In vitro and in vivo anticancer effect of pH-responsive paclitaxel-loaded niosomes

In this study, paclitaxel (PTX)-loaded pH-responsive niosomes modified with ergosterol were developed. This new formulation was characterized in terms of size, morphology, encapsulation efficiency (EE), and in vitro release at pH 5.2 and 7.4. The in vitro efficacy of free PTX and niosome/PTX was assessed using MCF7, Hela, and HUVEC cell lines. In order to evaluate the in vivo efficacy of niosomal PTX in rats as compared to free PTX, the animals were intraperitoneally administered with 2.5 mg/kg and 5 mg/kg niosomal PTX for two weeks. Results showed that the pH-responsive niosomes had a nanometric size, spherical morphology, 77% EE, and pH-responsive release in pH 5.2 and 7.4. Compared with free PTX, we found markedly lower IC50s when cancer cells were treated for 48 h with niosomal PTX, which also showed high efficacy against human cancers derived from cervix and breast tumors. Moreover, niosomal PTX induced evident morphological changes in these cell lines. In vivo administration of free PTX at the dose of 2.5 mg/kg significantly increased serum biochemical parameters and liver lipid peroxidation in rats compared to the control rats. The situation was different when niosomal PTX was administered to the rats: the 5 mg/kg dosage of niosomal PTX significantly increased serum biochemical parameters, but the group treated with the 2.5 mg/kg dose of niosomal PTX showed fewer toxic effects than the group treated with free PTX at the same dosage. Overall, our results provide proof of concept for encapsulating PTX in niosomal formulation to enhance its therapeutic efficacy.

Novel Long-Acting Drug Combination Nanoparticles Composed of Gemcitabine and Paclitaxel Enhance Localization of Both Drugs in Metastatic Breast Cancer Nodules

PURPOSE

To develop drug-combination nanoparticles (DcNPs) composed of hydrophilic gemcitabine (G) and hydrophobic paclitaxel (T) and deliver both drugs to metastatic cancer cells.

METHODS

GT DcNPs were evaluated based on particle size and drug association efficiency (AE%). The effect of DcNP on GT plasma time-course and tissue distribution was characterized in mice and a pharmacokinetic model was developed. A GT distribution study into cancer nodules (derived from 4 T1 cells) was performed.

RESULTS

An optimized GT DcNP composition (d = 59.2 nm ±9.2 nm) was found to be suitable for IV formulation. Plasma exposure of G and T were enhanced 61-fold and 3.8-fold when given in DcNP form compared to the conventional formulation, respectively. Mechanism based pharmacokinetic modeling and simulation show that both G and T remain highly associated to DcNPs in vivo (G: 98%, T:75%). GT DcNPs have minimal distribution to healthy organs with selective distribution and retention in tumor burdened tissue. Tumor bearing lungs had a 5-fold higher tissue-to-plasma ratio of gemcitabine in GT DcNPs compared to healthy lungs.

CONCLUSIONS

DcNPs can deliver hydrophilic G and hydrophobic T together to cancer nodules and produce long acting exposure, likely due to stable GT association to DcNPs in vivo.

Novel drug combination nanoparticles exhibit enhanced plasma exposure and dose-responsive effects on eliminating breast cancer lung metastasis

Early diagnosis along with new drugs targeted to cancer receptors and immunocheckpoints have improved breast cancer survival. However, full remission remains elusive for metastatic breast cancer due to dose-limiting toxicities of heavily used, highly potent drug combinations such as gemcitabine and paclitaxel. Therefore, novel strategies that lower the effective dose and improve safety margins could enhance the effect of these drug combinations. To this end, we developed and evaluated a novel drug combination of gemcitabine and paclitaxel (GT). Leveraging a simple and scalable drug-combination nanoparticle platform (DcNP), we successfully prepared an injectable GT combination in DcNP (GT DcNP). Compared to a Cremophor EL/ethanol assisted drug suspension in buffer (CrEL), GT DcNP exhibits about 56-fold and 8.6-fold increases in plasma drug exposure (area under the curve, AUC) and apparent half-life of gemcitabine respectively, and a 2.9-fold increase of AUC for paclitaxel. Using 4T1 as a syngeneic model for breast cancer metastasis, we found that a single GT (20/2 mg/kg) dose in DcNP nearly eliminated colonization in the lungs. This effect was not achievable by a CrEL drug combination at a 5-fold higher dose (i.e., 100/10 mg/kg GT). A dose-response study indicates that GT DcNP provided a therapeutic index of ~15.8. Collectively, these data suggest that GT DcNP could be effective against advancing metastatic breast cancer with a margin of safety. As the DcNP formulation is intentionally designed to be simple, scalable, and long-acting, it may be suitable for clinical development to find effective treatment against metastatic breast cancer.

A phase I study of an oral selective gamma secretase (GS) inhibitor RO4929097 in combination with neoadjuvant paclitaxel and carboplatin in triple negative breast cancer

Upregulation of Notch pathway is associated with poor prognosis in breast cancer. We present the results of a phase I study of an oral selective gamma secretase (GS) inhibitor (critical to Notch signaling), RO4929097 in combination with neoadjuvant chemotherapy for operable triple negative breast cancer. The primary objective was to determine the maximum tolerated dose (MTD) of RO4929097. Secondary objectives were to determine real-time pharmacokinetics of RO4929097 and paclitaxel, safety and pathologic (pCR) complete response to study treatment. Eligible patients, initiated carboplatin at AUC 6 administered intravenously (IV) on day 1, weekly paclitaxel at 80 mg/m2 IV and RO4929097 10 mg daily given orally (PO) on days 1-3, 8-10 and 15-17 for six 21-day cycles. RO4929097 was escalated in 10 mg increments using the 3 + 3 dose escalation design. Two DLTs were observed in 14 patients - Grade (G) 4 thrombocytopenia in dose level 1 (10 mg) and G3 hypertension in dose level 2 (20 mg). Protocol-defined MTD was not determined due to discontinuation of RO4929097 development. However, 4 of 5 patients enrolled to 20 mg dose of RO4929097 required dose reduction to 10 mg due to toxicities (including neutropenia, thrombocytopenia and hypertension) occurring during and beyond the DLT observation period. Thus, 10 mg would have been the likely dose level for further development. G3 or higher hematologic toxicities included neutropenia (N = 8, 57%) and thrombocytopenia (N = 5, 36%) patients. Six (43%) patients had G2-3 neuropathy requiring paclitaxel dose reduction. No signs of drug-drug interaction between paclitaxel and RO4929097 were evident. Five patients (36%) had pCR.

DHP23002 as a next generation oral paclitaxel formulation for pancreatic cancer therapy

OBJECTIVE

This study aimed to develop a new oral paclitaxel formulation (DHP23002) and to evaluate its absorption and antitumor effects in a pancreatic tumor mouse model.

METHODS

To investigate the oral absorption of DHP23002, a newly developed lipid-based orally active paclitaxel formulation, a pharmacokinetic study of DHP23002, was conducted in mice (62.5 and 125 mg/kg). Moreover, to evaluate the antitumor effect of DHP23002 in pancreatic cancer treatment, the drug was administered to female athymic nude mice at 0 (vehicle), 25, 62.5, and 125 mg/kg on alternate days; the efficacy of the agent was compared with the efficacy of intravenous Taxol® injections at 10 mg/kg once per week. After 3 weeks of administration, tumor growth in mice belonging to each group was further monitored for 4 weeks after discontinuing medication. Moreover, to examine paclitaxel (DHP23002) accumulation in the tumor tissue, the amount of paclitaxel in tumor/blood was quantified using liquid chromatography with quadruple-TOF mass spectrometry.

RESULTS

In the mouse pharmacokinetic study, oral Taxol® showed a negligible absorption, whereas DHP23002 showed a high absorption rate dependent on dosage, with a bioavailability of approximately 40% at a dose of 62.5 mg/kg. In efficacy-related studies, DHP23002 administration at a dose of 25, 62.5, or 125 mg/kg on alternate days for 3 weeks showed a superior tumor inhibitory effect of 80%, 92%, and 97% in a xenograft mouse model, respectively, after 7 weeks. Paclitaxel accumulation in tumors persisted for >24 h in mice, when orally administered once at doses of 25, 62.5, and 125 mg/kg DHP23002.

CONCLUSION

Oral chemotherapy with DHP23002 showed excellent absorption in animals owing to a strong antitumor activity in a pancreatic cancer mouse model. This demonstrates that paclitaxel is largely distributed and persists for a prolonged period at the tumor site owing to oral DHP23002 administration.

Self-Strengthened Oxidation-Responsive Bioactivating Prodrug Nanosystem with Sequential and Synergistically Facilitated Drug Release for Treatment of Breast Cancer

Although environment-sensitive prodrug-based nanoparticles (NPs) have developed rapidly, lots of prodrug NPs still show poor selectivity and efficiency of parent drug bioactivation because of tumor heterogeneity. Herein, self-strengthened bioactivating prodrug-based NPs are fabricated via co-encapsulation of oxidation-responsive thioether-linked linoleic acid-paclitaxel conjugates (PTX-S-LA) and β-lapachone (LPC) into polymeric micelles (PMs). Following cellular uptake, PMs first release LPC to significantly elevate the reactive oxidative species (ROS) level through NAD(P)H: quinone oxidoreductase-1 (NQO1) catalysis. Then, NQO1-generated ROS in combination with endogenous high ROS levels in tumor cells could synergistically facilitate PTX-S-LA to release the active cytotoxic agent PTX. Such a novel prodrug nanosystem exhibits self-strengthened prodrug bioactivation, ultraselective release, and cytotoxicity between cancer and normal cells, prolonged circulation time, and enhanced tumor accumulation, leading to high antitumor efficiency and superior biosafety. Our findings pave the new way for the rational design of oxidation-responsive prodrug NPs for high-efficacy cancer chemotherapy.

