Phase I and pharmacological study of daily oral administration of perifosine (D-21266) in patients with advanced solid tumours.

Alkylphosphocholines are a novel class of antitumour agents structurally related to ether lipids that interact with the cell membrane and influence intracellular growth signal transduction pathways. We performed a phase I trial with an analogue of miltefosine, perifosine (D-21266), which was expected to induce less gastrointestinal toxicity. Objectives of the trial were: to determine the maximum-tolerated dose (MTD) for daily administration, to identify the dose-limiting toxicity (DLT) of this schedule, to assess drug accumulation and to determine the relevant pharmacokinetic parameters. 22 patients with advanced solid tumours were treated at doses ranging from 50 to 350 mg/day for 3 weeks, followed by 1 week of rest. Toxicity consisted mainly of gastrointestinal side-effects: nausea was reported by 11 patients (52%, 10 patients Common Toxicity Criteria (CTC) grades 1-2 and 1 patient CTC grade 3), vomiting by 8 (38%, all CTC grades 1-2), and diarrhoea by 9 (43%, 8 patients CTC grades 1-2 and 1 patient CTC grade 3). The severity of these side effects appeared to increase with increasing doses. Another common side-effect was fatigue, occurring in 9 patients (43%). No haematology toxicity was observed. Dose-limiting toxicity (DLT) was not reached, but gastrointestinal complaints led to an early treatment discontinuation in an increasing number of patients at the higher dose levels. Therefore, MTD was established at 200 mg/day. The pharmacokinetic studies suggested dose proportionality.

Effects of miltefosine on various biochemical parameters in a panel of tumor cell lines with different sensitivities.

We investigated endocytosis activity, uptake of miltefosine (hexadecylphosphocholine), phospholipid and cholesterol content, the cell cycle, and apoptosis in 13 tumor cell lines (MCF7, MCF7/ADR, KB-3-1, KB-8-5, KB-C1, HeLa, HeLa-MDR1-G185, HeLa-MDR1-V185, CCRF/CEM, CCRF/VCR1000, CCRF/ADR5000, HL-60, HL-60/AR) with different sensitivities to treatment with the antitumor phospholipid analogues miltefosine and D-21266 (octadecyl-(N,N-dimethyl-piperidino-4-yl)-phosphate). In this panel of cell lines, MDR1 (multidrug resistance gene 1)- and MRP1 (multidrug resistance-associated protein)-expressing cells were found to be slightly more resistant to both compounds than sensitive parental cells. No correlation was found between resistance to miltefosine and endocytosis, intracellular concentration of miltefosine, the phospholipid and cholesterol content, induction of apoptosis, or cell cycle alterations in all the cell lines tested. Wild-type p53 containing WMN Burkitt's lymphoma cells and wild type p53-deficient CA46 exhibited similar sensitivities to miltefosine. The low percentage of apoptosis induced in MCF7 cells lacking caspase 3 indicated that caspase 3 seems to play an essential role in miltefosine-induced apoptosis.

Determination of retigabine and its acetyl metabolite in biological matrices by on-line solid-phase extraction (column switching) liquid chromatography with tandem mass spectrometry.

A HPLC assay with tandem mass spectrometric detection in the positive-ion atmospheric pressure chemical ionisation (APCI) mode for the sensitive determination of retigabine [(I), D-23129] and its acetyl metabolite [(II), ADW 21-360] in plasma was developed, utilising the structural analogue (D-10328), (III), as internal standard. Automated on-line solid-phase extraction of diluted plasma samples, based on 200-microl plasma aliquots, at pH 6.5, allowed a reliable quantification of retigabine and the acetyl metabolite down to 1 ng/ml. Injection of 500 microl of diluted plasma onto a C2 stationary phase-based column switching system in combination with a 75 mm x 4 mm reversed-phase analytical column at a flow-rate of 0.5 ml/min provided cycle times of 4 min per sample. The standard curves were linear from 1 to 1000 ng/ml using weighted linear regression analysis (1/x2). The method is accurate (mean accuracy < or = +/- 10%), precise (RSD < +/- 15%) and sensitive, providing lower limits of quantification in plasma of 1 ng/ml for retigabine (I), and 2.5 ng/ml for the metabolite (II) with limits of detection of 0.5 ng/ml for both analytes. Up to 200 unknowns may be analysed each 24 h per analyst.

