Novel factor-loaded polyphosphazene matrices: potential for driving angiogenesis

Currently employed bone tissue engineered scaffolds often lack the potential for vascularization, which may be enhanced through the incorporation of and regulated release of angiogenic factors. For this reason, the objective here was to fabricate and characterize protein-loaded amino acid ester polyphosphazene (Pphos)-based scaffolds and evaluate the novel sintering method used for protein incorporation, a method which will ultimately allow for the incorporation of proangiogenic agents. To test the hypothesis, Pphos and their composite microspheres with nanocrystalline hydroxyapatite (Pphos-HAp) were fabricated via the emulsion solvent evaporation method. Next, bovine serum albumin (BSA)-containing microsphere matrices were created using a novel solvent-non-solvent approach for protein loading. The resulting protein (BSA) loaded circular porous microsphere based scaffolds were characterized for morphology, porosity, protein structure, protein distribution and subsequent protein release pattern. Scanning electron microscopy revealed porous microsphere scaffolds with a smooth surface and sufficient level of sintering, illustrated by fusion of adjacent microspheres. The porosity measured for the poly(ethyl phenylalanato:glycinato)phosphazene (PNPhGly) and poly(ethyl phenylalanato:glycinato)phosphazene-hydroxyapatite (PNPhGly-HAp) scaffolds were 23 +/- 0.11% and 18 +/- 4.02%, respectively, and within the range of trabecular bone. Circular dichroism confirmed an intact secondary protein structure for BSA following the solvent sintering method used for loading and confocal microscopy verified that FITC-BSA was successfully entrapped both between adjacent microspheres and within the surface of the microspheres while sintering. For both Pphos and their composite microsphere scaffolds, BSA was released at a steady rate over a 21 day time period, following a zero order release profile. HAp particles in the composite scaffolds served to improve the release profile pattern, underscoring the potential of HAp for growth factor delivery. Moreover, the results of this work suggest that the solvent-non-solvent technique for protein loading is an optimal one that will allow for future development of angiogenic factor-loaded Pphos matrices with the capacity to invoke neovascularization.     

Emerging therapies: angiogenesis inhibitors for ovarian cancer

Introduction: Patients with epithelial ovarian cancer (EOC) have a high rate of recurrence, and overall survival remains at ～ 25%. There is a need for new treatments that can increase progression free survival and quality of life. Recent clinical trials focus on angiogenesis, VEGFs, and tyrosine kinase inhibitors that play a role in recurrence, metastasis, and ascites in EOC.

Areas covered: This review summarizes clinical rationale, mechanisms of action, and clinical data for angiogenesis inhibitors under evaluation in Phase II and III trials for EOC. Anti-angiogenesis agents reviewed in this paper include aflibercept, bevacizumab, cediranib, fosbretabulin, imatinib, nintedanib, pazopanib, saracatinib, sorafenib, sunitinib, and trebananib.

Expert opinion: These agents have particular rationale for potential use in EOC due to the molecular changes associated with EOC tumorigenesis, namely a significant increase in angiogenic activity. Due to the costs and toxicities associated with anti-angiogenics, biomarker or molecular signature selection strategy for patients who will most benefit would be ideal but no such strategy has been validated to date.     

Angiopoietin/Tie receptor system: emerging targets for therapeutic angiogenesis and anti-angiogenic therapy

Balanced regulation of endothelial cell function and co-ordination of endothelial cells and periendothelial support cells by angiogenic growth factors and cell type-specific receptor tyrosine kinases is crucially involved in physiological angiogenesis. Disturbance of this fine-tuned balance is associated with disease-related neoangiogenesis, such as in tumour angiogenesis or in retinopathy, or in insufficient angiogenesis in occlusive vascular disease. In addition to the well known function of vascular endothelial growth factor (VEGF) as an endothelial cell-specific angiogenesis inducer and survival factor, recent studies on angiopoietins and their receptors have provided insight into the interplay of these endothelium-specific ligand-receptor systems in formation, maintenance and remodelling of the vasculature. Knowledge of the mechanisms by which these ligand-receptor systems are involved in regulation of the interaction of endothelial cells and their periendothelial support cells opens new opportunities for therapeutic angiogenesis to induce formation of functional blood vessels in occlusive disease, as well as to complement and/or enhance current anti-VEGF-based strategies for anti-angiogenic therapy.     