Chemotherapy in pregnancy: exploratory study of the effects of paclitaxel on the expression of placental drug transporters

Introduction The use of paclitaxel in pregnant cancer patients is feasible in terms of fetal safety, but little is known about the effects of paclitaxel on the placenta. Using three experimental models, we aimed to assess the effects of paclitaxel on the expression of placental drug transporters. Methods In the in vitro model (human primary trophoblast culture), trophoblasts were isolated from normal term placentas and subsequently exposed to paclitaxel. The transcriptional regulation of 84 genes encoding for drug transporters, and the protein expression of ABCB1/P-gp and ABCG2/BCRP were assessed. In the in vivo model, placental tissues isolated from pregnant cancer patients treated with paclitaxel were analyzed to assess the protein expression of ABCB1/P-gp and ABCG2/BCRP. The same parameters were assessed in extracts from human placental cotyledons perfused ex vivo with paclitaxel. Results In the in vitro model, the expression of twelve drug-transporters genes was found to be significantly down-regulated after exposure to paclitaxel, including ABCC10, SLC28A3, SLC29A2, and ATP7B (involved in the transport of taxanes, antimetabolites, and cisplatin, respectively). The protein expression of ABCB1/P-gp increased by 1.3-fold after paclitaxel administration. Finally, the protein expression of ABCB1/P-gp and ABCG2/BCRP was higher in cotyledons from mothers treated with multiple doses of paclitaxel during pregnancy than in cotyledons perfused with a single dose of paclitaxel. Discussion Paclitaxel modulates the expression of placental drug transporters involved in the disposition of various anticancer agents. Further studies will be needed to assess the impact of repeated or prolonged exposure to paclitaxel on the expression and function of placental drug transporters.

A new high-performance liquid chromatography-tandem mass spectrometry method for the determination of paclitaxel and 6α-hydroxy-paclitaxel in human plasma: Development, validation and application in a clinical pharmacokinetic study

Paclitaxel belongs to the taxanes family and it is used, alone or in multidrug regimens, for the therapy of several solid tumours, such as breast-, lung-, head and neck-, and ovarian cancer. Standard dosing of chemotherapy does not take into account the many inter-patient differences that make drug exposure highly variable, thus leading to the insurgence of severe toxicity. This is particularly true for paclitaxel considering that a relationship between haematological toxicity and plasma exposure was found. Therefore, in order to treat patients with the correct dose of paclitaxel, improving the overall benefit–risk ratio, Therapeutic Drug Monitoring is necessary. In order to quantify paclitaxel and its main metabolite, 6α-hydroxy-paclitaxel, in patients’ plasma, we developed a new, sensitive and specific HPLC–MS/MS method applicable to all paclitaxel dosages used in clinical routine. The developed method used a small volume of plasma sample and is based on quick protein precipitation. The chromatographic separation of the analytes was achieved with a SunFire^™ C18 column (3.5 μM, 92 Å, 2,1 x 150 mm); the mobile phases were 0.1% formic acid/bidistilled water and 0.1% formic acid/acetonitrile. The electrospray ionization source worked in positive ion mode and the mass spectrometer operated in selected reaction monitoring mode. Our bioanalytical method was successfully validated according to the FDA-EMA guidelines on bioanalytical method validation. The calibration curves resulted linear (R² ≥0.9948) over the concentration ranges (1–10000 ng/mL for paclitaxel and 1–1000 ng/mL for 6α-hydroxy-paclitaxel) and were characterized by a good accuracy and precision. The intra- and inter-day precision and accuracy were determined on three quality control concentrations for paclitaxel and 6α-hydroxy-paclitaxel and resulted respectively <9.9% and within 91.1–114.8%. In addition, to further verify the assay reproducibility, we tested this method by re-analysing the incurred samples. This bioanalytical method was employed with success to a genotype-guided phase Ib study of weekly paclitaxel in ovarian cancer patients treated with a wide range of drug’s dosages.

TC > 0.05 as a Pharmacokinetic Parameter of Paclitaxel for Therapeutic Efficacy and Toxicity in Cancer Patients

BACKGROUND

Paclitaxel (PTX) has remarkable anti-tumor activity, but it causes severe toxicities. There is an urgent need to seek an appropriate pharmacokinetic parameter of PTX to improve treatment efficacy and reduce adverse effects.

OBJECTIVE

To evaluate the association of pharmacokinetic parameter TC > 0.05 of paclitaxel (PTX) and its therapeutic efficacy and toxicity in patients with solid tumors.

METHODS

A total of 295 patients with ovarian cancer, esophageal cancer, breast cancer, and non-small cell lung cancer (NSCLC), who were admitted to the Tumor Hospital of Shantou University Medical College, China, were recruited for this study. Patients received 3 weeks of PTX chemotherapy. The plasma concentrations of PTX were examined using the MyPaclitaxel™ kit. The patients' PTX TC > 0.05 (the time during which PTX plasma concentration exceed 0.05µmol/L) were calculated based on pharmacokinetic analysis.

RESULTS

The results showed that: (1) the concentrations of PTX in these 295 patients ranged from 0.0358-0.127 µmol/L; (2) the PTX TC > 0.05 ranged from 14 to 38h with a median time of 27h; (3) among all treatment cycles, there was a statistically significant difference in the PTX TC > 0.05 between CR+PR and SD+PD; (4) with the increasing value of TC > 0.05, level of leukopenia and leukopenic fever increased; (5) high PTX TC > 0.05 led to the occurrence of neutropenia, neutropenic fever, severe anemia, and severe peripheral neurotoxicity. Taken together, our results indicated that the pharmacokinetic parameter PTX TC > 0.05 was an effective measure of treatment efficacy and toxicity in patients with solid tumors. Maintaining PTX TC > 0.05 at 26 to 30h could improve its efficacy and reduce the incidence of leukopenia, neutropenia, anemia, and peripheral neurotoxicity in these patients.

CONCLUSION

PTX TC > 0.05 is a key pharmacokinetic parameter of PTX which should be monitored to optimize individual treatment in patients with solid tumors.

Paclitaxel-loaded folate-coated long circulating and pH-sensitive liposomes as a potential drug delivery system: A biodistribution study

A range of antitumor agents for cancer treatment is available; however, they show low specificity, which often limit their use. Recently, we have reported the preparation of folate-coated long-circulating and pH-sensitive liposomes (SpHL-folate-PTX) loaded with paclitaxel (PTX), an effective drug for the treatment of solid tumors, including breast cancer. The purpose of this study was to prepare and characterize SpHL-PTX and SpHL-folate-PTX radiolabeled with technetium-99m (^99mTc). Biodistribution studies and scintigraphic images were performed after intravenous administration of ^99mTc-PTX, ^99mTc-SpHL-PTX and ^99mTc-SpHL-folate-PTX into healthy and tumor-bearing mice. High radiochemical purity (>98%) and in vitro stability (>90%) were achieved for both liposome formulations. The pharmacokinetic properties of ^99mTc-SpHL-DTPA-PTX and ^99mTc-SpHL-folate-DTPA-PTX decreased in a monophasic manner showing half-life of 400.1 and 541.8min, respectively. Scintigraphic images and biodistribution studies showed a significant uptake in liver, spleen and kidneys, demonstrating these routes as way for excretion. At 8h post-injection, the liposomal tumor uptake was higher than ^99mTc-PTX. Interesting, 4h after administration, the liposome folate coated showed higher tumor-to-muscle ratio than ^99mTc-SpHL-DTPA-PTX and ^99mTc-PTX. In conclusion, the liposomal systems, showed high tumor uptake by scintigraphic images, especially the ^99mTc-SpHL-folate-DTPA-PTX that showed a sustained and higher tumor-to-muscle ratio than non-functionalized liposome, which indicate its feasibility as a PTX delivery system to folate positive tumors.

Simultaneous quantification of reparixin and paclitaxel in plasma and urine using ultra performance liquid chromatography-tandem mass spectroscopy (UHPLC-MS/MS): Application to a preclinical pharmacokinetic study in rats

A liquid chromatography-tandem mass spectroscopy (LC-MS/MS) assay was developed and validated to simultaneously quantify anticancer drugs reparixin and paclitaxel in this study. The compounds were extracted from plasma and urine samples by protein precipitation with acetone (supplemented with 0.1% formic acid). Chromatographic separation was achieved using a C18 column, and drug molecules were ionized using dual ion source electrospray and atmospheric pressure chemical ionization (DUIS: ESI-APCI). Reparixin and paclitaxel were quantified using negative and positive multiple reaction monitoring (MRM) mode, respectively. Stable isotope palcitaxel-D5 was used as the internal standard (IS). The assay was validated for specificity, recovery, carryover and sample stability under various storage conditions; it was also successfully applied to measure drug concentrations collected from a pharmacokinetic study in rats. The results confirmed that the assay was accurate and simple in quantifying both reparixin and paclitaxel in plasma and urine with minimal sample pretreatment.

