Taxol encapsulation in poly(epsilon-caprolactone) microspheres

Permeation of protein from porous poly(epsilon-caprolactone) films

The objective of this study was designed to extend the application of poly(epsilon-caprolactone) (PCL) in delivery of macromolecular proteins. The strategy applied here is to create a porous structure in PCL films in order to control the diffusion rate of protein. Various amounts of both high-molecular-weight and low-molecular-weight poly(ethylene glycol) (PEG) were used as pore-forming agents. The porous films were prepared by a solvent-casting-leaching method. The thicknesses of the prepared films were controlled to be in the range of 75.3 +/- 0.6 similar 81.7 +/- 0.6 mum. The pore fraction of films was determined to be 27.7 +/- 1.0% similar 52.5 +/- 0.8% for PEG(10000) and 26.6 +/- 1.8% similar 48.8 +/- 1.4% for PEG(4000). The pore fraction initially increased with increasing amounts of PEG, independent of the molecular weight of PEG. In the permeation study, lysozyme was used as a model diffuser. The permeation rate of protein increased as the pore fraction of films increased, especially when 30 similar 40% of PEG was added initially, and this phenomenon was more prominent when low-molecular-weight PEG was used. This result was probably due to the highly porous structure creating interconnected channels in the films, further enhancing protein diffusion. In addition, the size of micropores formed by PEG(4000) was observed to be larger than by PEG(10000), which also accounted for faster permeation rate of lysozyme through PCL-PEG(4000) porous films.

Multicenter, randomized trial for stage IIIB or IV non-small-cell lung cancer using weekly paclitaxel and carboplatin followed by maintenance weekly paclitaxel or observation

PURPOSE

To explore the efficacy and safety of three regimens of weekly paclitaxel plus carboplatin as initial therapy and the feasibility of subsequent maintenance therapy versus observation in patients with advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Four hundred one patients were randomly assigned to one of the following arms: arm 1, paclitaxel 100 mg/m2 weekly for 3 of 4 weeks with carboplatin (area under the curve [AUC] = 6) on day 1; arm 2, paclitaxel 100 mg/m2 and carboplatin (AUC = 2) weekly for 3 of 4 weeks; or arm 3, paclitaxel 150 mg/m2 cycle 1 and 100 mg/m2 cycle 2 and carboplatin (AUC = 2) weekly for 6 of 8 weeks. Patients who responded (n = 130) at week 16 were randomly assigned to either weekly paclitaxel therapy (70 mg/m2, 3 of 4 weeks; n = 65) or observation (n = 65).

RESULTS

For the 390 assessable patients, the objective response rates observed with initial therapy were 32% for arm 1, 24% for arm 2, and 18% for arm 3. The median time to progression and median survival times were 30 and 49 weeks for arm 1, 21 and 31 weeks for arm 2, and 27 and 40 weeks for arm 3, respectively. The 1-year survival rates were 47% for arm 1, 31% for arm 2, and 41% for arm 3.

CONCLUSION

Arm 1, paclitaxel 100 mg/m2 weekly for 3 of 4 weeks with carboplatin (AUC = 6) administered on day 1, demonstrates the most favorable therapeutic index in patients with advanced NSCLC.

Polymeric micelles of poly(2-ethyl-2-oxazoline)-block-poly(epsilon-caprolactone) copolymer as a carrier for paclitaxel

Polymeric micelles based on amphiphilic block copolymers of poly(2-ethyl-2-oxazoline) (PEtOz) and poly(epsilon -caprolactone) (PCL) were prepared in an aqueous phase. The loading of paclitaxel into PEtOz-PCL micelles was confirmed by 1H-NMR spectra. Paclitaxel was efficiently loaded into PEtOz-PCL micelles using dialysis method, and the loading content of paclitaxel in micelles was in the range 0.5-7.6 wt.% depending on the block composition of block copolymers, organic solvent used in the dialysis, and feed weight ratio of paclitaxel to block copolymer. The higher the content of hydrophobic block in the block copolymers, the higher the loading efficiency of micelles for paclitaxel. When acetonitrile was used as solvent, a higher drug loading efficiency was obtained than with THF. The loading efficiency decreased with increasing feed weight ratio of paclitaxel to block copolymer from 0.1:1 to 0.2:1. The hydrodynamic diameters of paclitaxel-loaded micelles were in the range 18.3-23.4 nm with narrow size distribution. The hemolysis test of PEtOz-PCL performed in vitro indicated that the toxicity of PEtOz-PCLs to lipid membrane was not significant compared with Tween 80, and was comparable to that observed with Cremophore EL. The proliferation inhibition activity of paclitaxel-loaded micelles for KB human epidermoid carcinoma cells was also evaluated in vitro. Paclitaxel-entrapped polymeric micelles exhibited comparable activity to that observed with Cremophore EL-based paclitaxel formulations in inhibiting the growth of KB cells.

