Antisense pharmacodynamics: critical issues in the transport and delivery of antisense oligonucleotides

Locked nucleic acid (LNA): A modern approach to cancer diagnosis and treatment

Cancer is responsible for about one in six deaths in the world. Conventional cancer treatments like chemotherapy, radiotherapy, and surgery are associated with drug poisoning and poor prognosis. Thanks to advances in RNA delivery and target selection, new cancer medicines are now conceivable to improve the quality of life and extend the lives of cancer patients. Antisense oligonucleotides (ASOs) and siRNAs are the most important tools in RNA therapies. Locked Nucleic Acids (LNAs) are one of the newest RNA analogs, exhibiting more affinity to binding, sequence specificity, thermal stability, and nuclease resistance due to their unique properties. Assays using LNA are also used in molecular diagnostic methods and provide accurate and rapid mutation detection that improves specificity and sensitivity. This study aims to review the special properties of LNA oligonucleotides that make them safe and effective antisense drugs for cancer treatment by controlling gene expression. Following that, we go over all of the molecular detection methods and cancer treatment antisense tactics that are possible with LNA technology.

Preclinical Safety Assessment of Therapeutic Oligonucleotides

During the last decade, therapeutic oligonucleotide drugs (OND) have witnessed a tremendous development in chemistry and mechanistic understanding that have translated into successful clinical applications. Depending on the specific OND mechanism, chemistry, and design, the DMPK and toxicity properties can vary significantly between different OND classes and delivery approaches, the latter including lipid formulations or conjugation approaches to enhance productive OND uptake. At the same time, with the only difference between compounds being the nucleobase sequence, ONDs with same mechanism of action, chemistry, and design show relatively consistent behavior, allowing certain extrapolations between compounds within an OND class. This chapter provides a summary of the most common toxicities, the improved mechanistic understanding and the safety assessment activities performed for therapeutic oligonucleotides during the drug discovery and development process. Several of the considerations described for therapeutic applications should also be of value for the scientists mainly using oligonucleotides as research tools to explore various biological processes.

Nucleic acid-based therapy for coronavirus disease 2019

The coronavirus disease 2019 (COVID-19), the pandemic that originated in China has already spread into more than 190 countries, resulting in huge loss of human life and many more are at the stake of losing it; if not intervened with the best therapeutics to contain the disease. For that aspect, various scientific groups are continuously involved in the development of an effective line of treatment to control the novel coronavirus from spreading rapidly. Worldwide scientists are evaluating various biomolecules and synthetic inhibitors against COVID-19; where the nucleic acid-based molecules may be considered as potential drug candidates. These molecules have been proved potentially effective against SARS-CoV, which shares high sequence similarity with SARS-CoV-2. Recent advancements in nucleic acid-based therapeutics are helpful in targeted drug delivery, safely and effectively. The use of nucleic acid-based molecules also known to regulate the level of gene expression inside the target cells. This review mainly focuses on various nucleic acid-based biologically active molecules and their therapeutic potentials in developing vaccines for SARS-CoV-2.

The nuclear concentration required for antisense oligonucleotide activity in myotonic dystrophy cells

Antisense oligonucleotides (ASOs) are a promising class of therapeutics that are starting to emerge in the clinic. Determination of intracellular concentrations required for biologic effects and identification of effective delivery vehicles are crucial for understanding the mode of action and required dosing. Here, we investigated which nuclear oligonucleotide concentration is needed for a therapeutic effect for a triplet repeat-targeting ASO in a muscle cell model of myotonic dystrophy type 1 (DM1). For cellular delivery, ASOs were complexed into nanoparticles using the cationic cell-penetrating peptides nona-arginine and PepFect14 (PF14). Although both peptides facilitated uptake, only PF14 led to a dose-dependent correction of disease-typical abnormal splicing. In line with this observation, time-lapse confocal microscopy demonstrated that only PF14 mediated translocation of the ASOs to the nucleus, which is the main site of action. Through fluorescence lifetime imaging, we could distinguish intact oligonucleotide from free fluorophore, showing that PF14 also shielded the ASOs from degradation. Finally, we employed a combination of live-cell fluorescence correlation spectroscopy and immunofluorescence microscopy and demonstrated that intranuclear blocking-type oligonucleotide concentrations in the upper nanomolar range were required to dissolve nuclear muscleblind-like protein 1 foci, a hallmark of DM1. Our findings have important implications for the clinical use of ASOs in DM1 and provide a basis for further research on other types of ASOs.-Van der Bent, M. L., Paulino da Silva Filho, O., Willemse, M., Hällbrink, M., Wansink, D. G., Brock, R. The nuclear concentration required for antisense oligonucleotide activity in myotonic dystrophy cells.

Delivering Combination Chemotherapies and Targeting Oncogenic Pathways via Polymeric Drug Delivery Systems

The side-effects associated with chemotherapy necessitates better delivery of chemotherapeutics to the tumor. Nanoparticles can load higher amounts of drug and improve delivery to tumors, increasing the efficacy of treatment. Polymeric nanoparticles, in particular, have been used extensively for chemotherapeutic delivery. This review describes the efforts made to deliver combination chemotherapies and inhibit oncogenic pathways using polymeric drug delivery systems. Combinations of chemotherapeutics with other drugs or small interfering RNA (siRNA) combinations have been summarized. Special attention is given to the delivery of drug combinations that involve either paclitaxel or doxorubicin, two popular chemotherapeutics in clinic. Attempts to inhibit specific pathways for oncotherapy have also been described. These include inhibition of oncogenic pathways (including those involving HER2, EGFR, MAPK, PI3K/Akt, STAT3, and HIF-1α), augmentation of apoptosis by inhibiting anti-apoptosis proteins (Bcl-2, Bcl-xL, and survivin), and targeting dysregulated pathways such as Wnt/β-catenin and Hedgehog.