In Vitro and In Vivo Evaluation of PEGylated Layer-by-Layer Polyelectrolyte-Coated Paclitaxel Nanocrystals

Drug nanocrystals (NCs) are colloidal dispersions composed almost entirely of drug. As such, there is substantial interest in targeting them to diseased tissues, where they can locally deliver high doses of the therapeutic. However, because of their uncontrolled dissolution characteristics in vivo and uptake by the monomolecular phagocyte system, achieving tumor accumulation is challenging. To address these issues, a layer-by-layer approach is adopted to coat paclitaxel NCs with alternating layers of oppositely charged polyelectrolytes, using a PEGylated copolymer as the top layer. The coating successfully slows down dissolution in comparison to the noncoated NCs and to Abraxane (an approved paclitaxel nanoformulation), provides colloidal stability in physiologically relevant media, and has no intrinsic effect on cell viability at the concentrations tested. Nevertheless, their pharmacokinetic and biodistribution profile indicates that the NCs are rapidly cleared from the bloodstream followed by accumulation in the mononuclear phagocyte system organs (i.e., liver and spleen). This is hypothesized to be a consequence of the shedding of the PEGylated polyelectrolyte from the NCs' surface. While therapeutic efficacy was not investigated (due to poor tumor accumulation), overall, this work questions whether approaches that rely solely on electrostatic interactions for retaining coatings on the surfaces of NCs are appropriate for use in vivo.

Neurotoxicity and low paclitaxel clearance associated with concomitant clopidogrel therapy in a 60-year-old Caucasian woman with ovarian carcinoma

AIM

The aim of the present case report was to describe a novel pharmacokinetic drug–drug interaction between the antiplatelet agent clopidogrel and the antineoplastic agent paclitaxel.

METHODS

The patient was identified in a previously described cohort of 93 patients with ovarian carcinoma treated with paclitaxel. The effect of clopidogrel acyl-β-D-glucuronide on the metabolism of paclitaxel was assessed in human liver microsomes. The analysis of clopidogrel in plasma and the quantification of paclitaxel and 6-hydroxypaclitaxel in in vitro samples were performed by liquid chromatography tandem mass spectrometry.

RESULTS

The patient was a 60-year-old female treated with an unknown dose of clopidogrel at the time of paclitaxel therapy. Clopidogrel was present in all three of the plasma samples obtained during paclitaxel dosing. Estimated unbound paclitaxel clearance was 238 l h−1, which was only 62% of the cohort geometric mean (385 l h−1; range 176–726). She was hospitalized three times, developed severe neuropathy and paclitaxel treatment was subsequently discontinued. In vitro, 30-min preincubation with 100 μM clopidogrel acyl-β-D-glucuronide inhibited the depletion rate of 0.5 μM paclitaxel by 51% and the formation rate of 6-hydroxypaclitaxel by 77%.

CONCLUSION

This is the first report of a clopidogrel–paclitaxel interaction, suggesting that clinically used doses of clopidogrel can reduce the cytochrome P450 2C8 (CYP2C8)-mediated systemic clearance of paclitaxel, leading to an increased risk of paclitaxel toxicity. Caution should be exercised whenever the simultaneous use of paclitaxel and clopidogrel cannot be avoided.

A phase 1 study evaluating the pharmacokinetics and preliminary efficacy of veliparib (ABT-888) in combination with carboplatin/paclitaxel in Japanese subjects with non-small cell lung cancer (NSCLC)

INTRODUCTION

Veliparib is a potent, orally bioavailable PARP inhibitor that enhances efficacy of DNA-damaging chemotherapeutic agents. The study objectives were to determine the recommended phase 2 dose (RPTD) of veliparib plus carboplatin and paclitaxel, and assess pharmacokinetics (PK), tolerability, and preliminary efficacy in Japanese patients with solid tumors.

METHODS

Carboplatin (AUC 6 mg/mL min) and paclitaxel (200 mg/m(2)) were administered on day 3 of a 21-day cycle. Oral veliparib (40, 80, or 120 mg BID) was administered on days 1-7. Patients received ≤6 cycles. Adverse events (AEs) were reported using NCI-CTCAE version 4.03, PK parameters were analyzed using noncompartmental methods, and responses were measured by RECIST version 1.1.

RESULTS

Twelve patients with non-small cell lung cancer (NSCLC) were treated. Common treatment-emergent AEs, consistent with toxicities associated with carboplatin and paclitaxel, included leukopenia (100 %), neutropenia (100 %), anemia (83 %), thrombocytopenia (75 %), increased alanine aminotransferase (67 %), and increased aspartate aminotransferase (67 %). Grade 3/4 AEs (in ≥2 patients) included neutropenia (100 %), leukopenia (33 %), anemia (25 %), and hyponatremia (17 %). No AEs led to veliparib, carboplatin, or paclitaxel interruption; no DLTs were observed. The RPTD was determined to be 120 mg BID. Veliparib C max and AUC were approximately dose proportional. Six partial responses were observed.

CONCLUSIONS

Veliparib PK was not impacted by carboplatin and paclitaxel. The safety profile was manageable. The 120 mg BID RPTD confirmed in Japanese patients is the dose being evaluated in global studies of veliparib. Preliminary efficacy suggests veliparib may enhance carboplatin and paclitaxel activity, providing benefit to patients with NSCLC.

Pharmacokinetic synergy from the taxane extract of Taxus chinensis improves the bioavailability of paclitaxel

BACKGROUND

Taxus chinensis (Pilger) Rehd is widely distributed in China and the northern hemisphere, and the most popular medicinal component isolated from Taxus chinensis is paclitaxel (PTX), which has now become the first-line chemotherapeutic drug for breast cancer and ovarian cancer. Oral administration of pure PTX as a potential anti-cancer agent is compromised by low bioavailability.

HYPOTHESIS/PURPOSE

In the clinical practice of traditional Chinese medicine, drug co-administration in the form of mixtures or formula could achieve pharmacokinetic/pharmacodynamic synergies. In this study, we aimed to investigate whether there exist any 'inherent' phytochemical synergy from Taxus chinensis extract that could improve PTX bioavailability.

STUDY DESIGN

Pharmacokinetic study of PTX after oral administration of Taxus chinensis extracts or single PTX was performed. In addition, comparative cytotoxic studies were carried out on the MCF-7 breast cancer cell lines.

METHODS

The plasma concentrations of PTX were determined using a validated high performance chromatography tandem mass spectrometry method. The cytotoxicity was compared using the MTT assay.

RESULTS

Oral administration of taxane fractions isolated from Taxus chinensis (containing 17.2% PTX) could achieve remarkably higher blood concentration and systemic exposure of PTX in rats, while the retention of PTX was significantly improved. Further tissue distribution analysis revealed that the penetration of PTX into major tissues was drastically increased compared with that of single PTX. In addition, in MCF-7 cells, the co-existing components in taxane mixtures could strengthen the inhibitory effects of PTX on tumor cell proliferation.

CONCLUSION

Together, these results support that administration of PTX in the form of taxane mixtures may become a novel approach to improve the poor bioavailability of PTX. Moreover, the inherent synergy from Taxus chinensis taxane extracts promises a novel strategy to strengthen PTX efficacy.

Safety, pharmacokinetics and efficacy findings in an open-label, single-arm study of weekly paclitaxel plus lapatinib as first-line therapy for Japanese women with HER2-positive metastatic breast cancer

Background

Lapatinib is the human epidermal growth factor receptor 2 (HER2) targeting agent approved globally for HER2-positive metastatic breast cancer (MBC). The efficacy, safety and pharmacokinetics (PK) of lapatinib combined with paclitaxel (L+P) were investigated in this study, to establish clear evidence regarding the combination in Japanese patients.

Methods

In this two-part, single-arm, open-label study, the tolerability of L+P as first-line treatment in Japanese patients with HER2-positive MBC was evaluated in six patients in the first part, and the safety, efficacy and PK were evaluated in a further six patients (making a total of twelve patients) in the second part. Eligible women were enrolled and received lapatinib 1500 mg once daily and paclitaxel 80 mg/m² weekly for at least 6 cycles.

Results

The only dose-limiting toxicity reported was Grade 3 diarrhea in one patient. The systemic exposure to maximum plasma concentration and area under the plasma concentration curve (AUC) for lapatinib, as well as the AUC of paclitaxel, were increased when combined. The most common adverse events (AEs) related to the study treatment were alopecia, diarrhea and decreased hemoglobin. The majority of drug-related AEs were Grade 1 or 2. The median overall survival was 35.6 months (95 % confidence interval 23.9, not reached). The response rate and clinical benefit rate were both 83 % (95 % confidence interval 51.6, 97.9).

Conclusions

The L+P treatment was well tolerated in Japanese patients with HER2-positive MBC. Although the PK profiles of lapatinib and paclitaxel influenced each other, the magnitudes were not greatly different from those in non-Japanese patients.