Progress in the development of alternative pharmaceutical formulations of taxanes

The currently available taxanes paclitaxel (Taxol) and docetaxel (Taxotere) are clinically effective against advanced breast, ovarian and non-small cell lung cancer. Due to their low aqueous solubility, both taxanes posed difficulties to the pharmaceutical scientists with respect to the development of an intravenous dosage form. At present, paclitaxel is formulated in a mixture of 50:50% (v/v) Cremophor EL and dehydrated ethanol. However, this formulation vehicle is associated with a number of pharmacological, pharmacokinetic and pharmaceutical concerns amongst which serious hypersensitivity reactions. This review deals with the attempts made into the development of alternative dosage forms of paclitaxel devoid of the Cremophor EL/ethanol excipients and potential future taxane formulations.

Regional drug delivery with radiation for the treatment of Ewing's sarcoma. In vitro development of a taxol release system

Recently, several studies have suggested the radiosensitizing effect of taxol, a microtubular inhibitor. Our overall hypothesis is that a combination of radiation and taxol may demonstrate therapeutic efficacy over doses of either individually. Studies examining taxol use have mostly focused on systemic administration, which can lead to undesired effects. To circumvent these side effects, we propose a locally administered polymeric microsphere delivery system combined with radiation therapy for the treatment of Ewing's sarcoma. The present study focuses on the in vitro ability of taxol when present as a microencapsulated drug delivery system, and delivered locally at the site of the sarcoma/tumor, to block cells in the G2/M phase of the cell cycle and potentially enhance the radiation sensitivity of cells. Using the bioresorbable poly(anhydride-co-imide), poly[pyromellityl-imidoalanine-1,6-bis(carboxy-phenoxy)hexane] (PMA-CPH), and the radiosensitizing agent taxol, a microsphere based delivery system was fabricated. A solvent evaporation technique was used to encapsulate taxol at doses of 1%, 5%, and 10% in PMA-CPH microspheres. Release kinetics studies demonstrated that the total amount of taxol released and the release rate were directly dependent on loading percentage. Taxol's bioactivity and radiosensitizing ability were measured using flow cytometry. Co-culture of Ewing's sarcoma cells with and without taxol-loaded microspheres demonstrated that released taxol retained its bioactivity and effectively blocked cells in the radiosensitive G2/M phase of mitosis. The taxol-radiation delivery system studied achieved an 83% decrease in tumor cell count compared to control. Taxol effectively sensitized Ewing's sarcoma cells to radiation with radiosensitivity shown to be independent of radiation dose at levels of dosages studied. This work has demonstrated that taxol can be effectively released from a biodegradable PMA-CPH microsphere delivery system while maintaining potent combined cytotoxic and radiosensitizing abilities.

Influence of pluronics on protein-loaded poly(epsilon-caprolactone) microparticles

The objective of this study was designed to elucidate the importance of adding pluronics to PCL microparticles for the delivery of proteins. The influences of the type and the amount of pluronic on the surface morphology and release properties of protein-loaded PCL microparticles were evaluated. Microparticles were prepared by the w/o/o/o solvent evaporation technique with an ultrasonicator. All of the microparticles prepared were spherical in shape, with a rough surface due to crystallization of PCL in the microparticles. The pluronics efficiently prevented microparticles from aggregation, and the size of microparticles prepared was significantly reduced. The significant increase in the encapsulation efficiency and decrease in the burst release of protein from PCL microparticles were achieved by using pluronic F127. Incorporation of pluronic F127 increased the hydrophilicity of the matrix, which further retained protein in blended microparticles. Both pluronics PE10100 and L61 significantly reduced the crystallinity of PCL microparticles. Nevertheless, this result did not further influence the release property of BSA from these microparticles.