Novel investigational vascular endothelial growth factor (VEGF) receptor antagonists for psoriasis

Introduction: Affecting 1 million people in the UK, psoriasis is a commonly diagnosed inflammatory disease arising from autoimmune processes that are triggered by environmental factors in genetically susceptible individuals. The pathophysiology of psoriasis has been widely studied and there is evidence that angiogenesis is a key component.

Areas covered: In this review the role of vascular endothelial growth factor-A (VEGF), as a key angiogenic mediator in psoriasis pathogenesis is discussed. VEGF is found in higher levels in plaques, normal skin and plasma of patients with psoriasis. The level of VEGF also fluctuates in accordance with disease activity and in response to conventional treatments. There are several VEGF inhibitors currently licenced for use; primarily in the fields of oncology and there are case reports of patients being treated with these therapies for metastatic cancer who have demonstrated significant improvement in their psoriasis. VEGF inhibitory agents have suggested promising utility for the treatment of psoriasis following animal studies.

Expert opinion: VEGF may represent a novel treatment target in psoriasis. However, VEGF inhibitors can cause significant side effects such as hypertension and left ventricular dysfunction. The risks of treatment must be carefully evaluated before VEGF inhibitors are trialled or advocated for psoriasis.     

Regulation of angiogenesis and vascular permeability by Src family kinases: opportunities for therapeutic treatment of solid tumors

Aberrant expression or activation of protein tyrosine kinases, including Src and related Src family kinases, is a common occurrence in many human cancers, resulting in deregulation of expression of numerous mediators of cellular functions, including pro-angiogenic molecules. In addition, Src activation regulates vascular permeability of endothelial cells. How these processes contribute to tumor progression and metastasis are the subjects of this review. As Src-selective inhibitors have entered clinical trials for a number of solid tumors, further understanding of the roles of Src kinases in mediating tumor angiogenesis as well as modulating tumor/microenvironment interactions will provide insights into the best use of these inhibitors in treating patients afflicted with tumors in which Src is activated.     

Therapeutic angiogenesis: protein-based therapy for coronary artery disease

Therapeutic angiogenesis is a promising treatment for ischaemic heart disease, particularly for patients who are not candidates for current methods of revascularisation. The goal of angiogenic therapy is the relief of symptoms of coronary artery disease and improvement of cardiac function by increasing perfusion to the ischaemic myocardium. Angiogenic cytokines such as fibroblast growth factor and vascular endothelial growth factor have been studied extensively in preclinical studies. Protein-based therapy with these growth factors has produced functionally significant angiogenesis in several animal models. Enthusiasm following these preclinical results led the way to clinical trials, which so far have shown only modest improvements in myocardial perfusion and clinical outcome. The attenuated angiogenic response to growth factor therapy observed in patients with coronary artery disease may be related to associated conditions such as endothelial dysfunction, regimens of single as opposed to multiple angiogenic agents and inefficiency of current delivery modalities, as illustrated by the disappointing results of the Phase II clinical trials using intravascular techniques of administration. The ultimate role angiogenesis will play clinically in the treatment of ischaemic heart disease will be determined by adequately powered, randomised, double-blind, placebo-controlled trials that include multi-agent angiogenic therapy and intramyocardial methods of delivery.     

TNP-470: an angiogenesis inhibitor in clinical development for cancer

TNP-470, an analogue of fumagillin, has been shown to inhibit angiogenesis in vitro and in vivo. In 1992, TNP-470 entered clinical development for cancer as an anti-angiogenic agent. It is currently in Phase I/II trials in Kaposi’s sarcoma, renal cell carcinoma, brain cancer, breast cancer, cervical cancer and prostate cancer. In early clinical reports, TNP-470 is tolerated up to 177 mg/m² with neurotoxic effects (fatigue, vertigo, ataxia, and loss of concentration) being the principal dose limiting toxicity (DLT). Terminal half-life values are short and have shown intermittent and intrapatient variation (range: 0.05 - 1.07 h). Recently, mechanistic studies have identified cell cycle mediators and the protein methionine aminopeptidase-2 (MetAP-2) as molecular targets of TNP-470 and fumagillin. Animal studies confirm some toxic effects on normal angiogenic processes such as the female reproductive system and wound healing, which will require caution and close monitoring in the clinic. TNP-470 is one of the first anti-angiogenic compounds to enter clinical trials, making it a valuable prototype for future trials of angiogenesis inhibitors in oncology.     