[Study of bioavailability of paclitaxel after sublingual administration]

The bioavailability of sublingual form of paclitaxel, developed in the pharmacology laboratory of pharmaceutical company - Legion "Provisus" is studied. Sublingual form of paclitaxel is an alcoholic solution of paclitaxel (1 mg/ml) with penetrator - dimethyl sulfoxide (DMSO) addition. Experiments were performed on 180 white mongrel male mice each of 25-30 g. The animals were divided into three groups. The first group served for control. 10 mg/kg of taxol was injected (once) in the lateral tail vein of the first group animals. A solution was prepared by diluting taxol with physiological sodium chloride solution until to a final concentration of paclitaxel to 1 mg/ml. The dose of 10 mg/kg (single dose) was applied under the tongue of the second group animals. Paclitaxel (substance) was extracted with dichloromethane - Taxol (by liquid-liquid extraction) for the manufacturing of a sublingual form. Unlike the second group, the third group animals took the same dose of sublingual form of paclitaxel orally (by gavage). The concentration of paclitaxel in plasma was studied by reversed-phase HPLC with spectrophotometric detection at λ = 227 nm by Woo JS et al. (2003) method. Bioavailability was determined by comparing the concentration of paclitaxel in blood after sublingual and intravenous use of Taxol (as an area under the curve of concentration versus time). It is established that the bioavailability of sublingual forms of paclitaxel was 42.4%, Cmax = 615 ± 73 ng × ml(-1) and tmax = 30-35 min. The value of the initial volume of distribution of paclitaxel (Vd = 3,14 ± 0,85 l × kg(-1)) also shows its intensive penetration to the organs and tissues. The half-life of the drug on the terminal segment of concentration-time curve was averaged 1,06 ± 0,21 h. The results create the preconditions for further preclinical study of sublingual form of paclitaxel, as the bioavailability of paclitaxel after sublingual application allows to have a systemic effect on the tumor process.

Electrochemical determination of the anticancer drug taxol at a ds-DNA modified pencil-graphite electrode and its application as a label-free electrochemical biosensor

In this study a novel biosensor for determination of taxol is described. The interaction of taxol with salmon-sperm double-stranded DNA (ds-DNA) based on the decreasing of the oxidation signals of guanine and adenine bases was studied electrochemically with a pencil-graphite electrode (PGE) using a differential pulse voltammetry (DPV) method. The decreases in the intensity of the guanine and adenine oxidation signals after interaction with taxol were used as indicator signals for the sensitive determination of taxol. DPV exhibits a linear dynamic range of 2.0×10(-7)-1.0×10(-5) M for taxol with a detection limit of 8.0×10(-8) M. Finally, this modified electrode was used for determination of taxol in some real samples.

Comparative in vitro properties and clinical pharmacokinetics of paclitaxel following the administration of Taxol® and Paxene®

PURPOSE

Taxol contains paclitaxel formulated in Cremophor EL-P (CrEL-P) and ethanol. Paxene is similar to Taxol, except for the use of Cremophor EL (CrEL) and the addition of citric acid. Here, we investigated the physicochemical properties and clinical pharmacokinetics of the two paclitaxel formulations.

EXPERIMENTAL DESIGN

The size and modality of distribution of CrEL-P and CrEL micelles was determined by dynamic-light scattering. The effect of vehicle composition on the fraction unbound paclitaxel in vitro was determined by equilibrium dialysis. Paclitaxel pharmacokinetics were studied in 61 cancer patients receiving Taxol and 26 patients receiving Paxene. Comparative pharmacokinetics of CrEL-P and CrEL were obtained in 14 and 6 patients, respectively.

RESULTS

The size of micelles present in Taxol was slightly smaller (9 to 13%) than those present in Paxene. Surface tension and critical micellar concentration were also similar for the two formulations, with mean values of 37.0 and 38.1 mN/m and 0.0387 and 0.0307 mg/mL, respectively. The fraction unbound paclitaxel was not significantly different for Taxol and Paxene (p > 0.05). Over the tested dose range, the mean clearance of paclitaxel decreased from 45.1 to 16.9 L/h for Taxol, and from 50.7 to 16.4 L/h for Paxene (p > 0.05). Concentrations of the excipient following the administration of CrEL-P or CrEL were also similar.

CONCLUSION

The differences in formulation between Taxol and Paxene do not significantly affect micelle formation and/or quantitative aspects of the vehicle-paclitaxel interaction in vitro and in vivo.

SPARC independent drug delivery and antitumour effects of nab-paclitaxel in genetically engineered mice

DESIGN

Pharmacokinetic and pharmacodynamic parameters of cremophor-paclitaxel, nab-paclitaxel (human-albumin-bound paclitaxel, Abraxane) and a novel mouse-albumin-bound paclitaxel (m-nab-paclitaxel) were evaluated in genetically engineered mouse models (GEMMs) by liquid chromatography-tandem mass spectrometry (LC-MS/MS), histological and biochemical analysis. Preclinical evaluation of m-nab-paclitaxel included assessment by three-dimensional high-resolution ultrasound and molecular analysis in a novel secreted protein acidic and rich in cysteine (SPARC)-deficient GEMM of pancreatic ductal adenocarcinoma (PDA).

RESULTS

nab-Paclitaxel exerted its antitumoural effects in a dose-dependent manner and was associated with less toxicity compared with cremophor-paclitaxel. SPARC nullizygosity in a GEMM of PDA, Kras(G12D);p53(flox/-);p48Cre (KPfC), resulted in desmoplastic ductal pancreas tumours with impaired collagen maturation. Paclitaxel concentrations were significantly decreased in SPARC null plasma samples and tissues when administered as low-dose m-nab-paclitaxel. At the maximally tolerated dose, SPARC deficiency did not affect the intratumoural paclitaxel concentration, stromal deposition and the immediate therapeutic response.

CONCLUSIONS

nab-Paclitaxel accumulates and acts in a dose-dependent manner. The interaction of plasma SPARC and albumin-bound drugs is observed at low doses of nab-paclitaxel but is saturated at therapeutic doses in murine tumours. Thus, this study provides important information for future preclinical and clinical trials in PDA using nab-paclitaxel in combination with novel experimental and targeted agents.

Sequentially releasing dual-drug-loaded PLGA-casein core/shell nanomedicine: design, synthesis, biocompatibility and pharmacokinetics

The present study reports an engineered poly-l-lactide-co-glycolic acid (PLGA)-casein polymer-protein hybrid nanocarrier 190±12nm in size entrapping a combination of chemically distinct (hydrophobic/hydrophilic) model drugs. A simple emulsion-precipitation route was adopted to prepare nearly monodispersed nanoparticles with distinct core/shell morphology entrapping paclitaxel (Ptx) in the core and epigallocatechin gallate (EGCG) in the shell, with the intention of providing a sequential and sustained release of these drugs. The idea was that an early release of EGCG would substantially increase the sensitivity of Ptx to cancer, thereby providing improved therapeutics at lower concentrations, with less toxicity. The hemo- and immunocompatibility of the core/shell nanomedicine was established in this study. The core/shell nanoparticles injected via the tail vein in Sprague-Dawley rats did not reveal any organ toxicity as was evident from histopathological evaluations of the major organs. In vivo pharmacokinetic studies in rats by high-performance liquid chromatography confirmed a sustained and sequential release of both the drugs in plasma, indicating prolonged circulation of the nanomedicine and enhanced availability of the drugs when compared to the bare drugs. Overall, the polymer-protein multilayered nanoparticles proved to be a promising platform for nanopolypharmaceutics.

Pharmacokinetics of carbon nanoparticle-paclitaxel suspension for use in intraperitoneal chemotherapy

BACKGROUND/AIMS

To study the pharmacokinetics of carbon nanoparticle-paclitaxel suspension (CNPS) in intraperitoneal chemotherapy.

METHODOLOGY

Thirty-three Wistar rats were randomly assigned to an experimental group (A) and a control group (B), to which intraperitoneal injections of CNPS and paclitaxel were administered, respectively. At time points ranging from 10 min to 7 days, we measured the concentration of paclitaxel in blood, mesenteric lymph nodes and peritoneal lavage.

RESULTS

The ratio of the area under the curve (AUC) in plasma of group A to that of group B was 0.6263. The ratio of AUC in lymph nodes of group A to group B was 0.7495 and that in peritoneal lavage was 1.25. The metabolic half-life of paclitaxel (t1/2) in plasma of group A was 1.607 times as long as that of group B. The t1/2 of paclitaxel in peritoneal lavage of group A was 0.879 as long as that of Group B. The t1/2 of paclitaxel in lymph nodes of group A was 1.097 as long as that of Group B.

CONCLUSIONS

Intraperitoneal chemotherapy by CNPS was characterized by low drug concentration in blood, high drug concentration in peritoneal and high security, but lack of significant lymph targeting and lymphatic retention effect.

[Comparative study on pharmacokinetics and tissue distribution of a novel microemulsion based on the paclitaxel/L-OH lipid complex and paclitaxel injection in cremophor]

The pharmacokinetics and tissue distributions of the novel paclitaxel microemulsion based on the L-OH lipid complex made in our laboratory were studied in this article with the commercial paclitaxel injection in cremophor as reference preparation by injected intravenously with single dose of 5 mg x kg(-1) in rats. LC-MS/MS method was used to determine the drug concentration in plasma and calculate the pharmacokinetic parameters. [3H]-paclitaxel was used to reveal the tissue distributions of different organs in 0.5 h, 3 h, 24 h and 120 h. The results indicated that the AUC of the emulsion group descended to 42.55%, with the CLz and Vz increased by 2.27 times and 3.81 times respectively. Tissue distribution results revealed that the emulsion showed a significantly increase in liver and spleen with a peak concentration up to 5 times; a slightly increase was observed in lung with no statistical differences; a significantly decrease in heart, kidney, gastrointestinal tract, bone marrow, aorta, thymus, pancreas, fat, muscle, skin, seminal vesicle, reproductive organs and brain with a drop of 40%-80%. These results indicated that paclitaxel microemulsion based on L-OH lipid complexes can remarkably reduced the blood exposure, accelerate plasma clearance rate and increase distribution volume. The fact that paclitaxel microemulsion tended to be uptake by reticuloendothelial system (RES) contributed to the target in liver, spleen and lung, and help to reduce the toxicity in blood, heart, kidney and gastrointestinal tract.

