Clinical and pharmacokinetic phase II study of fotemustine in refractory and relapsing multiple myeloma patients.

BACKGROUND: Patients with relapsing or refractory multiple myeloma have poor prognosis. Few compounds are active in these patients and response duration remains short. We report the results of an open phase II trial evaluating the efficacy and safety of fotemustine monotherapy. PATIENTS AND METHODS: Twenty-one patients with relapsing (17) or refractory (four) multiple myeloma received fotemustine 100 mg/m(2) on an outpatient basis on days 1 and 8 of the induction cycle, followed after a 6-week rest period by fotemustine 100 mg/m(2) every 3 weeks until progression or unacceptable toxicity. Fotemustine pharmacokinetics during the first day of induction was compared between patients with normal or abnormal renal function. RESULTS: Five of 20 eligible patients had an objective response giving an intention-to-treat response rate of 25% [95% confidence interval (CI) 6% to 44%] and a 35.7% response rate (95% CI 11% to 61%) in the 14 patients having received at least four injections of fotemustine. The median time to objective response was 8.9 months. The median times to progression and survival were 13.8 and 23.1 months, respectively, with a 2-year survival rate of 49%. The main toxicity was myelosuppression with grade 3-4 neutropenia and thrombocytopenia in 66% and 71% of patients, respectively. There was one toxic death by sepsis after induction. The pharmacokinetic parameters in renal-impaired patients were not significantly different from those in patients with normal renal function with a similar incidence of grade 3-4 toxicity in both groups. CONCLUSIONS: Fotemustine as a single agent has definite activity in patients with relapsing or refractory multiple myeloma, with acceptable toxicity and can be administered at conventional doses in patients with mild or moderate renal impairment.

Dose-finding, pharmacokinetic and phase II study of docetaxel in combination with gemcitabine in patients with inoperable non-small cell lung cancer.

BACKGROUND: The good efficacy-toxicity ratio of both docetaxel and gemcitabine in non-small cell lung cancer (NSCLC) stimulates the investigation of the combination of these drugs as a first line chemotherapy. This two-step study firstly aimed at determining the maximum tolerated and recommended doses of docetaxel given every 3 weeks in combination with a fixed dose of gemcitabine; the phase I study paid particular attention to pharmacokinetics. Afterwards, the safety and efficacy of the recommended dose was carefully assessed in the phase II-step. METHODS: The following range of docetaxel dosages were tested in the phase I study; 60, 75, 85, and 100 mg m(-2) given on day 8 in combination with gemcitabine 1000 mg m(-2) delivered on days 1 and 8 of a 3-week cycle. Haematopoietic growth factors were not allowed. The treatment was delivered on an outpatient basis. Main eligibility criteria consisted of stage III b or IV histologically proven NSCLC, Eastern Co-operative Oncology Group (ECOG) performance status PS < or =2, age < or =70 years, measurable disease, adequate blood counts, chemistry, and no symptomatic brain metastasis. RESULTS: Four centres enrolled 49 patients (eight having been pre-treated); 16 in phase I and 33 in phase II. The maximal tolerated dose was almost reached at the last dose level (i.e. docetaxel, 100 mg m(-2)). Consequently, we considered the 85 mg m(-2) level as the recommended dose. There was a positive relationship of the docetaxel dose to the area under the curve of this drug. Toxicity was assessable in all patients. Among the 200 cycles delivered, 192 were assessable for this feature. Main toxicity was grade 3-4 neutropenia affecting 23 patients (47% of the population; 23% of the cycles). Six febrile episodes were recorded leading to two treatment-related deaths. Another patient died from congestive cardiac failure. In addition, six patients experienced interstitial pneumonitis, (one half considered as severe), two of them having received the recommended dose. All patients recovered from this toxicity after corticosteroids. Fourteen patients out of the whole population (29%; 95% CI [17-43], including ten patients receiving the recommended dose), achieved an objective response. Median follow-up was 14 months (range, 0.3-29.4). Median survival was 11.2 months (95% CI [8.3-13.2]), and the 1-year survival rate was 45%. CONCLUSION: Gemcitabine, 1000 mg m(-2) days 1 and 8 in combination with docetaxel, 85 mg m(-2), day 8, given every 3 weeks could be considered as an active regimen with manageable toxicities in locally advanced or metastatic NSCLC. This study deserves further comparisons with classical platinum-based regimens.

