Showing papers in "Molecular Pharmaceutics in 2011"

Nanomedicine(s) under the Microscope

Abstract: Depending on the context, nanotechnologies developed as nanomedicines (nanosized therapeutics and imaging agents) are presented as either a remarkable technological revolution already capable of delivering new diagnostics, treatments for unmanageable diseases, and opportunities for tissue repair or highly dangerous nanoparticles, nanorobots, or nanoelectronic devices that will wreak havoc in the body. The truth lies firmly between these two extremes. Rational design of “nanomedicines” began almost half a century ago, and >40 products have completed the complex journey from lab to routine clinical use. Here we critically review both nanomedicines in clinical use and emerging nanosized drugs, drug delivery systems, imaging agents, and theranostics with unique properties that promise much for the future. Key factors relevant to the design of practical nanomedicines and the regulatory mechanisms designed to ensure safe and timely realization of healthcare benefits are discussed.

Drug resistance and cellular adaptation to tumor acidic pH microenvironment.

Abstract: Despite advances in developing novel therapeutic strategies, a major factor underlying cancer related death remains resistance to therapy. In addition to biochemical resistance, mediated by xenobiotic transporters or binding site mutations, resistance can be physiological, emerging as a consequence of the tumor’s physical microenvironment. This review focuses on extracellular acidosis, an end result of high glycolytic flux and poor vascular perfusion. Low extracellular pH, pHe, forms a physiological drug barrier described by an “ion trapping” phenomenon. We describe how the acid-outside plasmalemmal pH gradient negatively impacts drug efficacy of weak base chemotherapies but is better suited for weakly acidic therapeutics. We will also explore the physiologic changes tumor cells undergo in response to extracellular acidosis which contribute to drug resistance including reduced apoptotic potential, genetic alterations, and elevated activity of a multidrug transporter, p-glycoprotein, pGP. Since low pHe is ...

Transcriptomic and Quantitative Proteomic Analysis of Transporters and Drug Metabolizing Enzymes in Freshly Isolated Human Brain Microvessels

Abstract: We have investigated the transcriptomic and/or proteomic patterns of 71 solute carrier (SLC) and organic solute (OST) transporters, 34 ATP-binding cassette (ABC) transporters, and 51 metabolizing enzymes in human brain microvessels. We used quantitative RT-PCR and LC–MS/MS to examine isolated brain microvessels and cortex biopsies from 12 patients with epilepsia or glioma. SLC2A1/GLUT1, SLC1A3/EAAT1, and SLC1A2/EAAT2 were the main SLC proteins whereas ABCG2/BCRP, ABCB1/MDR1, ABCA2 and ABCA8 were the main ABC quantified in isolated brain microvessels; ABCG2/BCRP was 1.6-fold more expressed than ABCB1/MDR1, and ABCC4/MRP4 was 10 times less abundant than ABCB1/MDR1. CYP1B1 and CYP2U1 were the only quantifiable CYPs. Finally, GSTP1, COMT, GSTM3, GSTO1 and GSTM2 proteins were the main phase II enzymes quantified; UGTs and NATs were not detected. Our extensive investigation of gene and protein patterns of transporters and metabolizing enzymes provides new molecular information for understanding drug entry and m...

Cocrystals of Quercetin with Improved Solubility and Oral Bioavailability

Abstract: Flavonoids have been studied extensively due to the observation that diets rich in these compounds are associated with lower incidences of many diseases. One of the most studied flavonoids, quercetin, is also the most abundant of these compounds in the plant kingdom. Numerous therapeutic bioactivities have been identified in vitro. However, its in vivo efficacy in pure form is limited by poor bioavailability, primarily due to its low solubility and consequent low absorption in the gut. Cocrystallization has gained attention recently as a means for improving the physicochemical characteristics of a compound. Here, we synthesized and evaluated four new cocrystals of quercetin (QUE): quercetin:caffeine (QUECAF), quercetin:caffeine:methanol (QUECAF·MeOH), quercetin:isonicotinamide (QUEINM), and quercetin:theobromine dihydrate (QUETBR·2H2O). Each of these cocrystals exhibited pharmacokinetic properties that are vastly superior to those of quercetin alone. Cocrystallization was able to overcome the water insolu...