A rapid analytical method for the quantification of paclitaxel in rat plasma and brain tissue by high-performance liquid chromatography and tandem mass spectrometry

RATIONALE

Paclitaxel, an antitumor agent for the treatment of several types of cancers, has recently been reported to cause impaired cognitive function and neuropathic pain in humans. To assess the effects of paclitaxel on the central nervous system, a sensitive and accurate method is required to quantify paclitaxel concentrations in plasma and brain tissue obtained from rodents receiving paclitaxel.

METHODS

The biological samples were prepared by liquid-liquid extraction and separated by a 3.5 min reversed-phase liquid chromatography (RPLC) method using a BDS Hypersil C8 column under isocratic conditions. Paclitaxel was quantified using multiple reaction monitoring (MRM) with a triple quadrupole tandem mass spectrometer working in the positive electrospray ionization (ESI+) mode. A stable isotope labeled analogue of paclitaxel was used as the internal standard (IS).

RESULTS

The method was validated to be precise and accurate within the dynamic range of 0.5-100 ng/mL based on 100 μL plasma and 1.5-300 ng/g based on 33 mg of brain tissue in homogenate. This method was applied to samples from 2 mg/kg intravenously dosed rats. The plasma concentrations were observed to be 26.62 ± 8.93 ng/mL and brain concentrations 11.08 ± 4.18 ng/g when measured 4 h post-dose.

CONCLUSIONS

This rapid LC/MS/MS method was validated to be sensitive, specific, precise and accurate for the quantification of paclitaxel in rat plasma and brain tissue homogenate. Application of the method to study samples provided sufficient proof of blood-brain barrier penetration of paclitaxel, allowing further investigation of its influence on the central nervous system.

Quantitative determination of Lx2-32c, a novel taxane derivative, in rat plasma by liquid chromatography-tandem mass spectrometry

A sensitive and reliable LC-MS/MS method for the determination of Lx2-32c, a novel taxane derived from cephalomannine, has been developed and validated. Plasma samples containing Lx2-32c and paclitaxel (internal standard) were prepared based on a simple protein precipitation by the addition of two volumes of acetonitrile. The analyte and internal standard were separated on a Zorbax SB-C18 column (3.5μm, 2.1mm×100mm) with the mobile phase of acetonitrile/water containing 0.1% formic acid (v/v) with gradient elution at a flow rate of 0.2ml/min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) by multiple reactions monitoring (MRM) of the transitions at m/z 887.5→264.3 for Lx2-32c and 854.5→286.2 for IS. Linear detection responses were obtained for Lx2-32c ranging from 1 to 1000ng/ml. Inter- and intra-day precision (R.S.D.%) were all within 15% and the accuracy (R.E.%) was equal or lower than 8%. The lower limit of quantitation (LLOQ) was 1ng/ml and the average recovery was greater than 91.5%. The method was successfully applied to the pharmacokinetic study of Lx2-32c in rat plasma.

Comparative pharmacokinetic study of paclitaxel and docetaxel in streptozotocin-induced diabetic rats

The pharmacokinetics of paclitaxel and docetaxel were compared in diabetic rats induced by streptozotocin (DMIS rats) and the impact of altered expression of cytochrome P450 3A (Cyp3A) and P-glycoprotein (P-gp) in the diabetic state. The pharmacokinetics of paclitaxel and docetaxel were determined after intravenous (5 mg/kg) and oral (30 and 40 mg/kg, respectively) administration to both groups and the mRNA expression levels of Cyp3A isozymes and Mdr1a and Mdr1b in the liver and small intestine were determined in control and DMIS rats. After intravenous administration, the AUC and clearance of paclitaxel and docetaxel were not significantly different in DMIS vs control rats. After oral administration, the AUC and C(max) of paclitaxel in DMIS rats were significantly greater than those in the control rats, whereas those of docetaxel was not changed significantly. The mRNA expression levels of hepatic Cyp3A1, Cyp3A9 and Mdr1b were significantly increased in DMIS compared with the control rats. In the intestine, Cyp3A62 expression decreased in the DMIS rats compared with the controls. Thus the pharmacokinetic changes of taxanes observed in the DMIS rats were attributed to changes in P-gp and Cyp3A, predominant factors that control the absorption of paclitaxel and docetaxel, respectively. It seemed that there were different susceptibilities to intestinal P-gp and Cyp3A between the two taxanes.

A phase I, open-label dose-escalation study of continuous treatment with BIBF 1120 in combination with paclitaxel and carboplatin as first-line treatment in patients with advanced non-small-cell lung cancer

BACKGROUND

BIBF 1120 is an oral potent inhibitor of vascular endothelial growth factor receptor, fibroblast growth factor receptor and platelet-derived growth factor receptor, the three key receptor families involved in angiogenesis. This phase I, open-label dose-escalation study investigated BIBF 1120 combined with paclitaxel (Taxol) and carboplatin in first-line patients with advanced (IIIB/IV) non-small-cell lung cancer.

PATIENTS AND METHODS

Patients received BIBF 1120 (starting dose 50 mg b.i.d.) on days 2-21 and paclitaxel (200 mg/m2) and carboplatin [area under curve (AUC)=6 mg/ml/min] on day 1 of each 21-day cycle. Primary end points were safety and BIBF 1120 maximum tolerated dose (MTD) in this combination. Pharmacokinetics (PK) profiles were evaluated.

RESULTS

Twenty-six patients were treated (BIBF 1120 50-250 mg b.i.d.). BIBF 1120 MTD was 200 mg b.i.d. in combination with paclitaxel and carboplatin. Six dose-limiting toxicity events occurred during treatment cycle 1 (liver enzyme elevations, thrombocytopenia, abdominal pain, and rash). Best responses included 7 confirmed partial responses (26.9%); 10 patients had stable disease. BIBF 1120 200 mg b.i.d. had no clinically relevant influence on the PK of paclitaxel 200 mg/m2 and carboplatin AUC 6 mg/ml/min and vice versa.

CONCLUSIONS

BIBF 1120 MTD was 200 mg b.i.d when given with paclitaxel and carboplatin; this combination demonstrated an acceptable safety profile. No relevant changes in PK parameters of the backbone chemotherapeutic agents or BIBF 1120 were observed.

Figitumumab combined with carboplatin and paclitaxel in treatment-naïve Japanese patients with advanced non-small cell lung cancer

OBJECTIVES

The insulin-like growth factor (IGF) signaling pathway has been implicated in the pathogenesis of numerous tumor types, including non-small cell lung cancer (NSCLC). Figitumumab is a fully human IgG2 monoclonal antibody against IGF-1 receptor (IGF-1R).

METHODS

This phase I, open-label, dose-escalation study (ClinicalTrials.gov: NCT00603538) assessed the safety and tolerability of figitumumab (6, 10 and 20 mg/kg) in combination with carboplatin (area under the curve: 6 mg·min/mL) and paclitaxel (200 mg/m(2)) in Japanese patients (N = 19) with chemotherapy-naïve, advanced NSCLC. Treatments were administered intravenously on day 1 of a 21-day cycle for four to six cycles. Pharmacokinetics, biomarkers, and antitumor activity were also evaluated.

RESULTS

Figitumumab in combination with carboplatin and paclitaxel was well tolerated at doses up to 20 mg/kg; no dose-limiting toxicities were observed at this dose level. When given in combination, figitumumab plasma exposure increased in an approximately dose-proportional manner. The approximate 2-fold accumulation following repeated administration supported the 21-day regimen as appropriate for figitumumab administration. Serum total IGF-1 and IGF binding protein-3 concentrations increased following figitumumab dosing, but a clear dose-dependent relationship was not demonstrated. Seven of 18 evaluable patients experienced a partial response.

CONCLUSIONS

Figitumumab 20 mg/kg in combination with carboplatin and paclitaxel was well tolerated in chemotherapy-naïve Japanese patients with NSCLC. Further analysis of biomarker data is necessary for the development of figitumumab therapy.

[Comparative studies of paclitaxel injection "SAWAI" and Taxol® Injection on pharmacokinetics in dogs and in vitro/vivo antitumor activities]

We performed bioequivalent assessments of the generic (Paclitaxel Injection "SAWAI") and branded (Taxol Injection) formulations of paclitaxel injection on pharmacokinetics in dogs and in vitro/vivo antitumor activities. In the pharmacokinetics study in dogs, the 90% confidence intervals (CIs) for the differences in logarithm of C(max) and AUC(0-48) were log (1.01) to log (1.17) and log (1.01) to log (1.08), respectively. These were within the bioequivalent criteria of log (0.80) to log (1.25). In the in vitro study, both products showed concentration-dependent inhibition of the growth of 5 cultured human cancer cell lines, MCF7 (breast adenocarcinoma), A2780 (ovarian carcinoma), A549 (lung carcinoma), MKN45 (gastric adenocarcinoma) and MKN74 (gastric adenocarcinoma). The 90% CIs for the differences in logarithm of half maximal inhibitory concentration (IC(50)) were log (0.876) to log (1.110), log (0.856) to log (1.097), log (0.977) to log (1.167), log (0.879) to log (1.093) and log (0.936) to log (1.081), respectively. These were within the bioequivalent criteria. In the in vivo study, both products showed concentration-dependent inhibition of the growth of 3 human cancer cells, A2780 (ovarian carcinoma), A549 (lung carcinoma) and MDA-MB-231 (breast adenocarcinoma), xenografted in nude mice. And there are no significant differences between Paclitaxel Injection "SAWAI" and Taxol Injection. These results showed that Paclitaxel Injection "SAWAI" is bioequivalent to Taxol Injection.

