Nanoparticle albumin-bound paclitaxel: a novel Cremphor-EL®-free formulation of paclitaxel

A core-shell albumin copolymer nanotransporter for high capacity loading and two-step release of doxorubicin with enhanced anti-leukemia activity

The native transportation protein serum albumin represents an attractive nano-sized transporter for drug delivery applications due to its beneficial safety profile. Existing albumin-based drug delivery systems are often limited by their low drug loading capacity as well as noticeable drug leakage into the blood circulation. Therefore, a unique albumin-derived core-shell doxorubicin (DOX) delivery system based on the protein denaturing-backfolding strategy was developed. 28 DOX molecules were covalently conjugated to the albumin polypeptide backbone via an acid sensitive hydrazone linker. Polycationic and pegylated human serum albumin formed two non-toxic and enzymatically degradable protection shells around the encapsulated DOX molecules. This core-shell delivery system possesses notable advantages, including a high drug loading capacity critical for low administration doses, a two-step drug release mechanism based on pH and the presence of proteases, an attractive biocompatibility and narrow size distribution inherited from the albumin backbone, as well as fast cellular uptake and masking of epitopes due to a high degree of pegylation. The IC50 of these nanoscopic onion-type micelles was found in the low nanomolar range for Hela cells as well as leukemia cell lines. In vivo data indicate its attractive potential as anti-leukemia treatment suggesting its promising profile as nanomedicine drug delivery system.

Predictive models of diffusive nanoparticle transport in 3-dimensional tumor cell spheroids

The rapidly evolving nanotechnology field highlights the need of better understanding the relationship between nanoparticle (NP) properties and NP transport in solid tumors. The present study tested the hypothesis that the diffusive transport and spatial distribution of NP can be predicted based on the following parameters: interstitial NP diffusivity, NP-cell interaction parameters (cell surface binding capacity, rate constants of association, dissociation, and internalization). We (a) established the models and equations; (b) experimentally measured, in monolayer pharynx FaDu cells, the model parameters for three NP formulations (negatively charged polystyrene beads, near-neutral liposomes, and positively charged liposomes, with respective diameter of 20, 110, and 130 nm); and (c) used the models and parameters to simulate NP diffusion in 3-dimensional (3D) systems. We next measured the NP concentration-depth profiles in tumor cell spheroids, an avascular 3D system, and found good agreement between model-simulated and experimental data in spheroids for the negative and neutral NP (>90% predicted data points at three NP concentrations and three treatment times were within the 95% confidence intervals of experimental data). Model performance was inferior for positive liposomes containing a fusogenic lipid. The present study demonstrated the possibility of using in vitro NP-cell biointerface data in monolayer cultures with in silico studies to predict the NP diffusive transport and concentration-time-depth profiles in 3D systems, as functions of NP concentrations and treatment times. Extending this approach to include convective transport may yield a cost-effective means to predict the NP delivery and residence in solid tumors.

Incorporation of lapatinib into lipoprotein-like nanoparticles with enhanced water solubility and anti-tumor effect in breast cancer

AIM

The poor water solubility of many active compounds is a serious deterrent to their use as commercial drugs. Lapatinib is a dual inhibitor of the EGF receptor and EGF receptor 2 approved by the US FDA to treat advanced breast cancer. This study prepares lapatinib-incorporated lipoprotein-like nanoparticles (LTNPs) to enhance the water solubility and elevate the anti-tumor effect of lapatinib.

MATERIALS & METHODS

Bovine albumin was used to bind with lapatinib, and egg yolk lecithin was used to stabilize the conjugation of bovine albumin and lapatinib. The characteristics of LTNPs were evaluated by several experiments. Cell uptake and toxicity were performed on BT-474 cells. In vivo anti-tumor effect was performed on BT-474 xenograft-bearing mice.

RESULTS

LTNPs contained a lipid corona and a core of lapatinib and albumin. LTNPs could be effectively taken up by BT-474 cells and induced apoptosis. An in vivo study demonstrated that LTNPs could passively distribute into a tumor via the enhanced permeability and retention effect and induce anti-tumor activity in breast cancer.

CONCLUSION

The authors present a convenient nanoformulation with improved anti-tumor effect, which is a promising candidate for clinical trials.

