Docetaxel In Plasma Research Articles

Oral delivery system prolongs blood circulation of docetaxel nanocapsules via lymphatic absorption

An original oral formulation of docetaxel nanocapsules (NCs) embedded in microparticles elicited in rats a higher bioavailability compared with the i.v. administration of the commercial docetaxel solution, Taxotere. In the present study, various animal studies were designed to elucidate the absorption process of docetaxel from such a delivery system. Again, the docetaxel NC formulation elicited a marked enhanced absorption compared with oral Taxotere in minipigs, resulting in relative bioavailability and Cmax values 10- and 8.4-fold higher, respectively, confirming the previous rat study results. It was revealed that orally absorbed NCs altered the elimination and distribution of docetaxel, as shown in the organ biodistribution rat study, due to their reinforced coating, while transiting through the enterocytes by surface adsorption of apoproteins and phospholipids. These findings were demonstrated by the cryogenic-temperature transmission electron microscopy results and confirmed by the use of a chylomicron flow blocker, cycloheximide, that prevented the oral absorption of docetaxel from the NC formulation in an independent pharmacokinetic study. The lipoproteinated NCs reduced the docetaxel release in plasma and its distribution among the organs. The improved anticancer activity compared with i.v. Taxotere, observed in the metastatic lung cancer model in Severe Combined Immune Deficiency-beige (SCID-bg) mice, should be attributed to the extravasation effect, leading to the lipoproteinated NC accumulation in lung tumors, where they exert a significant therapeutic action. To the best of our knowledge, no study has reported that the absorption of NCs was mediated by a lymphatic process and reinforced during their transit.

The Effect of St John’s Wort on the Pharmacokinetics of Docetaxel

St John's wort (SJW), a herbal antidepressant, is commonly used by cancer patients, and its component hyperforin is a known inducer of the cytochrome P450 (CYP) isoenzyme 3A4. Here, the potential pharmacokinetic interaction between SJW and the sensitive CYP3A4 substrate docetaxel was investigated. In ten evaluable cancer patients, the pharmacokinetics of docetaxel (135 mg administered intravenously over 60 min) were compared before and after 14 days of supplementation with SJW (300 mg extract [Hyperiplant(®)] three times daily). SJW supplementation resulted in a statistically significant decrease in the mean area under the docetaxel plasma concentration-time curve extrapolated to infinity (AUC∞) from 3,035 ± 756 to 2,682 ± 717 ng · h/mL (P = 0.045). Furthermore, docetaxel clearance significantly increased from 47.2 to 53.7 L/h (P = 0.045) after SJW intake. The maximum plasma concentration and elimination half-life of docetaxel were (non-significantly) decreased after SJW supplementation. In addition, the incidence of docetaxel-related toxicities was lower after SJW supplementation. These results suggest that concomitant use of docetaxel and the applied SJW product should be avoided to prevent potential undertreatment of cancer patients.

Functional and Pharmacodynamic Evaluation of Metronomic Cyclophosphamide and Docetaxel Regimen in Castration-Resistant Prostate Cancer

The aim of our study was to investigate the association of docetaxel and metronomic cyclophosphamide (CYC) in castration-resistant prostate cancer (CRPC). CRPC xenografts were established with PC3 cells. Mice were treated with a combination of CYC (50 mg/kg/day) and docetaxel (10-30 mg/kg/week) or with docetaxel alone. Docetaxel plasma levels were analyzed in patients receiving the drug alone or combined with CYC. Metronomic CYC is an effective adjuvant in blocking tumor growth in vivo, with comparable efficacy and less toxic effects compared with docetaxel treatment. CYC acts by downregulating cell proliferation and inducing apoptosis thorough upregulation of p21 and inhibition of angiogenesis. Finally, CYC increases docetaxel plasma levels in patients. Metronomic CYC exerts anti-tumoral effects in an in vivo model of prostate cancer and in patients with CRPC, and also increases the bioavailability of docetaxel. These results explain the favorable toxicity and activity profiles observed in patients treated with this regimen.