Pharmacodynamics of tandem high-dose melphalan with peripheral blood stem cell transplantation in children with neuroblastoma and medulloblastoma.

Repeated high-dose (HD) chemotherapy with peripheral blood stem cell (PBSC) transplantation is a new modality aimed at increasing both the dose and its intensity in the treatment of chemosensitive tumours. The aim of this study was to evaluate the tolerance, pharmacokinetics (PK) and pharmacodynamics (PD) of HD single-agent melphalan administered over two consecutive courses (C1 and C2) in children. Twenty-one patients (10 girls) with a median age of 4.1 years (range 8 months-14 years) were entered into this study. Five had metastatic neuroblastoma (NB) and 16 a cerebral primitive neuroectodermal tumour (PNET). Melphalan was given at a dose of 100 mg/m(2) every 21 days. PBSCs were infused at a median number of 2.98 x 10(6) CD34(+) cells/kg. Forty courses, ie 21 C1 and 19 C2, were administered. Both courses were well tolerated. The median duration of ANC < 500/microl was 7 and 6 days after C1 and C2, respectively. Platelet recovery (not mandatory to continue the HD strategy) was achieved in 52% of courses. GI toxicity was mild to moderate. The melphalan AUC ranged from 177 to 475 microg small middle dotmin/ml (no difference between C1 and C2). Prolonged neutropenia was associated with a young age (P < 0.001) and a low amount of CFU-GM (P = 0.002). A long time to platelet recovery was associated with a high AUC (P = 0.004) and a young age (P = 0.02). Grade 1 or 2 GI toxicity was associated with a high AUC (P = 0.015). Partial remission was observed in 11/14 patients with measurable cerebral PNET. In conclusion, tandem HD melphalan is feasible and safe in children, and achieved a high response rate in cerebral PNET. The observed PK-PD relationships may help us design PK-guided outpatient treatment.

The prognostic value of etoposide area under the curve (AUC) at first chemotherapy cycle in small cell lung cancer patients: a multicenter study of the groupe Lyon-Saint-Etienne d'Oncologie Thoracique (GLOT).

PURPOSE: To assess the potential relationships between systemic exposure to doxorubicin, etoposide and ifosfamide at first chemotherapy cycle and therapeutic effect, tumor response, toxicity, and survival, in small cell lung cancer (SCLC) patients. PATIENTS AND METHODS: Twenty-four patients referred to five different centers with either thorax-limited or metastatic SCLC entered the study. All but one received two induction courses of the 3 day-AVI (doxorubicin 50 mg/m(2) day 1, etoposide 120 mg/m(2) day 1, 2, 3, ifosfamide 2000 mg/m(2) day 1, 2) regimen. Individual plasma samples were collected at the first course and complete concentration data on 24 courses were available. Drugs exposures were estimated using a population pharmacokinetic method and expressed as clearance (Cl), area under the curve (AUC), and AUC-intensity (AUC/cycle duration). Responding patients received thoracic irradiation+concomitant cisplatinum-etoposide (limited disease) or four more courses of AVI (extensive disease). The impact of exposure parameters on haematological toxicity, tumor response and overall survival was assessed using linear regression, the Mann-Whitney U-test and the log-rank test/Kaplan-Meier estimation, respectively. RESULTS: Twenty-three patients could be evaluated for response and survival. We found no relationship between drug exposure and haematological toxicity but all patients had received Granulocyte-Colony Stimulating Factor support. Tumor response was marginally influenced by ifosfamide AUC. In patients with etoposide AUC>254.8 mg h/l, 1-year survival was 50.0 vs. 9.1% in the other group (median 11.4 vs. 7.1 months, P=0.02), with respect to established prognostic factors. In patients with extensive disease only (n=15), 1-year survival was 42.9 vs. 0% (median 11.3 vs. 5.3 months, P=0.01). CONCLUSION: This study strongly suggests that SCLC patients should benefit from sufficient etoposide exposure at first cycle to improve survival. Adaptative control based on plasma concentration measurements should be tested in further studies assessing various polychemotherapy regimens.