Common pitfalls in nanotechnology: lessons learned from NCI's Nanotechnology Characterization Laboratory

The Nanotechnology Characterization Laboratory's (NCL) unique set-up has allowed our lab to handle and test a variety of nanoparticle platforms intended for the delivery of cancer therapeutics and/or imaging contrast agents. Over the last six years, the NCL has characterized more than 250 different nanomaterials from more than 75 different investigators. These submitted nanomaterials stem from a range of backgrounds and experiences, including government, academia and industry. This has given the NCL a unique and valuable opportunity to observe trends in nanoparticle safety and biocompatibility, as well as note some of the common mistakes and oversights of nanoformulation. While not exhaustive, this article aims to share some of the most common pitfalls observed by the NCL as they relate to nanoparticle synthesis, purification, characterization and analysis.

Paclitaxel Nano-Delivery Systems: A Comprehensive Review

Paclitaxel is one of the most effective chemotherapeutic drugs ever developed and is active against a broad range of cancers, such as lung, ovarian, and breast cancers. Due to its low water solubility, paclitaxel is formulated in a mixture of Cremophor EL and dehydrated ethanol (50:50, v/v) a combination known as Taxol. However, Taxol has some severe side effects related to Cremophor EL and ethanol. Therefore, there is an urgent need for the development of alternative Taxol formulations. The encapsulation of paclitaxel in biodegradable and non-toxic nano-delivery systems can protect the drug from degradation during circulation and in-turn protect the body from toxic side effects of the drug thereby lowering its toxicity, increasing its circulation half-life, exhibiting improved pharmacokinetic profiles, and demonstrating better patient compliance. Also, nanoparticle-based delivery systems can take advantage of the enhanced permeability and retention (EPR) effect for passive tumor targeting, therefore, they are promising carriers to improve the therapeutic index and decrease the side effects of paclitaxel. To date, paclitaxel albumin-bound nanoparticles (Abraxane®) have been approved by the FDA for the treatment of metastatic breast cancer and non-small cell lung cancer (NSCLC). In addition, there are a number of novel paclitaxel nanoparticle formulations in clinical trials. In this comprehensive review, several types of developed paclitaxel nano-delivery systems will be covered and discussed, such as polymeric nanoparticles, lipid-based formulations, polymer conjugates, inorganic nanoparticles, carbon nanotubes, nanocrystals, and cyclodextrin nanoparticles.

Advances in nanotechnology for the management of coronary artery disease

Nanotechnology holds tremendous potential to advance the current treatment of coronary artery disease. Nanotechnology may assist medical therapies by providing a safe and efficacious delivery platform for a variety of drugs aimed at modulating lipid disorders, decreasing inflammation and angiogenesis within atherosclerotic plaques, and preventing plaque thrombosis. Nanotechnology may improve coronary stent applications by promoting endothelial recovery on a stent surface utilizing bio-mimetic nanofibrous scaffolds, and also by preventing in-stent restenosis using nanoparticle-based delivery of drugs that are decoupled from stents. Additionally, nanotechnology may enhance tissue-engineered graft materials for application in coronary artery bypass grafting by facilitating cellular infiltration and remodeling of a graft matrix.

Inorganic nanoparticle biomolecular corona: formation, evolution and biological impact

Physicochemical changes to inorganic nanoparticles (NPs) in biological environments determine their impact. Blood, lymph, mucus, complete cell culture media and other biological fluids contain a large amount and variety of different molecules. NPs dispersed in these fluids are sensitive to such environments. One of the most significant alterations is the formation of the NP–protein corona (PC) as a result of the adsorption of proteins onto the inorganic surface. This process is currently gaining attention in the field of inorganic NPs since this spontaneous coating gives a biological identity to the composite NP–PC and determines the interactions between the NP and the host in living systems. Therefore, knowledge of NP–PC formation is crucial for understanding the evolution, biodistribution and reactivity of NPs inside organisms and, therefore, for the safe design of engineered NPs.

