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

Overcoming the blood–brain barrier: the role of nanomaterials in treating neurological diseases

Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood–brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial‐based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease‐targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial‐mediated treatment of neurological diseases

Pharmacokinetics and tissue distribution of PGG–paclitaxel, a novel macromolecular formulation of paclitaxel, in nu/nu mice bearing NCI-460 lung cancer xenografts

PGG–PTX is a water-soluble formulation of paclitaxel (PTX), made by conjugating PTX to poly(l-γ-glutamylglutamine) acid (PGG) via ester bonds, that spontaneously forms a nanoparticle in aqueous environments. The purpose of this study was to compare the pharmacokinetics and tissue distribution of PTX following injection of either free PTX or PGG–PTX in mice. Both [3H]PTX and PGG–[3H]PTX were administered as an IV bolus injection to mice bearing SC NCI-H460 lung cancer xenografts at a dose of 40-mg PTX equivalents/kg. Plasma, tumor, major organs, urine, and feces were collected at intervals out to 340 h. Total taxanes, taxane extractable into ethyl acetate, and native PTX were quantified by liquid scintillation counting and HPLC. Conjugation of PTX to the PGG polymer increased plasma and tumor C max, prolonged plasma half-life and the period of accumulation in tumor, and reduced washout from tumor. In plasma injection of PGG–PTX increased total taxane AUC0–340 by 23-fold above that attained with PTX. In tumors, it increased the total taxane by a factor of 7.7, extractable taxane by 5.7, and native PTX by a factor of 3.5-fold. Conjugation delayed and reduced total urinary and fecal excretion of total taxanes. Incorporation of PTX into the PGG–PTX polymer significantly prolonged the half-life of total taxanes, extractable taxane, and native PTX in both the plasma and tumor compartments. This resulted in a large increase in the amount of active PTX delivered to the tumor. PGG–PTX is an attractive candidate for further development

Efficacy assessment of sustained intraperitoneal paclitaxel therapy in a murine model of ovarian cancer using bioluminescent imaging

We evaluated the pre-clinical efficacy of a novel intraperitoneal (i.p.) sustained-release paclitaxel formulation (PTXePC) using bioluminescent imaging (BLI) in the treatment of ovarian cancer. Human ovarian carcinoma cells stably expressing the firefly luciferase gene (SKOV3Luc) were injected i.p. into SCID mice. Tumour growth was evaluated during sustained or intermittent courses of i.p. treatment with paclitaxel (PTX). In vitro bioluminescence strongly correlated with cell survival and cytotoxicity. Bioluminescent imaging detected tumours before their macroscopic appearance and strongly correlated with tumour weight and survival. As compared with intermittent therapy with Taxol®, sustained PTXePC therapy resulted in significant reduction of tumour proliferation, weight and BLI signal intensity, enhanced apoptosis and increased survival times. Our results demonstrate that BLI is a useful tool in the pre-clinical evaluation of therapeutic interventions for ovarian cancer. Moreover, these results provide evidence of enhanced therapeutic efficacy with the sustained PTXePC implant system, which could potentially translate into successful clinical outcomes

Natural and Synthetic Polymers as Inhibitors of Drug Efflux Pumps

Inhibition of efflux pumps is an emerging approach in cancer therapy and drug delivery. Since it has been discovered that polymeric pharmaceutical excipients such as Tweens® or Pluronics® can inhibit efflux pumps, various other polymers have been investigated regarding their potential efflux pump inhibitory activity. Among them are polysaccharides, polyethylene glycols and derivatives, amphiphilic block copolymers, dendrimers and thiolated polymers. In the current review article, natural and synthetic polymers that are capable of inhibiting efflux pumps as well as their application in cancer therapy and drug delivery are discussed

Pre-, on- and post-column derivatization in capillary electrophoresis.

This survey gives a short overview of the various reagents and procedures that can be used for pre-, post- and on-column derivatization in capillary electrophoresis. First there is an introduction about capillary electrophoresis as an analytical technique; this is followed by a discussion of the pros and cons of the various modes of derivatization and a comparison with liquid chromatography. In the following paragraphs the reagents for a number of functional groups are discussed. The emphasis is on derivatization of the amine group. Most of the information on the reagents and derivatization procedures is listed in tables together with information on the detection mode, analytes, sensitivity and samples. In addition to the amino group, information is given on labeling of aldehyde, keto, carboxyl, hydroxyl and sulfhydryl groups

Oral co-administration of elacridar and ritonavir enhances plasma levels of oral paclitaxel and docetaxel without affecting relative brain accumulation

BACKGROUND: The intestinal uptake of the taxanes paclitaxel and docetaxel is seriously hampered by drug efflux through P-glycoprotein (P-gp) and drug metabolism via cytochrome P450 (CYP) 3A. The resulting low oral bioavailability can be boosted by co-administration of P-gp or CYP3A4 inhibitors. METHODS: Paclitaxel or docetaxel (10 mg/kg) was administered to CYP3A4-humanised mice after administration of the P-gp inhibitor elacridar (25 mg kg(-1)) and the CYP3A inhibitor ritonavir (12.5 mg kg(-1)). Plasma and brain concentrations of the taxanes were measured. RESULTS: Oral co-administration of the taxanes with elacridar increased plasma concentrations of paclitaxel (10.7-fold, P<0.001) and docetaxel (four-fold, P<0.001). Co-administration with ritonavir resulted in 2.5-fold (paclitaxel, P<0.001) and 7.3-fold (docetaxel, P<0.001) increases in plasma concentrations. Co-administration with both inhibitors simultaneously resulted in further increased plasma concentrations of paclitaxel (31.9-fold, P<0.001) and docetaxel (37.4-fold, P<0.001). Although boosting of orally applied taxanes with elacridar and ritonavir potentially increases brain accumulation of taxanes, we found that only brain concentrations, but not brain-to-plasma ratios, were increased after co-administration with both inhibitors. CONCLUSIONS: The oral availability of taxanes can be enhanced by co-administration with oral elacridar and ritonavir, without increasing the brain penetration of the taxanes