Paclitaxel in self-micro emulsifying formulations: oral bioavailability study in mice

The anticancer drug paclitaxel is formulated for i.v. administration in a mixture of Cremophor EL and ethanol. Its oral bioavailability is very low due to the action of P-glycoprotein in the gut wall and CYP450 in gut wall and liver. However, proof-of-concept studies using the i.v. formulation diluted in drinking water have demonstrated the feasibility of the oral route as an alternative when given in combination with inhibitors of P-glycoprotein and CYP450. Because of the unacceptable pharmaceutical properties of the drinking solution, a better formulation for oral application is needed. We have evaluated the suitability of various self-micro emulsifying oily formulations (SMEOF’s) of paclitaxel for oral application using wild-type and P-glycoprotein knockout mice and cyclosporin A (CsA) as P-glycoprotein and CYP450 inhibitor. The oral bioavailability of paclitaxel in all SMEOF’s without concomitant CsA was low in wild-type mice, showing that this vehicle does not enhance intestinal uptake by itself. Paclitaxel (10 mg/kg) in SMEOF#3 given with CsA resulted in plasma levels that were comparable to the Cremophor EL-ethanol containing drinking solution plus CsA. Whereas the AUC increased linearly with the oral paclitaxel dose in P-glycoprotein knockout mice, it increased less than proportional in wild-type mice given with CsA. In both strains more unchanged paclitaxel was recovered in the feces at higher doses. This observation most likely reflects more profound precipitation of paclitaxel within the gastro-intestinal tract at higher doses. The resulting absolute reduction in absorption of paclitaxel from the gut was possibly concealed by partial saturation of first-pass metabolism when P-glycoprotein was absent. In conclusion, SMEOF’s maybe a useful vehicle for oral delivery of paclitaxel in combination with CsA, although the physical stability within the gastro-intestinal tract remains a critical issue, especially when applied at higher dose levels.

Disposition kinetics of taxanes after intraperitoneal administration in rats and influence of surfactant vehicles

Rats were intraperitoneally administered 40 mg kg−1 of paclitaxel or docetaxel dissolved in various drug solutions. The drug solutions were prepared using 20 mL of saline, adding 4.2% Cremophor EL (crEL) for paclitaxel (TXL), and 1.5% Polysorbate-80 (PS-80) (TXT), 7.5% PS-80 (TXT+PS-80) or 4.2% crEL (TXT+crEL) for docetaxel. The apparent first-order absorption rate constant from the peritoneal cavity (ka) of TXL was about one-twentieth of that of TXT. The ratio of the area under the concentration-time curve of drug in plasma over that in ascites for TXL was about one-third of that of TXT. The values of the above ratio and the ka of TXT+PS-80 and TXT+crEL were similar to those of TXL. After intraperitoneal administration, the values of the blood-to-plasma concentration ratio in the four groups were similar and independent of time. In the in-vitro study, PS-80 and crEL caused similar, concentration-dependent decreases of drug permeation into red blood cells after a 15-min incubation of rat blood with 10 μg mL−1 of TXL. We demonstrated that the disposition kinetics of taxanes after intraperitoneal administration to rats was strongly influenced, in a concentration-dependent manner, by the surfactant vehicle used, crEL or PS-80.

Significance of urinary glucaric acid measurement and its application to paclitaxel therapy

Individual variations in P-450 activity affect the in vivo pharmacokinetics as well as the efficacy and side effect of drugs. It is proposed that urinary glucaric acid (GA) level may indirectly represent P-450 activity and may therefore be an indicator of P- 450 activity in the clinical setting. However, no standard method has been developed so far. Metabolism of paclitaxel (PTX), an anticancer drug, is mediated by P-450. If P-450 activity could be predicted by measuring urinary GA level during PTX administration and individual blood PTX concentration could be inferred, urinary GA level would be a potent tool to predict the efficacy and side effects of the drug. We therefore measured the urinary GA levels of patients on antiepileptics that are suggested to induce P-450 and those of control subjects, to determine whether urinary GA level could be an indicator of P-450 activity. Then, we examined the relationship between urinary GA level and blood PTX concentration and looked into the possibility of predicting pharmacokinetics based on the relationship between urinary GA level and area under the blood concentration-time curve (AUC). The means+/-S. D. of urinary [(GA level)/(Cr level) x 10] levels of 16 patients on antiepileptic medication and 24 control subjects were 0. 98 mg/mL+/-0. 91 and 0. 19 mg/mL+/-0. 07, respectively. The urinary GA levels of patients on antiepileptic medication were significantly higher than those of control subjects. On the other hand, the relationship between AUC and urinary GA levels in eight patients on PTX showed that AUC tended to become large when urinary GA levels were low. The above results reveal that measuring urinary GA level by the easy and noninvasive way of urine collection would enable us to predict P-450 activity and infer blood PTX concentration.

[Pilot study of neo-adjuvant chemotherapy involving intraperitoneal administration of paclitaxel and oral S-1 for patients with T3 gastric cancer]

The prognosis of patients with T3 gastric cancer is poor, even if a curative resection is performed. Novel combination neo-adjuvant chemotherapy has been introduced for T3 gastric cancer patients. This pilot study involving 5 patients was performed between December 2002 and March 2003. They were diagnosed with gastric cancer with serosal invasion (T3) without P1 and CY1 by staging laparoscopy. We selected a combined chemotherapy with both paclitaxel and S-1. Paclitaxel at 60 mg/m2 was administered intraperitoneally on days 1 and 8, and S-1 at 80 mg/m2 was administered orally for 14 days followed by a 7-day-rest, as one course. After one course of this therapy, surgery was performed. The plasma concentration of paclitaxel was measured in two patients. Toxicites were generally mild, and no serious adverse reactions were observed. The plasma concentration of paclitaxel was about 100 ng/mL in the period of 1-6 hours after the administration. After one course, four patients underwent a total gastrectomy and one distal gastrectomy. The final histological stagings were included one stage IB, one stage II, one stage IIIA, one stage IIIB, and one stage IV. Three patients died at 10, 11, and 16 months after the initial treatment, and two have survived for 64 and 62 months. As the intraperitoneal administration of paclitaxel and oral S-1 was well-tolerated, further studies should be conducted involving T3 gastric cancer patients.

Quantitative determination of total and unbound paclitaxel in human plasma following Abraxane treatment

A simple, rapid liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay was developed and validated for the quantification of both unbound and total paclitaxel in plasma following treatment with Abraxane (ABI-007) or Taxol. Accurate and reproducible analysis of ABI-007, an albumin nanoparticle formulation of paclitaxel could not be achieved using previously published methodology designed for Taxol. The final validated method involved protein precipitation followed by vacuum filtration, in a 96-well format for rapid processing. The 4min run employed gradient elution on a Waters SymmetryShield C8 (2.1mmx50mm, 3.5microm) column, followed by tandem mass spectrometric detection, in electrospray positive mode. Calibrator samples were prepared daily with paclitaxel and analyzed with both ABI-007 and paclitaxel quality control samples. To measure unbound drug, sample preparation was preceded by ultrafiltration. The assay was linear over the range of 10-2500ng/mL, with dilution providing measurement up to 50,000ng/mL. Within-run and between-run precision for all QC samples was less than 5.0% and 10.4%, respectively. Accuracy was high, with deviation of less than 6.1% for all QCs. Measurement of unbound paclitaxel was precise (BRP and WRP <10%).

Effect of genistein on the pharmacokinetics of paclitaxel administered orally or intravenously in rats

As many anticancer agents paclitaxel is a substrate for ATP-binding cassette (ABC) transporters such as P-glycoprotein-mediated efflux, and its metabolism in humans mainly catalyzed by CYP 3A4 and 2C8. Genistein, an isoflavonoid, is supposed to be an inhibitor of some ABC transporters, and its oxidative metobolism catalyzed by CYP 3A4 and 2C8. The purpose of this study was to investigate the effect of orally administered genistein on the pharmacokinetics of paclitaxel administered through oral and intravenous (i.v.) route in rats. A single dose of paclitaxel administered orally (30 mg/kg) or i.v. (3mg/kg) alone or 30 min after oral administration of genistein (3.3mg/kg or 10mg/kg). The presence of 10mg/kg genistein significantly (p<0.05) increased the area under the plasma concentration-time curve (AUC, 54.7% greater) of orally administered paclitaxel, which was due to the significantly (p<0.05) decreased total plasma clearance (CL/F) of paclitaxel (35.2% lower). Genistein also increased the peak concentration (C(max)) of paclitaxel significantly (p<0.05 by 3.3mg/kg, 66.8% higher; p<0.01 by 10mg/kg, 91.8% higher). Consequently, the absolute bioavailability (F) of paclitaxel in the presence of genistein was 0.020-0.025, which was elevated more than the control group (0.016); and the relative bioavailability (Fr) of orally administered paclitaxel was increased from 1.26- to 1.55-fold. Ten milligrams per kilogram genistein also significantly (p<0.05) increased the AUC (40.5% greater) and reduced the total clearance (CLt, 30% lower) of i.v. administered paclitaxel. The presence of genistein improved the systemic exposure of paclitaxel in this study. The pharmacokinetic interaction between them should be taken into consideration when paclitaxel is used with genistein or the dietary supplements full of genistein.

