Hyaluronan-based delivery of therapeutic oligonucleotides for treatment of human diseases

Introduction: Oligonucleotide therapeutics such as antisense oligonucleotides and siRNA requires chemical modifications and nano-sized carriers to circumvent stability problems in vivo, to reach target tissues, and to overcome tissue and cellular barriers. Hyaluronic acid (HA), already utilized in drug delivery and tissue engineering, possess properties that are useful to solve these problems and achieve full potential of oligonucleotide therapeutics.

Areas covered: Complexes of oligonucleotide therapeutics with HA are discussed in terms of interactions providing the complexes formation and genes targeted by the therapeutics to cure diseases such as cancer, atherosclerosis, liver cirrhosis, and inflammation. The achieved therapeutic effects are rationalized as consequences of biodistribution, cell internalization and endosomal escape provided by HA.

Expert opinion: Design of electrostatic, coordination, and hydrophobic interactions as well as covalent conjugation between oligonucleotide drugs, HA macromolecules and intermediate ligands are crucial for carrier–cargo association and dissociation under different conditions to impart oligonucleotides stability in vivo, their accumulation in diseased organs, cellular uptake, and dissociation in cytoplasm intact. These are the delivery factors that provides eventual complex formation of oligonucleotide therapeutics with their mRNA, microRNA, or protein targets. Elucidation of the impact of structural parameters of oligonucleotide/HA complexes on their therapeutic effect in vivo is important for the future rational design of the delivery agents.     

Biodistribution and delivery of oligonucleotide therapeutics to the central nervous system: Advances,challenges, and future perspectives

Considerable advances have been made in the research and development of oligonucleotide therapeutics (OTs) for treating central nervous system (CNS) diseases, such as psychiatric and neurodegenerative disorders, because of their promising mode of action. However, due to the tight barrier function and complex physiological structure of the CNS, the efficient delivery of OTs to target the brain has been a major challenge, and intensive efforts have been made to overcome this limitation. In this review, we summarize the representative methodologies and current knowledge of biodistribution, along with the pharmacokinetic/pharmacodynamic (PK/PD) relationship of OTs in the CNS, which are critical elements for the successful development of OTs for CNS diseases. First, quantitative bioanalysis methods and imaging-based approaches for the evaluation of OT biodistribution are summarized. Next, information available on the biodistribution profile, distribution pathways, quantitative PK/PD modeling, and simulation of OTs following intrathecal or intracerebroventricular administration are reviewed. Finally, the latest knowledge on the drug delivery systems to the brain via intranasal or systemic administration as noninvasive routes for improved patient quality of life is reviewed. The aim of this review is to enrich research on the successful development of OTs by clarifying OT distribution profiles and pathways to the target brain regions or cells, and by identifying points that need further investigation for a mechanistic approach to generate efficient OTs.     

Comparative toxicity of silicon dioxide,silver and iron oxide nanoparticles after repeated oral administration to rats

Although silicon dioxide (SiO₂), silver (Ag) and iron oxide (Fe₂O₃) nanoparticles are widely used in diverse applications from food to biomedicine, in vivo toxicities of these nanoparticles exposed via the oral route remain highly controversial. To examine the systemic toxicity of these nanoparticles, well‐dispersed nanoparticles were orally administered to Sprague–Dawley rats daily over a 13‐week period. Based on the results of an acute toxicity and a 14‐day repeated toxicity study, 975.9, 1030.5 and 1000 mg kg^–1 were selected as the highest dose of the SiO₂, Ag and Fe₂O₃ nanoparticles, respectively, for the 13‐week repeated oral toxicity study. The SiO₂ and Fe₂O₃ nanoparticles did not induce dose‐related changes in a number of parameters associated with the systemic toxicity up to 975.9 and 1000 mg kg^–1, respectively, whereas the Ag nanoparticles resulted in increases in serum alkaline phosphatase and calcium as well as lymphocyte infiltration in liver and kidney, raising the possibility of liver and kidney toxicity induced by the Ag nanoparticles. Compared with the SiO₂ and Fe₂O₃ nanoparticles showing no systemic distribution in all tissues tested, the Ag concentration in sampled blood and organs in the Ag nanoparticle‐treated group significantly increased with a positive and/or dose‐related trend, meaning that the systemic toxicity of the Ag nanoparticles, including liver and kidney toxicity, might be explained by extensive systemic distribution of Ag originating from the Ag nanoparticles. Our current results suggest that further study is required to identify that Ag detected outside the gastrointestinal tract were indeed a nanoparticle form or ionized form. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and Bio‐Evaluation of New 18F‐Labeled Pyridaben Analogs with Improved Stability for Myocardial Perfusion Imaging in Mice

