A new method for the measurement of nitrosoureas in plasma: an h.p.l.c. procedure for the measurement of fotemustine kinetics

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

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.

Stability study of fotemustine in PVC infusion bags and sets under various conditions using a stability-indicating high-performance liquid chromatographic assay

The stability and compatibility of fotemustine, a nitrosourea anticancer agent, in 5% dextrose solution with polyvinyl chloride (PVC) containers and administration sets were studied under different conditions of temperature and light. The drug was diluted to 0.8 and 2 mg ml(-1) in 100 or 250 ml 5% dextrose injection solutions for 1-h simulated infusions using PVC bags and administration sets with protection from light. After preparation in the PVC bags containing 5% dextrose, fotemustine was also prepared at the same concentrations and stored at 4 degrees C for 48 h and at room temperature (22 degrees C) or at sunray exposure ( > 30 degrees C) over 8 h with or without protection from light. The solution samples were removed immediately at various time points of simulated infusions and storage, and stored at -20 degrees C until analysis. The physical compatibility with PVC and chemical stability in solution of fotemustine were assessed by visual examination and by measuring the concentration of the drug in duplicate using a stability-indicating high-performance chromatographic assay. When admixed with a 5% dextrose solution, fotemustine 2 and 0.8 mg ml(-1) was compatible and stable over 1-h of simulated infusion using PVC bags through PVC administration sets with protection from light. On the other hand, in the same diluent, fotemustine was compatible and stable with PVC bags for at least 8 h at 22 degrees C with protection from light and for at least 48 h at 4 degrees C with protection from light. There were no pH variation, no visual change, no color change, no visible precipitation and no loss of the drug. Conversely, when the solutions were exposed to light (ambient or solar), the drug concentration decreased rapidly, leading to the production of a degradation product as shown by mass spectral analysis and a discoloration of the solutions. Finally, in all cases, no DEHP (di-2-ethylhexyl phthalate) was detected in the injection solution.

Phase I pharmacological study of intra-arterially infused fotemustine for colorectal liver metastases

Fotemustine was investigated in 17 patients with progressive hepatic metastases from colorectal carcinoma to define the maximally tolerated dose for a daily hepatic intra-arterial infusion (HAI) schedule. Haematotoxicity was delayed, dose-dependent and related to pretreatment, with thrombo- and leucocytopenia being dose-limiting. Local side-effects at the liver were mild. Infection (WHO grade III) occurred in 1 patient due to neutropenia. Other side-effects, particularly renal, pulmonal, neurological or cardiac toxicity, mucositis and diarrhoea, hair loss or allergic reactions did not occur. Pharmacokinetic analysis indicated a short plasma half-life (t1/2 = 25.8 +/- 11.5 min) and a high body clearance (CL = 2193 +/- 870 ml/min) with large inter- and intra-individual variations. Of 15 evaluable patients, one complete and three partial responses were observed (ORR = 27%; CI95% [4.5-49.5%]). All tumour remissions appeared at higher dose levels in previously untreated patients. Considering the absence of mucosal side-effects, such as mucositis/diarrhoea and of hepatic toxicity, this agent was well tolerated. The recommended intra-arterial dose for consecutive phase II trials is 125 mg/m2/day1-3.

Specific high-performance liquid chromatographic assay with ultraviolet detection for the determination of 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea in plasma

