing activity was identified in the serum from every patient and correlated with cinchonine serum level. When infused at 30 mg/kg/d, cinchonine demonstrated a limited influence on doxorubicin pharmacokinetic. We conclude that i.v. infusion of cinchonine might be started 12 h before MDR-related chemotherapy infusion and requires continuous cardiac monitoring but no reduction of cytotoxic drug doses.

Schedule-dependent activity of topotecan in OVCAR-3 ovarian carcinoma xenograft: pharmacokinetic and pharmacodynamic evaluation.

Topotecan is a topoisomerase (Topo) I inhibitor used in ovarian carcinoma chemotherapy. Topo I inhibitors are thought to be more cytotoxic using protracted schedules of administration. We tested this hypothesis on a preclinical model: human ovarian carcinoma OVCAR-3 implanted i.p. Nude mice were treated i.p. with a total dose of topotecan of 12.5 mg/kg delivered in 1, 5, 10, 20, 40, or 80 daily injections. The toxicity was maximal when the total dose was delivered within 5 and 10 days of treatment. However, the efficacy was the greatest (all of the mice cured) in the 20-day schedule using 0.625 mg/kg/day, hence, making this latter schedule the most efficient without any major toxicity. A pharmacokinetic study was conducted to identify parameters related to the efficacy and toxicity of topotecan in our model. The use of a population pharmacokinetic approach allowed us to define a therapeutic window: maintaining plasma concentrations above 0.2 microM for >10 h was necessary for an optimal antitumor effect and avoiding plasma concentrations >0.7 microM allowed a manageable toxicity. Finally, Topo I activity was monitored in ascites from animals treated with different topotecan administration schedules. The optimal schedule defined above allowed for sustained inhibition of Topo I activity associated with a greater antitumor activity. These in vivo data constitute a rationale for clinical studies testing this type of administration.

Pharmacokinetic interrelationships of irinotecan (CPT-11) and its three major plasma metabolites in patients enrolled in phase I/II trials.

Irinotecan (CPT-11) is an analogue of 20(S)-camptothecin with promising activity against several tumor types. In patients, CPT-11 is metabolized to 7-ethyl-10-hydroxycamptothecin (SN-38) and to the beta-glucuronide of SN-38. Recently, we identified an additional metabolite of CPT-11, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino] carbonyloxycamptothecin (APC; L. P. Rivory et al. , Cancer Res., 56: 3689-3694, 1996). The aim of this study was to investigate the interrelationships of all four compounds to identify factors that might be responsible for the large interpatient variability in CPT-11 and SN-38 kinetics. The plasma kinetics of CPT-11, SN-38, the beta-glucuronide of SN-38, and APC were studied in 19 patients for a total of 33 cycles (115-600 mg/m2). Although the area under the concentration curves (AUCs) of all compounds studied increased with dose, there was considerable variability. Ratios of the AUCs of the appropriate compounds were used as estimates of the major routes of metabolism (conversion of CPT-11 to SN-38, metabolism of CPT-11 to APC, and glucuronidation of SN-38). Each ratio varied more than 10-fold across the patient population, and the apparent extent of conversion of CPT-11 to SN-38 was highest at the 115 mg/m2 dose level. Interestingly, AUCSN-38 was greater in patients with both high AUCCPT-11 and AUCAPC. We conclude that the variability of the pharmacokinetics of CPT-11 and SN-38 is likely to be due to extensive interpatient differences in the pathways implicated in the metabolism of CPT-11.

Dose and time dependencies of 5-fluorouracil pharmacokinetics.

