Small-Molecule Fms-like Tyrosine Kinase 3 Inhibitors: An Attractive and Efficient Method for the Treatment of Acute Myeloid Leukemia.

Fms-like tyrosine kinase 3 (FLT3) is an important member of the class III receptor tyrosine kinase (RTK) family, which is involved in the proliferation of hematopoietic cells and lymphocytes. In recent years, increasing evidence have demonstrated that the activation and mutation of FLT3 is closely implicated in the occurrence and development of acute myeloid leukemia (AML). The exploration of small-molecule inhibitors targeting FLT3 has aroused wide interest of pharmaceutical chemists and is expected to bring new hope for AML therapy. In this review, we specifically highlighted FLT3 mediated JAK/STAT, RAS/MAPK, and PI3K/AKT/mTOR signaling. The structural properties and biological activities of representative FLT3 inhibitors reported from 2014 to the present were also summarized. In addition, the major challenges in the current advance of novel FLT3 inhibitors were further analyzed, with the aim to guide future drug discovery.

Total synthesis, chemical modification and structure-activity relationship of bufadienolides.

Bufadienolides are a type of natural cardiac steroids and originally isolated from the Traditional Chinese Medicine Chan'Su, they have been used for the treatment of heart disease in traditional remedies as well as in modern medicinal therapy with potent anti-tumor activities. Due to their unique molecular structures with unsaturated six-membered lactones attached to the steroid core, bufadienolides have received great attention in the synthetic organic community. This review presents total synthetic efforts to some representative bufadienolides, chemical modification of bufadienolides will also be given to discuss their structure-activity relationship in anti-tumor.

Design, synthesis, and biological activity evaluation of BACE1 inhibitors with antioxidant activity.

The proteolytic enzyme ß-secretase (BACE1) plays a central role in the synthesis of the pathogenic ß-amyloid peptides (Aß) in Alzheimer's disease (AD), antioxidants could attenuate the AD syndrome and prevent the disease progression. In this study, BACE1 inhibitors (D1-D18) with free radical-scavenging activities were synthesized by molecular hybridization of 2-aminopyridine with natural antioxidants. The biological activity evaluation showed that D1 had obvious inhibitory activity against BACE1, and strong antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+• ) assay, which could be used as a lead compound for further study.

MRI Detectable Polymer Microspheres Embedded With Magnetic Ferrite Nanoclusters For Embolization: In Vitro And In Vivo Evaluation.

OBJECTIVE: The objective of this study was to develop magnetic embolic microspheres that could be visualized by clinical magnetic resonance imaging (MRI) scanners aiming to improve the efficiency and safety of embolotherapy. METHODS AND DISCUSSION: Magnetic ferrite nanoclusters (FNs) were synthesized with microwave-assisted solvothermal method, and their morphology, particle size, crystalline structure, magnetic properties as well as T2 relaxivity were characterized to confirm the feasibility of FNs as an MRI probe. Magnetic polymer microspheres (FNMs) were then produced by inverse suspension polymerization with FNs embedded inside. The physicochemical and mechanical properties (including morphology, particle size, infrared spectra, elasticity, etc.) of FNMs were investigated, and the magnetic properties and MRI detectable properties of FNMs were also assayed by vibrating sample magnetometer and MRI scanners. Favorable biocompatibility and long-term MRI detectability of FNMs were then studied in mice by subcutaneous injection. FNMs were further used to embolize rabbits' kidneys to evaluate the embolic property and detectability by MRI. CONCLUSION: FNMs could serve as a promising MRI-visualized embolic material for embolotherapy in the future.

Preparation and In vitro Evaluation of FDM 3D-Printed Ellipsoid-Shaped Gastric Floating Tablets with Low Infill Percentages.

The aim of the study is to investigate the feasibility of fabricating FDM 3D-printed gastric floating tablets with low infill percentages and the effect of infill percentage on the properties of gastric floating tablets in vitro. Propranolol hydrochloride was selected as a model drug, and drug-loaded polyvinyl alcohol (PVA) filaments were produced by hot melt extrusion (HME). Ellipsoid-shaped gastric floating tablets with low infill percentage of 15% and 25% (namely E-15 and E-25) were then prepared respectively by feeding the extruded filaments to FDM 3D printer. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) were employed to characterize the filaments and 3D-printed tablets, and a series of evaluations were performed to the 3D-printed tablets, including the weight variation, drug content, hardness, in vitro floating behavior, and drug release of the tablets. The SEM results showed that the drug-loaded filaments and 3D-printed tablets appeared intact without defects, and the printed tablets were composed of filaments deposited uniformly layer by layer. The model drug and the excipients were thermally stable under the process temperature of extruding and printing, with a small amount of drug crystals dispersing in the drug-loaded filaments and 3D-printed tablets. Both E-15 and E-25 could float on artificial gastric fluids without any lag time and released in a sustained manner. Compared with E-15, the E-25 presented less weight variation, higher tablet hardness, shorter floating time, and longer drug release time.

