On-line solid-phase extraction and determination of paclitaxel in human plasma

Quantification of taxanes in biological matrices: a review of bioanalytical assays and recommendations for development of new assays

Since the isolation of paclitaxel and its approval for the treatment of breast cancer, various taxanes and taxane formulations have been developed. To date, almost 100 bioanalytical assays have been published with the method development and optimization often extensively discussed by the authors. This Review presents an overview of assays published between January 1970 and September 2013 that described method development and validation of assays used to quantify taxanes in biological matrices such as plasma, urine, feces and tissue samples. For liquid chromatography assays, sample pretreatment, chromatographic separation and assay performance are compared. Since this Review discusses the limitations of previously developed liquid chromatography assays and gives recommendations for future assay development, it can be used as a reference for future development of liquid chromatography assays for the quantification of taxanes in various biological matrices to support preclinical and clinical studies.

Expression of thymidine phosphorylase in peripheral blood cells of breast cancer patients is not increased by paclitaxel

Background

A synergistic cytotoxic effect has been hypothesized for taxanes and capecitabine, a prodrug of 5-fluorouracil. Based on preclinical studies, this synergism has been attributed to an up-regulation of the enzyme thymidine phosphorylase (TP). Beside tumour tissue, TP is highly expressed in white blood cells, possibly causing increased hematotoxicity, when taxanes are combined with capecitabine. So far, this hypothesis has not been investigated in humans.

Methods

A total of 128 consecutive blood samples were collected from eight patients with advanced breast cancer receiving paclitaxel weekly at a dose of 80 mg/m². To assess the expression of TP in blood cells, samples were collected prior to first therapy, at the end of infusion, and up to 15 days thereafter. This procedure was repeated during the sixth application of paclitaxel. After isolation of the peripheral mononuclear blood cells, the expression of TP was assessed by ELISA. In parallel, paclitaxel level in plasma was evaluated at three selected time points as pharmacokinetic control parameter.

Results

Paclitaxel concentrations at the end of infusion did not change significantly from week 1 to week 6. The expression of TP in peripheral mononuclear blood cells decreased significantly after infusion below pretherapeutic values (p = 0.023; n = 8). After the nadir on day 3, the expression of TP increased moderately returning to baseline levels within one week. The overall picture in week 6 was similar to week 1. Using a trend analysis, neither a short-term nor a long-term induction of TP was observed.

Conclusion

TP in peripheral mononuclear blood cells was hardly regulated under therapy with paclitaxel. Therefore, no increased haematotoxicity due to TP upregulation is expected from the combination of taxanes and capecitabine.

Restricted access materials and large particle supports for on-line sample preparation: an attractive approach for biological fluids analysis

An analytical process generally involves four main steps: (1) sample preparation; (2) analytical separation; (3) detection; and (4) data handling. In the bioanalytical field, sample preparation is often considered as the time-limiting step. Indeed, the extraction techniques commonly used for biological matrices such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are achieved in the off-line mode. In order to perform a high throughput analysis, efforts have been engaged in developing a faster sample purification process. Among different strategies, the introduction of special extraction sorbents, such as the restricted access media (RAM) and large particle supports (LPS), allowing the direct and repetitive injection of complex biological matrices, represents a very attractive approach. Integrated in a liquid chromatography (LC) system, these extraction supports lead to the automation, simplification and speeding up of the sample preparation process. In this paper, RAM and LPS are reviewed and particular attention is given to commercially available supports. Applications of these extraction supports, are presented in single column and column-switching configurations, for the direct analysis of compounds in various biological fluids.

Rapid HPLC method for the determination of paclitaxel in pharmaceutical forms without separation

A HPLC method has been developed for the in-process determination of the paclitaxel from dosage pharmaceutical forms. This method ensures the rapid determination of paclitaxel in the presence of polyoxyl castor oil--the main constituent of paclitaxel's clinical formulation vehicle. The method is simple and rapid and does not require any preliminary treatment of the sample. The method was fully validated.