Hollow superparamagnetic iron oxide nanoshells as a hydrophobic anticancer drug carrier: intracelluar pH-dependent drug release and enhanced cytotoxicity

With curcumin and doxorubicin (DOX) base as model drugs, intracellular delivery of hydrophobic anticancer drugs by hollow structured superparamagnetic iron oxide (SPIO) nanoshells (hydrodynamic diameter: 191.9 ± 2.6 nm) was studied in glioblastoma U-87 MG cells. SPIO nanoshell-based encapsulation provided a stable aqueous dispersion of the curcumin. After the SPIO nanoshells were internalized by U-87 MG cells, they localized at the acidic compartments of endosomes and lysosomes. In endosome/lysosome-mimicking buffers with a pH of 4.5-5.5, pH-dependent drug release was observed from curcumin or DOX loaded SPIO nanoshells (curcumin/SPIO or DOX/SPIO). Compared with the free drug, the intracellular curcumin content delivered via curcumin/SPIO was 30 fold higher. Increased intracellular drug content for DOX base delivered via DOX/SPIO was also confirmed, along with a fast intracellular DOX release that was attributed to its protonation in the acidic environment. DOX/SPIO enhanced caspase-3 activity by twofold compared with free DOX base. The concentration that induced 50% cytotoxic effect (CC(50)) was 0.05 ± 0.03 μg ml(-1) for DOX/SPIO, while it was 0.13 ± 0.02 μg ml(-1) for free DOX base. These results suggested SPIO nanoshells might be a promising intracellular carrier for hydrophobic anticancer drugs.

Peptide ligand and PEG-mediated long-circulating liposome targeted to FGFR overexpressing tumor in vivo

Background and methods

Paclitaxel, a widely used antitumor agent, has limited clinical application due to its hydrophobicity and systemic toxicity. To achieve sustained and targeted delivery of paclitaxel to tumor sites, liposomes composed of egg phosphatidylcholine, cholesterol, and distearolyphosphatidyl ethanolamine-N-poly(ethylene glycol) (PEG₂₀₀₀) were prepared by a lipid film method. In addition, the liposomes also contained truncated fibroblast growth factor fragment-PEG-cholesterol as a ligand targeting the tumor marker fibroblast growth factor receptor. Physicochemical characteristics, such as particle size, zeta potential, entrapment efficiency, and release profiles were investigated. Pharmacokinetics and biodistribution were evaluated in C57BL/6 J mice bearing B16 melanoma after intravenous injection of paclitaxel formulated in Cremophor EL (free paclitaxel), conventional liposomes (CL-PTX), or in targeted PEGylated liposomes (TL-PTX).

Results

Compared with CL-PTX and free paclitaxel, TL-PTX prolonged the half-life of paclitaxel by 2.01-fold and 3.40-fold, respectively, in plasma and improved the AUC_0→t values of paclitaxel by 1.56-fold and 2.31-fold, respectively, in blood. Biodistribution studies showed high accumulation of TL-PTX in tumor tissue and organs containing the mononuclear phagocyte system (liver and spleen), but a considerable decrease in other organs (heart, lung, and kidney) compared with CL-PTX and free paclitaxel.

Conclusion

The truncated fibroblast growth factor fragment-conjugated PEGylated liposome has promising potential as a long-circulating and tumor-targeting carrier system.

Meta-analysis of nanoparticulate paclitaxel delivery system pharmacokinetics and model prediction of associated neutropenia

PURPOSE

Nanoparticulate paclitaxel carriers have entered clinical evaluation as alternatives to the Cremophor-based standard Taxol(®) (Cre-pac). Their pharmacokinetics (PK) is complex, and factors influencing their pharmacodynamics (PD) are poorly understood. We aimed to develop a unified quantitative model for 4 paclitaxel carriers that captures systems-level PK, predicts micro-scale PK processes, and permits correlations between carrier properties and observed PD.

METHODS

Data consisting of 54 PK profiles and 574 observations were extracted from 20 clinical studies investigating Cre-pac, albumin-(A-pac), liposome-(L-pac), and tocopherol-(T-pac) nanocarriers. A population-PK approach was used for data analysis. All datasets were simultaneously fitted to produce a unified model. Model-based simulations explored relationships between predicted PK and myelosuppression for each formulation.