Involvement of Wee1 in the Circadian Rhythm–Dependent Intestinal Damage Induced by Docetaxel

Docetaxel, a semisynthetic taxane, is effective for the treatment of some solid cancers; however, docetaxel-induced intestinal damage leads to poor prognosis in some patients. Although such adverse effects have been reported to depend on the dosing-time of docetaxel, the mechanisms involved remain unclear. Wee1 expression is controlled by the clock gene complex, clock/bmal1, and contributes to cell-cycle progression. The present study was undertaken to evaluate the potential role of Wee1 in the circadian rhythm-dependent profile of docetaxel. Male mice were maintained under a 12-hour light/dark cycle. Intestinal damage after repeated dosing of docetaxel (20 mg/kg) for 3 weeks was more severe at 14 hours after light on (HALO) than at 2 HALO. The intestinal protein expressions of Wee1, phosphorylated CDK1, and cleaved Caspase-3 were higher in the 14-HALO group than in the 2-HALO group, whereas that of survivin was lower in the 14-HALO group. Thus, it is speculated that elevated Wee1 expression inhibited CDK1 activity more by phosphorylation, which in turn caused the lower expression of survivin and consequently more activated Caspase-3 in the 14-HALO group. There were no significant differences in plasma docetaxel concentrations between the 2- and 14-HALO groups. Bindings of CLOCK and BMAL1 to the E-box regions at the wee1 gene promoter were not altered by docetaxel treatment at 2 and 14 HALO. These findings suggest that Wee1 is directly or indirectly involved in the mechanism of the circadian rhythm-dependent changes in docetaxel-induced intestinal damage. However, the mechanism for a circadian rhythm-dependent change in intestinal Wee1 expression by docetaxel remains to be determined.

A UFLC–MS/MS method coupled with one-step protein precipitation for determination of docetaxel in rat plasma: Comparative pharmacokinetic study of modified nanostructured lipid carrier

A rapid, simple and sensitive ultra fast liquid chromatography–tandem mass spectrometry (UFLC–MS/MS) method coupled with one-step protein precipitation procedure has been developed and validated for the pharmacokinetic study of docetaxel in rat plasma to investigate the influence of polyethylene glycol (PEG) molecular weights (chain length) using in the modified formulations. Separation was achieved on a Venusil MP C18 column (100mm×2.1mm, 3.0μm) with a mobile phase consisting of methanol–water, and the total running time was 3.5min. The standard curve was linear over the range of 5–5000ng/mL, with lower limits of quantification (LLOQ) of 5ng/mL. The method was shown to be reliable and reproducible with intra-day precision below 10.7%, inter-day precision below 11.2%, accuracy within ±5.2%, and mean extraction recovery of 84.6–90.2%. The validated method was successfully applied to the comparative pharmacokinetic study of docetaxel in rat plasma after intravenous administration of docetaxel-loaded nanostructured lipid carrier modified by copolymers consisting of series of PEG molecular weights (2000, 4000, 10,000Da), respectively. The results indicated that PEG-4000 possessed a better and longer circulation effect, which made the modified formulation one of the promising suspensions for the delivery of docetaxel in cancer.

Prediction of nanoparticle prodrug metabolism by pharmacokinetic modeling of biliary excretion