Preparation and evaluation of paclitaxel-loaded PEGylated immunoliposome

A sterically stabilized paclitaxel-loaded liposome tailored to target human breast cancer cells was developed, thereby promoting the efficiency of intracellular delivery of paclitaxel through receptor-mediated endocytosis. Results indicated that the targeting moiety (thiolated Herceptin) was successfully coupled to the distal reactive maleimide terminus of the poly (ethylene glycol)-phospholipid conjugate as well as being incorporated in the liposomal bilayers. The particle size of the PEGylated immunoliposome was maintained at about 200 nm. Confocal microscopy studies showed that the PEGylated immunoliposome was uptaken into the interior of the tumor cell through the receptor-mediated endocytosis pathway. The PEGylated immunoliposome showed substantially higher cellular uptake than the PEGylated liposome in cancer cells (BT-474 and SK-BR-3) over-expressing human epidermal growth factor receptor 2 (HER2) at 37 degrees C, while no difference was found in low HER2 expressing cells (MDA-MB-231) nor at low temperature (4 degrees C). Pharmacokinetics of paclitaxel in the PEGylated immunoliposome was compared with that in Taxol and in the PEGylated liposome in rats. The circulating time of paclitaxel in the PEGylated immunoliposome was prolonged compared to Taxol while slightly shortened than that in the PEGylated liposome. Therefore, the paclitaxel-loaded PEGylated immunoliposome using Herceptin could serve as a promising model for future tumor specific cancer therapy of HER2 over-expressing breast cancers.

Synthesis, characterization and in vitro cytotoxicity studies of a macromolecular conjugate of paclitaxel bearing oxytocin as targeting moiety

The present study describes the experimental synthetic procedure and the characterization of a new polyaspartamide macromolecular prodrug of paclitaxel, bearing oxytocin residues as targeting moieties. In vitro stability studies of bioconjugate, performed in media mimicking biological fluids (buffer solutions at pH 7.4 and 5.5) and in human plasma, evidenced the high stability of the targeting portion (oxytocin)-polymer linkage and the ability of this conjugate to release linked paclitaxel in a prolonged way in plasma. Moreover, preliminary in vitro antiproliferative studies, carried out on MCF-7 cells, that are oxytocin receptor positive cells, showed that the polymeric conjugate has the same cell growing inhibition ability of free drug.

Pharmacokinetic study of weekly administration dose of paclitaxel in patients with advanced or recurrent gastric cancer in Japan

BACKGROUND

We aimed to clarify the relationship between the maximum tolerated dose and plasma concentration of paclitaxel in Japanese patients with gastric cancer on a weekly paclitaxel administration regimen.

METHODS

Thirty-three patients with advanced or recurrent gastric cancer were treated with escalating doses of paclitaxel, administered weekly, along with a fixed dose of 5-fluorouracil or cisplatin.

RESULTS

The plasma concentration of paclitaxel remained above 8.5 ng/ml for 24 h after administration. The mean area under the curve increased significantly with escalating dosage levels (R = 0.63; P 0.001). At level 4, patients showing dose-limiting toxicity had a significantly higher plasma paclitaxel concentration than patients without it.

CONCLUSION

The weekly administration of paclitaxel, for which a single dose is about one-third of the dose for a tri-weekly treatment regimen, is clinically feasible and appropriate in terms of toxicity and the maintenance of an effective plasma concentration.

Development of a Physiology-Based Whole-Body Population Model for Assessing the Influence of Individual Variability on the Pharmacokinetics of Drugs

In clinical development stages, an a priori assessment of the sensitivity of the pharmacokinetic behavior with respect to physiological and anthropometric properties of human (sub-) populations is desirable. A physiology-based pharmacokinetic (PBPK) population model was developed that makes use of known distributions of physiological and anthropometric properties obtained from the literature for realistic populations. As input parameters, the simulation model requires race, gender, age, and two parameters out of body weight, height and body mass index. From this data, the parameters relevant for PBPK modeling such as organ volumes and blood flows are determined for each virtual individual. The resulting parameters were compared to those derived using a previously published model (P(3)M). Mean organ weights and blood flows were highly correlated between the two models, despite the different methods used to generate these parameters. The inter-individual variability differed greatly especially for organs with a log-normal weight distribution (such as fat and spleen). Two exemplary population pharmacokinetic simulations using ciprofloxacin and paclitaxel as model drugs showed good correlation to observed variability. A sensitivity analysis demonstrated that the physiological differences in the virtual individuals and intrinsic clearance variability were equally influential to the pharmacokinetic variability but were not additive. In conclusion, the new population model is well suited to assess the influence of individual physiological variability on the pharmacokinetics of drugs. It is expected that this new tool can be beneficially applied in the planning of clinical studies.

Determination of paclitaxel in human and rat blood samples after administration of low dose paclitaxel by HPLC-UV detection

A simple and sensitive HPLC-UV method was developed for the determination of paclitaxel (TXL) in human and rat blood samples. 4-Hydroxybenzoic acid n-hexyl ester was used as an internal standard. TXL was extracted by a liquid-liquid extraction with tert-butylmethyl ether. The disturbing peaks in the case of serum sample were removed by pre-extraction with hexane. The separation of TXL was achieved within 25 min using an ODS column with 50% acetonitrile aqueous solution as a mobile phase at a flow rate of 1.0 mL/min. The eluent was monitored at 230 nm, and the resulted retention times of TXL and IS were 11.2 and 20.4 min. The detection limits of TXL for human plasma, serum and rat plasma samples at a signal-to-noise ratio of 3 were 10, 9.5 and 7.5 ng/mL, respectively. The proposed methods were applicable to the determination of TXL in human patients' plasma ranging from 15 to 27 ng/mL. Furthermore, monitoring of the time course of TXL after its single administration to rat could be demonstrated.

[The inhibitory effect of paclitaxel nanoparticles on ovarian cancer xenografts and lymphatic targeting]

OBJECTIVE

To develop a polymeric drug delivery system for paclitaxel and determine whether paclitaxel can inhibit the growth of ovarian carcinoma xenografts in F344 rats by intraperitoneal administration.

METHODS

Paclitaxel loading nanoparticles (PLA) were synthesized by ultrasonic emulsification; rat ovarian carcinoma cells were injected into the peritoneal cavity of F344 rats. The antitumor effect of paclitaxel nanoparticles in vivo has been evaluated by measuring tumor weight and ascite volume. At the end of the procedure the rats were killed, tumors were excised and processed for PCNA staining, tissue terminal deoxynucleotide transferase-mediated dUTP nick and labeling (TUNEL) assay. Paclitaxel concentration in plasma, pelvic lymph nodes, liver, heart were determined by high-performance liquid chromatography (HPLC).

RESULTS

In the implanted carcinoma cells, paclitaxel nanoparticles significantly reduced tumor weight [(4.55 +/- 0.11) g vs (10.13 +/- 0.52) g]and ascites volume [(3.55 +/- 0.50) mL vs (30.45 +/- 1.55) mL], and induced apoptosis of tumor cells [(105 +/- 15) vs (55 +/- 10)]. The paclitaxel concentration of pelvic lymph nodes in PLA treated animals was significantly higher than that of free PTX treated animals 48 h after intraperitoneal administration [(0.75 +/- 0.05) microg/g vs (0.188 +/- 0.045) microg/g].

CONCLUSION

The intraperitoneal administration of paclitaxel nanoparticles can significantly inhibit the progression of ovarian carcinoma in peritoneal cavity of female F344 rats. The paclitaxel nanoparticle is safe and lymphatic targeting.

Altered pharmacokinetics of paclitaxel by the concomitant use of morin in rats

The purpose of this study was to investigate the effect of morin on the pharmacokinetics of orally and intravenously administered paclitaxel in rats. Pharmacokinetic parameters of paclitaxel were determined in rats after an oral (30 mg kg(-1)) or intravenous (3 mg kg(-1)) administration of paclitaxel to rats in the presence and absence of morin (3.3 and 10 mg kg(-1)). Compared to the control given paclitaxel alone, pretreatment with morin 30 min prior to the oral administration of paclitaxel increased C(max) and AUC of paclitaxel by 70-90% and 30-70%, respectively, while there was no significant change in T(max) and terminal plasma half-life (T(1/2)) of paclitaxel. Consequently, absolute and relative bioavailability values of paclitaxel in the rats after the pretreatment with morin were significantly higher (p<0.05) than those from the control. In contrast, following an intravenous administration of paclitaxel (3.3 mg kg(-1)), the pharmacokinetic profiles of paclitaxel were not altered significantly in the presence of morin. Those results suggest that the enhanced oral exposure of paclitaxel should be mainly due to the inhibition effect of morin on the gastrointestinal extraction of paclitaxel during the intestinal absorption. Therefore, the concurrent use of morin or morin-containing dietary supplement may provide a therapeutic benefit in the oral delivery of paclitaxel.