RESULTS

The final model employed nonlinear drug-binding mechanisms to describe Cre-pac and a delayed-release model for A-pac, L-pac, and T-pac. Estimated drug-release rate constants (h(-1)): Cre-pac (5.19), L-pac (1.26), A-pac (0.72), T-pac (0.74). Simulations of equivalent dosing schemes ranked neutropenia severity (highest to lowest): T-pac~Cre-pac>L-pac~A-pac and predicted remarkably well the clinically-observed relationships between neutropenia and free drug exposure relative to a threshold concentration.

CONCLUSIONS

Paclitaxel disposition was well-described for all formulations. The derived model predicts toxicodynamics of diverse paclitaxel carriers.

Inhaled chemotherapy in lung cancer: future concept of nanomedicine

Regional chemotherapy was first used for lung cancer 30 years ago. Since then, new methods of drug delivery and pharmaceuticals have been investigated in vitro, and in animals and humans. An extensive review of drug delivery systems, pharmaceuticals, patient monitoring, methods of enhancing inhaled drug deposition, safety and efficacy, and also additional applications of inhaled chemotherapy and its advantages and disadvantages are presented. Regional chemotherapy to the lung parenchyma for lung cancer is feasible and efficient. Safety depends on the chemotherapy agent delivered to the lungs and is dose-dependent and time-dependent. Further evaluation is needed to provide data regarding early lung cancer stages, and whether regional chemotherapy can be used as neoadjuvant or adjuvant treatment. Finally, inhaled chemotherapy could one day be administered at home with fewer systemic adverse effects.

Pharmacokinetics, tissue distribution and anti-tumour efficacy of paclitaxel delivered by polyvinylpyrrolidone solid dispersion

Objectives

Paclitaxel is a potent anti-cancer drug that has exhibited clinical activity against several tumours. Unfortunately, serious side effects are associated with Taxol, the commercial formulation of paclitaxel, which contains Cremophor EL (CrEL). Currently, the main focus of developing paclitaxel formulations is on improving efficacy and reducing toxicity. A novel, Cremophor-free, paclitaxel solid dispersion (PSD) was prepared in our laboratory previously. The primary aim of this study was to evaluate the pharmacokinetics, tissue distribution, acute toxicity and anti-tumour efficacy of the PSD compared with Taxol.

Methods

SD rats were used to examine the pharmacokinetics and tissue distribution of PSD. The acute toxicity of PSD was evaluated in ICR mouse. The anti-tumor activity of PSD was assessed in an in vivo anti-tumor nude mice model inoculated with human SKOV-3 cancer cells.

Key findings

The two formulations presented different pharmacokinetic behaviour. The plasma AUC of paclitaxel in the PSD was 5.84-fold lower than that of Taxol, and the mean residence time, total body clearance and apparent volume of distribution of paclitaxel in the PSD were increased by 1.73, 4.67 and 8.57 fold, respectively. However, the two formulations showed similar tissue distribution properties. CrEL, the vehicle in Taxol, decreased the clearance of paclitaxel from plasma. The LD50 (median lethal dose) was 34.8 mg/kg for Taxol, whereas no death was observed at 160 mg/kg for the PSD. The anti-tumour activity of PSD was similar to that of Taxol at a dose of 15 mg/kg. Most importantly, the improved tolerance of PSD enabled a higher administrable dose of paclitaxel, which resulted in improved efficacy compared with Taxol administered at its maximum tolerated dose.

Conclusions

These results suggest that the PSD, a CrEL-free formulation, is a promising approach to increase the safety and efficacy of paclitaxel.

Noncovalent functionalization of carbon nanovectors with an antibody enables targeted drug delivery

Current chemotherapeutics are characterized by efficient tumor cell-killing and severe side effects mostly derived from off-target toxicity. Hence targeted delivery of these drugs to tumor cells is actively sought. We previously demonstrated that poly(ethylene glycol)-functionalized carbon nanovectors are able to sequester paclitaxel, a widely used hydrophobic cancer drug, by simple physisorption and thereby deliver the drug for killing of cancer cells. The cell-killing when these drug-loaded carbon nanoparticles were used was equivalent to when a commercial formulation of paclitaxel was used. Here we show that by further mixing the drug-loaded nanoparticles with Cetuximab, a monoclonal antibody that recognizes the epidermal growth factor receptor (EGFR), paclitaxel is preferentially targeted to EGFR+ tumor cells in vitro. This supports progressing to in vivo studies. Moreover, the construct is unusual in that all three components are assembled through noncovalent interactions. Such noncovalent assembly could enable high-throughput screening of drug/antibody combinations.