Selective Small Molecule Recognition of RNA Base Pairs

Many types of RNAs exist in the human transcriptome, yet only the bacterial ribosome has been exploited as a small molecule drug target. Aside from rRNA, other cellular RNAs such as noncoding RNAs have primarily secondary structure and limited tertiary structure. Within these secondary structures of noncanonically paired and unpaired regions, more than 50% are base paired, with most efforts to target these structures focused on looped regions. A void exists in the availability of small molecules capable of targeting RNA base pairs. Using chemoinformatics, an RNA-focused library enriched for nitrogen-containing heterocycles was developed and tested for binding RNA base pairs, leading to the identification of six selective and previously unknown binders. While all binders were derivatives of benzimidazoles, those with expanded aromatic polycycles bound selectively to AU pairs, while those with flexible urea side chains bound selectively to GC pairs. Two of the three selective GC pair binders can distinguish between two different orientations, 5'GG/3'CC and 5'GC/3'CG pairs. Furthermore, all six molecules showed >50-fold selectivity for RNA over DNA. These studies provide foundational knowledge to better exploit RNA as targets for small molecule chemical probes or lead therapeutics by using modules that target RNA base pairs.

Delivery of Small Interfering RNA. A Review and an Example of Application to a Junction Oncogene

RNA interference strategies using small interfering RNA is one of the most important discoveries in biology in recent years. This technology alongside antisense oligonucleotides is very promising and our group has focused its work on the targeting of junction oncogenes with these molecules. We have taken, as first example, papillary thyroid carcinoma. But there is a great need in delivery methods for these molecules in the treatment of cancers. Indeed, many studies have shown that small interfering RNA and antisense oligonucleotides are made efficient by various innovative delivery methods and, under these conditions, offer a powerful new therapeutic tool in cancer treatment.

Intranasal drug delivery of small interfering RNA targeting Beclin1 encapsulated with polyethylenimine (PEI) in mouse brain to achieve HIV attenuation

We previously reported that activation of the host autophagic protein, Beclin1, by HIV-1 infection represents an essential mechanism in controlling HIV replication and viral-induced inflammatory responses in microglial cells. Existing antiretroviral therapeutic approaches have been limited in their ability to cross the blood-brain barrier effectively and recognize and selectively eliminate persistent HIV-infected brain reservoirs. In the present study and for the first time, the bio-distribution and efficacy of noninvasive intranasal delivery of small interfering RNA (siRNA) against the Beclin1 gene using the cationic linear polyethylenimines (PEI) as a gene carrier was investigated in adult mouse brain. Fluorescein isothiocyanate (FITC)-labeled control siRNA delivered intranasally was found in the cytoplasm of neurons and glial cells of the prefrontal cortex at 4 and 24 hours post-delivery, with no major adverse immune reaction encountered. Intranasal delivery of the siRNA targeting Beclin1 significantly depleted the target protein expression levels in brain tissues with no evidence of toxicity. Binding of siRNA to PEI-polymer was characterized and confirmed by Raman spectroscopy. These results indicate that the intranasal drug delivery allows for the direct delivery of the PEI-siRNA nano-complex to the central nervous system, which could potentially offer an efficient means of gene silencing-mediated therapy in the HIV-infected brain.

Building the design, translation and development principles of polymeric nanomedicines using the case of clinically advanced poly(lactide(glycolide))-poly(ethylene glycol) nanotechnology as a model: An industrial viewpoint

The design of the first polymeric nanoparticles could be traced back to the 1970s, and has thereafter received considerable attention, as evidenced by the significant increase of the number of articles and patents in this area. This review article is an attempt to take advantage of the existing literature on the clinically tested and commercialized biodegradable PLA(G)A-PEG nanotechnology as a model to propose quality building and outline translation and development principles for polymeric nano-medicines. We built such an approach from various building blocks including material design, nano-assembly - i.e. physicochemistry of drug/nano-object association in the pharmaceutical process, and release in relevant biological environment - characterization and identification of the quality attributes related to the biopharmaceutical properties. More specifically, as envisaged in a translational approach, the reported data on PLA(G)A-PEG nanotechnology have been structured into packages to evidence the links between the structure, physicochemical properties, and the in vitro and in vivo performances of the nanoparticles. The integration of these bodies of knowledge to build the CMC (Chemistry Manufacturing and Controls) quality management strategy and finally support the translation to proof of concept in human, and anticipation of the industrialization takes into account the specific requirements and biopharmaceutical features attached to the administration route. From this approach, some gaps are identified for the industrial development of such nanotechnology-based products, and the expected improvements are discussed. The viewpoint provided in this article is expected to shed light on design, translation and pharmaceutical development to realize their full potential for future clinical applications.