Population pharmacokinetics of doxorubicin, etoposide and ifosfamide in small cell lung cancer patients: results of a multicentre study.

AIMS: To determine the population pharmacokinetic (PK) parameters of doxorubicin (Dox), etoposide (Eto) and ifosfamide (Ifo) in small cell lung cancer (SCLC) patients, to assess the potential relationship between those parameters and to estimate the impact of individual morphological and biological covariates on patients' PK parameters. METHODS: Twenty-four patients with either SCLC limited to the thorax or extensive SCLC entered the study. All but one received at least two 3 day courses of the standard AVI (Dox 50 mg m-2 day 1, Eto 120 mg m-2 day 1,2,3, Ifo 2000 mg m-2 day 1,2) regimen. Individual blood samples were collected during each course and data on 47 courses were available. Data were analysed with the NONMEM program. Dox, Eto and Ifo plasma concentrations were studied with multicompartment (3, 2 and 2, respectively) models. Inter-individual and interoccasion (course-to-course) variabilities were estimated. The influence of individual covariates (age, sex, stage of the disease, weight, height, body-surface area, serum creatinine, total protein, LDH, ASAT, ALAT, alkaline phosphatase, gamma-GT, bilirubin) on PK parameters was also assessed. Correlations between individual PK parameters of Dox, Eto and Ifo were explored by using Pearson's correlation coefficient. RESULTS: Multiple data were available for each patient. Dox clearance (CL) and volume of distribution (Vd) were 32.0 l h-1 and 9.3 l (Inter-individual variability: 17.2% and 19.2%). Eto CL (l h-1) and Vd were, respectively, 3.34-0.0083* serum creatinine (micromol l-1) and 6.38 l (interindividual variability: 15.6% and 18.7%). Ifo CL and Vd at day 1 were 5.6 l h-1 and 26.0 l (interindividual variability: 10.1% and 17.2%, respectively). Estimation of course-to-course variability improved the precision of PK models in some cases. No correlation was observed between the respective PK parameters of each drug. Of individual covariates tested, only serum creatinine correlated with Eto CL (r = -0.37, P < 0.001). Self-induction of the metabolism of Ifo was apparent (mean CL increase from day 1 to day 2 : 42%) and individually correlated with the CL value at day 1 (r = -0.61, P < 0.001). CONCLUSIONS: Assessment of potential relationships between individual systemic exposure of chemotherapy and therapeutic endpoints (tumour response, toxicity and survival) will be required to adjust drugs dosages based on individual PK parameters rather than questionable body-surface area. However, all three drugs in the AVI regimen should be monitored simultaneously.

Multivariable analysis of prognostic factors for toxicity and survival for patients enrolled in phase I clinical trials.

BACKGROUND: Patients with advanced solid tumors may be included in phase I clinical trials. In such studies, the benefit expected is generally lower than the likelihood of toxicity and may even be non-existent if the patient's life expectancy is too short. This study was performed to identify prognostic variables for toxicity and survival in patients who participate in phase I clinical trials. PATIENTS AND METHODS: One hundred fifty-four patients treated on a phase I clinical trial in our institute were evaluated retrospectively. Univariable and multivariable analyses of patients' characteristics were undertaken to determine their effects on the probability of grade 3 and 4 toxicity and on survival. RESULTS: Grade 3 or 4 toxicity was experienced by 56 patients (36%): dosage level at entry (P < 0.001) and age over 65 years (P = 0.03) were independently associated with the risk of toxicity. Median overall survival was 5 months. The multivariable analysis identified performance status 2 or 3 (P < 0.001) and lactate dehydrogenase levels greater than 600 UI (P < 0.001) as independent adverse prognostic variables for overall survival. Using these two parameters, we determined a prognostic index which allowed us to discriminate three risk groups of patients with an observed median survival of 8.5, 4.5 and 1.5 months, respectively. CONCLUSIONS: Subgroups with different survival expectancy can be identified among patients who are eligible for phase I clinical trials. If confirmed, the proposed prognostic model may be useful for therapeutic decision making in palliative oncology.