Cancer cell invasion: treatment and monitoring opportunities in nanomedicine

Cell invasion is an intrinsic cellular pathway whereby cells respond to extracellular stimuli to migrate through and modulate the structure of their extracellular matrix (ECM) in order to develop, repair, and protect the body's tissues. In cancer cells this process can become aberrantly regulated and lead to cancer metastasis. This cellular pathway contributes to the vast majority of cancer related fatalities, and therefore has been identified as a critical therapeutic target. Researchers have identified numerous potential molecular therapeutic targets of cancer cell invasion, yet delivery of therapies remains a major hurdle. Nanomedicine is a rapidly emerging technology which may offer a potential solution for tackling cancer metastasis by improving the specificity and potency of therapeutics delivered to invasive cancer cells. In this review we examine the biology of cancer cell invasion, its role in cancer progression and metastasis, molecular targets of cell invasion, and therapeutic inhibitors of cell invasion. We then discuss how the field of nanomedicine can be applied to monitor and treat cancer cell invasion. We aim to provide a perspective on how the advances in cancer biology and the field of nanomedicine can be combined to offer new solutions for treating cancer metastasis.

Nanosizing for oral and parenteral drug delivery: a perspective on formulating poorly-water soluble compounds using wet media milling technology

A significant percentage of active pharmaceutical ingredients identified through discovery screening programs is poorly soluble in water. These molecules are often difficult to formulate using conventional approaches and are associated with innumerable formulation-related performance issues, e.g. poor bioavailability, lack of dose proportionality, slow onset of action and other attributes leading to poor patient compliance. In addition, for parenteral products, these molecules are generally administered with co-solvents and thus have many undesirable side effects. Wet media milling is one of the leading particle size reduction approaches that have been successfully used to formulate these problematic compounds. The approach is a water-based media milling process where micron-sized drug particles are shear-fractured into nanometer-sized particles. Nanoparticle dispersions are stable and typically have a mean diameter of less than 200 nm with 90% of the particles being less than 400 nm. The formulation consists only of water, drug and one or more GRAS excipients. Drug concentrations approaching 300-400mg/g can be targeted with the use of minimal amounts stabilizer. Typically, on average, the drug to stabilizer ratio on a weight basis ranges from 2:1 to 20:1. These liquid nanodispersions exhibit acceptable shelf-life and can be post-processed into various types of solid dosage forms. Nanoparticulate-based drug products have been shown to improve bioavailability and enhance drug exposure for oral and parenteral dosage forms. Suitable formulations for the most commonly used routes of administration can be identified with milligram quantities of drug substance providing the discovery scientist an alternate avenue for screening and identifying superior leads. In the last few years, formulating poorly water soluble compounds as nanosuspensions has evolved from a conception to a realization. The versatility and applicability of this drug delivery platform are just beginning to be realized.

Targeted albumin-based nanoparticles for delivery of amphipathic drugs

We report the preparation and physical and biological characterization of human serum albumin-based micelles of approximately 30 nm diameter for the delivery of amphipathic drugs, represented by doxorubicin. The micelles were surface conjugated with cyclic RGD peptides to guide selective delivery to cells expressing the α(v)β(3) integrin. Multiple poly(ethylene glycol)s (PEGs) with molecular weight of 3400 Da were used to form a hydrophilic outer layer, with the inner core formed by albumin conjugated with doxorubicin via disulfide bonds. Additional doxorubicin was physically adsorbed into this core to attain a high drug loading capacity, where each albumin was associated with about 50 doxorubicin molecules. The formed micelles were stable in serum but continuously released doxorubicin when incubated with free thiols at concentrations mimicking the intracellular environment. When incubated with human melanoma cells (M21+) that express the α(v)β(3) integrin, higher uptake and longer retention of doxorubicin was observed with the RGD-targeted micelles than in the case of untargeted control micelles or free doxorubicin. Consequently, the RGD-targeted micelles manifested cytotoxicity at lower doses of drug than control micelles or free drug.

