High-performance liquid chromatographic assay for the experimental anticancer agent oxantrazole

High-performance liquid chromatographic methods for the determination of topoisomerase II inhibitors

Various methods for separating eleven different types of topoisomerase II (TOPO-2) inhibitors, including epipodophyllotoxins, anthracyclines, anthracenediones, anthrapyrazoles, anthracenebishydrazones, indole derivatives, aminoacridines, benzisoquinolinediones, isoflavones, bisdioxopiperazines and thiobarbituric acids, are summarized. Proper sample preparation and storage is critical to the successful analysis of some TOPO-2 inhibitors due to difficulties associated with adsorption, instability and complex biological components. Solid-phase and liquid-liquid extractions are widely used to separate TOPO-2 inhibitors from biological samples, although simple deproteinization followed by direct analysis of the supernatant is preferable to extraction based on its speed and simplicity. High-performance liquid chromatography (HPLC) is the favored method for the bioanalysis of TOPO-2 inhibitors. UV or diode array detection is generally employed for early pharmacokinetic studies, while fluorescence or electrochemical detection is used more frequently for analytes with fluorescent or oxidative-reductive properties. For analyses requiring highly sensitive and/or specific detection, electrospray mass spectrometry (ESI-MS or ESI-MS-MS) provides a suitable alternative. A comprehensive compilation of the HPLC techniques currently used to separate TOPO-2 inhibitors will aid the future development of analytical methods for new TOPO-2 inhibitors.

Separation methods for anthraquinone related anti-cancer drugs

The quinoid anthracycline-related anti-cancer agents represent an important group of anti-tumour drugs with a wide spectrum of activity. We review here some of the separation techniques used for the analysis of anthracyclines and related compounds. In this review we have covered a range of compounds from the early anthracycline antibiotics such as doxorubicin to the more recent anthracenediones and anthrapyrazoles such as mitoxantrone and losoxantrone, respectively. We also include novel compounds such as AQ4N and C1311, both awaiting clinical trial. Separations of the anthraquinone related anti-cancer agents are predominantly by HPLC. These separation techniques have been used for a variety of applications including drug stability, protein binding and therapeutic drug monitoring as well as detailed pharmacokinetic and metabolic studies. Pharmacokinetics, and therefore drug analysis, plays a central role in both the development of new agents and also leads to a better understanding of clinically established agents in this class. Sample preparation and extraction methods including solid-phase and liquid-liquid extraction have also been highlighted. Many anthraquinone related compounds are highly coloured and fluoresce. They are suitable for a range of detection methods including UV-Vis, electrochemical and fluorescence. The methods described are used for sometimes complex separations that are needed for the evaluation of such compounds in biological samples.

Pharmacokinetics, cerebrospinal fluid penetration, and metabolism of piroxantrone in the rhesus monkey

Piroxantrone is an anthrapyrazole derivative with broad anti-tumor activity in vitro and less cardiac toxicity than the anthracyclines. The metabolic pathways and central nervous system penetration of piroxantrone have not been determined. In this study we examined the pharmacokinetic behavior of piroxantrone in plasma and cerebrospinal fluid in a non-human primate model. In addition, a urinary metabolite of piroxantrone was isolated and its cytotoxicity evaluated in vitro. The disappearance of piroxantrone from plasma after an intravenous dose of 150 mg/m2 given over 60 minutes was biexponential with mean t1/2 alpha of 1.0 minutes and a mean t1/2 beta of 180 minutes. The mean area under the curve was 220 microM.min and the clearance was 1420 ml/min/m2. Piroxantrone was not detectable in the cerebrospinal fluid. Piroxantrone and three other compounds not present in pre-treatment samples were detected in urine. The major urinary metabolite was isolated. Its cytotoxicity against MOLT-4 cells in vitro was at least one log less than that of piroxantrone. In addition, one of the other compounds detected in urine was determined to be a glucuronide conjugation product of the major metabolite. The results of this study may be useful in the interpretation of the activity and toxicity of piroxantrone in clinical trials.

Targeting anticancer drugs to the brain: II. Physiological pharmacokinetic model of oxantrazole following intraarterial administration to rat glioma-2 (RG-2) bearing rats

The disposition of the anticancer drug oxantrazole (OX) was characterized in rats bearing the rat glioma-2 (RG-2) brain tumor. Following intraarterial administration of 3 mg/kg of OX, serial sacrifices were completed from 5 min to 5 hr after administration. Blood and tissue samples collected at the time of sacrifice were processed and measured for OX concentrations by HPLC. The kidney had the greatest affinity for OX with the Cmax being 40.6 micrograms/ml at 15 min after administration. OX concentrations in brain tumor were higher than in normal right and left brain hemispheres, and consistent with enhanced drug blood-tumor barrier (BTB) permeability seen in experimental models for brain tumors. Observed heart, liver, lung, and spleen OX concentrations were similar, ranging from approximately 2 micrograms/ml to 20 micrograms/ml. A unique technique was used to develop a global physiological pharmacokinetic model for OX. A hybrid or forcing function method was used to estimate individual tissue compartment biochemical parameters (i.e., partition and mass transfer coefficients). A log likelihood optimization scheme was used to determine the best model structure and parameter sets for each tissue. Most tissues required a 3-subcompartment structure to adequately describe the observed data. The global model was then reconstructed with an arterial blood and rest of body compartments that provided predicted OX concentrations in agreement with the data. The model development strategy provides a systematic approach to physiological pharmacokinetic model development.