Pharmacokinetic modeling and simulation is a powerful tool for the prediction of drug concentrations in the absence of analytical techniques that allow for direct quantification. The present study applied this modeling approach to determine active drug release from a nanoparticle prodrug formulation. A comparative pharmacokinetic study of a nanoscale micellar docetaxel (DTX) prodrug, Procet 8, and commercial DTX formulation, Taxotere, was conducted in bile duct cannulated rats. The nanoscale (~40nm) size of the Procet 8 formulation resulted in confinement within the plasma space and high prodrug plasma concentrations. Ex vivo prodrug hydrolysis during plasma sample preparation resulted in unacceptable error that precluded direct measurement of DTX concentrations. Pharmacokinetic modeling of Taxotere and Procet 8 plasma concentrations, and their associated biliary metabolites, allowed for prediction of the DTX concentration profile and DTX bioavailability, and thereby evaluation of Procet 8 metabolism.Procet 8 plasma decay and in vitro plasma hydrolytic rates were identical, suggesting that systemic clearance of the prodrug was primarily metabolic. The Procet 8 and Taxotere plasma profiles, and associated docetaxel hydroxy-tert-butyl carbamate (HDTX) metabolite biliary excretion, were best fit by a two compartment model, with both linear and non-linear DTX clearance, and first order Procet 8 hydrolysis. The model estimated HDTX clearance rate agreed with in vitro literature values, supporting the predictability of the proposed model. Model simulation at the 10mg DTX equivalent/kg dose level predicted DTX formation rate-limited kinetics and a peak plasma DTX concentration of 39ng/mL at 4h for Procet 8, in comparison to 2826ng/mL for Taxotere. As a result of nonlinear DTX clearance, the DTX AUCinf for the Procet 8 formulation was predicted to be 2.6 times lower than Taxotere (775 vs. 2017h×ng/mL, respectively), resulting in an absolute bioavailability estimate of 38%. As DTX clearance in man is considered linear, this low bioavailability is likely species-dependent. These data support the use of pharmacokinetic modeling and simulation in cases of complex formulations, where analytical methods for direct measurement of free (released) drug concentrations are unavailable. Uses of such models may include interpretation of preclinical toxicology studies, selection of first in man dosing regimens, and PK/PD model development.

Quantification of cabazitaxel, its metabolite docetaxel and the determination of the demethylated metabolites RPR112698 and RPR123142 as docetaxel equivalents in human plasma by liquid chromatography–tandem mass spectrometry

We present a sensitive validated LC-MS/MS assay for the simultaneous determination of cabazitaxel and docetaxel in human plasma, with calibration ranges of 1.0-150 ng/mL for cabazitaxel and 0.1-15 ng/mL for docetaxel. Sample pretreatment consisted of liquid-liquid extraction with tert-butyl methyl ether. Chromatographic separation was achieved on a Zorbax Extend C18 column using a gradient mixture of 10mM ammonium hydroxide and methanol. Mass detection was carried out by turbo ion spray ionization in positive ion multiple reaction monitoring mode. All inter-day accuracies and precisions were within ±15% of the nominal value and within ±20% at the lower limit of quantitation. Demethylations of cabazitaxel yielding the metabolites RPR112698 and RPR123142 were monitored semi-quantitatively and quantified as ng docetaxel equivalents. Plasma samples of a prostate cancer patient treated with cabazitaxel were analyzed to demonstrate the usefulness of the presented assay for clinical drug monitoring. In conclusion, this method can be applied to support clinical pharmacokinetic studies with the novel anticancer drug cabazitaxel.

Pharmacokinetics of docetaxel in gastric cancer patients with malignant ascites

The purpose of this study was to investigate whether intravenous (i.v.) administration allowed docetaxel to penetrate ascites in gastric cancer patients with peritoneal dissemination. Twelve patients with disseminated gastric carcinoma were enrolled in the study. All patients received docetaxel-containing drug regimens: i.v. administration of 40 mg/m(2) docetaxel in 6 patients, and 60 mg/m(2) in the remainder. Docetaxel concentrations in the plasma and ascites were measured. Docetaxel was detected in the ascites of 4 patients in the 40 mg/m(2) group and 5 patients in the 60 mg/m(2) group. The highest concentration of docetaxel in plasma was detected at immediately after administration (median: 1,660 ng/mL, 501-2,560 ng/mL), after which it gradually decreased. The highest concentration of docetaxel in ascites was observed at ~7 h after administration and varied among cases (median: 18 ng/mL, 11-52 ng/mL). Intravenous administration allows to penetrate ascites in gastric cancer patients with peritoneal dissemination.

Plasma, tumor and tissue pharmacokinetics of Docetaxel delivered via nanoparticles of different sizes and shapes in mice bearing SKOV-3 human ovarian carcinoma xenograft