Quantification of perifosine, an alkylphosphocholine anti-tumour agent, in plasma by pneumatically assisted electrospray tandem mass spectrometry coupled with high-performance liquid chromatography.

An HPLC assay with tandem mass spectrometric detection in the positive-ion Turbo-Ion-Spray (TISP) mode for the fast and sensitive determination of perifosine ((I), D-21266) in human plasma was developed, utilising the structural analogue, miltefosine ((II), D-18506), as internal standard. Automated solid-phase extraction of diluted plasma samples, based on 250-microl plasma aliquots, at pH 6.5, allowed a reliable quantification of perifosine down to 4 ng/ml. Injection of 200 microl of plasma extracts onto a 100x3 mm normal-phase analytical column at a flow-rate of 0.5 ml/min provided retention-times of 2.4 and 2.1 min for perifosine (I) and the internal standard (II), respectively. The standard curves were linear from 4 to 2000 ng/ml using weighted linear regression analysis (1/Y2). The inter-assay and intra-assay accuracies for the calibration standards were within +0.9% and -0.2%, exhibiting precisions (C.V.) of +/-6.5 and +/-7.3%, respectively. Up to 100 unknowns may be analysed each 24 h per analyst.

Rapid and automated determination of the beta2-agonist reproterol in human plasma by atmospheric pressure chemical ionisation high-performance liquid chromatography-tandem mass spectrometry.

An on-line HPLC assay with tandem mass spectrometric detection for the fast and sensitive determination of reproterol in human plasma was developed, utilising a methylated structural analogue as the internal standard. Automated solid-phase extraction of diluted plasma samples, based on 250 microl plasma aliquots, at pH 6.5, allowed a reliable quantification of reproterol down to 400 pg/ml. Injection of 100 microl of plasma extracts onto a 30 mm x 4.6 mm reversed-phase guard column provided retention times ranging from 20 to 30 s for reproterol and the internal standard. The standard curves were linear from 0.2 to 200 ng/ml using weighted linear regression analysis (1/y2). The inter-assay and intra-assay accuracies were -0.9% and +3.2%, exhibiting a precision (C.V.) of +/- 11% and +/- 9.3%, respectively. Up to 100 unknowns may be analysed each 24 h per analyst.

Rapid quantitative determination of a collagenase inhibitor and its major metabolite by on-line liquid chromatography with ionspray tandem mass spectrometric detection.

A rapid, sensitive and specific analytical method has been developed and validated to quantify the collagenase inhibitor N2-(2(5)-[(hydroxycarbamoyl)methyl)-4-methylvaleryl]-N1, 3-dimethyl-L-valin-amide (I) and its major metabolite (II) from plasma and urine. This method employs an automated solid-phase extraction procedure to isolate the analytes and the internal standard from the biological matrix. Reconstituted extracts were analyzed by HPLC-ionspray MS-MS. Chromatography was performed on a 4.6 mm I.D. reversed-phase guard column. The retention times of the analytes and the internal standard were approximately 1.3 min. The assay has a limit of quantification of 5 ng/ml plasma and a limit of detection of 1 ng/ml, based on 100-micro l plasma aliquots. No sample-drying step was required. The standard curves were linear form 5 to 5000 ng/ml using weighted linear regression analysis (1/y2). The intra- and inter-assay precision were better than + or - 10% with intra- and inter-assay accuracies between 95 and 105%. this new HPLC-MS-MS assay procedure for I and II in plasma and urine has proven to be specific, sensitive, accurate and robust, and is being used routinely for the analysis of I in pre-clinical and clinical trial samples. Up to 200 unknowns may be analyzed each 24 h per analyst.