OBJECTIVES: The purpose of this study was to examine the interpatient and intrapatient variability of the Michaelis-Menten plasma parameters of 5-fluorouracil administered according to a schedule combining a bolus of 400 mg/m2 followed by 22-hour infusion of 600 mg/m2 for 2 consecutive days. PATIENTS: A pharmacokinetic population approach was used to analyze the data from 21 patients with colorectal cancer. RESULTS: The 5-fluorouracil plasma concentrations versus time were best described by a two-compartment model with nonlinear elimination from the central compartment. The relationships between the pharmacokinetic parameters and patient characteristics were tested. On day 1 the mean values (with interindividual variability as expressed by the coefficient of variation) were 1390 mg x h(-1) (20%), and 5.57 mg x L(-1) (22%) for the maximum rate of elimination, and the half-saturating plasma concentration. The maximum rate of elimination was positively correlated to the body surface area and the percentage of liver involvement by metastatic disease determined by tomodensitometric examination. The model was successfully tested with independent data sets corresponding to other schedules. The analysis of this intrapatient variability showed that the half-saturating plasma concentration increased from day 1 to day 2, especially in the patients with low lymphocyte cell dihydropyrimidine dehydrogenase activity. CONCLUSION: The pharmacokinetic parameters obtained in this study would be useful to predict the 5-fluorouracil plasma concentrations following other schedules of administration of 5-fluorouracil and to study the possible pharmacokinetic interactions between 5-fluorouracil and other drugs.

Human pharmacokinetics of N-L-leucyl-doxorubicin, a new anthracycline derivative, and its correlation with clinical toxicities.

A pharmacokinetic study of N-L-leucyl-doxorubicin, a new derivative of doxorubicin, has been undertaken during a phase I trial in 19 patients with advanced cancer after intravenous bolus administration at doses ranging from 30 to 240 mg/m2. The pharmacokinetics of N-L-leucyl-doxorubicin was linear with a total body clearance of 41.3 +/- 25.7 L/hr/m2. N-L-leucyl-doxorubicin was extensively metabolized into doxorubicin, which appeared in plasma immediately after N-L-leucyl-doxorubicin infusion. The mean molar doxorubicin/N-L-leucyl-doxorubicin area under the curve (AUC) ratio was 0.49 +/- 0.22 and was independent of the administered dose. A relationship has been established between the doxorubicin AUC (r = 0.74; p less than 0.001) and the surviving factor in white blood cell counts. Other toxic side effects (thrombocytopenia or stomatitis) did not correlate with any pharmacokinetic parameter. These findings suggest that the degree of metabolization of N-L-leucyl-doxorubicin into doxorubicin may be responsible for the toxicity, that is, N-L-leucyl-doxorubicin may simply represent a pro-drug for doxorubicin.

Population pharmacokinetics of carboplatin in children.

OBJECTIVES: In pediatric patients, administration of carboplatin according to body surface area results in a large variation in the area under the plasma ultrafilterable carboplatin concentration versus time curve. A population pharmacokinetic study using the NONMEM program was undertaken to determine the effects of a variety of covariates on the clearance of ultrafilterable carboplatin. PATIENTS: Plasma carboplatin pharmacokinetics were determined in 57 children (2 months to 18 years old, with serum creatinine levels ranging from 27 to 268 mumol/L) treated for various tumor types. RESULTS: The best fit corresponded to the formula: clearance (ml/min) = 2.85.weight.(1-0.00357.serum creatinine).(1-0.372.Np) + 8.7 (with serum creatinine in micromoles per liter, weight in kilograms, and Np = 1 or 0 for unilateral nephrectomy or not, respectively). The interindividual variability in clearance, as expressed by the coefficient of variation, decreased from 74% (no covariates) to 49% by taking account of weight, and to 29% under the final regression formula. CONCLUSION: The ability of this formula to predict carboplatin clearance in children should be evaluated prospectively and compared to a method based on the determination of the glomerular filtration rate.

Cellular determinants of oxaliplatin sensitivity in colon cancer cell lines.

