Abstract: A polymer represented by the following formula (I): wherein each symbol is as described in the specification, is useful as a drug carrier in effectively delivering a drug to a target site.

Abstract: A novel anti-tumor agent capable of delivering siRNA or shRNA specifically to pancreatic cancer cells and suppressing tumor growth, invasion, and metastasis of pancreatic cancer is provided. The present invention provides a nucleic acid delivery enhancer for delivering siRNA or shRNA into cells, which consists of a folic acid-cationic oligopeptide complex. The present invention also provides an anti-tumor agent having siRNA or shRNA capable of binding to mRNA or snoRNA expressed in pancreatic cancer cells to inhibit its expression and a folic acid-cationic oligopeptide complex. The siRNA is capable of binding to RNA selected from the group consisting of, for example, SNORA18 snoRNA, NUP85 mRNA, WASF2 mRNA, and SNORA22 snoRNA.

Abstract: An object of the present invention is to provide a double-stranded nucleic acid complex having a reduced number of PS modifications in an antisense strand and maintaining an antisense effect. An optimal PS modification pattern for double-stranded nucleic acid complexes is disclosed. Such a nucleic acid complex comprising an antisense strand having an optimal PS modification pattern has a characteristic of having low toxicity and high bioavailability. The double-stranded nucleic acid complex comprising an antisense strand having an optimal PS modification pattern according to the present invention is useful when used as a nucleic acid drug that utilizes inhibition of expression of a specific gene (knockdown), activity that changes the function of coating or non-coding RNA for a specific gene, or activity that changes the function of RNA by inducing exon skipping during processing of pre-mRNA for a specific gene.

Abstract: A nucleic acid oligomer for RNA hybrid formation, including a structure formed of from 3 to 50 continuous units of at least one unit of a nucleotide unit represented by the following General Formula (1) or a nucleotide unit represented by the following General Formula (2); and having a base length of from 8 bases to 50 bases: in which in the formulae, R1 represents a hydrogen atom, an alkoxy group, an alkenyloxy group, an acyloxy group, a trialkylsilyloxy group, or a halogenyl group, and, in the formulae, each Bs1 independently represents a pyrimidine base that may have a protecting group, a hydrogen atom bonded to a carbon atom at the 5-position of the pyrimidine base may be substituted with a group other than a hydrogen atom, in the formulae, each X independently represents S?Z+ or BH3—Z+, Z+ represents a counter cation, each R2 and R3 independently represents a hydrogen atom, or an alkyl group having from 1 to 10 carbon atoms, and R2 and R3 may be bonded to each other to form a ring.