Simultaneous determination of the peptide-mitomycin KW-2149 and its metabolites in plasma by high-performance liquid chromatography.

A gradient high-performance liquid chromatographic (HPLC) method is described for the quantification of KW-2149 and its two major metabolites in plasma. The method involves a sample clean-up by solid-phase extraction on C18 columns, separation of the respective compounds by HPLC on a YMC ODS-AQ column (5-microm particle size, 150x6 mm I.D.), using a methanol-water gradient system as an eluent, and measurement by UV absorbance detection at 375 nm. The limits of quantitation were 10 ng/ml for KW-2149 and M-16, and 15 ng/ml for M-18. Recoveries from plasma were higher than 92% on C18 extraction columns. Intra-day precision, expressed as %C.V., was between 1.4 and 6.5%. Intra-day accuracy ranged from 94 to 107%. Precision and accuracy of variability of inter-assays increased somewhat; however, were still within acceptable ranges. The ability of the method to quantify KW-2149 and two major metabolites simultaneously, with precision, accuracy and sensitivity, make it useful in monitoring the fate of this new mitomycin in cancer patients.

A limited-sampling strategy for estimation of etoposide pharmacokinetics in cancer patients.

Etoposide (VP16), a widely used anticancer drug, is a topoisomerase II inhibitor. A number of studies have highlighted a correlation between hematologic toxicity and pharmacokinetic or physiological parameters. Other studies have also suggested that the anti-tumor response could be related to the plasma etoposide concentration. Therefore, it would seem of interest to individualize VP16 dose regimens on the basis of pharmacokinetic parameters. The aim of this study was to develop and validate a limited-sampling strategy allowing VP16 pharmacokinetic evaluation with minimal disturbance to the patient. A total of 34 patients (54 kinetics) received VP16 at various dose regimens, with doses ranging between 30 and 200 mg and infusion times varying between 0.5 and 2 h. The statistical characteristics of the pharmacokinetic parameters were assessed from the first courses of treatment performed in 23/34 patients; then the following three-sample protocol was designed: the end of the infusion and 5 and 24 h after the start of the infusion. For validation of the model the main pharmacokinetic parameters (clearance, half-lives, volume of distribution) were estimated in the 11 remaining patients by maximum-likelihood estimation (ML) and by Bayesian estimation (BE) using the three sampling times designed. Statistical comparison showed a good concordance between ML and BE estimates (the bias for clearance was -1.72%). The limited-sampling strategy presented herein can thus be used for accurate estimation of VP16 pharmacokinetic parameters.

A sensitive docetaxel assay in plasma by solid-phase extraction and high performance liquid chromatography-UV detection: validation and suitability in phase I clinical trial pharmacokinetics.

We have developed a specific and sensitive method aiming at docetaxel (Taxotere) determination in plasma of treated patients. This involved solid-phase extraction of 1 ml of plasma onto carboxylic acid (CBA) grafted silica cartridges followed by reversed-phase liquid chromatography with UV detection. The best selectivity was obtained through the use of C18 Uptisphere as stationary phase. The low limit of quantitation obtained (LOQ: 5 ng/ml) allowed measurements of docetaxel up to 24 hours after one-hour infusions with low dosages of drug (60 mg/m2). The method was applied successfully to monitor docetaxel plasma levels within two protocols associating fixed dosages of either methotrexate or gemcitabine with escalating doses of Taxotere.

Phase I clinical and pharmacokinetic study of S9788, a new multidrug-resistance reversal agent given alone and in combination with doxorubicin to patients with advanced solid tumors.