Oxaliplatin (L-OHP) is a new platinum analogue that has shown antitumour activity against colon cancer both in vitro and in vivo and is now used in the chemotherapeutic treatment of metastatic colon and rectal cancer. L-OHP like cisplatin (CDDP), is detoxified by glutathione (GSH)-related enzymes and forms platinum (Pt)-DNA adducts lesions that are repaired by the nucleotide excision repair system (NER). We investigated the cytotoxicity and the pharmacology of L-OHP and CDDP on a panel of six colon cell lines in vitro. We showed that GSH and glutathione S-transferase (GST) activity were not correlated to oxaliplatin cytotoxicity. Pt-DNA adducts formation and repair were correlated with CDDP, but not with L-OHP cytotoxicity. The determination of ERCC1 and XPA expression, two enzymes of the NER pathway, by reverse transcriptase-polymerase chain reaction (RT-PCR), demonstrated that ERCC1 expression was predictive of L-OHP sensitivity (r(2)=0.67, P=0.02) and XPA level after oxaliplatin exposure was also correlated to L-OHP IC(50) (r(2)=0.5; P=0.04). The knowledge of such correlations could help predict the sensitivity of patients with colon cancer to L-OHP.

A limited sampling strategy for determining carboplatin AUC and monitoring drug dosage.

There are several convincing reports showing relationships between the area under the curve of ultrafilterable concentration versus time (AUC) and pharmacodynamics of carboplatin. It is advisable, in treated patients, to check the AUC that is effectively delivered as compared with the prescribed AUC. To this end, limited sampling strategy seems to be an adequate approach since it limits the constraints of repeated blood sampling for both patients and nursing staff. A flexible limited sampling method for assessing ultrafilterable carboplatin AUC was developed. This method was based on a Bayesian estimation of carboplatin clearance using the NON linear Mixed Effect Model (NONMEN) program and a large pharmacokinetic and covariates database (103 patients). The optimal sampling design was a two-sample schedule (1 and 4 h after the end of infusion). During a prospective evaluation, it allowed an adequate estimation of carboplatin clearance with a non-significant bias (-4.5%) and a good precision (9%). In a second stage, this method was clinically applied to monitor carboplatin AUC in a group of 5 patients with metastatic germ cell tumours treated with intensified high dose carboplatin-based chemotherapy for 4 days. Dosage adjustments were performed according to daily controls of their AUC in order to obtain a total AUC of 20 mg/ml x min. By using this strategy all patients effectively received a total AUC very close to this targeted AUC, thus proving the clinical usefulness of this limited sampling method.

Modulation of cisplatin cytotoxicity by human recombinant interferon-gamma in human ovarian cancer cell lines.

Cytotoxic interactions between recombinant human interferon-gamma (IFN gamma) and cisplatin have been studied in six ovarian cell lines (IGROV1, NIHOVCAR3, SKOV3, OVCCR1, 2008 and its cisplatin resident variant 2008/C13*). Studies were performed using a cell survival assay. Results were assessed using median effect analysis. Synergy between these two drugs was observed in cell lines sensitive to IFN gamma, whatever their relative sensitivity or resistance to cisplatin, suggesting that IFN gamma enhances the cytotoxic activity of cisplatin. This interaction is not due to an increase in platinum accumulation in cells. This combination of drugs should be evaluated against human ovarian cancer xenografts in nude mice before its use in clinical practice.

Co-variables influencing 5-fluorouracil clearance during continuous venous infusion. A NONMEM analysis.

The objective of this study was to attempt to identify patient co-variables which could influence interpatient variability in 5-fluorouracil (5-FU) clearance during a 5-day continuous venous infusion (CVI, cisplatin 100 mg/m2 day 1 then 5-FU 1 g/m2/day days 2-6). The analysis was performed using a NONMEM program according to a linear one-compartment model. A total of 186 cycles (2 samples per day, 8 a.m. and 5 p.m.) were analysed from 104 patients with various cancers (the majority of head and neck and oesophagus). The study co-variables were age, sex, body surface area, hepatic metastases, peripheral mononuclear cell dihydropyrimidine dehydrogenase activity (PMNC-DPD), liver enzymes, clock-time (8 a.m. versus 5 p.m.), elapsed time during CVI. The data showed that 5-FU clearance was significantly reduced by increased age, low PMNC-DPD, high serum alkaline phosphatase and elapsed time during infusion. These data may be useful for improving knowledge of predictive factors which can influence 5-FU exposure and thus predispose to toxic manifestations.

