Over the past decade, oligonucleotide-based therapeutics such as antisense oligonucleotides, small interfering RNAs (siRNAs), decoy and aptamer have been developed extensively. For example, mipomersen (Kynamro; Isis Pharmaceuticals), which is a second-generation antisense oligonucleotide administered by subcutaneous injection, has recently been approved by the FDA for the treatment of homozygous familial hypercholesterolemia. In addition, microRNA (miRNA)-related oligonucleotide therapeutics, such as miRNA-targeting antisense oligonucleotides and miRNA mimics, and CpG-motif oligodeoxynucleotides (CpG ODN) have also been developed recently. The increase in research of oligonucleotide therapeutics was largely a result of improvements in the methods used for DNA sequencing, synthesizing oligonucleotides and chemically-modified nucleic acids. The most notable discovery was the addition of a phosphorothioate backbone to the oligonucleotides (S-oligo), leading to a significant increase in their stability. Other important milestone was development of a series of sugar-modified nucleic acids, including 2′-O-methyl, 2′-O-methoxyethyl, 2′-flouro and bridged nucleic acids, that remarkably increase the efficacy, stability and patentability of the oligonucleotide therapeutics. In this review, I would like to overview fundamental characteristics of oligonucleotide therapeutics, such as classification, sizes, lengths, modifications, forms, mechanism of action, kinetics and drug delivery system, and introduce global developmental trends of antisense oligonucleotides, siRNAs, miRNA-related oligonucleotide therapeutics, decoy, aptamer and CpG ODN.

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Development of the nanotechnologies to control an intracellular trafficking, and release of the cargos are required to open a new-generation of therapeutics using genes or nucleic acids. Quantitative analysis of the intracellular trafficking of lipoplex with adenovirus revealed that the poor post-nuclear delivery events, as well as nuclear delivery process (i.e. transcription and translation) are key processes to be overcome in the conventional cationic carriers. Especially, less effective transcription and translation is most likely due to the poor nuclear decondensation and association between mRNA and cationic carrier, respectively via electrostatic interaction. Also, when the cationic particle was administered intravenously, they formed large aggregates, and then stacked in the lung capillary. Also, in vivo gene expression was peaked at 6 h after the transfection, and then rapidly decreased within 2 days. To overcome these drawback, we recently developed a SS-cleavable and pH-activated lipid-like material (ssPalm) to prepare a neutral nanoparticle, that can be charged positive in acidic environment in endosome, and be collapsed in response to the reductive environment in cytoplasm. Since the vitamins have unique physicochemical properties, transport system and physiological function, we employed vitamin A and vitamin E as a hydrophobic scaffold to functionalize the ssPalm particle. When the particle was taken up by endocytosis, the vesicles were transferred to the lysosomal degradation pathway. In this process, endosomal pH gradually decreased. Thus, we design a particle that can detect a slight change of endosomal acidification, and then charged positive for the rapid endosomal escape at earlier stage. Based on this concept, we modified the amine structure so as to allow it to receive protons readily. The particle is a novel nanoDDS platform that can deliver genes, nucleic acids and low-molecular compounds. In this manuscript, we focused on the application of the ssPalm particle as a carrier of DNA and siRNA.

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Nucleic acid medicines are expected as promising therapeutic agents. While several nucleic acid medicines have already moved forward to clinical trials, it is still eagerly anticipated for treating a diverse range of diseases to develop safe nanocarriers that could deliver nucleic acids efficiently to specific targets in vivo. Conventionally, cationic carriers that interact with nucleic acids electrostatically have been used mainly in vitro, but they are potentially toxic and unstable in vivo. To address these issues, various non-cationic carriers showing higher biocompatibility, higher safety, and in vivo stability have so far been developed as forthcoming nanocarriers, though they often repel nucleic acids electrostatically. In this review, we summarized the current progress in nucleic acid delivery systems, mainly non-cationic nanocarriers. Next, we described a new method for encapsulating high contents of siRNA into non-cationic liposomes, which is simple, feasible, and readily scalable. After arming the surface of liposomes with targeting molecules (e.g., bio-nanocapsule (BNC) harboring hepatitis B virus-derived human hepatocyte-specific infection machinery), they could deliver siRNA into the cells in an active targeting manner. Finally, we discussed the important issues for developing the future nucleic acid delivery technology.

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Nucleic acid drugs have a strong therapeutic potential for treatment of many intractable diseases, including cancer. However, their bioavailability seems to be miserable owing to their high susceptibility to enzymatic degradation and negatively charged macromolecular structures that hamper their cellular entry. To overcome these bottlenecks, a variety of delivery vehicles, such as ligand-nucleotide conjugates, lipid nanoparticles, and polymeric nanoparticles, have been developed for successful nucleotide therapeutics. This article describes the design strategies of synthetic block copolymer-based nucleic acid delivery systems, particularly highlighting "smart" polyion complex (PIC) micelles that can exert the desired functions in response to biological microenvironment signals. Also, our recent results related to small interfering RNA (siRNA) and messenger RNA delivery are introduced with details. Notably, the ligand-installed PIC micelle has achieved efficient tumor-targeted siRNA delivery through systemic route, leading to the significant antitumor activity in subcutaneous tumor models.

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Recently, as more than 1 in 3 people get cancer in their lifetime in Japan, the development of innovative anticancer drugs have been desired. We focused on small interfering RNA (siRNA) and microRNA (miRNA) as a candidate of next generation anticancer drugs because they can induce cancer cell death selectively in a sequence-dependent manner. Because these small RNAs are not stable in the body and not permeable across cell membrane, it is necessary to develop drug delivery systems. We have revealed that lipid nanoparticle-mediated delivery of small RNAs is useful for selective delivery to tumors, resulting in induction of RNA interference-mediated gene silencing in vivo. In this review, we summarize our recent findings on small RNA delivery with polycation liposomes, or with lipid nanoparticles.

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Liver fibrosis is resulted from long standing hepatic damage with chronic inflammation, and when advanced to cirrhotic state, it becomes a cause of high mortality often due to associated hepatic insufficiency and hepatic cancer development. Although highly efficient anti-viral drug against HCV and HBV have been recently introduced into clinical field, because of the fact that these drugs are not directly targeting. On liver fibrosis, development of anti-fibrosis drugs is still unmet medical need. We are currently conducting phase1b/2 clinical trials on patients with advanced hepatic fibrosis in US, Europe and Japan, using siRNA against collagen specific chaperone, HSP47 encapsulated in liposomes which are coupled with vitamin A to deliver the liposome to collagen producing cells, stellate cells which specifically take up vitamin A. In this review, we will discuss about our anti-fibrosis drug, mainly focusing on its clinical development on hepatic fibrosis, and some experimental attempt to extend its application for other organ fibrosis.

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