Nanotechnology and human health: risks and benefits

Nanotechnology is expected to be promising in many fields of medical applications, mainly in cancer treatment. While a large number of very attractive exploitations open up for the clinics, regulatory agencies are very careful in admitting new nanomaterials for human use because of their potential toxicity. The very active research on new nanomaterials that are potentially useful in medicine has not been counterbalanced by an adequate knowledge of their pharmacokinetics and toxicity. The different nanocarriers used to transport and release the active molecules to the target tissues should be treated as additives, with potential side effects of themselves or by virtue of their dissolution or aggregation inside the body. Only recently has a systematic classification of nanomaterials been proposed, posing the basis for dedicated modeling at the nanoscale level. The use of in silico methods, such as nano-QSAR and PSAR, while highly desirable to expedite and rationalize the following stages of toxicological research, are not an alternative, but an introduction to mandatory experimental work.

A novel paclitaxel microemulsion containing a reduced amount of Cremophor EL: pharmacokinetics, biodistribution, and in vivo antitumor efficacy and safety

The purpose of this study was to prepare a novel paclitaxel (PTX) microemulsion containing a reduced amount of Cremophor EL (CrEL) which had similar pharmacokinetics and antitumor efficacy as the commercially available PTX injection, but a significantly reduced allergic effect due to the CrEL. The pharmacokinetics, biodistribution, in vivo antitumor activity and safety of PTX microemulsion was evaluated. The results of pharmacokinetic and distribution properties of PTX in the microemulsion were similar to those of the PTX injection. The antitumor efficacy of the PTX microemulsion in OVCRA-3 and A 549 tumor-bearing animals was similar to that of PTX injection. The PTX microemulsion did not cause haemolysis, erythrocyte agglutination or simulative reaction. The incidence and degree of allergic reactions exhibited by the PTX microemulsion group, with or without premedication, were significantly lower than those in the PTX injection group (P < .01). In conclusion, the PTX microemulsion had similar pharmacokinetics and anti-tumor efficacy to the PTX injection, but a significantly reduced allergic effect due to CrEL, indicating that the PTX microemulsion overcomes the disadvantages of the conventional PTX injection and is one way of avoiding the limitations of current injection product while providing suitable therapeutic efficacy.

Paclitaxel nanocrystals for overcoming multidrug resistance in cancer

Here we described a paclitaxel (PTX) nanocrystal formulation using d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as the sole excipient for overcoming multidrug resistance (MDR), a key challenge in current cancer therapy. To the best of our knowledge, it is the first report on PTX nanocrystals which can reverse MDR. TPGS serves as a surfactant to stabilize the nanocrystals and a P-gp inhibitor to reverse MDR. The size and morphology of the nanocrystals were studied by transmission electron microscopy, and the crystalline structure was determined by powder X-ray diffraction. An in vitro drug release profile showed that the nanocrystals exhibited sustained release kinetics compared to Taxol, which is the clinical paclitaxel formulation. The cytotoxicity and antitumor efficacy in xenograft models were also investigated. It is demonstrated that PTX/TPGS nanocrystals have significant advantages over Taxol in achieving better therapeutic effect in Taxol-resistant cancer cells both in vitro and in vivo, which was also confirmed by apoptosis assays. We envision that further development of this type of nanocrystal will provide a novel strategy for drug delivery and multidrug resistance treatment.

Effective drug delivery, in vitro and in vivo, by carbon-based nanovectors noncovalently loaded with unmodified Paclitaxel

Many new drugs have low aqueous solubility and high therapeutic efficacy. Paclitaxel (PTX) is a classic example of this type of compound. Here we show that extremely small (<40 nm) hydrophilic carbon clusters (HCCs) that are PEGylated (PEG-HCCs) are effective drug delivery vehicles when simply mixed with paclitaxel. This formulation of PTX sequestered in PEG-HCCs (PTX/PEG-HCCs) is stable for at least 20 weeks. The PTX/PEG-HCCs formulation was as effective as PTX in a clinical formulation in reducing tumor volumes in an orthotopic murine model of oral squamous cell carcinoma. Preliminary toxicity and biodistribution studies suggest that the PEG-HCCs are not acutely toxic and, like many other nanomaterials, are primarily accumulated in the liver and spleen. This work demonstrates that carbon nanomaterials are effective drug delivery vehicles in vivo when noncovalently loaded with an unmodified drug.