High-performance liquid chromatographic analysis of the anticancer drug oxantrazole in rat whole blood and tissues

A reversed-phase high-performance liquid chromatographic (HPLC) assay was developed for the antitumor anthrapyrazole analogue, oxantrazole (OX), in rat whole blood and tissues. Blood samples were mixed with equal volumes of a 25% (w/v) aqueous solution of L-ascorbic acid, whereas tissue samples were homogenized with 1.5-3 volumes of an L-ascorbic acid-methanol-water (1:10:1, w/v/v) mixture to prevent oxidative degradation of OX. Samples were then treated with 60% (v/v) perchloric acid (25-30 microliters/ml of stabilized sample) to precipitate proteins, and centrifuged, with the resultant supernatants analyzed on HPLC utilizing a C8 column. The mobile phase for blood and urine samples consisted of 8% (v/v) glacial acetic acid, 13% (v/v) acetonitrile, 79% (v/v) water, 0.16% (w/v) sodium acetate, and 0.05% (w/v) L-ascorbic acid (final pH 2.7), and was pumped at 1.8 ml/min. Tissue samples were eluted at 2 ml/min with a mobile phase consisting of 8% (v/v) glacial acetic acid, 12% (v/v) acetonitrile, 80% (v/v) water, 0.16% (w/v) sodium acetate, and 0.0;5% (w/v) L-ascorbic acid. OX and internal standard were detected at 514 nm and had retention times of 2.3 and 3.1 min, respectively. The limit of quantitation of OX was 25-50 ng/g. Recovery of OX from biological samples ranged from 50 +/- 0.9% in spleen to 102.8 +/- 1.8% in RG-2 glioma. The analytical method was applied to a pharmacokinetic study in rats.

The impact of pharmacokinetically guided dose escalation strategies in phase I clinical trials: critical evaluation and recommendations for future studies

Phase I studies requiring multiple dose escalation steps have led to the development of pharmacokinetically guided dose escalation (PGDE) strategies to expedite the conduct of early clinical trials. This article critically reviews PGDE strategies for a number of new anticancer agents including amphethinile, brequinar sodium, iodo-doxorubicin, the anthrapyrazoles (DuP 941, DuP 942 and DuP 937), rhizoxin, and aphidicolin glycinate. The benefits and problems associated with PGDE are examined. Recommendations are made for the optimal deployment of pharmacological information in future phase I studies.

Preclinical pharmacology of the anthrapyrazole analog oxantrazole (NSC-349174, piroxantrone)

Oxantrazole (now designated as piroxantrone) is an anthrapyrazole analog under evaluation as a potentially useful anthracycline-like antitumor agent. In preparation for phase I clinical trials, we characterized certain aspects of oxantrazole preclinical pharmacology, including plasma stability, murine pharmacokinetics, in vitro/in vivo metabolism, and DNA damage following incubation with human tumor cells in culture. Oxantrazole was relatively unstable in fresh mouse and dog plasma and particularly unstable in fresh human plasma (t 1/2 less than 5 min at 37 degrees C). Its decomposition in plasma was prevented by the addition of ascorbic acid, suggesting oxidative degradation. Following rapid i.v. administration of oxantrazole to mice, plasma elimination was best described by a two-compartment open model with an elimination-phase half-life, total body clearance, and steady-state volume of distribution of 330 min, 458 ml/min per m2, and 87.9 l/m2, respectively. The c x t value calculated following i.v. administration of 90 mg/m2 oxantrazole to mice was 177 micrograms-min/ml. This value was subsequently used in a pharmacologically guided dose-escalation scheme for the oxantrazole phase I clinical trial. Oxantrazole was converted to a polar conjugate, presumably a beta-glucuronide, by rat but not mouse hepatic microsomal preparations and in vivo by the mouse. Oxantrazole introduced protein-associated DNA strand breaks following incubation with a human rhabdomyosarcoma cell line. Repair of the damage was complete by 15 h. Clinical pharmacologic studies are currently under way in conjunction with the phase I clinical trial of oxantrazole.

High-performance liquid chromatographic bioanalysis of anthracycline cytostatic drugs

In the past decade high-performance liquid chromatography (HPLC) has developed into the most powerful tool available for the analysis of anthracycline antitumour drugs in all kinds of biological matrices. The results of drug level monitoring studies have contributed significantly to a better understanding of the pharmacokinetics and metabolic disposition of these drugs. Some aspects of anthracycline HPLC analysis in plasma samples are discussed, including the chromatographic separation and detection, sampling procedures, storage of plasma samples and sample pre-treatment.