Simultaneous analysis of docetaxel and the formulation vehicle polysorbate 80 in human plasma by liquid chromatography/tandem mass spectrometry

Binding of gefitinib, an inhibitor of epidermal growth factor receptor-tyrosine kinase, to plasma proteins and blood cells: in vitro and in cancer patients

Gefitinib exhibits wide inter-subject pharmacokinetic variability which may contribute to differences in treatment outcome. Unbound drug concentrations are believed to be more relevant to pharmacological and toxicological responses than total drug. Thus it is desirable to determine gefitinib binding in plasma and factors affecting this process. An equilibrium dialysis method using 96-well microdialysis plates was optimized and validated for determining the fraction unbound (fu) gefitinib in human plasma. Gefitinib binding in plasma from four different species and isolated protein solutions as well as drug partitioning in human blood cells were investigated. Unbound gefitinib plasma concentrations were measured in 21 cancer patients receiving daily oral gefitinib 250 mg or 500 mg. It was found that gefitinib was extensively bound in human rat mouse and dog plasma with mean fu values of 3.4%, 3.8%, 5.1% and 6.0% respectively. In isolated protein solutions approximately 90% and 78% of gefitinib was bound to human serum albumin (HSA) (40 mg/dL) and alpha1-acid glycoprotein (AAG) (1.4 mg/dL) with binding constants of 1.85 x 10(4) M(-1) and 1.13 x 10(5) M(-1) respectively. In whole blood 2.8% of gefitinib existed as the free drug while 79.4% and 17.8% was bound to plasma proteins and blood cells respectively. In plasma from cancer patients fu at pre-treatment varied 2.4-fold (mean 3.4 +/- 0.6%; range 2.2-5.4%) and fu was constant over the 28-days of treatment (P > 0.05). Pre-treatment AAG concentration was negatively correlated with pre-treatment fu (R2 = 0.28, P = 0.01). In conclusion gefitinib is highly protein bound (approximately 97%) in human plasma. Variable AAG concentrations observed in cancer patients may affect gefitinib fu with implications for inter-subject variation in drug toxicity and response.

High sensitivity assays for docetaxel and paclitaxel in plasma using solid-phase extraction and high-performance liquid chromatography with UV detection

Background

The taxanes paclitaxel and docetaxel have traditionally been used in high doses every third week in the treatment of cancer. Lately there has been a trend towards giving weekly low doses to improve the therapeutic index. This article describes the development of high performance liquid chromatographic (HPLC) methods suitable for monitoring taxane levels in patients, focusing on patients receiving low-dose therapy.

Methods

Paclitaxel and docetaxel were extracted from human plasma by solid phase extraction, and detected by absorbance at 227 nm after separation by reversed phase high performance liquid chromatography. The methods were validated and their performance were tested using samples from patients receiving paclitaxel or docetaxel.

Results

The limits of quantitation were 1 nM for docetaxel and 1.2 nM for paclitaxel. For both compounds linearity was confirmed from the limit of quantitation up to 1000 nM in plasma. The recoveries ranged between 92% and 118% for docetaxel and between 76% and 104% for paclitaxel. Accuracy and precision were within international acceptance criteria, that is within ± 15%, except at the limit of quantitation where values within ± 20% are acceptable. Low-dose patients included in an on going clinical trial had a median docetaxel concentration of 2.8 nM at 72 hours post infusion. Patients receiving 100 mg/m² of paclitaxel had a mean paclitaxel concentration of 21 nM 48 hours after the end of infusion.

Conclusion

We have developed an HPLC method using UV detection capable of quantifying 1 nM of docetaxel in plasma samples. The method should be useful for pharmacokinetic determinations at all relevant doses of docetaxel. Using a similar methodology paclitaxel can be quantified down to a concentration of 1.2 nM in plasma with acceptable accuracy and precision. We further demonstrate that the previously reported negative influence of Cremophor EL on assay performance may be overcome by degradation of the detergent by incubation with lipase.

Development and validation of a liquid chromatography-tandem mass spectrometry assay for the quantification of docetaxel and paclitaxel in human plasma and oral fluid

A quantitative method for the simultaneous determination of docetaxel (Taxotere), paclitaxel (Taxol), 6alpha-hydroxypaclitaxel, and p-3'-hydroxypaclitaxel in human plasma and oral fluid is developed and validated. Oral fluid (this term is now preferred to saliva) was sampled with a Salivette collection device. The procedure used a simple liquid/liquid extraction with methyl tert-butyl ether followed by LC-ESI-MS/MS. Gradient elution was applied and provided increased robustness to ion suppression by the drug formulation vehicle (polysorbate 80 and Cremophor EL). Adduct ion formation with sodium and potassium was noticed and controlled by mobile-phase optimization. The protonated analytes generated in the positive ion mode were monitored through multiple reaction monitoring. Calibration was performed by internal standardization with cephalomannine, and regression curves were constructed ranging between 2 and 1000 ng/mL in plasma and 0.125 and 62.5 ng/mL in oral fluid, using a weighing factor of 1/x2. The regression curves were quadratic for paclitaxel and docetaxel and linear for the paclitaxel metabolites. Accuracy varied from 91.3 to 103.6%, and imprecision did not exceed 12.7% for all analytes in plasma and oral fluid. In conclusion, a sensitive and robust method was obtained, which fulfilled all validation criteria.