Electro-Magnetic Nano-Particle Bound Beclin1 siRNA Crosses the Blood-Brain Barrier to Attenuate the Inflammatory Effects of HIV-1 Infection in Vitro

The purpose of this study was to evaluate a novel drug delivery system comprised of ferric-cobalt electro-magnetic nano-material (CoFe2O4@ BaTiO3; MENP) bound to siRNA targeting Beclin1 (MENP-siBeclin1) to cross the blood-brain barrier (BBB) and attenuate the neurotoxic effects of HIV-1 infection in the central nervous system following on-demand release of siRNA using an in vitro primary human BBB model. Beclin1 is a key protein in the regulation of the autophagy pathway and we have recently demonstrated the importance of Beclin1 in regulating viral replication and viral-induced inflammation in HIV-1-infected microglia. The MENP-siBeclin1 nano-formulation did not compromise the physiological function or integrity of the BBB model. Furthermore, the in vitro BBB data revealed that MENP-siBeclin1 could efficiently attenuate viral replication and viral-induced inflammation, likely due to STAT1/ NF-κB signaling pathways. MENP-siBeclin1 also silenced Beclin1 protein expression in HIV-1-infected microglial cells within the model system. In addition, the cytotoxic effects of direct treatment with siBeclin1 and MENP alone or in nano-formulation on primary human neuronal cells showed a minimal amount of cell death. Overall, the data shows that the nano-formulation can silence the BECN1 gene as an effective mechanism to attenuate HIV-1 replication and viral-induced inflammation in the context of the BBB.

A specific aptamer-cell penetrating peptides complex delivered siRNA efficiently and suppressed prostate tumor growth in vivo

Specific and efficient delivery of siRNA into intended tumor cells remains as a challenge, even though RNAi has been exploited as a new strategy for prostate cancer therapy. This work aims to address both specificity and efficiency of SURVIVIN-siRNA delivery by constructing a therapeutic complex using combinatorial strategies. A fusion protein STD was first expressed to serve as a backbone, consisting of streptavidin, a cell-penetrating peptide called Trans-Activator of Transcription (TAT) and a double-stranded RNA binding domain. A biotinylated Prostate Specific Membrane Antigen (PSMA) specific aptamer A10 and SURVIVIN-siRNA were then linked to STD protein to form the therapeutic complex. This complex could specifically targeted PSMA(+) tumor cells. Compared to lipofectamine and A10-siRNA chimera, it demonstrated higher efficiency in delivering siRNA into target cells by 19.2% and 59.9%, and increased apoptosis by 16.8% and 26.1% respectively. Upon systemic administration, this complex also showed significant efficacy in suppressing tumor growth in athymic mice (p <0.001). We conclude that this therapeutic complex could specifically and efficiently deliver SURVIVIN-siRNA to target cells and suppressed tumor growth in vivo, which indicates its potential to be used as a new strategy in prostate cancer therapy.

Mannosylated chitosan nanoparticles for delivery of antisense oligonucleotides for macrophage targeting

The therapeutic potential of antisense oligonucleotides (ASODN) is primarily dependent upon its safe and efficient delivery to specific cells overcoming degradation and maximizing cellular uptake in vivo. The present study focuses on designing mannosylated low molecular weight (LMW) chitosan nanoconstructs for safe ODNs delivery by macrophage targeting. Mannose groups were coupled with LMW chitosan and characterized spectroscopically. Mannosylated chitosan ODN nanoparticles (MCHODN NPs) were formulated by self-assembled method using various N/P ratio (moles of amine groups of MCH to phosphate moieties of ODNs) and characterized for gel retardation assay, physicochemical characteristics, cytotoxicity and transfection efficiency, and antisense assay. Complete complexation of MCH/ODN was achieved at charge ratio of 1:1 and above. On increasing the N/P ratio of MCH/ODN, particle size of the NPs decreased whereas zeta potential (ZV) increased. MCHODN NPs displayed much higher transfection efficiency into Raw 264.7 cells (bears mannose receptors) than Hela cells and no significant toxicity was observed at all MCH concentrations. Antisense assay revealed that reduction in lipopolysaccharide (LPS) induced serum TNF-α is due to antisense activity of TJU-2755 ODN (sequence complementary to 3′-UTR of TNF-α). These results suggest that MCHODN NPs are acceptable choice to improve transfection efficiency in vitro and in vivo.

Reliable assessment and quantification of the fluorescence-labeled antisense oligonucleotides in vivo

The availability of fluorescent dyes and the advances in the optical systems for in vivo imaging have stimulated an increasing interest in developing new methodologies to study and quantify the biodistribution of labeled agents. However, despite these great achievements, we are facing significant challenges in determining if the observed fluorescence does correspond to the quantity of the dye in the tissues. In fact, although the far-red and near-infrared lights can propagate through several centimetres of tissue, they diffuse within a few millimetres as consequence of the elastic scattering of photons. In addition, when dye-labeled oligonucleotides form stable complex with cationic carriers, a large change in the fluorescence intensity of the dye is observed. Therefore, the measured fluorescence intensity is altered by the tissue heterogeneity and by the fluctuation of dye intensity. Hence, in this study a quantification strategy for fluorescence-labeled oligonucleotides was developed to solve these disadvantageous effects. Our results proved that upon efficient homogenization and dilution with chaotropic agents, such as guanidinium thiocyanate, it is possible to achieve a complete fluorescence intensity recovery. Furthermore, we demonstrated that this method has the advantage of good sensitivity and reproducibility, as well as easy handling of the tissue samples.