The particle fabrication technique PRINT® was used to fabricate monodisperse size and shape specific poly(lactide-co-glycolide) particles loaded with the chemotherapeutic Docetaxel. The pharmacokinetics of two cylindrical shaped particles with diameter=80nm; height=320nm (PRINT-Doc-80×320) and d=200nm; h=200nm (PRINT-Doc-200×200) were compared to Docetaxel in mice bearing human ovarian carcinoma SKOV-3 flank xenografts. The Docetaxel plasma exposure was ~20-fold higher for both particles compared to docetaxel. Additionally, the volume of distribution (Vd) of Docetaxel in PRINT formulations was ~18-fold (PRINT-Doc-80×320) and ~33-fold (PRINT-Doc-200×200) lower than Docetaxel. The prolonged duration of Docetaxel in plasma when dosed with PRINT formulations subsequently led to increased tumor exposure of Docetaxel from 0 to 168h (~53% higher for PRINT-Doc-80×320 and ~76% higher for PRINT-Doc-200×200 particles). PRINT-Doc-80×320 had lower exposures in the liver, spleen and lung compared with PRINT-Doc-200×200. Thus, the use of particles with smaller feature size may be preferred to decrease clearance by organs of the mononuclear phagocyte system. From the Clinical EditorIn this study, the plasma, tumor, and tissue pharmacokinetics of different Docetaxel nanoparticles of precise shape and size were characterized in mice with human ovarian carcinoma xenograft. It is concluded that the use of particles with smaller feature size may be preferred to decrease clearance by organs of the mononuclear phagocyte system.

422 Antitumor Activity of BAL27862 (active Moiety of the Prodrug BAL101553) is Associated with the Generation of Short Non-centrosomal Microtubules

Background: Docetaxel is used as first line chemotherapy for metastatic castrate resistant prostate cancer (mCRPC). It has been reported that castrated men have substantially increased docetaxel clearance (CL) compared to uncastrated men treated for mCRPC (Franke et al, J Clin Oncol 28: 4562−7, 2010). These results were obtained from 20 castrated men, with 10 non-castrated men serving as controls. In this study, we aimed to validate these findings in a larger and independent cohort of patients. Material and Methods: All male patients treated within the context of a pharmacokinetic study (Dutch Trial Registry; NTR2311) with docetaxel for solid tumors were included in this analysis (n = 74). As chemotherapy alone does not result in alterations in testosterone levels, out of these 74 patients, all men with non-prostate tumors served as controls (n = 36) of the castrated mCRPC patients (n = 38). Five of these control patients received docetaxel in combination with SU014813 in a clinical phase I study, all other patients received monotherapy. SU014813 has no clinically relevant pharmacokinetic (PK) interaction with docetaxel (de Jonge et al, Eur J Cancer 47: 1328−35, 2011). Dosage ranged from 30mg/m to 100mg/m, given in different schedules. Plasma docetaxel levels were determined by HPLC or LC-MS/MS. Individual PK parameters were estimated from previously developed population PK models by non-linear mixed effects modelling using NONMEM software. P-values were calculated using an independent samples T-test, while linear regression analysis was used to adjust for age, ethnicity, body surface area, concomitant use of other anticancer drugs, and dose when analysing haematological toxicity. Results: In the castrated patients, there was an increased docetaxel CL compared to the CL of uncastrated men (48.4 L/h versus 42.1 L/h, P = 0.051). In addition, both absolute neutrophil count nadir (n = 66) and white blood cell count nadir (n = 68) were significantly higher in castrated patients during chemotherapy with docetaxel (4.1 versus 1.7 ×109/L, P = 0.003 and 5.3 versus 3.1×109/L, P = 0.016, respectively). Conclusions: Androgen deprived prostate cancer patients in this study show an increased CL. In addition, castrated patients show less pronounced haematological toxicity compared to the control group of uncastrated men treated with docetaxel. Adding these results to the existing knowledge provides a solid foundation for further investigations regarding the increase in clearance related to castration-status and also for the individualization of docetaxel treatment in male patients.