To improve the stability of ¹⁸F‐labeled pyridaben analogs for myocardial perfusion imaging, three new analogs of pyridaben ([¹⁸F]FPTP2, [¹⁸F]FPTP‐P2, and [¹⁸F]FPTP‐P3) were synthesized with ‘side chain’ modifications. The radiolabeled tracers and corresponding non‐radioactive compounds were obtained by substituting tosyl group with ^18/19F. The effect of structure modification on myocardial targeting and physicochemical properties of new tracers were evaluated in vitro and in vivo. The total radiosynthesis time of these tracers was approximately 70–90 min with high decay‐corrected radiochemical yields (36–65%) and good radiochemical purity (> 98%). These lipophilic tracers exhibited obvious improved stability in water. Studies of their biodistribution in normal Kunming mice demonstrated that [¹⁸F]FPTP2 exhibited very high initial heart uptake (39.70 ± 2.81 %ID/g at 2 min after injection) and low background in the liver, blood, and soft tissues. The heart‐to‐liver, heart‐to‐lung, and heart‐to‐blood ratios were 3.59, 19.34, and 67.34 at 15 min postinjection, respectively. Favorable myocardial targeting property and remarkable improvement of stability of [¹⁸F]FPTP2 suggest that the substitution of the phenyl ‘sidechain’ with other non‐phenyl rings has no effect on the myocardial targeting property of ¹⁸F‐labeled pyridaben analogs.     

N-（5-硝基吲唑-3-甲酰）酪氨酸钠的制备、乏氧增敏与体内分布研究

目的：在硝基吲唑母核上引入酪氨酸并成盐,制备N-（5-硝基吲唑-3-甲酰）酪氨酸钠并考察其乏氧增敏活性和体内分布情况。方法用缩合剂法合成N-（5-硝基吲唑-3-甲酰）酪氨酸钠,通过小鼠移植瘤模型评价其乏氧增敏活性,通过放射性碘标记法考察其在荷瘤小鼠体内的分布情况。结果合成了目标化合物并对结构进行了确证。移植瘤模型增敏实验表明其对H22移植瘤具有一定的乏氧增敏活性,平均放射增敏比为1．5。体内分布实验中其在肿瘤部位与脑和肌肉部位的分布比值均大于5,表明其具有较好的体内分布特性。结论 N-（5-硝基吲唑-3-甲酰）酪氨酸钠具有良好的乏氧增敏活性和体内分布特性,具有进一步开发价值。     

Gallium(III) complexes of NOTA‐bis (phosphonate) conjugates as PET radiotracers for bone imaging

Ligands with geminal bis(phosphonic acid) appended to 1,4,7‐triazacyclonone‐1,4‐diacetic acid fragment through acetamide (NOTAM^BP) or methylenephosphinate (NO2AP^BP) spacers designed for ⁶⁸Ga were prepared. Ga^III complexation is much faster for ligand with methylenephosphinate spacer than that with acetamide one, in both chemical (high reactant concentrations) and radiolabeling studies with no‐carrier‐added ⁶⁸Ga. For both ligands, formation of Ga^III complex was slower than that with NOTA owing to the strong out‐of‐cage binding of bis(phosphonate) group. Radiolabeling was efficient and fast only above 60 °C and in a narrow acidity region (pH ~3). At higher temperature, hydrolysis of amide bond of the carboxamide‐bis(phosphonate) conjugate was observed during complexation reaction leading to Ga–NOTA complex. In vitro sorption studies confirmed effective binding of the ⁶⁸Ga complexes to hydroxyapatite being comparable with that found for common bis(phosphonate) drugs such as pamindronate. Selective bone uptake was confirmed in healthy rats by biodistribution studies ex vivo and by positron emission tomography imaging in vivo. Bone uptake was very high, with SUV (standardized uptake value) of 6.19 ± 1.27 for [⁶⁸Ga]NO2AP^BP) at 60 min p.i., which is superior to uptake of ⁶⁸Ga–DOTA‐based bis(phosphonates) and [¹⁸F]NaF reported earlier (SUV of 4.63 ± 0.38 and SUV of 4.87 ± 0.32 for [⁶⁸Ga]DO3AP^BP and [¹⁸F]NaF, respectively, at 60 min p.i.). Coincidently, accumulation in soft tissue is generally low (e.g. for kidneys SUV of 0.26 ± 0.09 for [⁶⁸Ga]NO2AP^BP at 60 min p.i.), revealing the new ⁶⁸Ga complexes as ideal tracers for noninvasive, fast and quantitative imaging of calcified tissue and for metastatic lesions using PET or PET/CT. Copyright © 2014 John Wiley & Sons, Ltd.     

Rapid spread of mannan to the immune system,skin and joints within 6 hours after local exposure

Psoriasis (Ps), psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are common diseases dependent on environmental factors that activate the immune system in unknown ways. Mannan is a group of polysaccharides common in the environment; they are potentially pathogenic, because at least some of them induce Ps-, PsA- and RA-like inflammation in mice. Here, we used positron emission tomography/computed tomography to examine in-vivo transport and spread of mannan labelled with fluorine-18 [¹⁸F]. The results showed that mannan was transported to joints (knee) and bone marrow (tibia) of mice within 6 h after intraperitoneal injection. The time it took to transport mannan, and its presence in blood, indicated cellular transport of mannan within the circulatory system. In addition, mannan was filtered mainly through the spleen and liver. [¹⁸F]fluoromannan was excreted via kidneys, small intestine and, to some extent, the mouth. In conclusion, mannan reaches joints rapidly after injection, which may explain why mannan-induced inflammatory disease is targeted to these tissues.     