Design, synthesis and evaluation of 2-amino-imidazol-4-one derivatives as potent ß-site amyloid precursor protein cleaving enzyme 1 (BACE-1) inhibitors.

Inhibition of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) to prevent brain ß-amyloid (Aß) peptide's formation is a potential effective approach to treat Alzheimer's disease. In this report we described a structure-based optimization of a series of BACE1 inhibitors derived from an iminopyrimidinone scaffold W-41 (IC50 = 7.1 µM) by Wyeth, which had good selectivity and brain permeability but low activity. The results showed that occupying the S3 cavity of BACE1 enzyme could be an effective strategy to increase the biological activity, and five compounds exhibited stronger inhibitory activity and higher liposolubility than W-41, with L-5 was the most potent inhibitor against BACE1 (IC50 = 0.12 µM, logP = 2.49).

A novel and efficient synthesis of phenanthrene derivatives via palladium/norbornadiene-catalyzed domino one-pot reaction.

Herein we report a novel palladium-catalyzed reaction that results in phenanthrene derivatives using aryl iodides, ortho-bromobenzoyl chlorides and norbornadiene in one pot. This dramatic transformation undergoes ortho-C-H activation, decarbonylation and subsequent a retro-Diels-Alder process. Pleasantly, this protocol has a wider substrate range, shorter reaction times and higher yields of products than previously reported methods.

Synthesis and Biological Evaluation of Scutellarein Alkyl Derivatives as Preventing Neurodegenerative Agents with Improved Lipid Soluble Properties.

BACKGROUND: Exogenous antioxidants are considered as a promising therapeutic approach to treat neurodegenerative diseases since they could prevent and/or minimize the neuronal damage by oxidation. OBJECTIVE: Three series of lipophilic compounds structurally based on scutellarein (2), which is one metabolite of scutellarin (1) in vivo, have been designed and synthesized. METHODS: Their antioxidant activity was evaluated by detecting the 2-thiobarbituric acid reactive substance (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids, which were present in microsomal membranes of rat hepatocytes. The lipophilicity of these compounds indicated as partition coefficient between n-octanol and buffer was investigated by ultraviolet (UV) spectrophotometer. RESULTS: This study indicated that compound 5e which had a benzyl group substituted at the C4'- OH position showed a potent antioxidant activity and good lipophilicity. CONCLUSION: 5e could be an effective candidate for preventing or reducing the oxidative status associated with the neurodegenerative processes.

Poly(acrylic acid) microspheres loaded with superparamagnetic iron oxide nanoparticles for transcatheter arterial embolization and MRI detectability: In vitro and in vivo evaluation.

To develop embolic microspheres with MRI detectability, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized and mixed with monomer of acrylic acid to prepare SPIONs-loaded polymerized microspheres (SPMs) by inverse suspension polymerization method. The SPMs were evaluated for the ability of embolization by investigating the morphology, particle size, elasticity and renal arterial embolization to rabbits. Meanwhile, the loading of SPIONs was verified by optical microscope, transmission electron microscope, Fourier transform infrared spectrum, vibrating sample magnetometer, X-ray diffraction and X-ray photoelectron spectroscopy, and the content of SPIONs in SPMs was measured quantitatively. Furthermore, the MRI detectability of SPMs was testified in gel phantom, mice and rabbits respectively by a clinical 3.0T MRI scanner. The results revealed the SPMs were potential MRI detectable embolic microspheres for improving the effectiveness and safety of embolotherapy in the future.

Preparation and In Vitro Evaluation of a MRI Contrast Agent Based on Aptamer-Modified Gadolinium-Loaded Liposomes for Tumor Targeting.