A facile, sensitive and highly specific HPLC method for assaying 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) in plasma has been developed. The drug was efficiently isolated from plasma by extraction with tert.-butyl methyl ether. A structurally related compound with similar physicochemical properties served as the internal standard (I.S.). Following evaporation of the organic solvent, the extract was reconstituted with 0.05 M ammonium acetate buffer, pH 5.0, and loaded onto a 4 micron Nova-Pak C18 column (15 cm x 3.9 mm), which was preceded by a 7 micron Brownlee RP-18 precolumn (1.5 cm x 3.2 mm). Chromatography was performed at ambient temperature using a mobile phase of methanol-0.1 M ammonium formate buffer, pH 3.7 (25:75, v/v). UV absorbance of the effluent was monitored at 240 nm. A flow-rate of 1.0 ml/ min was used for analyzing mouse and dog plasma extracts. Under these conditions, the drug eluted at 4.0 min and was followed by the I.S. at 6.1 min. An automatic switching valve was employed to allow the precolumn to be flushed 1.5 min into the run, without interrupting the flow of the mobile phase to the analytical column, thereby preventing the apparent build-up of extractable, strongly retained, UV-absorbing components present in mouse and dog plasma. Operating in this manner, more than 100 samples could be analyzed during a day using a refrigerated autosampler for overnight injection. The method was readily adapted to the determination of SarCNU in human plasma by simply decreasing the eluent flow-rate to 0.6 ml/min, whereby SarCNU and the I.S. eluted at approximately 5.8 and 9.1 min, respectively. Furthermore, the switching valve was not necessary for the analysis of human plasma samples. With a 50-microliter sample volume, the lowest concentration of SarCNU included in the plasma standard curves, 0.10 micrograms/ml, was quantified with a 7.8% R.S.D. (n = 27) over a 2 month period. Plasma standards, with concentrations of 0.26 to 5.1 micrograms/ml, exhibited R.S.D. values ranging from 1.3 to 4.7%. Thermospray-ionization MS detection was used to definitively establish the specificity of the method. The sensitivity of the assay was shown by application to be more than adequate for characterizing the plasma pharmacokinetics of SarCNU in mice.

Pharmacokinetics and pharmacodynamics of nitrosourea fotemustine: a French cancer centre multicentric study

The nitrosourea, fotemustine, was given intravenously in 1 h constant-rate infusion to 66 patients in a multicentric study to assess both fotemustine pharmacokinetic behaviour and the pharmacokinetic-pharmacodynamic relationships. Depending on the tumour type treated, two administration and sampling protocols were used: 100 mg/m2/week as a conventional dose (six samples, 44 patients) and 300-500 mg/m2/day as a high dose (10 samples, 22 patients). The 91 time-concentration curves were best described by either a one-(55) or a two-compartment (36) model, and their mean clearance values did not differ significantly (85.3 +/- 6.5 and 101.3 +/- 9.5 l/h, respectively, P = 0.1727). Fotemustine pharmacokinetics were not influenced by repeated treatment (time-independence) nor by dose level (dose-independence). The pharmacodynamic effect observed on white blood cell count was expressed by a logit regression model involving the area under the curve mainly and the total administered dose. White blood cell toxicity could be predicted as a function of the dose for a given patient with a known fotemustine clearance value.

Phase I-II and pharmacokinetic study of a new fotemustine schedule in advanced non-small cell lung cancer

Fotemustine, a new nitrosourea derivative has already demonstrated activity in non-small cell lung cancer (NSCLC). In order to improve its therapeutic index, we designed a protocol in which Fotemustine was delivered with dose escalation on 3 consecutive days as induction therapy followed by a 5-week rest period. Maintenance therapy consisted of 100 mg/m2 once every 3 weeks. Pharmacokinetic data were assessed during this Phase I-II study and reported here.

PATIENTS AND METHODS

Nineteen patients with metastatic (17) or locally advanced (2) NSCLC were included in the present study. Ten of those with metastatic disease had brain metastases and 15 had previously received chemotherapy. Fotemustine was given at 50 mg/m2 on day 1-2-3 (group 1: four patients), 75 mg/m2 on day 1-2-3 (group 2: 16 patients including two who had already received 50 mg/m2) and 100 mg/m2 on day 1-2-3 (group 3: one patient).

RESULTS

The maximal tolerated dose was 75 mg/m2 on day 1-2-3 (total cumulated dose 225 mg/m2). At this dose level, we observed 25% of Grade 3-4 neutropenia and 31% of Grade 3-4 thrombocytopenia. One patient died of pulmonary infection during aplasia. No other significant toxicity occurred. Of the 17 evaluable patients, one obtained a PR lasting 6 months in group 2 and 1 PR lasting 3 months in group 3. No significant difference was noted in the AUC between days 1, 2 or 3 in any of the seven patients in whom a pharmacokinetic study of Fotemustine was performed.

CONCLUSION

Administered on 3 consecutive days, Fotemustine seems to be less effective and more toxic than other schedules tested in NSCLC. Despite the quality of the two responses observed, this protocol has been discontinued and the standard administration on days 1 and 8 remains the schedule of choice in NSCLC.