Determination of docetaxel in rat plasma and its application in the comparative pharmacokinetics of Taxotere and SID530, a novel docetaxel formulation with hydroxypropyl‐β‐cyclodextrin

In this study, a sensitive, simple and reliable method for the quantification of docetaxel in rat plasma was developed and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The plasma samples were prepared by protein precipitation, and paclitaxel was used as an internal standard (IS). Chromatographic separation was achieved using a Gemini C(18) column (2.0 × 150 mm, 5 µm) with a mobile phase consisting of 0.1% formic acid-acetonitrile (30:70, v/v). The precursor-product ion pairs used for multiple reaction monitoring were m/z 808.5 → 527.5 (docetaxel) and m/z 854.2 → 286.5 (IS, paclitaxel). A calibration curve for docetaxel was constructed over the range 1-1000 ng/mL. The developed method was specific, precise and accurate, and no matrix effect was observed. The validated method was applied in a comparative pharmacokinetic study in which two docetaxel formulations, SID530, a new parenteral formulation of docetaxel with hydroxypropyl-β-cyclodextrin (HP-β-CD), and Taxotere, were administered to rats at a dose of 5 mg/kg. For SID530 and Taxotere, the mean C(0) values were 1494 and 1818 ng/mL, respectively, and the AUC(last) values were 837 and 755 h ng/mL, respectively. These two formulations did not show any statistical differences with regard to the pharmacokinetic parameters, thus establishing that the SID530 and Taxotere products are pharmacokinetically comparable in male rats.

Pharmacokinetic Equivalence of Taxotere and SID530, a Novel Docetaxel Formulation Containing Hydroxypropyl-beta-cyclodextrin in Monkeys

SID530 is a new parenteral formulation of docetaxel containing hydroxypropyl-beta-cyclodextrin (HP-β-CD). In this study, a comparative pharmacokinetic study of 2 docetaxel parenteral solutions, SID530 and Taxotere, was carried out. In a crossover experimental design, 6 male cynomolgus monkeys received each formulation by intravenous infusion of a single dose. The concentration of docetaxel in whole blood and plasma was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The 2 formulations showed similar pharmacokinetic parameters in both whole blood and plasma, and displayed comparable values for maximum serum concentration (Cmax), time to peak concentration (Tmax), and area under the concentration-time curve (AUC). The 90% confidence intervals for the ratios of Cmax and AUC values for SID530 to Taxotere were within the acceptable range of 0.80-1.20 in both plasma and whole blood. These findings indicate that SID530 and Taxotere are comparable in terms of their distribution in the blood and their plasma profile; consequently, these drugs are bioequivalent in the monkey.

Abstract 761: Phase I interaction study of docetaxel with supplementation of St. John's wort

Abstract Introduction St. John's wort (SJW, Hypericum perforatum) is a herbal antidepressant, which is often used by cancer patients. In healthy volunteers, SJW has previously been shown to induce hepatic CYP3A4 using the selective CYP3A4 substrate midazolam (Wang et al., 2001). In cancer patients, CYP3A4 induction by SJW could result in a decreased exposure to anticancer drugs metabolized by CYP3A4 (e.g. docetaxel), possibly resulting in a decreased therapeutic effect. Induction of docetaxel metabolism by the SJW constituent hyperforin has already been established in vitro (Komoroski et al., 2005). This pharmacokinetic interaction, however, has never been studied before in a clinical setting. Therefore, the aim of this study was to assess the effects of SJW on the pharmacokinetics of docetaxel in cancer patients. Methods In a one-sequence crossover study performed at the Netherlands Cancer Institute and approved by the Institute's Medical Ethical Committee, ten cancer patients received two cycles of docetaxel (135 mg, 60 min IV infusion). Seven days after cycle 1 (docetaxel alone), a commercial SJW extract in a recommended dose of one tablet (containing 300 mg SJW extract) three times daily was supplemented for fourteen days. After this supplementation period, cycle 2 of docetaxel was administered. During cycle 1 and cycle 2, blood samples were collected from 0-48 h after the start of the docetaxel infusion for pharmacokinetic analysis of docetaxel. Docetaxel plasma concentrations were determined by a validated LC-MS/MS assay (Kuppens et al., 2005). The pharmacokinetic endpoint for docetaxel was the area under the plasma concentration-time curve from time 0 to 48 h (AUC0-48), reflecting systemic exposure to docetaxel. By comparing the AUC0-48 of docetaxel in cycle 1 and 2, the effect of SJW on docetaxel pharmacokinetics was determined. Statistical analysis was performed with a paired Student's t test (α = 0.05). Differences in AUC0-48 between cycle 1 and 2 were considered clinically relevant if the 90% CI of the geometric mean ratio was not completely within no-effect limits of 0.80-1.25. Results (preliminary) In eight evaluable patients, supplementation of SJW decreased the mean docetaxel AUC0-48 from 2745 ± 650 to 2364 ± 483 ng/mL*h (p = 0.048, geometric mean ratio 0.86 (90% CI: 0.81-0.92)). Conclusion In this study, the observed decrease of docetaxel AUC0-48 after SJW administration was statistically significant, possibly even clinically relevant. This result indicates that concomitant use of the present SJW formulation in the recommended dose may decrease the therapeutic efficacy of docetaxel and presumably also other anticancer drugs primarily metabolized by CYP3A4. Acknowledgements This study was supported by the Dutch Cancer Society grant UU 2007-3795. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 761. doi:1538-7445.AM2012-761