Improved oral delivery of paclitaxel following administration in nanoemulsion formulations

Nanoemulsion formulations were designed for enhancing the oral bioavailability of hydrophobic drugs. Paclitaxel was selected as a model hydrophobic drug, which is also a substrate for the P-glycoprotein efflux system. The oil-in-water (o/w) nanoemulsions were formulated with pine nut oil as the internal oil phase, egg lecithin as the primary emulsifier, and water as the external phase. Stearylamine and deoxycholic acid were used to impart positive and negative charge to the emulsions, respectively. Nanoemulsions were prepared by sonication method and characterized for particle size and surface charge. The control and nanoemulsion formulations with tritiated [3H]-paclitaxel were administered orally to female C57BL/6 mice and the distribution of the drug was examined. The formulated nanoemulsions had a particle size range of approximately 90-120 nm (laser diffraction method) and zeta potential values ranging from -56 mV to +34 mV. Following oral administration, a significantly higher concentration of paclitaxel was observed in the systemic circulation when administered in the nanoemulsion relative to control aqueous solution. The absorbed drug was found to be distributed in the liver, kidneys, and lungs. The results of this study suggest that nanoemulsions are promising novel formulations that can enhance the oral bioavailability of hydrophobic drugs, like paclitaxel.

Effects of paclitaxel, docetaxel and their combinations on subcutaneous lymphomas in inbred Sprague-Dawley/Cub rats

We investigated, whether the effects on paclitaxel, docetaxel or their combinations on T-cell lymphomas in Sprague-Dawley/Cub rats were mainly caused by their different efficiency or combination of different mechanism of action, or limited by metabolic inactivation by P450 enzymes or drug efflux caused by P-glycoprotein (P-gp). Docetaxel most effectively prolonged the survival of rats and the time of lymphoma appearance, inhibited their intravital size and weight after sacrifice. Paclitaxel was poorly effective and combined administration had intermediate effects. Blood levels of both drugs were similar. Repeated administration of paclitaxel, but not docetaxel, decreased its area under concentration, but the effect disappeared 6h after dosing and was not sufficient to explain lower effects of paclitaxel. The faster metabolism of docetaxel than paclitaxel in vitro did not limit its higher efficiency and repeated administration of paclitaxel did not induce its metabolism to decrease its blood levels sufficiently. Likewise, undetectable expression of P-gp protein in tumours could not explain lower effects of paclitaxel, which is a better substrate of P-gp. Docetaxel was three-fold more effective than paclitaxel against P388D1 lymphoma cell line, used as a model of the T-cell lymphoma and combined action was dominated by the effects of docetaxel. Thus, docetaxel was effective against T-cell lymphomas and may be a potential anticancer drug in similar indications.

Effect of the ET(B) receptor agonist, IRL-1620, on paclitaxel plasma pharmacokinetics of breast tumor rats

Endothelin (ET)-B receptors are expressed in human breast carcinoma. We previously demonstrated that intravenous administration of the ET(B) receptor agonist, IRL-1620, to tumor-bearing rats, increased blood perfusion and enhanced delivery of paclitaxel to breast tumor tissue. The present study was conducted to determine whether IRL-1620 alters the pharmacokinetics of paclitaxel. Breast tumor-bearing rats were given 0.3 ml/kg saline or 3 nmol/kg IRL-1620 by intravenous (iv) administration. Fifteen minutes after saline or IRL-1620, 40 microCi/rat 3H-Paclitaxel was administered iv and serial plasma samples were collected until 24 hrs. 3H-Paclitaxel radioactivity in the plasma samples was measured by liquid scintillation counting. Data were fit to a three-compartment model and pharmacokinetic parameters were generated using WinNonlin software. IRL-1620 did not produce any change in the plasma paclitaxel pharmacokinetics of tumor-bearing rats. The AUC(0-infinity) (9.43 +/- 3.18 microg-hr/ml), clearance (0.69 +/- 0.17 l/hr/kg), volume of distribution (10.31 +/- 4.54 l/kg), and half-life (1.0 +/- 0.32 hrs) of paclitaxel were similar between rats treated with saline or IRL-1620. In conclusion, the ET(B) receptor agonist, IRL-1620, does not alter paclitaxel plasma pharmacokinetics and, therefore, could be used to augment the delivery of paclitaxel to the tumor tissue.

Genetic variation in ABCB1 influences paclitaxel pharmacokinetics in Japanese patients with ovarian cancer

Paclitaxel, an antineoplastic agent used for the treatment of ovarian cancer, is metabolized by cytochrome P450 (CYP)3A4 and CYP2C8 and is excreted from cells by ATP-binding cassette (ABCB1) (multi-drug resistance [MDR1], P-glycoprotein). Expression of these proteins is regulated by pregnane X receptor (PXR). Although there are common genetic polymorphisms in the genes encoding these proteins, their effect on the clinical efficacy of paclitaxel is unclear. We therefore examined the relationship of the paclitaxel pharmacokinetics in 13 patients with ovarian cancer to polymorphisms in CYP2C8, CYP3A5, ABCB1, and PXR. We found high interindividual variability in the plasma concentrations of two metabolites, 6alpha-hydroxypaclitaxel and p-3'-hydroxypaclitaxel. All the patients were genotyped as CYP2C8*1/*1. Neither the CYP3A5 A6986G (CYP3A5*3) nor the PXR C-25385T alleles were associated with altered plasma concentrations of paclitaxel and its metabolites. ABCB1 T-129C, T1236C, and G2677(A,T), however, was associated with lower area under the plasma concentration-time curve (AUC) of paclitaxel. We also observed a significant correlation between the AUC (r=-0.721) or the total clearance of paclitaxel (CL(tot)) (r= 0.673) and the ABCB1 mutant allele dosage in each patient. Taken together, our findings suggest that interindividual variability in paclitaxel pharmacokinetics could be predicted by ABCB1 genotyping.

Determination of paclitaxel in rat plasma by LC-MS-MS

A simple, rapid, and sensitive liquid chromatography-mass spectrometry (MS)-MS method for quantitating paclitaxel in rat plasma is developed. Liquid-liquid extraction with tert-butyl methyl ether is used for sample preparation, and docetaxel is used as the internal standard. Paclitaxel and docetaxel are separated on a C18 column and quantitated using a triple-quadrupole MS operating in positive ion electrospray selective reaction monitoring mode with a total run time of 6.0 min. The peak area of the m/z 876.3 --> 307.9 transition of paclitaxel is measured versus that of the m/z 830.3 --> 549.1 transition of docetaxel to generate the standard curve. The standard curve is linear over the concentration range of 0.2008-1004 ng/mL for rat plasma. The method has high extraction recovery (> 90%) and accuracy (> 90%), with the intra- and interday precision < 15%. Frozen stability, freeze-and-thaw stability, extracted stability, and room temperature solution stability are also examined. This assay is used to support a pharmacokinetic study of paclitaxel self-assembled nanoliposome in rats.

In vivo pharmacokinetic and tissue distribution studies in mice of alternative formulations for local and systemic delivery of Paclitaxel: gel, film, prodrug, liposomes and micelles

The aim of this study was to increase the understanding on the pharmacokinetic and tissue distribution of paclitaxel as influenced by formulation approach. For this purpose, various formulations investigated in Swiss mice included liposomes, poloxamer 407 gel and chitosan film for subcutaneous route; and water-soluble methacrylate prodrug, liposomes and poloxamer micelles for systemic administration. During this study, the currently marketed formulation of Cremophor EL of paclitaxel was used as the reference. A highest plasma concentration following intravenous administration of paclitaxel was observed for rigid and 'Stealth((R))' liposomes containing the prodrug while, least was for covalently incorporated paclitaxel micelles. Further, poloxamer micelles demonstrated both the highest mean residence time of 7.34 h and volume of distribution (VSS=4.82 and VZ=5.87 L/kg) for paclitaxel. This was followed by prodrug loaded 'Stealth' liposomes, which showed a mean residence time of 4.96 h but were least distributed into apparent physiological volume (VSS=2.12 and VZ=3.16 L/kg). These results clearly signify the role of formulation/excipient in drug disposition and possible interactions. Importantly, due to decrease in the clearance rate of drug, the area under curve values of paclitaxel increased by 1.64- and 2.5-fold for micellar and prodrug loaded 'Stealth' liposomal formulations, respectively over reference formulation. While thermoreversible gels served to decrease plasma concentration of paclitaxel (8-fold) after subcutaneous administration, systemic levels were totally absent after implantation of films. In tissue distribution studies, maximum percent of paclitaxel was observed in liver for reference formulation, conventional liposomes and micelles whereas highest levels of prodrug and 'Stealth((R))' liposomes were in kidney and spleen, respectively. The novel formulations significantly altered tissue accumulation profiles of paclitaxel relative to the reference formulation, for example, reduction in uptake by heart from liposomes and micelles, as well as the major recognition mechanism for elimination. It is proposed that a combination therapy with liposomes and micelles of paclitaxel for systemic delivery along with implantation of chitosan film for local delivery, may serve not only to improve patient compliance by obliterating the need to administer Cremophor EL, but also increase patient survival.

Determination of Docetaxel and Paclitaxel in Human Plasma by High-Performance Liquid Chromatography

Taxanes, docetaxel and paclitaxel, represent important antineoplastic agents with broad spectra of antitumor activity. The authors developed and validated a high-performance liquid chromatography method with ultraviolet detection for quantifying both taxanes in human plasma. The assay uses liquid-liquid extraction as sample treatment and an isocratic mobile phase and reversed-phase chromatography to determine docetaxel with paclitaxel as internal standard and vice versa. The lower limit of quantification was 0.015 mg/L. The assay had good recovery (87.96+/-14.05 and 90.57+/-9.63 for docetaxel and paclitaxel respectively) and precision: the within-day and between-days relative standard deviation of the mean for docetaxel (0.015-3 mg/L) and paclitaxel was always <10%. The method presented has been fully validated following the U.S. Food and Drug Administration requirements and has been successfully applied for the pharmacokinetic investigation of docetaxel or paclitaxel.