Estimation of the absolute bioavailability of flecainide using stable isotope technique.

Data on the absolute bioavailability of flecainide are controversial. We have investigated whether differences in metabolic clearances and/or the absorption profile might be responsible for the variability in its absolute bioavailability. Six subjects with a wide range of flecainide metabolic clearances (85-407 ml.min-1) simultaneously received the drug by the IV and oral routes; the oral dose was labelled with deuterium. Besides estimation of absolute bioavailability, this design permitted assessment of metabolic clearance after IV and oral administration, and absorption could be assessed from the urinary excretion of labelled and unlabelled drug and metabolites. The absolute bioavailability of flecainide ranged from 79.9 to 101.1% (mean 93.6%). The absorption was 86.1 to 101.3% (mean 93.2%). The data indicate that the variable bioavailability of flecainide is due both to metabolism and absorption. The study highlights the potential of stable isotope technique in the investigation of such issues.

Variable disposition kinetics and electrocardiographic effects of flecainide during repeated dosing in humans: contribution of genetic factors, dose-dependent clearance, and interaction with amiodarone.

We studied the influence of cytochrome P450 2D6 (CYP2D6) on the steady-state disposition kinetics and the electrocardiographic effects of flecainide at two doses and during combination with amiodarone. Seven extensive and five poor metabolizers of dextromethorphan were studied during a three-period crossover study. All subjects received 50 mg flecainide every 12 hours, alone or together with 200 mg amiodarone every 12 hours, and 100 mg flecainide every 12 hours for 5 days. Mean steady-state plasma concentration of flecainide and QRS change from predrug value did not differ significantly among extensive and poor metabolizer subjects during each study period. Except for a shortened elimination half-life and nonlinear kinetics in extensive metabolizer subjects, phenotype had no significant influence on flecainide pharmacokinetics. Combination with amiodarone resulted in an increase in mean flecainide plasma concentration and effect in subjects with both phenotypes. Our findings indicate that CYP2D6 phenotype predicts flecainide nonlinear kinetics and flecainide half-life but has no influence on electrocardiographic effects during repeated administration of flecainide or on the extent of the amiodarone-flecainide interaction.

2-Phenylindole-linked [2-(aminoalkyl)pyridine]dichloroplatinum(II): complexes with a selective action on estrogen receptor positive mammary tumors.

A number of [2-(aminomethyl)pyridine]dichloroplatinum(II) complexes, linked to 5-hydroxy-2-(4-hydroxyphenyl)indoles by alkyl spacer groups of varying lengths, were synthesized and studied for their binding affinities for the calf uterine estrogen receptor. Their relative binding affinity (RBA) values ranged from 1.0 to 5.2% (estradiol, RBA = 100%). Highest affinities were found with complexes possessing a (CH2)5- or (CH2)6-bridge between the pyridine aminomethyl group and the indole nitrogen. Endocrine activities of the complexes and their ligands, determined in the mouse uterine weight test, were low. All compounds entered comparative tests using estrogen receptor positive and negative mammary tumor models. In cell culture, a growth inhibiting effect was only observed in hormone-sensitive MCF-7 cells, but not in hormone-independent MDA-MB 231 cells. In this assay, there was no significant difference between complexes and their ligands. In vivo, the growth of estrogen receptor positive MXT mouse mammary tumors was strongly inhibited by the complexes whereas the hormone-independent MXT mammary tumors showed only a minor response. At a dose of 3 X 20 mg/kg per week, complexes 10d-g reduced the tumor weight by ca. 80% after 6 weeks of treatment. This effect was generally stronger than that exerted by the ligands. The doses applied were well tolerated. Since the complexes described in this paper require the estrogen receptor for their action, a mechanism similar to that of antiestrogens is assumed.