The aim of this study was to prepare aptamer-modified liposomes loaded with gadolinium (Gd) to enhance the effective diagnosis for tumor by MRI. A modified GBI-10 (GBI-10m) was used to prepare targeted liposomes (GmLs). Liposomes with GBI-10 aptamer (GLs) and without aptamer (non-targeted liposomes (NLs)) were also prepared as controls. The particle size and zeta potential of GmLs, GLs, and NLs were all assayed. A clinical 3.0 T MR scanner was employed to assess the imaging efficiency and measure the longitudinal relaxivity (r 1) of the above liposomes. Confocal laser scanning microscopy and flow cytometry were used to analyze and compare the targeting effects of GmLs, GLs, and NLs to MDA-MB-435s cells at 37°C. The particle size of the prepared liposomes was scattered at 100-200 nm, and their values of r 1 were ∼4 mM-1 s-1. The images of confocal laser scanning microscopy showed that GmLs in the cytoplasm were significantly more than GLs and both GmLs and GLs were more than NLs. The fluorescence intensity of GmLs was increased by about two times than that of GLs and three times than that of NLs by flow cytometry. Therefore, the GmLs in this initial study were suggested to be a potential MRI contrast agent at 37°C for diagnosing tumors with the protein of tenascin-C over-expressed.

Preparation and evaluation of MRI detectable poly (acrylic acid) microspheres loaded with superparamagnetic iron oxide nanoparticles for transcatheter arterial embolization.

To monitor the spatial distribution of embolic particles inside the target tissues during and after embolization, blank poly (acrylic acid) microspheres (PMs) were initially prepared by inverse suspension polymerization method and then loaded with superparamagnetic iron oxide (SPIO) nanoparticles by in situ precipitation method to obtain magnetic resonance imaging (MRI) detectable SPIO-loaded poly (acrylic acid) microspheres (SPMs). The loading of SPIO nanoparticles in SPMs was confirmed by vibrating sample magnetometer, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and infrared spectrum, respectively. The results showed that SPMs exhibited excellent superparamagnetism and the SPIO embedded in SPMs were proved to be inverse spinel magnetite. The content of SPIO loaded in wet SPMs of subgroups of 100-300, 300-500, 500-700 and 700-900µm was measured to be 11.84±0.07, 10.20±0.05, 9.98±0.00 and 8.79±0.01mg/ml, corresponding to the weight percentage in freeze-dried SPMs to be 18.07±0.28%, 18.54±0.13%, 18.66±0.01% and 18.50±0.07%, respectively. The SPMs were spherical in shape, had smooth surface, and were within the size range of clinical demands for embolization. The compression tests indicated that SPMs were more rigid than PMs and commercially used Embospheres (P<0.01). The MRI detectability of SPMs was evaluated with the SPMs embedded in gel phantom in vitro and injected subcutaneously into the back of mice in vivo. Both the results demonstrated that the SPMs could provide distinct negative contrast enhancement and be sensitively detected by T2-weighted MR imaging. All the results show that SPMs are potential MRI detectable embolic microspheres for the future embolotherapy.

In vitro study of novel gadolinium-loaded liposomes guided by GBI-10 aptamer for promising tumor targeting and tumor diagnosis by magnetic resonance imaging.

Novel gadolinium-loaded liposomes guided by GBI-10 aptamer were developed and evaluated in vitro to enhance magnetic resonance imaging (MRI) diagnosis of tumor. Nontargeted gadolinium-loaded liposomes were achieved by incorporating amphipathic material, Gd (III) [N,N-bis-stearylamidomethyl-N'-amidomethyl] diethylenetriamine tetraacetic acid, into the liposome membrane using lipid film hydration method. GBI-10, as the targeting ligand, was then conjugated onto the liposome surface to get GBI-10-targeted gadolinium-loaded liposomes (GTLs). Both nontargeted gadolinium-loaded liposomes and GTLs displayed good dispersion stability, optimal size, and zeta potential for tumor targeting, as well as favorable imaging properties with enhanced relaxivity compared with a commercial MRI contrast agent (CA), gadopentetate dimeglumine. The use of GBI-10 aptamer in this liposomal system was intended to result in increased accumulation of gadolinium at the periphery of C6 glioma cells, where the targeting extracellular matrix protein tenascin-C is overexpressed. Increased cellular binding of GTLs to C6 cells was confirmed by confocal microscopy, flow cytometry, and MRI, demonstrating the promise of this novel delivery system as a carrier of MRI contrast agent for the diagnosis of tumor. These studies provide a new strategy furthering the development of nanomedicine for both diagnosis and therapy of tumor.

Preparation and evaluation of biocompatible long-term radiopaque microspheres based on polyvinyl alcohol and lipiodol for embolization.