Pharmacokinetics of cysteamine bitartrate following intraduodenal delivery

Cysteamine is approved for the treatment of cystinosis and is being evaluated for Huntington's disease and non‐alcoholic fatty liver disease. Little is known about the bioavailability and biodistribution of the drug. The aim was to determine plasma, cerebrospinal fluid (CSF), and tissue (liver, kidney, muscle) cysteamine levels following intraduodenal delivery of the drug in rats pretreated and naïve to cysteamine and to estimate the hepatic first‐pass effect on cysteamine. Healthy male rats (n = 66) underwent intraduodenal and portal (PV) or jugular (JVC) venous catheterization. Half were pretreated with cysteamine, and half were naïve. Following intraduodenal cysteamine (20 mg/kg), serial blood samples were collected from the PV or the JVC. Animals were sacrificed at specific time points, and CSF and tissue were collected. Cysteamine levels were determined in plasma, CSF, and tissue. The C_max was achieved in 5–10 min from PV and 5–22.5 min from JVC. The PV‐C_max (P = 0.08), PV‐AUC_0–t (P = 0.16), JVC‐C_max (P = 0.02) and JVC‐AUC_0–t (P = 0.03) were higher in naive than in pretreated animals. Plasma cysteamine levels returned to baseline in ≤120 min. The hepatic first‐pass effect was estimated at 40%. Peak tissue and CSF cysteamine levels occurred ≤22.5 min, but returned to baseline levels ≤180 min. There was no difference in CSF and tissue cysteamine levels between naïve and pretreated groups, although cysteamine was more rapidly cleared in the pretreated group. Cysteamine is rapidly absorbed from the small intestine, undergoes significant hepatic first‐pass metabolism, crosses the blood brain barrier, and is almost undetectable in plasma, CSF, and body tissues 2 h after ingestion. Sustained‐release cysteamine may provide prolonged tissue exposure.     

Optimization on biodistribution and antitumor activity of tripterine using polymeric nanoparticles through RES saturation

Systemic delivery of tripterine (TPR) is challenged by its insoluble property and unsuitable pharmacokinetics. This work aimed to develop polymeric nanoparticles (NPs) combined with the reticuloendothelial system (RES) saturation to improve the in vivo distribution and antitumor activity of TPR. TPR-loaded nanoparticles (TPR-NPs) were prepared by the low-energy emulsification/evaporation method and characterized with particle size, entrapment efficiency, and morphology. The resulting TPR-NPs were 75?nm around in particle size and displayed a sustained drug release in pH 7.4 medium. Pharmacokinetic studies revealed that TPR-NPs had the advantage in bettering the pharmacokinetic properties of TPR over the solution formulation. However, the ameliorative effect on pharmacokinetics was more significant in the case of RES saturation (i.e. preinjection of blank NPs). Preinjection of blank NPs followed by injection of TPR-NPs resulted in higher distribution of TPR into the tumor due to reduced sequestration of TPR-NPs by RES. In tumor-bearing mice (prostatic cancer model), TPR-NPs treatment with RES saturation exhibited a superior antitumor efficacy to free TPR and TPR-NPs alone. It can be concluded that formulating TPR into polymeric NPs in combination with RES saturation is an effective means to address the systemic delivery of TPR.     

Bone marrow-targeted liposomal carriers

Introduction: Bone marrow-targeted drug delivery systems appear to offer a promising strategy for advancing diagnostic, protective and/or therapeutic medicine for the hematopoietic system. Liposome technology can provide a drug delivery system with high bone marrow targeting that is mediated by specific phagocytosis in bone marrow.

Area covered: This review focuses on a bone marrow-specific liposome formulation labeled with technetium-99 m. Interspecies differences in bone marrow distribution of the bone marrow-targeted formulation are emphasized. This review provides a liposome technology to target bone marrow. In addition, the selection of proper species for the investigation of bone marrow targeting is suggested.

Expert opinion: It can be speculated that the bone marrow macrophages have a role in the delivery of lipids to the bone marrow as a source of energy and for membrane biosynthesis or in the delivery of fat-soluble vitamins for hematopoiesis. This homeostatic system offers a potent pathway to deliver drugs selectively into bone marrow tissues from blood. High selectivity of the present bone marrow-targeted liposome formulation for bone marrow suggests the presence of an active and specific mechanism, but specific factors affecting the uptake of the bone marrow mononuclear phagocyte system are still unknown. Further investigation of this mechanism will increase our understanding of factors required for effective transport of agents to the bone marrow, and may provide an efficient system for bone marrow delivery for therapeutic purposes.