A rapid and sensitive LC/ESI–MS/MS method for quantitative analysis of docetaxel in human plasma and its application to a pharmacokinetic study

Docetaxel is a taxane family antineoplastic agent widely employed in cancer chemotherapy. We developed a liquid chromatography/tandem mass spectrometry method for the determination of docetaxel in human plasma. Plasma samples were deproteinized by acetonitrile containing internal standard paclitaxel. Chromatographic separation was performed on a TSKgel ODS-100V 3μm (50mm×2.0mm i.d.) column using a mobile phase composed of acetonitrile–methanol–water–formic acid (50:5:45:0.1, v/v/v/v). Detection was performed on a triple-quadrupole tandem mass spectrometer with multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. This method covered a linearity range of 5–5000ng/mL with the lower limit of quantification of 5ng/mL. The intra-day precision and inter-day precision (R.S.D.) of analysis were less than 6.7%, and the accuracy (R.E.) was within ±9.0% at the concentrations of 5, 20, 200, and 2000ng/mL. The total run time was 5.0min. This method was successfully applied for clinical pharmacokinetic investigation.

Pharmacokinetics and tissue distribution of docetaxel by liquid chromatography–mass spectrometry: Evaluation of folate receptor-targeting amphiphilic copolymer modified nanostructured lipid carrier

A novel amphiphilic copolymer, folate-poly(PEG-cyanoacrylate-co-cholesteryl cyanoacrylate) (FA-PEG-PCHL) was synthesized to modify docetaxel-loaded nanostructured lipid carrier to lead to a long blood circulating effect and targeting ability for the delivery of antitumor drug in cancer. To investigate the characteristics of modified docetaxel-loaded nanostructured lipid carrier in vivo, a liquid chromatography–mass spectrometry method was developed and validated for the determination of docetaxel in rat plasma and tumor-bearing mouse tissue samples. The biosamples were extracted by liquid–liquid extraction method with ether and separated on a C 18 column (150 mm × 4.6 mm, 5 μm) using a mobile phase consisting of methanol–0.01% formic acid water (82:18, v/v). The standard curves were linear over the ranges of 0.01–4.0 μg/mL for plasma and 0.02–8.0 μg/g for tissue samples, respectively. The validated method was successfully applied to the pharmacokinetic study in rat plasma and tissue distribution study in mouse tissues of docetaxel after an intravenous administration of docetaxel injection (DTX injection), docetaxel-loaded nanostructured lipid carrier (DTX-NLC) and FA-PEG-PCHL-modified docetaxel-loaded nanostructured lipid carrier (FA-DTX-NLC), respectively. The results indicated that the FA-DTX-NLC led to significant differences in pharmacokinetic profile and tissue distribution. Nanostructured lipid carrier modified by FA-PEG-PCHL could be one of the promising suspensions for the delivery of docetaxel in cancer.

A sensitive combined assay for the quantification of paclitaxel, docetaxel and ritonavir in human plasma using liquid chromatography coupled with tandem mass spectrometry