Impact of the biochemical assay for serum creatinine measurement on the individual carboplatin dosing: a prospective study.

We previously developed a formula to estimate the individual carboplatin clearance (CL) based on serum creatinine (Scr) determined by an enzymatic assay using creatinine amidohydrolase. An analytical comparison had shown systematic differences between this method and the commonly used Jaffé method (with Jaffé Scr (in microM)=1.08 x enzymatic Scr+1.6, as regression equation). We performed a pharmacokinetic prospective clinical study using the Jaffé assay to evaluate the impact of the method used for Scr measurement on the prediction of the carboplatin CL. In forty patients, carboplatin dosing was performed according to the Chatelut formula where the serum creatinine level was corrected according to the above equation. The population pharmacokinetics of carboplatin were analysed using the NONMEM program to determine the individual carboplatin CL from a limited sampling strategy. Thanks to the correction of the Jaffé Scr, no significant difference was observed between the administered and the optimal dose. In contrast, if no correction of the Scr was done, the patients would have been significantly under-dosed. Moreover, a covariate analysis using NONMEM gave a very consistent result showing that Scr should be decreased by 11.6% when the Jaffé value is used within the Chatelut equation. This study confirmed that differences in the Scr assay has consequences with regard to carboplatin dosing. The correction we propose for Scr obtained by the Jaffé method may help to standardise clinical practice.

Phase I/II pharmacokinetic study of mitoxantrone by continuous venous infusion in patients with solid tumours and lymphoproliferative diseases.

Phase I and pharmacokinetic studies were performed in order to evaluate the maximum tolerated dose and the efficiency of 120 h continuous venous infusion (CVI) of mitoxantrone. 25 patients suffering from either metastatic solid tumour or refractory lymphoproliferative disease were included in the study. The starting dose was 2 mg/m2 per day and was increased by a 0.2 mg/m2 per day step dose. The main toxicity observed was leukopenia which became limiting in more than 50% of the patients receiving 2.4 mg/m2 per day (12 mg/m2 over a 120 h period); this dose was defined as the maximal tolerated dose in these pretreated patients. One partial response and three stable diseases were observed. A plasma plateau concentration of mitoxantrone (2.13 [S.D. 0.54] micrograms/1 at 2 mg/m2 per day, 2.56 [1.32] micrograms/1 at 2.2 per day and 3.46 [1.32] micrograms/l at 2.4 mg/m2 per day) was reached within 24-48 h. It was linearly related to the administered dose. The mean plasma clearance of mitoxantrone was 27.8 [14.2] l/h/m2 and the volume of distribution of the beta phase averaged 2327 [2125] l/m2. An inverse relationship was established between the mitoxantrone clearance and the degree of hematologic toxicity. This 120 h CVI mitoxantrone schedule was safe and could be repeated every 3 weeks in an outpatient setting. The relationship between mitoxantrone clearance and the drug related haematotoxicity could be used for an individual dose adjustment.

Pharmacokinetics of Ro 03-8799 in mice bearing melanosarcoma: comparison with tumors without melanin.

The pharmacokinetics of Ro 03-8799 has been studied in melanic and non-melanic tumor bearing mice after iv administration of 150 mg/kg. The peak concentration in B16 melanosarcoma tumor reached 152 micrograms/g, that is 7.6-fold higher than the plasma concentration at the same time. This concentration is 3-times greater than that obtained in the tumor of mice bearing non melanic sarcoma (DB16) or Lewis lung carcinoma (3LL). The exposure of B16 tumor (AUC) is respectively 15-times and 11-times higher than the 3LL and the DB16 ones. These experimental data confirm that this 2-nitro-imidazol compound has an important affinity for melanin and suggest that it might be used as a radiosensitizer for the treatment of malignant melanoma.