Antiangiogenic activity of sterically stabilized liposomes containing paclitaxel (SSL-PTX): in vitro and in vivo

The purpose of this present study was to evaluate the antiangiogenic activity of sterically stabilized liposomes containing paclitaxel (SSL-PTX). The SSL-PTX was prepared by the thin-film method. The release of paclitaxel from SSL-PTX was analyzed using a dialysis method. The effect of SSL-PTX on endothelial cell proliferation and migration was investigated in vitro. The antitumor and antiangiogenic activity of SSL-PTX was evaluated in MDA-MB-231 tumor xenograft growth in BALB/c nude mice. The release of paclitaxel from SSL-PTX was 22% within 24 h. Our in vitro results indicated that SSL-PTX could effectively inhibit the endothelial cell proliferation and migration at a concentration-dependent manner. We also observed that metronomic SSL-PTX induced marked tumor growth inhibition in MDA-MB-231 xenograft model via the antiangiogenic mechanism, unlike that in paclitaxel injection (Taxol) formulated in Cremophor EL (CrEL). Overall, our results suggested that metronomic chemotherapy with low-dose, CrEL-free SSL-PTX should be feasible and effective.

Bone marrow CFU-GM and human tumor xenograft efficacy of three tubulin binding agents

PURPOSE

The dynamic instability of microtubules in cells is one of the key targets of anticancer therapeutics. Microtubule-disrupting agents such as vinca alkaloids and microtubule-stabilizing agents such as taxanes are important antitumor agents. The bone marrow toxicity and human tumor xenograft activity of three tubulin-binding compounds, vincristine, paclitaxel, and tasidotin were compared.

METHODS

Mouse and human bone marrow were subjected to colony-forming (CFU-GM) assays over a 5-log concentration range in culture. In vivo, a range of tasidotin doses was compared with vincristine, paclitaxel, and docetaxel for efficacy in several human tumor xenografts.

RESULTS

The IC(90) concentrations for vincristine and paclitaxel for mouse CFU-GM were 30 and 27 nM, and for human CFU-GM were 3 and 9 nM, giving mouse to human differentials of ten- and threefold. Tasidotin produced IC(90)s of >300 nM in mouse and 65 nM in human CFU-GM, thus a >4.6-fold differential between species. In vivo, tasidotin resulted in a dose-dependent increase in tumor growth delay in the RL lymphoma, the RPMI 8226 multiple myeloma, and MX-1 breast carcinoma models. Vincristine and tasidotin were also very effective against these tumors. The PC-3 prostate carcinoma was very responsive to full-dose paclitaxel and docetaxel while tasidotin generated a dose dependent effect.

CONCLUSIONS

Bringing together bone marrow toxicity data, pharmacokinetic parameters, and human tumor xenograft efficacy provides valuable information for the translation of preclinical findings to the clinic.

Paclitaxel and docetaxel in the treatment of breast cancer

BACKGROUND

Paclitaxel and docetaxel are considered fundamental drugs in the treatment of breast cancer.

OBJECTIVES

To review the current role of taxanes in the treatment breast cancer, with emphasis on data from randomized trials comparing the two taxanes.

METHODS

We have reviewed the available evidence in the literature to gauge the results of therapy of early and advanced breast cancer with taxanes.

RESULTS

Clinically benefits were first shown in metastatic setting. More recently, benefits have also been seen in the therapy of early-stage disease. It seems reasonable to consider either drug as standard treatment for node-positive early stage or metastatic breast cancer. Future studies should explore the optimal way of combining taxanes with novel biological and cytotoxic drugs.

CONCLUSION

Based on existing evidence, clinicians should choose a taxane-based regimen for their patients, according to clinical activity, toxicity profile, pharmacokinetics, and a dosing schedule that best meets the therapeutic needs and convenience.