Cellular uptake and intracellular trafficking of oligonucleotides: implications for oligonucleotide pharmacology

One of the major constraints on the therapeutic use of oligonucleotides is inefficient delivery to their sites of action in the cytosol or nucleus. Recently it has become evident that the pathways of cellular uptake and intracellular trafficking of oligonucleotides can strongly influence their pharmacological actions. Here we provide background information on the basic processes of endocytosis and trafficking and then review recent literature on targeted delivery and subcellular trafficking of oligonucleotides in that context. A variety of approaches including molecular scale ligand-oligonucleotide conjugates, ligand-targeted nanocarriers, and the use of small molecules to enhance oligonucleotide effects are discussed.

The Uptake Mechanism of the Cell-Penetrating pVEC Peptide

Peptide based drug design efforts have gained renewed interest with the discovery of cargo-carrying or cell-penetrating peptides. Understanding the translocation mechanism of these peptides and identifying the residues or elements that contribute to uptake can provide valuable clues toward the design of novel peptides. To this end, we have performed steered molecular dynamics (SMD) simulations on the pVEC peptide from murine vascular endothelial-cadherin protein and its two variants. Translocation was found to occur in three stages, adsorption via the cationic residues, inclusion of the whole peptide inside the membrane accompanied by formation of a water defect, and exit of both peptide and water molecules from the bilayer. Our simulation results suggest that the precise order in which the hydrophobic, cationic, and the polar regions are located in the amphipathic pVEC peptide contributes to its uptake mechanism. These results present new opportunities for the design of novel cell-penetrating and antimicrobial peptides.

Lipid conjugated oligonucleotides: a useful strategy for delivery

Oligonucleotides, including antisense oligonucleotides and siRNA, are promising therapeutic agents against a variety of diseases. Effective delivery of these molecules is critical in view of their clinical application. Therefore, cation-based nanoplexes have been developed to improve the stability as well as the intracellular penetration of these short fragments of nucleic acids. However, this approach is clearly limited by the strong interaction with proteins after administration and by the inherent toxicity of these positively charged transfection materials. Neutral lipid-oligonucleotide conjugates have become a subject of considerable interest to improve the safe delivery of oligonucleotides. These molecules have been chemically conjugated to hydrophobic moieties such as cholesterol, squalene, or fatty acids to enhance their pharmacokinetic behavior and trans-membrane delivery. The present review gives an account of the main synthetic methods available to conjugate lipids to oligonucleotides and will discuss the pharmacological efficacy of this approach.

Cellular uptake and intracellular trafficking of antisense and siRNA oligonucleotides

Significant progress is being made concerning the development of oligonucleotides as therapeutic agents. Studies with antisense, siRNA, and other forms of oligonucleotides have shown promise in cellular and animal models and in some clinical studies. Nonetheless, our understanding of how oligonucleotides function in cells and tissues is really quite limited. One major issue concerns the modes of uptake and intracellular trafficking of oligonucleotides, whether as "free" molecules or linked to various delivery moieties such as nanoparticles or targeting ligands. In this review, we examine the recent literature on oligonucleotide internalization and subcellular trafficking in the context of current insights into the basic machinery for endocytosis and intracellular vesicular traffic.

Antisense oligonucleotide inhibits avian influenza virus H5N1 replication by single chain antibody delivery system

H5N1 avian influenza virus (AIV) causes widespread infections in poultry and wild birds, and has the potential to emerge as a pandemic threat to human. Antisense oligonucleotides (AS ODNs) are highly effective at inhibiting gene replication. Antibody-mediated delivery is a novel approach to target specific cells and tissues. In this study, we designed and synthesized three AS ODNs (PA4, PA492 and PA1203) specific for conserved region of AIV PA protein, and all the three AS ODNs could inhibit viral replication. The PA492 ODN showed the best antiviral effect by viral titers and quantitative RT-PCR in MDCK cells. The fusion protein scFv-tP was constructed as a single chain variable fragment (scFv) against AIV hemaglutinin antigen with a truncated protamine (tP). The results showed that scFv-tP fusion improved the antiviral effectiveness of PA492 in MDCK cells as measured by viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, scFv-tP-delivered PA492 was also found to partially protect mice from lethal H5N1 influenza virus challenge. Using scFv-tP delivery, fluorescein isothiocyanate labeled-PA492 was found to be significantly localized in the lungs, compared to liposome-delivered PA492. Moreover, the fusion protein mediated PA492 had a lower lung index and viral titers in the infected mice as compared with the liposome method. These results provided a potential method for using anti-HA fusion protein for the targeted delivery of AS ODNs against AIV H5N1.