A combined assay for the determination of paclitaxel, docetaxel and ritonavir in human plasma is described. The drugs were extracted from 200 μL human plasma using liquid–liquid extraction with tertiar-butylmethylether, followed by high performance liquid chromatography analysis using 10 mM ammonium hydroxide pH 10:methanol (3:7, v/v) as mobile phase. Chromatographic separation was obtained using a Zorbax Extend C 18 column. Labelled analogues of the analytes are used as internal standards. For detection, positive ionization electrospray tandem mass spectrometry was used. Method development including optimisation of the mass transitions and response, mobile phase optimisation and column selection are discussed. The method was validated according to FDA guidelines and the principles of Good Laboratory Practice (GLP). The validated range was 0.5–500 ng/mL for paclitaxel and docetaxel and 2–2000 ng/mL for ritonavir. For quantification, quadratic calibration curves were used ( r 2 > 0.99). The total runtime of the method is 9 min and the assay combines analytes with differences in ionisation and desired concentration range. Inter-assay accuracy and precision were tested at four concentration levels and were within 10% and less than 10%, respectively, for all analytes. Carry-over was less than 6% and endogenous interferences or interferences between analytes and internal standards were less than 20% of the response at the lower limit of quantification level. The matrix factor and recovery were determined at low, mid and high concentration levels. The matrix factor was around 1 for all analytes and total recovery between 77.5 and 104%. Stability was investigated in stock solutions, human plasma, dry extracts, final extracts and during 3 freeze/thaw cycles. The described method was successfully applied in clinical studies with oral administration of docetaxel or paclitaxel in combination with ritonavir.

Quantification of docetaxel plasma concentrations using a novel nanoparticle-based immunoassay.

e11545 Background: Docetaxel is a commonly used antineoplastic agent of the taxoid family. The pharmacokinetic profile of docetaxel has up to 10-fold inter-patient variability in total clearance and up to 7-fold in total exposure (AUC). This variability may result in severe toxicities and poor outcomes. Docetaxel AUC was shown to be a significant predictor of time to progression (TTP) and severe adverse events in non-small cell lung cancer. A new nanoparticle-based docetaxel immunoassay provides a rapid, simple and cost-effective drug concentration measurement as compared to current chromatographic methods. Methods: Novel antibodies to docetaxel were covalently linked to nanoparticles to develop a prototype automated, homogenous immunoassay. The assay was applied to the Beckman Coulter AU400 clinical analyzer. Total imprecision and linearity of the assay were evaluated by testing normal human plasma pools spiked with different levels of docetaxel. Background was determined by measuring >200 normal human plasma samples. Results: Within a quantitation range of 50 to 1000ng/mL and using instrument auto-dilution, plasma levels of docetaxel can be measured up to 10,000ng/mL with only 2µl sample size. This test range covers clinically relevant drug concentrations and can be used to calculate the systemic exposure (AUC) of docetaxel. Time-to-first result was < 9min, and 400 samples per hour could be measured. The total imprecision of plasma pools spiked with docetaxel at four concentrations across the assay range was <6% CV and the assay was linear from 50 to 1000ng/mL. Background of the assay was found to be < 10 ng/mL. The assay cross-reactivity to docetaxel hydroxy-tertbutyl carbamate, the major metabolite of docetaxel, was 20%, and <1% for 10-deacetylbaccatin, a degradation product of docetaxel. These were shown to have no significant impact on the quantitation of docetaxel. Conclusions: This rapid immunoassay is suitable for routine measurement of plasma docetaxel concentrations with only 2ul sample size and within ten minutes and could provide a tool for optimization of docetaxel blood levels for pharmacokinetic-guided dosing.

Effects of experimental hyperlipidaemia on the pharmacokinetics of docetaxel in rats

Hyperlipidaemia correlates with an increased risk of occurrence of various cancers. In this study, the effects of hyperlipidaemia on the pharmacokinetics of docetaxel, a member of the taxane class of anti-cancer drugs, were investigated in rats with experimental hyperlipidaemia; we focused on the alterations in docetaxel metabolism and plasma distribution.Docetaxel (5 mg/kg intravenously (i.v.) and 40 mg/kg per oral (p.o.)) was administered to control rats and rats with poloxamer-407 (P-407)–induced hyperlipidaemia (1 g/kg, intraperitoneally). In vitro studies were conducted on hepatic metabolism in S9 fractions and plasma protein binding using the ultrafiltration method.Hyperlipidaemia dramatically increased the area under the plasma concentration–time curve from time 0 to infinity (AUC0–∞) of docetaxel after i.v. (1.86-fold) or p.o. (10.8-fold) administration and decreased total body clearance (0.574-fold) and apparent volume of distribution at steady state (0.615-fold) of docetaxel after i.v. administration. Compared with the control rats, the metabolism of docetaxel by hepatic S9 fractions and the unbound fraction in the plasma in the hyperlipidaemic rats were decreased, i.e., by 20.1 and 79.8%, respectively.In conclusion, the alterations in docetaxel pharmacokinetics in rats with P-407-induced hyperlipidaemia may be due, at least in part, to a decrease in hepatic metabolism and the unbound fraction of docetaxel in the plasma. These findings have potential therapeutic implications for predicting human pharmacokinetic responses to hyperlipidaemia.