Evaluation of the anti-tumor and anti-angiogenic effect of paclitaxel and thalidomide on the xenotransplanted oral squamous cell carcinoma

Angiogenesis is an essential process for the growth and invasion of cancer. However, it is uncertain that anti-angiogenic effects can be a major treatment strategy of oral cancer. The aim of this study was to investigate whether thalidomide and paclitaxel, which are known to be potent inhibitors of angiogenesis, have inhibitory effects on the growth of oral squamous cell carcinoma (OSCC) xenotransplanted into nude mice and whether anti-angiogenesis can be included as a major treatment strategy of oral cancer. After human OSCC cell line, KB, was subcutaneously inoculated into 32 nude mice, the volume of tumor was measured every 3 days. When the tumor mass reached 300-500 mm3, thalidomide (200 mg/kg) and paclitaxel (13 mg/kg) were administered into the animals and tumor volume change was checked. The excised tumor masses on the 30th day after administration were frozen and processed for immunohistochemistry using vascular endothelial growth factor (VEGF) and CD31, and for real-time reverse transcription-polymerase chain reaction (RT-PCR). We evaluated VEGF expression and the expression of its mRNA and CD31 for vessel density. Paclitaxel showed an inhibitory effect on the growth of transplanted human OSCC and reduced the immunohistochemical expression of VEGF and CD31 and VEGF mRNA (P<0.01). Thalidomide also lowered remarkably VEGF expression (P<0.01) and CD31 (P<0.01) as well as VEGF mRNA (P<0.05), but it did not show statistically significant inhibitory effect on the tumor growth. These results suggest that the growth of human OSCC is not simply dependent on VEGF-induced angiogenesis and that anti-angiogenic therapy alone is not likely to be effective for the treatment of OSCC, but might be regarded as adjuvant chemotherapeutic strategy.

Emulsion/solvent evaporation as an alternative technique in pellet preparation

Paracetamol/Eudragit RS, paracetamol/ethylcellulose, and paracetamol/cellulose acetate pellets of different drug/polymer ratios (w/w) were prepared by the dissolution/solvent evaporation technique. These pellets were then characterized by particle size distribution analysis, ultraviolet (UV) spectroscopy, differential thermal analysis, and scanning electron microscopy (SEM). Hard gelatin capsules were filled with each particle size fraction of these pellets, and in vitro dissolution studies were performed to verify the capability of each series of pellets to control drug release. Pellets were spherical, presented a polynucleated microcapsule structure, and under certain experimental conditions, the yield of the preparation process reached very high values. The dissolution studies pointed out the slow paracetamol release from these pellets.

Paclitaxel loaded poly(L-lactic acid) microspheres for the prevention of intraperitoneal carcinomatosis after a surgical repair and tumor cell spill

A controlled release delivery system for paclitaxel was developed using poly(L-lactic acid) to provide local delivery to the peritoneal cavity. Microspheres were made in 1-40 and 30-120 microm size ranges. In an in vitro release study, 30-120 microm microspheres loaded with 10, 20 and 30% paclitaxel exhibited a burst phase of release for 3 days followed by an apparently zero-order phase of release. At all loadings, 20-25% of the original load of paclitaxel was released after 30 days. The effect of microsphere size on retention in the peritoneal cavity was assessed. Control 1-40 microm microspheres were injected intraperitoneally in rats. The rats received either insufflation of the peritoneal cavity using 11 mmHg CO2 or no further treatment. After sacrifice, microspheres with diameters less than 24 microm were observed in the lymphatic system after being cleared from the peritoneal cavity through fenestrations in the diaphragm. Insufflation of the peritoneal cavity had no effect on the size of microspheres that were cleared. Efficacy studies were carried out using 30-120 microm microspheres that were of sufficient size to be retained in the peritoneal cavity. In a model of a tumor cell spill after a cecotomy repair, 100 mg of 30-120 microm microspheres containing 30% paclitaxel were effective in preventing growth of tumors in the peritoneal cavity at both 2 and 6 weeks post-surgery. No gross or histologically evident tumor growth was observed on any peritoneal surfaces or in the surgical wound site. Rats receiving control microspheres all showed tumor cell implantation and growth after 2 weeks.