Sustained delivery and efficacy of polymeric nanoparticles containing osteopontin and bone sialoprotein antisenses in rats with breast cancer bone metastasis

Poor prognosis in mammary carcinoma is associated with a certain expression profile of a defined set of genes including osteopontin and bone sialoprotein. Efficient and specific delivery of antisenses (AS) and a protection of the sequences from degradation are the crucial conditions for AS therapeutic efficiency. We hypothesized that effective and safe AS delivery direceted against these genes could be achieved by polymeric nanoparticles (NP) fabricated from a biocompatible polymer. Due to their nano-size range and small negative charge, AS-NP can overcome the absorption barrier offering increased resistance to nuclease degradation, sustained duration of AS administration, and consequently, prolonged antisense action. The ASs designed against OPN and BSP-II were successfully encapsulated in NP composed of the biodegradable and biocompatible polylactide-co-glycolide polymer (PLGA), exhibiting sustained release and stability of the ASs. The therapeutic efficacy of the AS-NP delivery system was examined in vitro, and in a breast cancer bone metastasis animal model of MDA-MB-231 human breast cancer cells in nude rats. Treatment with OPN-AS or BSP-AS loaded NP in comparison with osmotic mini-pumps (locoregional injection and SC implants, respectively) resulted in a significant decrease in both, tumor bone metastasis incidence and in the size of the lesions in rats with metastases. Despite its smaller dose, AS-NP exhibited a better therapeutic efficacy than osmotic mini-pumps in terms of lesion ratio at later time periods (8-12 weeks). It may be concluded that AS delivery by NP is a promising therapeutic modality providing stability of the encapsulated AS and a sustained release.

Specific down regulation of 3T3-L1 adipocyte differentiation by cell-permeable antisense HIF1alpha-oligonucleotide

Hypoxia is a strong modulator of angiogenesis, accelerating adipose tissue expansion, suggesting that hypoxia inducible factor 1alpha (HIF1alpha) can be a novel target for anti-obesity. We conjugated antisense-HIF1alpha-oligonucleotide (ASO) with low molecular weight protamine (LMWP), a cell-penetrating peptide, to enhance its ability to block hypoxic-angiogenesis, thereby eliciting an anti-obesity effect. Nano-sized ASO-LMWP (AS-L) conjugates enhanced cellular uptake of ASO without yielding a cytotoxic effect and protected the ASO against enzymatic attack and chemical reduction. AS-L showed enhanced intra-cellular localization compared to naked ASO and the complex of ASO with lipofectamine during hypoxic-differentiation. Consequently AS-L induced significant down-regulation of leptin and VEGF gene expressions, thereby reducing fat accumulation in the cell. This proof-of-concept study shows that AS-L produces an inhibitory effect on adipogenesis and angiogenesis during differentiation, indicating LMWP mediated ASO delivery can potentially be a safe and promising treatment for obesity.

Biological barriers to therapy with antisense and siRNA oligonucleotides

Attaining the full therapeutic utility of antisense and siRNA oligonucleotides will require understanding of the biological barriers that stand between initial administration of these drugs and their final actions within cells. This review examines some of the key barriers that affect the biodistribution of oligonucleotides both in molecular form and when they are associated with nanocarriers. An understanding of the biological processes underlying these barriers will aid in the design of more effective delivery systems.

Bioconjugate-based molecular umbrellas

Molecular umbrellas are "amphomorphic" compounds that can produce a hydrophobic or hydrophilic exterior when exposed to a hydrophobic or hydrophilic microenvironment, respectively. Such molecules are composed of two or more facial amphiphiles that are connected to a central scaffold. Molecular umbrellas that have been synthesized to date, using bile acids as umbrella "walls", polyamines such as spermidine and spermine as scaffold material, and l-lysine as "branches", have been found capable of transporting certain hydrophilic peptides, nucleotides, and oligonucleotides across liposomal membranes by passive diffusion. They have also have been shown to increase water solubility and hydrolytic stability of a hydrophobic drug, and to exhibit significant antiviral activity. The ability of a fluorescently labeled molecular umbrella to readily enter live HeLa cells suggests that such conjugates could find use as drug carriers.

Viewing membrane-bound molecular umbrellas by parallax analyses

Fluorescence quenching measurements have been made for a series of di-walled and tetra-walled molecular umbrellas having moderate (i.e., hydroxyl-) and strong (i.e., sulfate-) facial hydrophilicity, using Cascade Blue as the fluorophore. Through the use of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphotempocholine, 1-palmitoyl-2-stearoyl-(5-DOXYL)-sn-glycero-3-phosphocholine, and 1-palmitoyl-2-stearoyl-(12-DOXYL)-sn-glycero-3-phosphocholine as fluorescence quenchers, evidence has been obtained for a membrane-bound state in which the umbrella molecules lie on the surface of the lipid bilayer. In the case of the sulfated molecular umbrellas, evidence has also been obtained for a subpopulation in which the fluorophore lies deeper within the membrane. Probable structures for the shallow-lying and deep-lying molecular umbrellas are discussed.

Magnetic nanoparticles in MR imaging and drug delivery

Magnetic nanoparticles (MNPs) possess unique magnetic properties and the ability to function at the cellular and molecular level of biological interactions making them an attractive platform as contrast agents for magnetic resonance imaging (MRI) and as carriers for drug delivery. Recent advances in nanotechnology have improved the ability to specifically tailor the features and properties of MNPs for these biomedical applications. To better address specific clinical needs, MNPs with higher magnetic moments, non-fouling surfaces, and increased functionalities are now being developed for applications in the detection, diagnosis, and treatment of malignant tumors, cardiovascular disease, and neurological disease. Through the incorporation of highly specific targeting agents and other functional ligands, such as fluorophores and permeation enhancers, the applicability and efficacy of these MNPs have greatly increased. This review provides a background on applications of MNPs as MR imaging contrast agents and as carriers for drug delivery and an overview of the recent developments in this area of research.