In vitro and in vivo mRNA delivery using lipid-enveloped pH-responsive polymer nanoparticles.

Abstract: Biodegradable core−shell structured nanoparticles with a poly(β-amino ester) (PBAE) core enveloped by a phospholipid bilayer shell were developed for in vivo mRNA delivery with a view toward delivery of mRNA-based vaccines. The pH-responsive PBAE component was chosen to promote endosome disruption, while the lipid surface layer was selected to minimize toxicity of the polycation core. Messenger RNA was efficiently adsorbed via electrostatic interactions onto the surface of these net positively charged nanoparticles. In vitro, mRNA-loaded particle uptake by dendritic cells led to mRNA delivery into the cytosol with low cytotoxicity, followed by translation of the encoded protein in these difficult-to-transfect cells at a frequency of ∼30%. Particles loaded with mRNA administered intranasally (i.n.) in mice led to the expression of the reporter protein luciferase in vivo as soon as 6 h after administration, a time point when naked mRNA given i.n. showed no expression. At later time points, luciferase expres...

Coamorphous drug systems: enhanced physical stability and dissolution rate of indomethacin and naproxen.

Abstract: One of the challenges in drug development today is that many new drug candidates are poorly water-soluble, and one of the approaches to overcome this problem is to transfer a crystalline drug into its amorphous form, thus increasing dissolution rate and apparent solubility of the compound. In this study, a coamorphous drug/drug combination between the two nonsteroidal anti-inflammatory drugs, naproxen and γ-indomethacin, was prepared and investigated. At molar ratios of 2:1, 1:1 and 1:2, the drugs were quench cooled in order to obtain a coamorphous binary phase. Physical stability was examined at 277.15 and 298.15 K under dry conditions (phosphorus pentoxide) and analyzed with X-ray powder diffraction (XRPD). Intrinsic dissolution testing was carried out to identify dissolution advantages of the coamorphous form over its crystalline counterparts or amorphous indomethacin. Fourier transform infrared spectroscopy (FTIR) was used for analyses at the molecular level to detect potential molecular interactions. Differential scanning calorimetry (DSC) thermograms were employed to assess the glass transition temperatures (T(g)), and the results were compared with predicted T(g)s from the Gordon-Taylor equation. Results showed that naproxen could be made amorphous in combination with indomethacin while this was not possible with naproxen alone. Peak shifts in the FTIR spectra indicated molecular interactions between both drugs, and it is suggested that the two drugs formed a heterodimer. Therefore, samples at the 1:2 and 2:1 ratios showed recrystallization of the excess drug upon storage whereas the 1:1 ratio samples remained amorphous. Intrinsic dissolution testing showed increased dissolution rate of both drugs in the coamorphous form as well as a synchronized release for the 1:1 coamorphous blend. All T(g)s displayed negative deviations from the Gordon-Taylor equation with the 1:1 ratio showing the largest deviation. In a novel approach of predicting the glass transition temperature, the 1:1 drug ratio was inserted as an individual component in the Gordon-Taylor equation with the excess drug representing the second compound. This approach resulted in a good fit to the experimentally determined T(g)s.

Indocyanine green-containing nanostructure as near infrared dual-functional targeting probes for optical imaging and photothermal therapy.

Abstract: Indocyanine green (ICG) is a near-infrared (NIR) imaging agent and is also an ideal light absorber for laser-mediated photothermal therapy. This NIR dye could serve as a basis of a dual-functional ...

The Art of Engineering Viral Nanoparticles

Abstract: Viral nanotechnology is an emerging and highly interdisciplinary field in which viral nanoparticles (VNPs) are applied in diverse areas such as electronics, energy and next-generation medical devices VNPs have been developed as candidates for novel materials, and are often described as “programmable” because they can be modified and functionalized using a number of techniques In this review, we discuss the concepts and methods that allow VNPs to be engineered, including (i) bioconjugation chemistries, (ii) encapsulation techniques, (iii) mineralization strategies, and (iv) film and hydrogel development With all these techniques in hand, the potential applications of VNPs are limited only by the imagination