Prospective evaluation of the pharmacokinetics and toxicity profile of docetaxel in the elderly

PURPOSE

To prospectively study the pharmacokinetics and toxicity profile of docetaxel in elderly patients with cancer.

PATIENTS AND METHODS

Docetaxel was administered at a dose 75 mg/m(2) once every 3 weeks to 25 elderly cancer patients aged >/= 65 years and 26 cancer patients aged younger than 65 years. Pharmacokinetic studies and toxicity assessments were performed during the first cycle of therapy.

RESULTS

Of 51 patients treated, 20 aged >/= 65 years (median, 71 years; range, 65 to 80 years) and 20 aged younger than 65 years (median, 53 years; range, 26 to 64 years) were assessable for pharmacokinetic studies, and 39 were assessable for toxicity. Patient characteristics were similar (P >/= .15) between the two cohorts. Mean docetaxel clearance was not altered in the elderly versus younger patients: 30.1 L/h (standard deviation [SD] 18.3 L/h) v 30.0 L/h (SD, 14.8 L/h; P = .98). The percentage of patients with grade 4 and febrile neutropenia was higher in the elderly (63% and 16%, respectively) versus younger (30% and 0%, respectively) cohort, although this observation did not reach a level of statistical significance (P = .056). From logistic regression analysis, the odds ratio for a patient aged 65 years was 1.98 for developing grade 4 neutropenia compared with a patient aged 50 years (P = .091).

CONCLUSION

Docetaxel plasma pharmacokinetics are unaltered in elderly patients. Patients aged >/= 65 years appear to be more sensitive to docetaxel-induced neutropenia.

Polysorbate 80 increases the susceptibility to oxidative stress in rat thymocytes

Effect of simultaneous application of polysorbate 80, a nonionic surfactant widely used in pharmaceutical products, and hydrogen peroxide on rat thymocytes was examined to see if polysorbate 80 increases the susceptibility to oxidative stress because this surfactant decreases the cellular content of glutathione. Polysorbate 80 at clinically-relevant concentrations increases the cytotoxicity of hydrogen peroxide under the in vitro condition. Result suggests that polysorbate 80 may increase the susceptibility of cells to oxidative stress.

Quantification of docetaxel and its main metabolites in human plasma by liquid chromatography/tandem mass spectrometry

Docetaxel is an antineoplastic agent widely used in therapeutics. The objective of this study was to develop and validate a routine assay, using liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS), for the simultaneous quantification of docetaxel and its main hydroxylated metabolites in human plasma. A structural analogue, paclitaxel, was used as the internal standard. Determination of docetaxel and four metabolites (M1, M2, M3 and M4) was achieved using only 100 microL of plasma. Liquid-liquid extraction was used for sample preparation, with extraction efficiency of at least 90% for all analytes. Detection used positive-mode electrospray ionization in selected reaction monitoring mode. The lower limit of quantification (LLOQ) was 0.5 ng/mL for all analytes. The assay was linear in the calibration curve range 0.5-1000 ng/mL and acceptable precision and accuracy (<15%) were obtained with concentrations above the LLOQ. This method was sufficiently selective and sensitive for quantification of metabolites in plasma from cancer patients receiving docetaxel chemotherapy, and is suitable for routine analyses during pharmacokinetic studies.

Limited cerebrospinal fluid penetration of docetaxel

Our purpose was to investigate the cerebrospinal fluid (CSF) penetration of docetaxel in cancer patients. Docetaxel was administered as a 1-h infusion at a dose of 75 mg/m2 to two patients with metastatic breast cancer and leptomeningeal carcinomatosis. CSF samples were obtained using a lumbar puncture up to a 72-h time period. Total and unbound docetaxel concentrations in plasma and CSF were determined by liquid chromatography (lower limit of quantitation: 0.5 nM for plasma and 0.050 nM for CSF) and equilibrium dialysis, respectively. The pharmacokinetics of docetaxel in plasma are in line with data of previous studies. The concentrations of docetaxel in CSF did not follow the general pattern in plasma, with relatively stable concentrations over the 72-h time period. The fraction of unbound docetaxel in plasma ranged from 6 to 13%, while that in CSF ranged from 67 to 103%. For total and unbound docetaxel, the CSF to plasma concentration ratio progressively increased in 72 h from 0.01 to 0.6% and from 0.1 to 9%, respectively. These data suggest that measurement of unbound docetaxel is required to accurately assess the extent of drug penetration into CSF and that the drug can produce distribution to CSF at levels associated with significant antitumor activity in experimental models.