Anti-VEGF therapies for malignant glioma: treatment effects and escape mechanisms

Background: Glioblastoma multiforme (GBM) has a very poor prognosis and novel treatment strategies are urgently needed. GBM appears to be an optimal target for anti-angiogenic therapy as the tumour shows a high degree of endothelial cell proliferation and pro-angiogenic growth factor expression. Objective: To examine the role of angiogenic factors (particularly VEGF) in glioma and whether inhibition of these factors can be used as a treatment. Methods: A review of relevant literature. Results/conclusions: Anti-angiogenic therapy has fulfilled the proof of concept in glioma animal models. In glioma patients, the efficacy of anti-angiogenic mono-therapies initially has been disappointing. However recent clinical trials combining bevacizumab, an anti-VEGF antibody, with chemotherapy reported very encouraging response rates. Although randomized phase III clinical trials with anti-angiogenic molecules are not yet available for GBM patients, this treatment regimen is already applied off protocol in several clinical centers. It should be kept in mind though that tumours can develop escape mechanisms. In particular invasive cells, which migrate away from the highly vascularized tumour core, are not targeted by anti-angiogenic therapies. In our opinion, the future of anti-angiogenic therapy will rely on a combination strategy including chemotherapy and drugs that target invasive glioma cells.     

A practical synthesis of [18F]FtRGD: an angiogenesis biomarker for PET

Integrins have become increasingly attractive targets for molecular imaging of angiogenesis with positron emission tomography or single‐photon emission computed tomography, but the reliable production of radiopharmaceuticals remains challenging. A strategy for chemoselective labeling of the integrin ligand—c(RGDyK) peptide—has been developed on the basis of the Cu(I)‐catalyzed conjugation reaction. Recently, we reported a nucleophilic detagging and fluorous solid‐phase extraction method providing an easy way to implement an approach for obtaining 2‐[¹⁸F]fluoroethyl azide. In this work, we report the practical use of this method for the preparation of the 2‐[¹⁸F]fluoroethyl‐triazolyl conjugated c(RGDyK) peptide: [¹⁸F]FtRGD. The two‐step, two‐pot synthesis, HPLC purification, and reformulation could be readily performed with a standard nucleophilic radiofluorination synthesizer (GE TRACERlab FX_FN), with minimal modifications. [¹⁸F]FtRGD was obtained in a solution for injection (>500 MBq/mL) in 10–30% nondecay‐corrected radiochemical yield, excellent radiochemical purity (>98%), and 28 ± 13 GBq/µmol specific activity. [¹⁸F]FtRGD (K_i = 54 ± 14 nM for α_Vβ₃ and 1.7 ± 0.2 nM for α_Vβ₅) was evaluated in mice and showed good stability in vivo, good tumor‐to‐background ratio (1.6 ± 0.3 %ID/g at 1.5 h post‐injection in U87‐MG tumors), and rapid urinary excretion. Therefore, [¹⁸F]FtRGD proved valuable for preclinical positron emission tomography imaging of integrin expression.     

Supercooled Smectic Nanoparticles: A Potential Novel Carrier System for Poorly Water Soluble Drugs

PURPOSE: The possibility of preparing nanoparticles in the supercooled thermotropic liquid crystalline state from cholesterol esters with saturated acyl chains as well as the incorporation of model drugs into the dispersions was investigated using cholesteryl myristate (CM) as a model cholesterol ester. METHODS: Nanoparticles were prepared by high-pressure melt homogenization or solvent evaporation using phospholipids, phospholipid/ bile salt, or polyvinyl alcohol as emulsifiers. The physicochemical state and phase behavior of the particles was characterized by particle size measurements (photon correlation spectroscopy, laser diffraction with polarization intensity differential scattering), differential scanning calorimetry, X-ray diffraction, and electron and polarizing light microscopy. The viscosity of the isotropic and liquid crystalline phases of CM in the bulk was investigated in dependence on temperature and shear rate by rotational viscometry. RESULTS: CM nanoparticies can be obtained in the smectic phase and retained in this state for at least 12 months when stored at 230C in optimized systems. The recrystallization tendency of CM in the dispersions strongly depends on the stabilizer system and the particle size. Stable drug-loaded smectic nanoparticles were obtained after incorporation of 10% (related to CM) ibuprofen, miconazole, etomidate, and 1% progesterone. CONCLUSIONS: Due to their liquid crystalline state, colloidal smectic nanoparticles offer interesting possibilities as carrier system for lipophilic drugs. CM nanoparticles are suitable model systems for studying the crystallization behavior and investigating the influence of various parameters for the development of smectic nanoparticles resistant against recrystallization upon storage.     