Coformulation of Doxorubicin and Curcumin in Poly(d,l-lactide-co-glycolide) Nanoparticles Suppresses the Development of Multidrug Resistance in K562 Cells

Abstract: Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic used to treat a variety of cancers including leukemia. Chronic myeloid leukemia (CML) blasts like K562 cells are resistant to apoptosis induced by DOX due to several reasons, the primary being the sequestration of drug into cytoplasmic vesicles and induction of multidrug resistance (MDR) gene expression with DOX treatment resulting in intracellular resistance to this drug. Moreover, expression of antiapoptotic protein BCL-2 and the hybrid gene bcr/abl in K562 cells contributes resistance to DOX. Studies have shown that curcumin (CUR) has a pleiotropic therapeutic effect in cancer treatment, as it is an inhibitor of nuclear factor kappa B (NFκB) as well as a potent downregulator of MDR transporters. In this study, we investigated the potential benefit of using DOX and CUR in a single nanoparticle (NP) formulation to inhibit the development of drug resistance for the enhancement of antiproliferative activity of DOX in K562 cells. Results illustr...

Characterization of CD44-Mediated Cancer Cell Uptake and Intracellular Distribution of Hyaluronan-Grafted Liposomes

Abstract: Hyaluronan (HA) is a biocompatible and biodegradable linear polysaccharide which is of interest for tumor targeting through cell surface CD44 receptors. HA binds with high affinity to CD44 receptors, which are overexpressed in many tumors and involved in cancer metastasis. In the present study, we investigated the impact of HA molecular weight (MW), grafting density, and CD44 receptor density on endocytosis of HA-grafted liposomes (HA–liposomes) by cancer cells. Additionally, the intracellular localization of the HA–liposomes was determined. HAs of different MWs (5–8, 10–12, 175–350, and 1600 kDa) were conjugated to liposomes with varying degrees of grafting density. HA surface density was quantified using the hexadecyltrimethylammonium bromide turbidimetric method. Cellular uptake and subcellular localization of HA–liposomes were evaluated by flow cytometry and fluorescence microscopy. Mean particle sizes of HA–liposomes ranged from 120 to 180 nm and increased with increasing size of HA. HA–liposome upta...

The emergence of drug transporter-mediated multidrug resistance to cancer chemotherapy.

Abstract: Chemotherapy is currently one of the most effective ways to treat metastatic cancers. However, of the various mechanisms that are involved in conferring resistance, upregulation of drug efflux ATP-binding cassette (ABC) transporters, such as P-glycoprotein (ABCB1), multidrug resistance protein 1 (ABCC1) and ABCG2, has become a major obstacle to cancer chemotherapy and seriously affects the clinical outcome. To date, at least 15 ABC drug transporters have been identified and characterized to transport and confer resistance to practically the entire spectrum of cancer drugs, causing multidrug resistance (MDR) in cancers. Unfortunately, despite decades of research, there is still no real solution to MDR. This review highlights some of the major findings, the roles and problems associated with MDR-linked ABC drug transporters in metastatic cancers and solid tumors, and the current strategies to improve the clinical outcome in cancer chemotherapy.

Aerosolized PLA and PLGA Nanoparticles Enhance Humoral, Mucosal and Cytokine Responses to Hepatitis B Vaccine

Abstract: Porous poly(L-lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) nanoparticles were tested for pulmonary delivery of hepatitis B vaccine. In particular, the effects of particle size and hydrophobicity on mucosal and cell-mediated immune responses were investigated. Three formulations of PLA and PLGA nanoparticles containing a fixed amount of hepatitis B surface antigen (HBsAg) were prepared by a double-emulsion-solvent-evaporation method and characterized for surface morphology, charge, size, density and in vitro release. The immune responses were studied by measuring secretory IgA levels in mucosal fluids and quantitating cytokine levels in rat spleen homogenates. Particle uptake was studied in rat alveolar macrophages. Scanning electron microscopy revealed particles with smooth surfaces. Zeta potential measurements indicated that the particles carried negative surface charges. The antigen was continuously released for 42 days in phosphate buffer. Hydrophobic particles >500 nm elicited a more robust increase in secretary IgA, interleukin-2 and interferon-γ levels compared to hydrophilic particles <500 nm. Large hydrophobic particles were more efficiently internalized by rat alveolar macrophages compared to smaller hydrophilic particles. Calu-3 cell viability studies indicate that the viability of cells is not affected by nanoparticulate formulations. This study demonstrates that inhalable nanoparticles of HBsAg produce an enhancement of immune responses.