PURPOSE: The objectives of this phase I study were to evaluate the toxic effects and the maximum tolerated dose (MTD) of S9788, a new modifier of multidrug resistance (MDR), when given alone and in combination with doxorubicin to patients with advanced solid tumors; to achieve a potentially active plasma concentration of S9788; and to study the pharmacokinetics of both drugs. METHODS: A total of 26 patients (median age 58 years) entered the study. S9788 was given alone as a 30-min infusion at day 1 and in combination with a 50-mg/m2 bolus of doxorubicin at days 8 and 29. Dose levels of S9788 were escalated from 8 to 96 mg/m2 according to the modified Fibonacci scheme. Plasma samples were taken predose as well as during and up to 48 h after the beginning of infusion for S9788 and doxorubicin quantitation. Fractionated urine samples were also collected for up to 24 h for S9788 determination. RESULTS: The dose-limiting side effects of S9788 consisted of bradycardia, sometimes associated with faintness or dizziness. The MTD of S9788 was 96 mg/m2. No enhancement of doxorubicin toxicity was observed. One partial response (duration 140 days) was observed at 96 mg/m2 in a patient with multiple lung metastases from a refractory urothelial carcinoma. Pharmacokinetic studies were performed in 24 patients. Since the mean apparent elimination half-life of S9788 was 46 +/- 23 h and the last plasma sampling time was 48 h, only model-independent parameters were considered. Plasma levels of S9788 were below the limit of quantitation (4 x 10[-3] microM) before each drug administration. S9788 plasma levels of up to 3.7 microM could be obtained with this administration schedule. The urinary elimination of the unchanged drug was negligible, whatever the collection period. In spite of the large inter- and intraindividual variability, plasma pharmacokinetics of S9788 given as a 30-min i.v. infusion were linear up to 96 mg/m2 and were not modified by doxorubicin administration. Doxorubicin pharmacokinetic parameters did not seem to be influenced by S9788 coadministration. CONCLUSION: The dose-limiting toxicity of S9788 consisted of bradycardia or clinical symptoms suggesting a vasovagal impact such as faintness or dizziness. The MTD of S9788 was 96 mg/m2. The pharmacokinetic parameters of doxorubicin in this study were close to those usually described and were not influenced by escalation of the S9788 dose. No pharmacokinetic interaction was observed between S9788 and doxorubicin. The clinical tolerability of the combined treatment is in good agreement with the pharmacokinetic findings, since no enhancement of doxorubicin toxicity was observed.

[Bayesian estimation of pharmacokinetic parameters of etoposide]. / Estimation bayésienne des paramètres pharmacocinétiques de l'étoposide.

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.

[Cytotoxic chemotherapy in elderly patients: present and future]. / Chimiothérapies cytotoxiques et sujets âgés: constats et perspectives.

Cancer in elderly people accounts for more than 50% of the malignant tumors treated per year in France and this population of patients has a rather high-life expectancy. Chemotherapy is active in these elderly patients but clearly more toxic than for young ones. The general tendency among the physicians to empirically reduce the doses is due to the known increased risk of unexpected toxicities. That is why there is such a large variety of conflicting opinions in the literature concerning the benefit and toxic effects of cytostatic drugs in the elderly. Therefore, it appears consistent to adjust chemotherapy regimen according to physiological criteria. Among them is biological age which is a better parameter than chronological age to describe the biological heterogeneity of this population of patients. Nakamura et al have published an interesting model for the calculation of biological age by principal component analysis using 11 easily measurable biological and clinical variables in a series of healthy elderly people. This kind of approach is not at present available for cancer patients but it allows to demonstrate that the chronological age is only one among many other age-related variables and is not sufficient to fully describe it. The variations in pharmacokinetic data are more frequent in the elderly than in younger people and this reflects age-related physiological heterogeneity. This factor is well taken into account in recently described population pharmacokinetic models, bayesian fittings and adaptative control which may represent promising approaches of cytostatics dose adjustments. Such models have been successfully developed in young patients receiving doxorubicin, methotrexate, melphalan and teniposide. They require a low number of blood samples to determine individual parameters and further adjust the doses, and are therefore of potential interest in old patients. Prospective studies are warranted in the future in order to recommend their use in the elderly.

