Chemical Modification of Paclitaxel (Taxol) Reduces P-Glycoprotein Interactions and Increases Permeation across the Blood−Brain Barrier in Vitro and in Situ

Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States
Journal of Medicinal Chemistry (Impact Factor: 5.45). 03/2005; 48(3):832-8. DOI: 10.1021/jm040114b
Source: PubMed


The purpose of this work was to introduce a chemical modification into the paclitaxel (Taxol) structure to reduce interactions with the product of the multidrug resistant type 1 (MDR1) gene, P-glycoprotein (Pgp), resulting in improved blood-brain barrier (BBB) permeability. Specifically, a taxane analogue, Tx-67, with a succinate group added at the C10 position of Taxol, was synthesized and identified as such a candidate. In comparison studies, Tx-67 had no apparent interactions with Pgp, as demonstrated by the lack of enhanced uptake of rhodamine 123 by brain microvessel endothelial cells (BMECs) in the presence of the agent. By contrast, Taxol exposure substantially enhanced rhodamine 123 uptake by BMECs through inhibition of Pgp. The transport across BMEC monolayers was polarized for both Tx-67 and Taxol with permeation in the apical to basolateral direction greater for Tx-67 and substantially reduced for Taxol relative to basolateral to apical permeation. Taxol and cyclosporin A treatments also did not enhance Tx-67 permeation across BMEC monolayers. In an in situ rat brain perfusion study, Tx-67 was demonstrated to permeate across the BBB at a greater rate than Taxol. These results demonstrate that the Taxol analogue Tx-67 had a reduced interaction with Pgp and, as a consequence, enhanced permeation across the blood-brain barrier in vitro and in situ.

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    • "The expression and activity of P-gp is the major factor that limits the use of paclitaxel for the treatment of brain tumours (Fellner et al., 2002; Geney et al., 2002). Different attempts have been made to circumvent or diminish the interaction between paclitaxel and P-gp at the BBB by chemical modification of the paclitaxel molecule (Cisternino et al., 2003; Rice et al., 2005). We investigated the influence of the P-gp-mediated efflux across the BBB on the accumulation of paclitaxel and ANG1005 in the brain. "
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    ABSTRACT: Paclitaxel is highly efficacious in the treatment of breast, head and neck, non-small cell lung cancers and ovarian carcinoma. For malignant gliomas, paclitaxel is prevented from reaching its target by the presence of the efflux pump P-glycoprotein (P-gp) at the blood-brain barrier. We investigated the utilization of a new drug delivery system to increase brain delivery of paclitaxel. Paclitaxel molecules were conjugated to a brain peptide vector, Angiopep-2, to provide a paclitaxel-Angiopep-2 conjugate named ANG1005. We determined the brain uptake capacity, intracellular effects and antitumour properties of ANG1005 in vitro against human tumour cell lines and in vivo in human xenografts. We then determined ANG1005 activity on brain tumours with intracerebral human tumour models in nude mice. We show by in situ brain perfusion that ANG1005 enters the brain to a greater extent than paclitaxel and bypasses the P-gp. ANG1005 has an antineoplastic potency similar to that of paclitaxel against human cancer cell lines. We also demonstrate that ANG1005 caused a more potent inhibition of human tumour xenografts than paclitaxel. Finally, ANG1005 administration led to a significant increase in the survival of mice with intracerebral implantation of U87 MG glioblastoma cells or NCI-H460 lung carcinoma cells. These results demonstrate the antitumour potential of a new drug, ANG1005, and establish that conjugation of anticancer agents with the Angiopep-2 peptide vector could increase their efficacy in the treatment of brain cancer.
    British Journal of Pharmacology 07/2008; 155(2):185-97. DOI:10.1038/bjp.2008.260 · 4.84 Impact Factor
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    ABSTRACT: P-glycoprotein (P-gp) is a 170 kDa membrane-bound protein, an energy-dependent efflux transporter driven by ATP hydrolysis. It is responsible for multidrug resistance of many drugs. Physiologically, it is involved in limiting the harmful exposure of toxins, drugs, and xenobiotics to the body by extruding them out of cells. It is increasingly recognized to play an important modulating role in the pharmacokinetic properties of many clinically important therapeutic agents and because of its importance in pharmacokinetics, its screening has to be incorporated into the drug discovery process. The modulation of drug transporters through inhibition or induction by various drugs or herbs can lead to significant drug-drug or drug-herb interactions by affecting various pharmacokinetic parameters of the drug. In addition, genetic polymorphism of P-gp has also been reported, which may affect drug disposition, produce variable drug effects, and may change disease risk susceptibility. As drug interactions and genetic polymorphism are important factors to be considered during drug development, P-gp may have an impact on drug development in future.
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