HSA Coated Iron Oxide Nanoparticles as Drug Delivery Vehicles for Cancer Therapy

Abstract: An ongoing effort in the field of nanomedicine is to develop nanoplatforms with both imaging and therapeutic functions, the "nanotheranostics". We have previously developed a human serum albumin (HSA) coated iron oxide nanoparticle (HINP) formula and used multiple imaging modalities to validate its tumor targeting attributes. In the current study, we sought to impart doxorubicin (Dox) onto the HINPs and to assess the potential of the conjugates as theranostic agents. In a typical preparation, we found that about 0.5 mg of Dox and 1 mg of iron oxide nanoparticles (IONPs, Fe content) could be loaded into 10 mg of HSA matrices. The resulting D-HINPs (Dox loaded HINPs) have a hydrodynamic size of 50 nm and are able to release Dox in a sustained fashion. More impressively, the HINPs can assist the translocation of Dox across the cell membrane and even its accumulation in the nucleus. In vivo, D-HINPs retained a tumor targeting capability of HINPs, as manifested by both in vivo MRI and ex vivo immunostaining results. In a follow-up therapeutic study on a 4T1 murine breast cancer xenograft model, D-HINPs showed a striking tumor suppression effect that was comparable to that of Doxil and greatly outperformed free Dox. Such a strategy can be readily extended to load other types of small molecules, making HINP a promising theranostic nanoplatform.

Polymeric nanoparticles with precise ratiometric control over drug loading for combination therapy

Abstract: We report a novel approach for nanoparticle-based combination chemotherapy by concurrently incorporating two different types of drugs into a single polymeric nanoparticle with ratiometric control over the loading of the two drugs. By adapting metal alkoxide chemistry, we synthesize highly hydrophobic drug–poly-l-lactide (drug–PLA) conjugates, of which the polymer has the same chain length while the drug may differ. These drug–polymer conjugates are then encapsulated into lipid-coated polymeric nanoparticles through a single-step nanoprecipitation method. Using doxorubicin (DOX) and camptothecin (CPT) as two model chemotherapy drugs, various ratios of DOX–PLA and CPT–PLA conjugates are loaded into the nanoparticles with over 90% loading efficiency. The resulting nanoparticles are uniform in size, size distribution and surface charge. The loading yield of DOX and CPT in the particles can be precisely controlled by simply adjusting the DOX–PLA:CPT–PLA molar ratio. Cellular cytotoxicity results show that the ...

The solubility-permeability interplay: Mechanistic modeling and predictive application of the impact of micellar solubilization on intestinal permeation

Abstract: Surfactants are routinely employed to increase the apparent aqueous solubility of poorly soluble drugs. Yet the impact of micellar solubilization on the intestinal membrane permeability of a lipophilic drug is often overlooked and poorly understood. In this work, the interplay between the apparent solubility increase and intestinal membrane permeability decrease that exists when surfactants are used as drug solubility enhancers is described. A quasi-equilibrium mechanistic mass transport analysis was developed and employed to describe the effect of micellar solubilization by sodium taurocholate (STC) and sodium lauryl sulfate (SLS) on the intestinal membrane permeability of the lipophilic drug progesterone. The model considers the effects of micellar solubilization on both the membrane permeability (Pm) and the unstirred water layer (UWL) permeability (Paq), to predict the overall effective permeability (Peff) dependence on surfactant concentration (CS). The analysis reveals that (1) the effective UWL thi...