Phase I and pharmacokinetic study of a novel mitomycin C analog KW-2149.

KW-2149 is a new, semisynthetic, C-7-N-substituted, mitomycin C (MMC) analog showing equal or superior antitumor activity in both in vitro and in vivo assays. The preclinical activity profile combined with the hematological toxicity data in rodents and the water solubility of the compound compare favorably with MMC. The aim of this phase I study was to determine the toxicity profile and the optimal dosage of KW-2149. In this phase I study 37 patients received 97 courses of KW-2149 administered as an i.v. bolus injection every 21 days at sequential dose levels: 5, 10, 17, 25, 35, 47, 60, 75, 90 and 100 mg/m2. Hematological toxicity was moderate even at the 100 mg/m2 dose level. Grade IV leucopenia and thrombocytopenia were observed in one of three patients at the 100 mg/m2 dose level. There was some evidence of a delayed-type bone marrow toxicity. Pulmonary toxicity was dose limiting, with grade III toxicity occurring in all three patients treated at a dose of 100 mg/m2. The type of lung toxicity was similar to the one observed with other antitumor antibiotics. No renal or cardiac toxicity was observed. Other toxicities were generally mild. Antitumor activity was observed in four patients. Data of drug monitoring demonstrated rapid metabolism and/or distribution of KW-2149 with a short half-life and the emergence of the cytotoxic metabolites M-16 and M-18. The dose-limiting toxicity of KW-2149 is pulmonary toxicity.

Phase I and pharmacokinetic study of KW-2149 given by 24 hours continuous infusion.

KW-2149 is a new mitomycin C (MMC) analog, forming DNA-DNA and DNA-protein crosslinking 20-fold more effectively than MMC. Because of its equal or superior in vitro and in vivo activity compared to MMC, a phase I study was initiated with an intravenous bolus injection every three weeks. This study was interrupted after dose escalation from 5 mg/m2 to 100 mg/m2 because of subacute and dose dependent pulmonary toxicity. Because of the lack of other end-organ toxicity, the moderate hematological toxicity and the observed antitumor effect, a second phase I study was initiated with a 24 hour continuous infusion. The starting dose was 50 mg/m2 and further escalation depended on observed pulmonary toxicity. Four patients were entered into this study and the received in total 17 courses. Toxicity was again mainly restricted to the lungs with one patient suffering grade 2 dyspnoe and another one grade 1 dyspnoe. Three patients had a substantial change in the carbon monoxide (CO) diffusion capacity. Pharmacokinetic data from these patients showed very low plasma levels both for KW-2149, as for both known metabolites M-16 and M-18. This study demonstrates that pulmonary toxicity continues to occur with KW-2149, in spite of the assurance of low plasma levels of both the parent compound and the known metabolites. The interesting activity of this compound has stimulated further in-depth research towards mechanisms of pulmonary toxicity and means of preventing them.

[Effect of carboplatin on the pharmacokinetics of melphalan administered intravenously]. / Effet du carboplatine sur la pharmacocinétique du melphalan administré par voie intraveineuse.

In order to perform melphalan dosage adjustment, the linearity of melphalan kinetics was studied, in the case of previous carboplatin administration. Eleven patients with various solid tumors entered the present study. Carboplatin was administered during 5 days over 1-hour infusions; the day after, the melphalan test-dose was administered and followed 24 hours after by the complement dose. Melphalan kinetics were determined from only three plasma samples by using bayesian estimation. The present study showed that previous carboplatin administrations induced wide variations of melphalan pharmacokinetic parameters between the two administrations. As part of this protocol, the order of drug administration should be taken into account, in order to perform melphalan dosage adjustment.

Pharmacokinetics of alkylating agents.

Alkylating agents have been used for over 30 years in the treatment of malignant disease. Because of their very reactive nature, studies of their intermediate metabolism have been difficult. However, this is now possible with modern analytical techniques. Further understanding of their metabolism and pharmacokinetics should lead to a more rational use in the clinic.

Value of early pharmacodynamic and pharmacokinetic investigations with anticancer drugs: data from phase I tolerance studies on a new vinca alkaloid derivative.