The aim of this work was to develop long-term radiopaque microspheres (LRMs) by entrapping lipiodol in biocompatible polyvinyl alcohol with multiple emulsions chemical crosslinking method. The high content of lipiodol (0.366 g/mL) was hardly released from LRMs in vitro and the radiopacity could maintain at least 3 months after subcutaneous injection in mice without weakening. A series of tests was performed to evaluate the feasibility of LRMs for embolization. LRMs were proved to be smooth, spherical, and well dispersed with diameter range of 100-1200 µm. Young's modulus of LRMs was 55.39 ± 9.10 kPa and LRMs could be easily delivered through catheter without aggregating or clogging. No toxicity of LRMs was found to mouse L929 fibroblasts cells and only moderate inflammatory in surrounding tissue of mice was found after subcutaneous injection of LRMs. After LRMs were embolized in renal artery of a rabbit, the distribution and radiopacity of LRMs in vivo were easily detectable by X-ray fluoroscopy and computed tomography (CT) imaging, respectively. More accurate distribution of LRMs in embolized kidney and vessels could be detected by high-revolution visualization of micro-CT ex vivo. In conclusion, the LRMs were proved to be biocompatible and provide long-term radiopacity with good physical and mechanical properties for embolization.

[Preparation and in vitro evaluation of crosslinked polyvinyl alcohol microspheres for embolization].

OBJECTIVE: To develop and study the properties of crosslinked polyvinyl alcohol microspheres (PVA-Ms) for embolization. METHODS: The PVA-Ms were produced by emulsion chemical crosslinking method. Fourier transform infrared spectroscopy (FT-IR) was used to investigate the special functional groups of PVA-Ms; the morphology and particle size of PVA-Ms were determined by optical microscope; the ratio of water absorption and the swelling ratio were also investigated; the compressibility was examined by texture analyzer. A new device was designed to measure the pressure of PVA-Ms during their delivery through catheter for embolization. RESULTS: The crosslinking reaction of PVA and formaldehyde was proved by FT-IR. The PVA-Ms were round with smooth surface. The average diameter of lyophilized PVA-Ms was 574.2 µm with a range of 80-1 800 µm and of wet PVA-Ms was 602.2 µm with a range of 100-1 900 µm. The average ratio of water absorption was 175% and the swelling ratio was 48.6%. The PVA-Ms were mechanically stable with appropriate elasticity and delivered through the catheter without any difficulty, and the pressure was higher for larger size of microspheres to be delivered. CONCLUSION: PVA-Ms prepared in this study was supposed to be suitable for clinical embolization according to the physicochemical properties. The study provides a series of methods to evaluate the properties of microspheres systemically for embolization in vitro.

[Preparation and investigation of MRI-traceable Eudragit-E liquid embolic agent].

OBJECTIVE: To develop and investigate the properties of MRI-traceable Eudragit-E liquid embolic agent (MR-E). METHODS: Polyethylene glycol-modified superparamagnetic iron oxides (PEG-SPIO) was synthesized by chemical co-precipitation method. MR-E was prepared by mixing PEG-SPIO and Eudragit-E liquid embolic agent homogeneously. An in vitro MR phantom study was carried out to measure MR traceability of MR-E and to determine the concentration of PEG-SPIO for further studies. The microcatheter deliverability and sol-gel transition process of MR-E were investigated. MR-E was injected into the kidney of a Japanese white big ear rabbit via an angiographic microcatheter, and detected by MRI. RESULTS: A PEG-SPIO concentration of 2 g/L was considered to be suitable for further studies. MR-E was injected through the microcatheter without any difficulty. MR-E instantly solidified on release into saline. Then 0.2 mL of MR-E effectively embolized distal renal arteries, and MR-E could be detected by MRI in the embolized kidney. CONCLUSION: MR-E seems to be a promising MRI-traceable liquid embolic agent.

[Preparation and property study of doxorubicin loaded microspheres].

OBJECTIVE: To prepare doxorubicin-loaded polyvinylalcohol-acrylic acid (PVA-AA) microspheres and evaluate properties of this chemoembolic agent. METHODS: PVA-AA microspheres were synthesized by inverse suspension polymerization method and then verified by infrared spectroscopy. drug loading (DL) and entrapment efficiency (EE%) were measured after doxorubicinwas loaded on PVA-AA microspheres. Their morphology and elasticity were investigated by optical microscope, environmental scanning electron microscope and texture analyzer, respectively. T-cell apparatus was used to evaluate the in vitro release behavior of doxorubicin-loaded microspheres.The external carotid of the rabbit was chosen as an embolization site to evaluate the in vivo embolic property of the microspheres. RESULTS: PVA-AA microspheres, which were transparent spheres,turned into red spheres after doxorubicin loading. DL of the microspheres was (20.56 ± 0.69)g/L and (23.25 ± 0.27) g/L,and EE% was 82.22% ± 2.76% and 93.00% ± 1.06% within 20 min and 6 h, respectively. The in vitro release results showed a significantly delayed release of the drug for 10.32% ± 0.47% after 24 h. The Young's modulus was (178.30 ± 12.33) kPa and (213.29 ± 15.61) kPa for blank microspheres and doxorubicin-loaded microspheres, respectively. Both blank microspheres and doxorubicin-loaded microspheres exhibited good elasticity. In vivo embolization showed that 0.3 mL of microspheres could produce distal embolic efficiency. CONCLUSION: The doxorubicin-loaded microspheres are expected to be a promising new chemoembolic agent.