Mechanisms and strategies for effective delivery of antisense and siRNA oligonucleotides

The potential use of antisense and siRNA oligonucleotides as therapeutic agents has elicited a great deal of interest. However, a major issue for oligonucleotide-based therapeutics involves effective intracellular delivery of the active molecules. In this Survey and Summary, we review recent reports on delivery strategies, including conjugates of oligonucleotides with various ligands, as well as use of nanocarrier approaches. These are discussed in the context of intracellular trafficking pathways and issues regarding in vivo biodistribution of molecules and nanoparticles. Molecular-sized chemical conjugates and supramolecular nanocarriers each display advantages and disadvantages in terms of effective and nontoxic delivery. Thus, choice of an optimal delivery modality will likely depend on the therapeutic context.

Cellular uptake mechanisms and potential therapeutic utility of peptidic cell delivery vectors: progress 2001-2006

Cell delivery vectors (CDVs) are short amphipathic and cationic peptides and peptide derivatives, usually containing multiple lysine and arginine residues. They possess inherent membrane activity and can be conjugated or complexed with large impermeable macromolecules and even microscopic particles to facilitate cell entry. Various mechanisms have been proposed but it is now becoming clear that the main port of entry into cells of such CDV constructs involves adsorptive-mediated endocytosis rather than direct penetration of the plasma membrane. It is still unclear, however, how and to what extent CDV constructs are capable of exiting endosomal compartments and reaching their intended cellular site of action, usually the cytosol or the nucleus. Furthermore, although many CDVs can mediate cellular uptake of their cargo and appear comparatively non-toxic to cells in tissue culture, the utility of CDVs for in vivo applications remains poorly understood. Whatever the mechanisms of cell entry and disposition, the overriding question as far as potential pharmacological application of CDV conjugates is concerned is whether or not a therapeutic margin can be achieved by their administration. Such a margin will only result if the intracellular concentration in the target tissues necessary to elicit the biological effect of the CDV cargo can be achieved at systemic CDV exposure levels that are non-toxic to both target and bystander cells. It is proposed that the focus of CDV research now be shifted from mechanistic in vitro studies with labeled but otherwise unconjugated CDVs to in vivo pharmacological and toxicological studies using CDV-derivatized and other cationized forms of inherently non-permeable macromolecules of true therapeutic interest.

On The Biomedical Promise of Cell Penetrating Peptides: Limits Versus Prospects

The cell membrane poses a substantial hurdle to the use of pharmacologically active biomacromolecules that are not per se actively translocated into cells. An appealing approach to deliver such molecules involves tethering or complexing them with so-called cell penetrating peptides (CPPs) that are able to cross the plasma membrane of mammalian cells. The CPP approach is currently a major avenue in engineering delivery systems that are hoped to mediate the non-invasive import of problematic cargos into cells. The large number of different cargo molecules that have been efficiently delivered by CPPs ranges from small molecules to proteins and even liposomes and particles. With respect to the involved mechanism(s) there is increasing evidence for endocytosis as a major route of entry. Moreover, in terms of intracellular trafficking, current data argues for the transport to acidic early endosomal compartments with cytosolic release mediated via retrograde delivery through the Golgi apparatus and the endoplasmic reticulum. The focus of this review is to revisit the performance of cell penetrating peptides for drug delivery. To this aim we cover both accomplishments and failures and report on new prospects of the CPP approach. Besides a selection of successful case histories of CPPs we also review the limitations of CPP mediated translocation. In particular, we comment on the impact of (i) metabolic degradation, (ii) the cell line and cellular differentiation state dependent uptake of CPPs, as well as (iii) the regulation of their endocytic traffic by Rho-family GTPases. Further on, we aim at the identification of promising niches for CPP application in drug delivery. In this context, as inspired by current literature, we focus on three principal areas: (i) the delivery of antineoplastic agents, (ii) the delivery of CPPs as antimicrobials, and (iii) the potential of CPPs to target inflammatory tissues.

Gene modulation for treating liver fibrosis

Despite tremendous progress in our understanding of fibrogenesis, injury stimuli process, inflammation, and hepatic stellate cell (HSC) activation, there is still no standard treatment for liver fibrosis. Delivery of small molecular weight drugs, proteins, and nucleic acids to specific liver cell types remains a challenge due to the overexpression of extracellular matrix (ECM) and consequent closure of sinusoidal gaps. In addition, activation of HSCs and subsequent release of inflammatory cytokines and infiltration of immune cells are other major obstacles to the treatment of liver fibrosis. To overcome these barriers, different therapeutic approaches are being investigated. Among them, the modulation of certain aberrant protein production is quite promising for treating liver fibrosis. In this review, we describe the mechanism of antisense, antigene, and RNA interference (RNAi) therapies and discuss how the backbone modification of oligonucleotides affects their in vivo stability, biodistribution, and bioactivity. Strategies for delivering these nucleic acids to specific cell types are discussed. This review critically addresses various insights developed with each individual strategy and for multipronged approaches, which will be helpful in achieving more effective outcomes.