High Plasma Levels and Effective Lymphatic Uptake of Docetaxel in an Orally Available Nanotransporter Formulation

Docetaxel, an efficient chemotherapeutic drug, exhibits low and variable oral bioavailability due to the active efflux by P-glycoprotein (P-gp) and more so to CYP3A4 gut metabolism. Using a spray-drying technique, docetaxel was incorporated in PLGA [poly(lactic-co-glycolic acid)] nanocapsules (NC) which were embedded in entero-coated microparticles. An oral administration of the NC formulation elicited a higher absolute bioavailability than both a docetaxel solution (276%) and a free docetaxel NC formulation (400%) injected intravenously, a 5-mg/kg dose. The batches (B) I and II NC formulations elicited C(max) values that were 1,735% and 2,254%, respectively; higher than the C(max) value of the oral docetaxel solution combined with blank microparticles, a 10-mg/kg dose. No significant difference in AUC (area under curve) was observed between the batches. These unexpected results can be explained only if the pharmacokinetics of docetaxel had been modified. It was shown that NCs released from the microparticles penetrated the enterocytes, bypassing P-gp; apparently circumventing gut metabolism and accumulating within the lymphatic system from where both intact or biodegraded NCs and free docetaxel were progressively released into the circulation as plausibly supported by the fluorescent imaging results. Furthermore, the circulating docetaxel in plasma was unencapsulated and circulated either in free form or bound to albumin. Both free docetaxel NCs and microparticles exhibited in vitro efficacy on WRC 256 cells suggesting that the activity of docetaxel was not altered. This delivery concept has potential for clinical translation, perhaps allowing docetaxel chemotherapy to be switched from intravenous to oral delivery.

Docetaxel Distribution Following Intraperitoneal Administration in Mice

Intraperitoneal (IP) chemotherapy with high molecular weight lipophilic antineoplastic agents such as the taxanes has shown promise in clinical trial evaluation for treatment of localized peritoneal cancers. We have previously developed an IP injectable hydrogel formulation (PoLigel) for sustained peritoneal delivery of docetaxel (DTX), and observed significant efficacy in murine models of ovarian cancer when compared to Taxotere®, the FDA approved formulation of DTX. In order to understand the relationship between drug distribution and efficacy, the current study compares the tissue distribution and pharmacokinetics of DTX administered IP in the PoLigel or Taxotere® formulations. The PoLigel was prepared by blending a water-soluble chitosan derivative, egg phosphatidylcholine and lauric aldehyde with DTX (drug to material ratio 1:8 w/w). DTX concentrations in plasma, heart, liver, spleen, stomach, intestine, kidney and peritoneal muscle were measured over a five day period following IP administration of the PoLigel and Taxotere® formulations in CD-1 female mice. Three days after Taxotere® administration, no detectable levels of DTX were seen in plasma, while sustained DTX plasma levels of 0.06 ug/ml ± 0.01 per day were observed with PoLigel. At five days post Taxotere® administration, only intestine, stomach and peritoneal muscle showed detectable DTX concentrations whereas all tissues and plasma showed sustained DTX levels in mice that received PoLigel. DTX concentrations that resulted from PoLigel administration were significantly higher in the peritoneal cavity and 200 fold higher than concentrations found in plasma. Overall, the PoLigel formulation increases tissue and plasma drug retention and provides sustained DTX levels compared to the clinically used Taxotere® formulation. The sustained DTX levels seen in the peritoneal cavity following IP administration of the PoLigel may be responsible for the improvement in efficacy that has been observed in our previous studies.