MicroRNA Delivery by Cationic Lipoplexes for Lung Cancer Therapy

Abstract: Lung cancer is the leading cause of cancer deaths in western countries and carries a poor overall five year survival rate. Several studies demonstrate that microRNAs (miRNAs or miRs) are actively involved in tumor development by serving as tumor suppressors, oncogenes or both. In lung cancer, miRNAs may serve as both diagnostic and prognostic biomarkers as well as regulate in vitro and in vivo tumor progression. However, miRNA-based therapy is faced with several challenges including lack of tissue specificity, lack of optimal delivery systems, poor cellular uptake and risk of systemic toxicity. Here, we report a cationic lipid based miRNA delivery system to address some of these challenges. Among many lung cancer related miRNAs, miR-133b, a tumor suppressor, was selected as a therapeutic target because it directly targets the prosurvival gene MCL-1 thus regulating cell survival and sensitivity of lung cancer cells to chemotherapeutic agents. The efficacy of pre-miR-133b containing lipoplexes was evaluated...

The Suppressive Tumor Microenvironment: A Challenge in Cancer Immunotherapy

Abstract: In this review, we introduce the changing public perception of vaccines and immunotherapy in cancer treatments. We discuss the roles that different immunosuppressive cells play in the tumor microenvironment. Tumor associated macrophages (TAMs) and M1 and M2 macrophage phenotypes are discussed in depth. Additionally, the role that myeloid derived suppressor cells (MDSC) and T regulatory cells (Tregs) play in the tumor microenvironment is addressed. Highlighted are examples of therapies used against each suppressive cell type, which vary from the hypothetical to the ineffective; the inefficient to the successful. A variety of treatments have been tried to combat this fundamental problem, indeed the cause that allows cancerous mutated cells to survive, multiply and overtake the body. Efficient methods to disable each particular suppressive type of cell have been introduced; this review summarizes the discussion with a table to guide future development. We see gene therapy as the most innovative and flexible ...

Imaging drug delivery to skin with stimulated Raman scattering microscopy.

Abstract: Efficient drug delivery to the skin is essential for the treatment of major dermatologic diseases, such as eczema, psoriasis and acne. However, many compounds penetrate the skin barrier poorly and require optimized formulations to ensure their bioavailability. Here, stimulated Raman scattering (SRS) microscopy, a recently developed, label-free chemical imaging tool, is used to acquire high resolution images of multiple chemical components of a topical formulation as it penetrates into mammalian skin. This technique uniquely provides label-free, nondestructive, three-dimensional images with high spatiotemporal resolution. It reveals novel features of (trans)dermal drug delivery in the tissue environment: different rates of drug penetration via hair follicles as compared to the intercellular pathway across the stratum corneum are directly observed, and the precipitation of drug crystals on the skin surface is visualized after the percutaneous penetration of the cosolvent excipient in the formulation. The high speed three-dimensional imaging capability of SRS thus reveals features that cannot be seen with other techniques, providing both kinetic information and mechanistic insight into the (trans)dermal drug delivery process.

ADME evaluation in drug discovery. 10. Predictions of P-glycoprotein inhibitors using recursive partitioning and naive Bayesian classification techniques.

Abstract: P-Glycoprotein (P-gp), an efflux transporter, plays a crucial role in drug pharmacokinetic properties (ADME), and is critical for multidrug resistance (MDR) by mediating the active transport of anticancer drugs from the intracellular to the extracellular compartment. Here we reported an original database of 1273 molecules that are categorized into P-gp inhibitors and noninhibitors. The impact of various physicochemical properties on P-gp inhibition was examined. We then built the decision trees from a training set of 973 compounds using the recursive partitioning (RP) technique and validated by an external test set of 300 compounds. The best decision tree correctly predicted 83.5% of the inhibitors and 67.0% of the noninhibitors in the test set. Finally, we applied naive Bayesian categorization modeling to establish classifiers for P-gp inhibitors. The Bayesian classifier gave average correct prediction for 81.7% of 973 compounds in the training set with leave-one-out cross-validation procedure and 81.2% ...