Analysis of interaction between dendriplexes and bovine serum albumin

Dendrimers are new nanotechnological carriers for gene delivery. Short oligodeoxynucleotides (ODNs) are a new class of antisense therapy drugs for cancer and infectious or metabolic diseases. The interactions between short oligodeoxynucleotides (GEM91, CTCTCGCACCCATCTCTCTCCTTCT; SREV, TCGTCGCTGTCTCCGCTTCTTCCTGCCA; unlabeled or fluorescein-labeled), novel water-soluble carbosilane dendrimers, and bovine serum albumin were studied by fluorescence and gel electrophoresis. The molar ratios of the dendrimer/ODN dendriplexes ranged from 4 to 7. The efficiency of formation and stability of the dendriplexes depended on electrostatic interactions between the dendrimer and the ODNs. Dendriplex formation significantly decreased the interactions between ODNs and albumin. Thus, the formation of dendriplexes between carbosilane dendrimers and ODNs may improve ODN delivery.

Single-injection ornithine decarboxylase-directed antisense therapy using atelocollagen to suppress human cancer growth

BACKGROUND

Substantial evidence supports a direct role of ornithine decarboxylase (ODC) in the development and maintenance of human tumors. Although antisense oligonucleotide therapy targeting various genes are useful for cancer treatment, 1 of the major limitations is the problem of delivery. A novel antisense oligonucleotide delivery method is described that allows prolonged sustainment and release of ODC antisense oligonucleotides in vivo using atelocollagen.

METHODS

The effect of ODC antisense oligonucleotides in the atelocollagen on cell growth of gastrointestinal cancer (MKN 45 and COLO201) and rhabdomyosarcoma (RD) was studied in vitro using a cell-counting method with a hemocytometer. In vivo, the effect of intratumoral, intramuscular, and intraperitoneal single administration of ODC antisense oligonucleotides in the atelocollagen on tumor growth of MKN45, COLO201, and RD cells was studied. ODC activity and polyamine contents were measured.

RESULTS

In vitro, ODC antisense oligonucleotides in the atelocollagen remarkably suppressed MKN45, COLO201, and RD cell growth. A single administration of antisense oligonucleotides in the atelocollagen via 3 routes remarkably suppressed the growth of MKN45, COLO201, and RD tumor over a period of 35-42 days.

CONCLUSIONS

As various human cancers significantly express ODC, the results strongly suggest that this new antisense method may be of considerable value for treatment of human cancers.

Dendritic alpha,epsilon-poly(L-lysine)s as delivery agents for antisense oligonucleotides

PURPOSE

To evaluate the potential use of dendritic alpha,epsilon-poly(L-lysine)s (DPL) for the efficient cellular delivery of antisense oligonucleotides.

METHODS

A series of dendritic alpha,epsilon-polylysines of various generations were prepared. Their physical properties and the ability to form complex with oligonucleotide were investigated by polyacrylamide gel electrophoresis, capillary zone electrophoresis (CZE), agarose gel electrophoresis, fluorescence titration and atomic force microscopy (AFM). The efficiency to deliver oligonucleotide to HeLa cells, stably transfected with plasmid pLuc/705, was evaluated by using antisense splicing correction assay and confocal microscopy.

RESULTS

DPLs formed the complexes with antisense oligonucleotide with modest cytotoxicity. The charge ratio of oligonucleotide to DPL and the size (generation) of DPLs were all critical variables for the antisense effect. Compared to low generation DPLs, high generation DPLs were more effective in delivering oligonucleotide into cells.

CONCLUSIONS

High generation DPL-oligonucleotide complexes were moderately effective for delivery antisense oligonucleotide. The complex formation provides a promise for in vivo therapeutic application of DPLs or their derivatives in the delivery of gene or oligonucleotide.

Intracellular delivery of oligonucleotide conjugates and dendrimer complexes

Enhancing the delivery of antisense and siRNA molecules to cells and tissues is a key issue for oligonucleotide therapeutics. Cell-penetrating peptides (CPPs) have the ability to convey linked "cargo" molecules into the cytosol; thus we have explored the use of CPPs as delivery agents for oligonucleotides. We have extensively evaluated CPP-oligonucleotide conjugates, and have recently begun to explore the use of CPP-dendrimer-oligonucleotide complexes. We have found that CPP-antisense oligonucleotide conjugates can be taken up by cells and can effectively modify gene expression in cell culture and in tissues. Although not as potent in cell culture as cationic lipid delivery agents, CPP-oligonucleotide conjugates offer the advantage of being molecules rather than particles, and may have substantial advantages over particle-based delivery in the in vivo setting.

Encapsulation of nucleic acids and opportunities for cancer treatment

The development of nucleic acid drugs for the treatment of various cancers has shown great promise in recent years. However, efficient delivery of these drugs to target cells remains a significant challenge towards the successful development of such therapies. This review provides a comprehensive overview of encapsulation technologies being developed for the delivery of nucleic acid-based anti-cancer agents. Both micro and nanoparticles systems are discussed along with their use in delivering plasmid DNA as well as oligonucleotides. The majority of the systems discussed have used DNA immunotherapy as the potential mode of anticancer therapy, which requires targeting to antigen presenting cells. Other applications, including those with oligonucleotides, focus on targeting tumor cells directly. The results obtained so far show the excellent promise of encapsulation as an efficient means of delivering therapeutic nucleic acids.