Development and evaluation of liquid embolic agents based on liquid crystalline material of glyceryl monooleate.

New type of liquid embolic agents based on a liquid crystalline material of glyceryl monooleate (GMO) was developed and evaluated in this study. Ternary phase diagram of GMO, water and ethanol was constructed and three isotropic liquids (ILs, GMO:ethanol:water=49:21:30, 60:20:20 and 72:18:10 (w/w/w)) were selected as potential liquid embolic agents, which could spontaneously form viscous gel cast when contacting with water or physiological fluid. The ILs exhibited excellent microcatheter deliverability due to low viscosity, and were proved to successfully block the saline flow when performed in a device to simulate embolization in vitro. The ILs also showed good cytocompatibility on L929 mouse fibroblast cell line. The embolization of ILs to rabbit kidneys was performed successfully under monitoring of digital subtraction angiography (DSA), and embolic degree was affected by the initial formulation composition and used volume. At 5th week after embolization, DSA and computed tomography (CT) confirmed the renal arteries embolized with IL did not recanalize in follow-up period, and an obvious atrophy of the embolized kidney was observed. Therefore, the GMO-based liquid embolic agents showed feasible and effective to embolize, and potential use in clinical interventional embolization therapy.

Research of novel biocompatible radiopaque microcapsules for arterial embolization.

Embolic agents, such as microparticles, microspheres or beads used in current embolotherapy are mostly radiolucent, which means the agents are invisible under X-ray imaging during and after the process of embolization, and the fate of these particles cannot be precisely assessed. In this research, a radiopaque embolic agent was developed by encapsulating lipiodol in polyvinyl alcohol. The lipiodol-containing polyvinyl alcohol microcapsules (LPMs) were characterized and evaluated for their morphology, size distribution, lipiodol content, lipiodol release, elasticity, and deliverability through catheter. The radiopacity of LPMs in vials and in living mice was both detected by an X-ray imaging system. The biocompatibility of LPMs was investigated with L929 cells and in mice after subcutaneous injection. Embolization of LPMs to a rabbit kidney was performed under digital subtraction angiography (DSA) and the radiopacity of LPMs was verified by computed tomography (CT).

Poly(acrylic acid) microspheres loaded with lidocaine: preparation and characterization for arterial embolization.

A new embolic agent, poly(acrylic acid) microspheres (PMs), was synthesized and the cytocompatibility was proved by mouse L929 fibroblast cells. An analgesic drug, lidocaine, was loaded on the PMs to relief pain caused by embolization. PMs and lidocaine loaded microspheres (LMs) were characterized by investigating infrared spectrum, morphology, particle size, and equilibrium water contents (EWC). A series of tests were employed to evaluate the elasticity of PMs, LMs and Embosphere™, including once compression, twice compression, and stress relaxation test. The pressures of PMs and LMs passing through a catheter were measured on line by our new designed device. Drug release was studied with T-cell apparatus. The properties of PMs and LMs were proved to be suitable for embolization. Both PMs and LMs in this study might be potential embolic agents in the future.

[Optimization and property evaluation of gelatin microspheres for embolization].

OBJECTIVE: To optimize the preparation of gelatin microspheres for embolization and to evaluate the physicochemical properties of the optimized microspheres. METHODS: The gelatin microspheres were prepared using emulsification crosslink method. The response surface methodology (RSM) was used in order to achieve gelatin microspheres with satisfactory degradable time and elasticity. The response values considered in this study were degradable time and elasticity, and the factors were the concentration of formaldehyde solution and the time of cross-linking reaction. The optimized microspheres were achieved by RSM. The properties of the optimized microspheres were investigated, including degradable time, elasticity, particle size, ratio of water absorption and the swelling ratio. RESULTS: The elasticity of the optimized microspheres was appropriate. The degradable time of the optimized microspheres was 2-3 weeks. The average diameter for dried gelatin microsphere was 377.6 µm, and for wet gelatin microsphere was 535.6 µm. The gelatin microsphere achieved the rate of water absorption balance at 20 min, and the average swelling ratio of gelatin microsphere was 41.9%. CONCLUSION: The gelatin microspheres optimized by RSM seemed to be suitable for clinical embolization according to the physicochemical properties.