Interaction of the anticancer agent Taxol (paclitaxel) with phospholipid bilayers

Taxol (paclitaxel), a promising agent for use in ovarian and breast cancer, was incorporated into lipid vesicles (liposomes) composed of different saturated and unsaturated phosphatidylcholines, as well as saturated phosphatidylcholines mixed with the anionic phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphatidylserine (DMPS) at different molar ratios, to yield information about Taxol-liposome interactions. For the physicochemical characterization of the thermodynamic, structural, and dynamic properties of these mixtures, differential scanning calorimetry (DSC), steady-state fluorescence depolarization, and Fourier transform IR spectroscopy was used. Time-dependent DSC measurements on 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC)/Taxol mixtures of different concentrations were performed to yield information on the long-term stability of Taxol-liposome complexes. Partitioning of Taxol into saturated lipid bilayers results in changes of membrane physical properties, such as phase transition temperatures and lipid order parameter, that are different from those observed for unsaturated and charged phospholipid bilayers. Taxol incorporated into saturated phospholipids changes their thermotropic phase behavior: it reduces the lipid order parameter (i.e., has a "fluidizing" effect) in the gel phase of the lipid bilayers. On the contrary, partitioning of Taxol into unsaturated fluid phospholipid bilayers has a slight "rigidization" effect. The saturated lipid bilayer systems DPPC and 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine/DMPS have been identified with the highest incorporation efficiency for Taxol and are thus candidates for drug vehicles that can improve the therapeutic efficacy of Taxol.

Localized paclitaxel delivery

While the search for new antineoplastic agents is in progress, optimization of delivery for existing drugs will remarkably improve the current scenario in the management of cancer. Paclitaxel, a new antineoplastic agent, is one such drug deserving attention in the field of regional drug delivery, offering immense pharmacokinetic as well as therapeutic advantage via localized delivery. The antiangiogenic activity of paclitaxel has been demonstrated using the chick chorioallantoic membrane model (CAM). This review focuses on the antiangiogenic activity of paclitaxel supported by the evidence that angiogenesis inhibitors display potential synergism with cytotoxic agents in the treatment of primary and metastatic cancers. Preclinical trials have confirmed that the biological and cytotoxic effects of paclitaxel on several tumor cell lines are enhanced by the increase in both the drug concentration and the duration of exposure. Sufficient experimental evidence has accumulated to state that localized delivery will exploit the multiple pharmacological effects of paclitaxel in the treatment of refractory and metastatic cancerous diseases. The drug delivery systems, namely, microspheres, surgical pastes and implants, fabricated for localized paclitaxel delivery are reviewed explaining the concept of increased tumor burden alleviating body burden as a consequence of such delivery systems. Some of the preclinical trials are very encouraging and speculate a promising future for these devices in the battle against solid tumors. Finally, the review briefs on the possibilities for better paclitaxel delivery and the future drug delivery systems for localized cancer chemotherapy.

Development of nonionic surfactant/phospholipid o/w emulsion as a paclitaxel delivery system

Paclitaxel is an anticancer agent with low aqueous solubility. More extensive clinical use of this drug is somewhat delayed due to lack of appropriate delivery vehicles. An attempt was made to adopt an o/w emulsion as the drug carrier which incorporated paclitaxel in the triacylglycerol stabilized by a mixed-emulsifier system. A suitable formulation was found in this study: 0.75 mg/ml paclitaxel, 10% (w/v) oil blend, 4% (w/v) EPC, 3% (w/v) Tween 80 in 2.25% (w/v) glycerol solution. The formulated emulsion has very good stability when stored at 4 degrees C, and the paclitaxel containment efficiency can be maintained above 95% and the mean emulsion diameter around 150 nm for at least 3 months. Paclitaxel-emulsion displayed cytotoxicity against HeLa cells with IC50 at 30 nM. The average life span of ascitic-tumor-bearing mice was prolonged significantly by the treatment of paclitaxel-emulsion (P<0.05). The formulated emulsion is a promising carrier for paclitaxel and other lipophilic drugs.

Alternative formulations of paclitaxel

Paclitaxel, a novel antitumour agent, is active clinically against advanced ovarian and breast cancer and under investigation for various other cancers. One of the problems associated with the intravenous administration of paclitaxel is its low solubility in water. The current pharmaceutical formulation consists of a 1:1 (v/v) mixture of ethanol and Cremophor EL. This formulation, however, has been demonstrated to cause some severe hypersensitivity reactions. Therefore the development of a safer intravenous formulation devoid of Cremophor EL is an important investigational issue. This review deals with some of the most promising formulation alternatives.