Development of EGFR-Targeted Polymer Blend Nanocarriers for Combination Paclitaxel/Lonidamine Delivery to Treat Multi-Drug Resistance in Human Breast and Ovarian Tumor Cells

Abstract: Multi-drug resistant (MDR) cancer is a significant clinical obstacle and is often implicated in cases of recurrent, nonresponsive disease. Targeted nanoparticles were made by synthesizing a poly(D,L-lactide-co-glycolide)/poly(ethylene glycol)/epidermal growth factor receptor targeting peptide (PLGA/PEG/EGFR-peptide) construct for incorporation in poly(epsilon-caprolactone) (PCL) nanoparticles. MDR was induced in a panel of nine human breast and ovarian cancer cell lines using hypoxia. EGFR-targeted polymer blend nanoparticles were shown to actively target EGFR overexpressing cell lines, especially upon induction of hypoxia. The nanoparticles were capable of sustained drug release. Combination therapy with lonidamine and paclitaxel significantly improved the therapeutic index of both drugs. Treatment with a nanoparticle dose of 1 μM paclitaxel/10 μM lonidamine resulted in less than 10% cell viability for all hypoxic/MDR cell lines and less than 5% cell viability for all normoxic cell lines. Comparatively, treatment with 1 μM paclitaxel alone was the approximate IC₅₀ value of the MDR cells while treatment with lonidamine alone had very little effect. The PLGA/PEG/EGFR-peptide delivery system actively targets a MDR cell by exploiting the expression of EGFR. This system treats MDR by inhibiting the Warburg effect and promoting mitochondrial binding of pro-apoptotic Bcl-2 proteins (lonidamine), while hyperstabilizing microtubules (paclitaxel). This nanocarrier system actively targets a MDR associated phenotype (EGFR receptor overexpression), further enhancing the therapeutic index of both drugs and potentiating the use of lonidamine/paclitaxel combination therapy in the treatment of MDR cancer.

A comparative study of neural and mesenchymal stem cell-based carriers for oncolytic adenovirus in a model of malignant glioma.

Abstract: Glioblastoma multiforme is a primary malignancy of the central nervous system that is universally fatal due to its disseminated nature. Recent investigations have focused on the unique tumor-tropic properties of stem cells as a novel platform for targeted delivery of anticancer agents to the brain. Neural stem cells (NSCs) and mesenchymal stem cells (MSCs) both have the potential to function as cell carriers for targeted delivery of a glioma restricted oncolytic virus to disseminated tumor due to their reported tumor tropism. In this study, we evaluated NSCs and MSCs as cellular delivery vehicles for an oncolytic adenovirus in the context of human glioma. We report the first preclinical comparison of the two cell lines and show that, while both stem cell lines are able to support therapeutic adenoviral replication intracellularly, the amount of virus released from NSCs was a log higher than the MSC (p < 0.001). Moreover, only virus loaded NSCs that were administered intracranially in an orthotopic glioma ...

The effect of multiple N-methylation on intestinal permeability of cyclic hexapeptides.

Abstract: Recent progress in peptide synthesis simplified the synthesis of multiple N-methylation of peptides. To evaluate how multiple N-methylation affects the bioavailability of peptides, a poly alanine cyclic hexapeptide library (n = 54), varying in the number of N-methyl (N-Me) groups (1-5 groups) and their position, was synthesized. The peptides were evaluated for their intestinal permeability in vitro using the Caco-2 model. Further evaluation of the transport route of chosen analogues was performed using rat excised viable intestinal tissue, a novel colorimetric liposomal model and the parallel artificial membrane permeability assay (PAMPA). While most members were found to have poor permeability (permeability coefficient, P(app) 1 x 10⁻⁵ cm/s, similar to testosterone, a marker of transcellular permeability). No correlation was found between the number of N-methylated groups and the enhanced permeability. However, 9/10 permeable peptides in the Caco-2 model included an N-Me placed adjacently to the D-Ala position. While the exact transport route was not fully characterized, the data suggests a facilitated diffusion. It can be concluded that multiple N-methylation of peptides may improve intestinal permeability, and therefore can be utilized in the design of orally available peptide-based therapeutics.

Mannose-functionalized "pathogen-like" polyanhydride nanoparticles target C-type lectin receptors on dendritic cells.