Targeted nanomedicines: effective treatment modalities for cancer, AIDS and brain disorders

Novel technology in the nanomedicine field is expected to develop innovative products as targeted drug-delivery approaches. Targeted drug delivery of various drugs for the treatment of cancer, AIDS and brain disorders is the primary research area in which nanomedicines have a major role and need. This review is concerned with emerging targeted nanomedicines (polymeric nanoparticles, solid lipid nanoparticles, polymeric micelles, dendrimers, liposomes, gold nanoparticles and magnetic nanoparticles) and multifunctional carriers capable of combining targeted drug delivery and imaging (polymeric micelles, dendrimers and magnetic nanoparticles) in the field of pharmaceutical applications. The significant toxicity issues associated with these nanomedicines are also explored here.

Paclitaxel loading in PLGA nanospheres affected the in vitro drug cell accumulation and antiproliferative activity

BACKGROUND

PTX is one of the most widely used drug in oncology due to its high efficacy against solid tumors and several hematological cancers. PTX is administered in a formulation containing 1:1 Cremophor EL (polyethoxylated castor oil) and ethanol, often responsible for toxic effects. Its encapsulation in colloidal delivery systems would gain an improved targeting to cancer cells, reducing the dose and frequency of administration.

METHODS

In this paper PTX was loaded in PLGA NS. The activity of PTX-NS was assessed in vitro against thyroid, breast and bladder cancer cell lines in cultures. Cell growth was evaluated by MTS assay, intracellular NS uptake was performed using coumarin-6 labelled NS and the amount of intracellular PTX was measured by HPLC.

RESULTS

NS loaded with 3% PTX (w/w) had a mean size < 250 nm and a polydispersity index of 0.4 after freeze-drying with 0.5% HP-Cyd as cryoprotector. PTX encapsulation efficiency was 30% and NS showed a prolonged drug release in vitro. An increase of the cytotoxic effect of PTX-NS was observed with respect to free PTX in all cell lines tested.

CONCLUSION

These findings suggest that the greater biological effect of PTX-NS could be due to higher uptake of the drug inside the cells as shown by intracellular NS uptake and cell accumulation studies.

Newer cytotoxic agents: attacking cancer broadly

The plasticity and instability of the cancer genome is impressive and is characterized by gene amplifications and deletions, rearrangements, and many silent and active mutations. Although targeted therapeutics have had effect in some diseases, there remains a large role for new cytotoxic agents that have the potential to be broadly active across multiple cancers. Platinum-based regimens are the basis for treatment of several common tumors. Satraplatin and picoplatin are newer platinum complexes that form bulkier lesions in DNA than their forerunners. Microtubules are a key target for anticancer agents. Vinca alkaloid and similar compounds fragment these critical structures, whereas taxanes stabilize them. Vinflunine is a new fluorinated Vinca alkaloid derivative with vascular disrupting effects, as well as antitumor effects. Epothilones are a new class of microtubule stabilizers. Mitosis has been targeted directly and indirectly by many anticancer agents. The aurora kinases are new targets in this class. Inhibitors of aurora kinases are likely to be cytotoxic. Finally, protein regulation is essential for cellular integrity. With the approval of bortezomib (Velcade, PS-341), the proteosome, a master protein regulator, has been validated as an anticancer target. The five articles in this issue of CCR Focus present the current status of these next generation cytotoxic agents.

Mixed PEG-PE/vitamin E tumor-targeted immunomicelles as carriers for poorly soluble anti-cancer drugs: improved drug solubilization and enhanced in vitro cytotoxicity

Two poorly soluble, potent anti-cancer drugs, paclitaxel and camptothecin, were successfully solubilized by mixed micelles of polyethylene glycol-phosphatidyl ethanolamine (PEG-PE) and vitamin E. Drug-containing micelles were additionally modified with anti-nucleosome monoclonal antibody 2C5 (mAb 2C5), which can specifically bring micelles to tumor cells in vitro. The optimized micelles had an average size of about 13-22 nm and the immuno-modification of micelles did not significantly change it. The solubilization of both drugs by the mixed micelles was more efficient than by micelles made of PEG-PE alone. Solubilization of camptothecin in micelles prevented also the hydrolysis of active lactone form of the drug to inactive carboxylate form. Drug-loaded mixed micelles and mAb 2C5-immunomicelles demonstrated significantly higher in vitro cytotoxicity than free drug against various cancer cell lines.