Modulation of gene expression by antisense and antigene oligodeoxynucleotides and small interfering RNA

Antisense oligodeoxynucleotides, triplex-forming oligodeoxynucleotides and double-stranded small interfering RNAs have great potential for the treatment of many severe and debilitating diseases. Concerted efforts from both industry and academia have made significant progress in turning these nucleic acid drugs into therapeutics, and there is already one FDA-approved antisense drug in the clinic. Despite the success of one product and several other ongoing clinical trials, challenges still exist in their stability, cellular uptake, disposition, site-specific delivery and therapeutic efficacy. The principles, strategies and delivery consideration of these nucleic acids are reviewed. Furthermore, the ways to overcome the biological barriers are also discussed so that therapeutic concentrations at their target sites can be maintained for a desired period.

Drug delivery to tumours: recent strategies

Despite several advancements in chemotherapy, the real therapy of cancer still remains a challenge. The development of new anti-cancer drugs for the treatment of cancer has not kept pace with the progress in cancer therapy, because of the nonspecific drug distribution resulting in low tumour concentrations and systemic toxicity. The main hindrance for the distribution of anti-cancer agents to the tumour site is the highly disorganized tumour vasculature, high blood viscosity in the tumour, and high interstitial pressure within the tumour tissue. Recently, several approaches such as drug modifications and development of new carrier systems for anti-cancer agents have been attempted to enhance their tumour reach. Approaches such as drug delivery through enhanced permeability and retention (EPR) effect have resulted in a significant improvement in concentration in tumours, while approaches such as drug-carrier implants and microparticles have resulted in improvement in local chemotherapy of cancer. This review discusses different strategies employed for the delivery of anti-cancer agents to tumours, such as through EPR effect, local chemotherapeutic approaches using drug delivery systems, and special strategies such as receptor-mediated delivery, pH-based carriers, application of ultrasound and delivery to resistant tumour cells and brain using nanoparticles.

Oligonucleotide-Based Therapeutic Options against Hepatitis C Virus Infection

The hepatitis C virus (HCV) is the cause of a silent pandemic that, due to the chronic nature of the disease and the absence of curative therapy, continues to claim an ever-increasing number of lives. Current antiviral regimens have proven largely unsatisfactory for patients with HCV drug-resistant genotypes. It is therefore important to explore alternative therapeutic stratagems whose mode of action allows them to bypass viral resistance. Antisense oligonucleotides, ribozymes, small interfering RNAs, aptamers and deoxyribozymes constitute classes of oligonucleotide-based compounds designed to target highly conserved or functionally crucial regions contained within the HCV genome. The therapeutic expectation for such compounds is the elimination of HCV from infected individuals. Progress in oligonucleotide-based HCV antivirals towards clinical application depends on development of nucleotide designs that bolster efficacy while minimizing toxicity, improvement in liver-targeting delivery systems, and refinement of small-animal models for preclinical testing.

Recent advances in discovery and development of promising therapeutics against hepatitis C virus NS5B RNA-dependent RNA polymerase

Lack of highly effective and safe therapeutics for hepatitis C virus (HCV) infection provides an opportunity as well as a challenge to discover novel and potent anti-HCV drugs. HCV NS5B RNA-dependent RNA polymerase (RdRp) is responsible for viral genome replication and thus constitutes a valid target for therapeutic intervention. To date, numerous HCV NS5B RdRp inhibitors have been discovered. This review focuses on the recent advances in discovery, mechanism of action studies and biological characterization of several distinct classes of potent inhibitors for NS5B RdRp. The clinical efficacy and developmental status of several promising compounds are also outlined.

Enhanced Hepatic Uptake and Bioactivity of Type α1(I) Collagen Gene Promoter-Specific Triplex-Forming Oligonucleotides after Conjugation with Cholesterol

A triplex-forming oligonucleotide (TFO) specific for type alpha1(I) collagen promoter is a promising candidate for treating liver fibrosis. Earlier, we determined the pharmacokinetics and biodistribution of TFO after systemic administration into normal and fibrotic rats. In this study, we conjugated cholesterol to the 3' end of the TFO via a disulfide bond and determined its cellular and nuclear uptake and bioactivity using HSC-T6 cell lines in vitro, followed by biodistribution at whole-body, organ (liver), and subcellular levels. Conjugation with cholesterol had little effect on the triplex-forming ability of the TFO with target duplex DNA, and the cellular uptake of (33)P-TFO-cholesterol (Chol) increased by 2- to approximately 4-fold. Real-time reverse transcriptase-polymerase chain reaction analysis after transfection of HSC-T6 cells with TFO-Chol or TFO indicated that TFO-Chol had higher inhibition on type alpha1(I) collagen primary transcript than naked TFO at low concentration (200 nM) but showed similar inhibition at higher concentration (500 and 1000 nM). There was increase in the inhibition on primary transcript with transfection time. The hepatic uptake of (33)P-TFO-Chol after systemic administration was 72.22% of the dose compared with 45.8% of (33)P-TFO. There was significant increase in the uptake of (33)P-TFO-Chol by hepatic stellate cells and hepatocytes. More importantly, the nuclear uptake of TFO-Chol was higher than TFO in cell culture system and in vivo studies. In conclusion, TFO-Chol is a potential antifibrotic agent.