Abstract: Targeting pathogen recognition receptors on dendritic cells (DCs) offers the advantage of triggering specific signaling pathways to induce a tailored and robust immune response. In this work, we describe a novel approach to targeted antigen delivery by decorating the surface of polyanhydride nanoparticles with specific carbohydrates to provide “pathogen-like” properties that ensure nanoparticles engage C-type lectin receptors on DCs. The surface of polyanhydride nanoparticles was functionalized by covalent linkage of dimannose and lactose residues using an amine–carboxylic acid coupling reaction. Coculture of functionalized nanoparticles with bone marrow-derived DCs significantly increased cell surface expression of MHC II, the T cell costimulatory molecules CD86 and CD40, the C-type lectin receptor CIRE and the mannose receptor CD206 over the nonfunctionalized nanoparticles. Both nonfunctionalized and functionalized nanoparticles were efficiently internalized by DCs, indicating that internalization of fu...

Oncolytic adenoviruses for the treatment of human cancer: focus on translational and clinical data.

Abstract: Although results of cancer treatment have improved steadily, metastatic solid tumors can be cured only rarely and therefore new modalities are needed. Tumors often become apoptosis-resistant and capable of excluding drugs during therapy. Similar mechanisms of resistance apply to many treatment regimens, and cross-resistance between different chemotherapeutics often limits the treatment options. Therefore, loss of efficacy may occur simultaneously for different chemotherapeutics. One experimental strategy with an increasing amount of clinical evidence is oncolytic viruses, which replicate preferentially in tumor cells by taking advantage of cancer-specific cellular changes. Adenoviruses are the most widely clinically used oncolytic agents. Replication of oncolytic virus per se kills tumor cells, but oncolysis can also activate the immune system, which may play a role in tumor control. Viruses can be modified in a variety of ways to improve their selectivity and efficacy. The adenovirus genome can be easily...

Excipient-mediated supersaturation stabilization in human intestinal fluids.

Abstract: It was the purpose of this study to investigate excipient-mediated precipitation inhibition upon induction of supersaturation of poorly water-soluble drugs in aspirated human intestinal fluids (HIF) representing both the fasted and fed state. Etravirine, ritonavir, loviride, danazol and fenofibrate were selected as model compounds. For comparative purposes, precipitation inhibition was also evaluated in simple aqueous buffer, and in intestinal simulation media representative for the fasted and fed state (FaSSIF and FeSSIF, respectively). Supersaturation was induced in the test media containing predissolved excipient (HPMC-AS, HPMC-E5, HPMC-E50, HPMC-E4M, HPMC-P and PVP) at a defined degree of supersaturation (DS = 20) using the solvent shift method. The results illustrate that cellulosic polymers can reduce the precipitation rate and stabilize supersaturation in HIF. The extent of stabilization was compound and excipient dependent but independent of the nutritional state. Whenever excipient effects were o...

Liposomal Drug Formulations in the Treatment of Rheumatoid Arthritis

Abstract: Liposomes have been extensively investigated as drug delivery systems in the treatment of rheumatoid arthritis (RA). Low bioavailability, high clearance rates and limited selectivity of several important drugs used for RA treatment require high and frequent dosing to achieve sufficient therapeutic efficacy. However, high doses also increase the risk for systemic side effects. The use of liposomes as drug carriers may increase the therapeutic index of these antirheumatic drugs. Liposomal physicochemical properties can be changed to optimize penetration through biological barriers and retention at the site of administration, and to prevent premature degradation and toxicity to nontarget tissues. Optimal liposomal properties depend on the administration route: large-sized liposomes show good retention upon local injection, small-sized liposomes are better suited to achieve passive targeting. PEGylation reduces the uptake of the liposomes by liver and spleen, and increases the circulation time, resulting in i...

A 3-in-1 polymeric micelle nanocontainer for poorly water-soluble drugs.

Abstract: Poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles have a proven capacity for drug solubilization and have entered phase III clinical trials as a substitute for Cremophor EL in the delivery of paclitaxel in cancer therapy. PEG-b-PLA is less toxic than Cremophor EL, enabling a doubling of paclitaxel dose in clinical trials. We show that PEG-b-PLA micelles act as a 3-in-1 nanocontainer for paclitaxel, 17-allylamino-17-demethoxygeldanamycin (17-AAG), and rapamycin for multiple drug solubilization. 3-in-1 PEG-b-PLA micelles were ca. 40 nm in diameter; dissolved paclitaxel, 17-AAG, and rapamycin in water at 9.0 mg/mL; and were stable for 24 h at 25 °C. The half-life for in vitro drug release (t1/2) for 3-in-1 PEG-b-PLA micelles was 1–15 h under sink conditions and increased in the order of 17-AAG, paclitaxel, and rapamycin. The t1/2 values correlated with log Po/w values, implicating a diffusion-controlled mechanism for drug release. The IC50 value of 3-in-1 PEG-b-PLA micelles for MCF-7 and...