Randomized phase II trial of docetaxel plus thalidomide in androgen-independent prostate cancer

PURPOSE

Both docetaxel and thalidomide have demonstrated activity in androgen-independent prostate cancer (AIPC). We compared the efficacy of docetaxel to docetaxel plus thalidomide in patients with AIPC.

METHODS

Seventy-five patients with chemotherapy-naïve metastatic AIPC were randomly assigned to receive either docetaxel 30 mg/m(2) intravenously every week for 3 consecutive weeks, followed by a 1-week rest period (n = 25); or docetaxel at the same dose and schedule, plus thalidomide 200 mg orally each day (n = 50). Prostate-specific antigen (PSA) consensus criteria and radiographic scans were used to determine the proportion of patients with a PSA decline, and time to progression.

RESULTS

After a median potential follow-up time of 26.4 months, the proportion of patients with a greater than 50% decline in PSA was higher in the docetaxel/thalidomide group (53% in the combined group, 37% in docetaxel-alone arm). The median progression-free survival in the docetaxel group was 3.7 months and 5.9 months in the combined group (P =.32). At 18 months, overall survival in the docetaxel group was 42.9% and 68.2% in the combined group. Toxicities in both groups were manageable after administration of prophylactic low-molecular-weight heparin in the combination group.

CONCLUSION

In this randomized phase II trial, the addition of thalidomide to docetaxel resulted in an encouraging PSA decline rate and overall median survival rate in patients with metastatic AIPC. After the prophylactic low-molecular-weight heparin was instituted to prevent venous thromboses, the combination regimen was well tolerated. Larger randomized trials are warranted to assess the impact of this combination.

Phase I Trial of the Cyclin-Dependent Kinase Inhibitor Flavopiridol in Combination with Docetaxel in Patients with Metastatic Breast Cancer

PURPOSE

The purpose of this study was to determine the toxicities and characterize the pharmacokinetics of docetaxel and flavopiridol in patients with metastatic breast cancer.

EXPERIMENTAL DESIGN

Docetaxel was administered at an initial dose of 60 mg/m(2) followed in 24 hours by a 72-hour infusion of flavopiridol at 50 mg/m(2)/d every 3 weeks. Because dose-limiting myelosuppression occurred, the schedule was amended to docetaxel, 50 mg/m(2), followed by escalating doses of flavopiridol (starting dose, 26 mg/m(2)/d) as a 1-hour infusion daily for 3 days. Pharmacokinetic studies were performed. Ki67, p53, and phosphorylated retinoblastoma protein (phospho-Rb) in paired tumor and buccal mucosa biopsies (obtained pre- and posttreatment) were examined by immunohistochemistry.

RESULTS

Eleven patients were enrolled. Five patients received docetaxel and 72-hour flavopiridol. Dose-limiting toxicity was grade 4 neutropenia. Six patients received docetaxel and 1-hour flavopiridol, and the dose-limiting toxicity was grade 3 hypotension. Pharmacokinetics of flavopiridol and docetaxel were consistent with historical data. Nuclear staining with p53 increased and phospho-Rb decreased in 10 pairs of buccal mucosa biopsies posttreatment (P = 0.002 and P = 0.04, respectively). No significant changes in Ki67, p53, or phospho-Rb were detected in six paired tumors. Two patients sustained stable disease for >3 months (72-hour flavopiridol), and one partial response was observed (1-hour flavopiridol).

CONCLUSIONS

Docetaxel combined with 72-hour flavopiridol was not feasible because of dose-limiting neutropenia. Dose escalation of a 1-hour infusion of flavopiridol with docetaxel was also not possible. The changes in p53 and phospho-Rb in buccal mucosa suggest that a biological effect with flavopiridol was achieved.

Simple and rapid docetaxel assay in plasma by protein precipitation and high-performance liquid chromatography–tandem mass spectrometry

A simple, rapid and low cost sample preparation method was developed for quantification of docetaxel in mouse plasma by high-performance liquid chromatography/tandem mass spectrometry with paclitaxel as the internal standard. A small volume of plasma (40 microl) and one-step protein precipitation using methanol and acetonitrile (1:1 (v/v)) were used for sample preparation. The calibration curve for docetaxel in mouse plasma was linear over the range 25-2500 nM. The detection limit was 8 nM. The lower limit of quantitation is 25 nM. The intra- and inter-day precisions (CV) of analysis were 9.5 and 9.7% for the low quality control (LQC), 5.5 and 4.9% for the medium quality control (MQC) and 3.9 and 6.3% for the high quality control (HQC), respectively. The accuracy was 102.5% for LQC, 97.9% for MQC and 108.8% for HQC. This assay has now been applied to evaluation of mouse pharmacogenetics and other clinical pharmacology applications.