Fotemustine in the treatment of brain primary tumors and metastases

Fotemustine is a new chloroethylnitrosourea characterized by the grafting of a phosphonoalanine group onto a nitrosourea radical. Clinical studies using fotemustine have been conducted in malignant glioma, brain metastasis of non-small cell lung cancer, and disseminated malignant melanoma. In recurrent malignant glioma, fotemustine has been used as a single agent: assessed by computed tomography scan, after 8 weeks, the objective response rate was 26.3% among 38 evaluable patients. Median duration of response was 33 weeks. The main toxicity was hematological (thrombocytopenia and leucopenia). A trial with high-dose fotemustine and autologous bone marrow rescue in newly diagnosed glioma was conducted in 26 patients, and 6 showed a partial response. The median overall survival was approximately 11 months. Myelosuppression was noted in all patients except 1, and other toxicity reported was central nervous system toxicity and epigastric pain. Combined with radiotherapy in 55 patients, a 29% response rate was observed, and this combination was well tolerated and easily manageable on an outpatient basis. Finally, fotemustine has been used intraarterially, with 10 objective responses observed among 26 evaluable patients. In brain metastases of non-small cell lung cancer, fotemustine proved to be active with a response rate of 16.7%. Combined with cisplatinum, fotemustine is still under study, but preliminary results are promising. In cerebral metastases of disseminated malignant melanoma, fotemustine has been evaluated in a total of 140 patients in the various studies: median response rate is 24.3%, ranging from 8.3% to 60.0%. Fotemustine appears to be a good candidate in the treatment of primary brain tumors and metastases.

Phase I pharmacokinetics study of high-dose fotemustine and its metabolite 2-chloroethanol in patients with high-grade gliomas

The pharmacokinetics of high-dose fotemustine followed by autologous bone-marrow transplantation during a phase I-II clinical trial in 24 patients with glioblastoma or astrocytoma (grade III-IV) was investigated. Plasma levels of fotemustine were determined by high-performance liquid chromatography (HPLC) and UV detection. The metabolite, 2-chloroethanol, was simultaneously followed in six patients by gag liquid chromatography and electron capture detection (GLC-ECD) assay. The drug was given as a 1-h infusion on 2 consecutive days. In all, 40 pharmacokinetic determinations of fotemustine were made at dose levels ranging from 2 x 300 to 2 x 500 mg/m2. Plasma drug elimination was best described by a bi-exponential model, with short distribution and elimination half-lives of 4.15 +/- 2.57 and 28.8 +/- 12.1 min being observed, respectively. No significant difference in half-lives or clearance was seen between the first and the second administration. During dose escalation, the mean area under the concentrationtime curve (AUC) increased from 5.96 +/- 2.89 to 12.22 +/- 3.95 mg l-1 h. Drug clearance was independent of the dose given and equal to 109 +/- 65 l/h, indicating no possible saturation of metabolism and elimination mechanisms at these high-dose levels. The metabolite 2-chloroethanol appeared very early in plasma samples. Its elimination was rapid and rate-limited by the kinetics of the parent compound, giving the same apparent terminal half-life. A close relationship between AUC and C45 values was evidenced (r = 0.890). Associated with the stability of fotemustine kinetic parameters, this could be used in future studies for individual dose adjustment, particularly for high-dose fractionated regimens.

Hepatic intra-arterial infusion of fotemustine: pharmacokinetics

Fotemustine is a new nitrosourea derivative that contains an alpha-aminophosphonic acid and has a short half-life and a high plasma clearance. As myelosuppression occurs as the dose-limiting toxicity, local drug delivery has been investigated in the treatment of liver metastases arising from colorectal cancer. A pharmacokinetic study was undertaken in patients who received either i.v. or hepatic intra-arterial (HIA) infusion of 100 mg/m2 fotemustine so as to estimate the advantage of local chemotherapy, considering the pharmacokinetic differences between the two routes together with the resultant toxicities (when available). Our findings substantiated the hypothesis that a 4-h HIA infusion of foetmustine would result in a lower exposure of healthy tissues to the drug, since the AUC measured in systemic plasma was reduced by approximately 50% following such treatment as compared with i.v. infusion. This reduction in AUC should indicate a manyfold increase in exposure of the liver tumour to the alkylating properties of the drug, since it represents the proportion of the dose that has degraded within the liver. The first-pass liver-extraction ratio of fotemustine given as a 4-h HIA infusion, which ranged from 0.4 to 0.9 as estimated in patients receiving i.v. and HIA infusions in a cross-over study, argues for further investigation of HIA foetemustine infusion for the treatment of liver metastases so as to increase the response rate and decrease the occurrence of major toxic side effects in such patients.