Liquid chromatography solvent optimization: Potential pitfalls when using a black ☐ for developing a quality separation

ICOS and DIAMOND are two commercially available, semi-automated HPLC solvent optimization software packages. The resultant optimized chromatographic separation is dependent on a combination of the operator's objective, the capability of the software system and the appropriateness of the data input. The latter contains components that represent the match between the requirements of the algorithms used and the information content of the data on which those algorithms operated. Knowledge about the sample content, stability and potential sample-solvent interactions can have a significant effect on the quality of the optimal solvent composition that is calculated. The results generated during the optimization of the separation of a mixture of U-83,757 and a variety of related compounds illustrate the need to consider the significance of the contribution to the calculated optimal separation of each of these potential pitfalls, both individually and in combination with the mode of operation of the relevant algorithms. Our results indicate that the quality of the final result is highly dependent on the intelligence content of the data used.     

Synthesis of Novel 2,5‐Disubstituted 1,3,4‐Thiadiazoles for Their Potential Anticonvulsant Activity: Pharmacophoric Model Studies

A series of novel N¹‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N⁴‐(4‐substituted benzaldehyde)‐semicarbazone 1 – 12 , N¹‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N⁴‐[1‐(4‐substituted phenyl)ethanone]‐semicarbazone 13 ‐ 16 , and N¹‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N⁴‐[1‐(4‐substituted phenyl) (phenyl) methanone]‐semicarbazone 17 – 20 were synthesized for their anticonvulsant activity. The chemical structures of the compounds were proved by elemental and spectral (IR, ¹H‐NMR, ¹³C‐NMR, and MS) analysis. The anticonvulsant potential of the compounds was investigated using maximal electroshock seizure (MES) and subcutaneous pentylenetrtrazole (scPTZ) models. Compound 19 was found to possess significant anticonvulsant activity in both the models employed for anticonvulsant evaluation. Compounds 8 , 13 , 15 , and 16 also demonstrated a marked anticonvulsant property. The results of the present study validated that the pharmacophore model with four binding sites is essential for anticonvulsant activity. The efforts were also made to establish structure‐activity relationships among the synthesized compounds.     

Cellular Fingerprints: A Novel Approach Using Large‐Scale Cancer Cell Line Data for the Identification of Potential Anticancer Agents

The cellular fingerprint, a novel in silico screening approach, was developed to identify new biologically active compounds in combination with structural fingerprints. To this end, high‐throughput screening (HTS) data from the National Cancer Institute have been used. To validate this method, we have selected the proapoptotic, natural compound betulinic acid (BA). Because of its antiproliferative effect on a variety of cancer cell lines, the identification of novel BA analogs is of great interest. Novel analogs have been identified and validated in different apoptosis assays. In addition, the novel approach exhibited a strong correlation between structural similarity and biological activity, so that it offers enormous potential for the identification of novel biologically active compounds.     

Novel Potent and Selective Acetylcholinesterase Inhibitors as Potential Drugs for the Treatment of Alzheimer's Disease: Synthesis,Pharmacological Evaluation,and Molecular Modeling of Amino‐Alkyl‐Substituted Fluoro‐Chalcones Derivatives

A new series of‐fluoro chalcones‐substituted amino‐alkyl derivatives ( 3a?3l ) were designed, synthesized, characterized and evaluated for the inhibitory activity against acetylcholinesterase and butyrylcholinesterase. The results showed that the alteration of fluorine atom position and amino‐alkyl groups markedly influenced the activity and the selectivity of chalcone derivates in inhibiting acetylcholinesterase and butyrylcholinesterase. Among them, compound 3l possesses the most potent inhibitory against acetylcholinesterase (IC₅₀ = 0.21 ± 0.03 μmol/L), and the highest selectivity for acetylcholinesterase over butyrylcholinesterase (IC₅₀ (BuChE)/IC₅₀ (AChE) = 65.0). Molecular modeling and enzyme kinetic study on compound 3l supported its dual acetylcholinesterase inhibitory profile, simultaneously binding at the catalytic active and peripheral anionic site of the enzyme.