Fibroblasts Contribute to Melanoma Tumor Growth and Drug Resistance

Abstract: The role of tumor–stromal interactions in progression is generally well accepted, but their role in initiation or treatment is less well understood. It is now generally agreed that, rather than consisting solely of malignant cells, tumors consist of a complex dynamic mixture of cancer cells, host fibroblasts, endothelial cells and immune cells that interact with each other and microenvironmental factors to drive tumor progression. We are particularly interested in stromal cells (for example fibroblasts) and stromal factors (for example fibronectin) as important players in tumor progression since they have also been implicated in drug resistance. Here we develop an integrated approach to understand the role of such stromal cells and factors in the growth and maintenance of tumors as well as their potential impact on treatment resistance, specifically in application to melanoma. Using a suite of experimental assays we show that melanoma cells can stimulate the recruitment of fibroblasts and activate them, r...

Dendritic poly(ethylene glycol) bearing paclitaxel and alendronate for targeting bone neoplasms.

Abstract: Poly(ethylene glycol) (PEG) is the most popular polymer for protein conjugation, but its potential as carrier of low molecular weight drugs has been limited by the intrinsic low loading, owing to its chemical structure. In fact, only the two end chain groups of PEG can be modified and exploited for drug coupling. We have demonstrated that by synthesizing a dendrimer structure at the polymer end chains, it is possible to increase the drug payload and overcome this limitation. Furthermore, this approach can be improved by using heterobifunctional PEG. These polymers allow the precise linking of two different drugs, or a drug and a targeting agent, on the same polymeric chain. Heterobifunctional PEG-dendrimers have been obtained with defined chemical structures leading to their attractive use as drug delivery systems. In fact, they offer a double benefit; first, the possibility to choose the best drug/targeting agent ratio, and second, the separation of the two functions, activity and targeting, which are coupled at the opposite polymer end chains. In this study, we investigated the role of a PEG-dendrimer, H(2)N-PEG-dendrimer-(COOH)(4), as carrier for a combination of paclitaxel (PTX) and alendronate (ALN). PTX is a potent anticancer drug that is affected by severe side effects originating from both the drug itself and its solubilizing formulation, Cremophor EL. ALN is an aminobiphosphonate used for the treatment of osteoporosis and bone metastases as well as a bone-targeting moiety. The PTX-PEG-ALN conjugate was designed to exploit active targeting by the ALN molecule and passive targeting through the enhanced permeability and retention (EPR) effect. Our conjugate demonstrated a great binding affinity to the bone mineral hydroxyapatite in vitro and an IC(50) comparable to that of the free drugs combination in human adenocarcinoma of the prostate (PC3) cells. The PTX-PEG-ALN conjugate exhibited an improved pharmacokinetic profile compared with the free drugs owed to the marked increase in their half-life. In addition, PTX-PEG-ALN could be solubilized directly in physiological solutions without the need for Cremophor EL. The data presented in this manuscript encourage further investigations on the potential of PTX-PEG-ALN as treatment for cancer bone metastases.

Atomistic simulation and measurement of pH dependent cancer therapeutic interactions with nanodiamond carrier.

Abstract: In this work, we have combined constant-pH molecular dynamics simulations and experiments to provide a quantitative analysis of pH dependent interactions between doxorubicin hydrochloride (DOX) cancer therapeutic and faceted nanodiamond (ND) nanoparticle carriers. Our study suggests that when a mixture of faceted ND and DOX is dissolved in a solvent, the pH of this solvent plays a controlling role in the adsorption of DOX molecules on the ND. We find that the binding of DOX molecules on ND occurs only at high pH and requires at least ∼10% of ND surface area to be fully titrated for binding to occur. As such, this study reveals important mechanistic insight underlying an ND-based pH-controlled therapeutic platform.