Metabolism of the chloroethylnitrosoureas

1. The chemical degradation and metabolism of the 2-chloroethylnitrosoureas (CENUSs) have been critically reviewed with the objective of gaining a better understanding of factors that could aid in the design of new, more effective, anticancer drugs. 2. The CENUs are chemically unstable under normal physiological conditions and can rapidly degrade to give a variety of reactive intermediates capable of carbamoylating proteins and/or alkylating both proteins and DNA. 3. Carbamoylation is thought to make a minimal contribution to the cytotoxic effect of the CENUs, although it may be involved in some of the unwanted side-effects. It would seem desirable, therefore, to design new CENUs with low carbamoylating activity. 4. The main action of the CENUs is by alkylation of DNA via a chloroethyldiazo-hydroxide intermediate. Chloroethylation is important, as opposed to hydroxyethylation, since the former leads to inter-strand DNA cross-linking via an intramolecular rearrangement with the removal of chloride. It is this inter-strand cross-linking which prevents subsequent DNA repair and loss of cytotoxicity. 5. Metabolism usually, although not exclusively, leads to deactivation of the CENUs either by dechlorination or denitrosation of the molecule, generally with the former being the dominant route. These reactions occur very rapidly, and before chemical degradation can take place, and can be an important determinant in the final cytotoxicity. Moreover, both these pathways involve the cytochrome P-450 system and can be induced with phenobarbital.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic profile of fotemustine in rat plasma by electrochemical detection

1. A differential pulse polarographic (DDP) assay of diethyl-1-[3-(2-chloroethyl)-3-nitrosoureido] ethylphosphonate (fotemustine) was developed to determine the kinetics of this nitrosourea in plasma, brain, liver, lung and kidney. The optimized polarographic determination, previously applied to BCNU and CCNU, attained a limit of detection of 0.3 micrograms fotemustine/ml plasma and 1 microgram/g in other tissues; the calibration curve in electrolyte or in plasma was linear between 0.5 and 100 micrograms/ml. 2. The choice of electrolyte, the effects of pH, temperature, light, and the stability of fotemustine in samples were investigated. Recovery of fotemustine was 76-90% from lung greater than kidney greater than plasma greater than brain greater than liver; the variability coefficients were low (4.0-7.3%). Tissue samples could be stored for 20 days at -20 degrees C without loss of the compound. 3. Plasma kinetics of fotemustine and BCNU given to male rats at therapeutic doses (20 mg/kg i.v.) fitted a bi-exponential equation. Two minutes after injection plasma, levels of unchanged nitrosoureas were 15 and 11 micrograms/ml respectively. Fotemustine could be measured (0.92 microgram/ml) for 3 h, while BCNU could not be detected after 60 min. Unchanged fotemustine was cleared from the blood stream 3-5 times more slowly than BCNU.

Disposition, pharmacokinetics, and metabolism of 14C-fotemustine in cancer patients

The pharmacokinetics and metabolism of intravenously infused 14C-fotemustine (about 100 mg/m2) were examined in 2 cancer patients. Plasma levels of radioactivity increased to a maximum of 4.1 and 5.5 micrograms equivalents per g when the infusion stopped then declined triexponentially with mean half-lives of about 1/2, 10 and 80 h for the initial, mid and terminal phases, respectively. Plasma levels of intact drug were lower, with maximum levels of 1.1 and 2.8 micrograms/ml, and declined monophasically with a half-life of about 24 min. Plasma clearance was high (1426 and 764 ml/min) with the volume of distribution based on areas of 47.7 and 26.4 l. Most of the radioactivity was eliminated in urine (50.1 and 61.3%) over 7 days with smaller amounts in the feces (6.8 and 0.3%) and only minimal quantities (under 0.1%) as expired carbon dioxide. Metabolites of fotemustine were identified as chloroethanol and N-nitroso-1-imidazolone-ethyl-diethylphosphonate in plasma and as 1-hydantoin-ethyl-diethyl-phosphonate and acetic acid in urine.