1. A novel anticancer vinca alkaloid derivative (I) has been given as an i.v. bolus to cancer patients, using four different dosage regimens with dose levels ranging from 0.04 to 0.84 mg/m2 (equivalent to between 0.12 and 1.35 mg per dose), and the pharmacokinetics determined up to 72 h after dosing. In addition, secondary effects of leukopenia and neutropenia, were related to drug exposure using a sigmoid Emax model. 2. Plasma levels of I declined in a triphasic manner with a terminal half-life of approximately 50 h; most drug elimination (55%) being associated with the terminal phase. 3. Clearance of I was relatively low (245 +/- 160 ml/min) and remained constant with increasing doses. Initial distribution volume was low (approximately 71) but once distribution was complete, it was comparatively high (327 +/- 2121). 4. Both leukopenia and neutropenia were fitted successfully to a sigmoid Emax model showing that these effects were related to the total exposure to the drug. The Hill constant was less than 1, indicating a relatively shallow exposure/response curve and a predictable, graded increase in response with increasing I exposure, rather than a sudden quantal response. 5. Pharmacokinetically, I shows some similarities to other vinca alkaloids in its plasma level decline profile, although there are some notable differences which can be exploited clinically. In addition, the ability to model both leukopenia and neutropenia to the exposure to I, provides a valuable tool in the design of the most appropriate dosage regimen for the drug, as well as for dose adjustment taking into account inter-individual variations.

Confluence-dependent resistance in human colon cancer cells: role of reduced drug accumulation and low intrinsic chemosensitivity of resting cells.

In vitro sensitivity of HT29 human colon cancer cells to doxorubicin (DXR), vincristine (VCR), etoposide (VP16), cisplatin (CDDP), melphalan (L-PAM) and 5-fluorouracil (5FU) was markedly reduced when cell-culture density increased. For some drugs, confluence-dependent resistance (CDR) was partly due to decreased intracellular drug accumulation; the ratio of mean intracellular drug content of non confluent to confluent cells (NC/C) was 2.5 for DXR, 4.1 for VCR and 7.4 for VP16. Altered drug penetration with confluence could be related to decrease of plasma membrane fluidity as measured by the fluorescence polarization method. Reduction of drug intracellular accumulation was nil or weak for L-PAM (NC/C = 1.0), CDDP (NC/C = 1.2) and 5 FU (NC/C = 1.8). Even if drug concentration was adjusted in culture medium to produce similar intracellular drug content in confluent and non confluent cells, higher intrinsic resistance of confluent cells was still evidenced for DXR and VP16 but not for VCR, the only agent without direct interaction with DNA. DXR- and VP16-induced DNA breakage was also less important in confluent than in non-confluent cells. CDR appeared closely related to an increased proportion of non-cycling cells at confluence, as demonstrated by flow cytometry, expression of nuclear antigen recognized by Ki67 MAb and expression of topoisomerase II. CDR is probably a major factor in the poor sensitivity of colorectal adenocarcinomas to chemotherapy.

Pharmacokinetically guided dosing for intravenous melphalan: a pilot study in patients with advanced ovarian adenocarcinoma.

Pharmacokinetically guided administration of melphalan was investigated during a pilot study in patients with advanced ovarian adenocarcinoma. The schedule involved a fixed dose on day 1 (7.9 mg) followed by a second dose on day 2, calculated on the basis of pharmacokinetic data to achieve a target area under the concentration-time curve (AUC). 20 courses of intravenous melphalan were administered to 7 patients. AUC, standardised to 1 mg/m2, ranged between 4.3 and 8.9 (mg/l) min. In 12 fully evaluable courses, less than 15% deviation from the target AUC was found, showing that AUC monitoring was possible by means of the test dose. Pharmacodynamic effects showed a positive correlation with melphalan AUC. Myelosuppression appeared at 47 (mg/l) min and grade 3 or 4 haematological toxicities were observed in 4 cycles, associated with AUC values ranging between 86 and 112 (mg/l) min. Relative leucocyte decreases were well correlated with AUC values.