Patent ID: 7642343

Claim:
A conjugate of oligonucleotide with poly(ethylene oxide) which is expressed by a formula (A): FuNT-L 1 -L 2 -PEG (A) in which FuNT stands for the residue of a functional oligonucleotide bound to L 1 -L 2 -PEG via a phosphate ester bond at 3′ or 5′ hydroxyl terminal of ribose or 2-deoxyribose, wherein the functional oligonucleotide a) is composed of an oligonucleotide sequence which either is complementary to the nucleotide sequence participating in expression of target genes, or hybridizes with the nucleotide sequence under stringent condition; and which has, at 6-position of at least one 2-aminopurine ring present in the oligonucleotide sequence, a group of the formula —CH 2 CH 2 S(O)nR (wherein n stands for an integer of 0-2; and R stands for C 1 -C 6 alkyl optionally substituted with oxy (═O), cyano or carboxy; or phenyl optionally substituted with oxy (═O), cyano, nitro, carboxy, C 1 -C 6 alkyl or halo); or b) is complementary to the nucleotide sequence participating in expression of the target genes and the phosphate moiety of each nucleotide therein is selected from the group consisting of phosphorothioate, phosphoroamidate and 2′-O-methylphosphate; L 1 stands for an alkylene group of 3-30 in total atom number, which may be interrupted with oxygen atom or sulfur atom at one, two or more places; L 2 stands for a linking group cleavable under physiological conditions; and PEG stands for poly(ethylene oxide) group carrying at the L 2 -binding terminal hydrogen atom, alkyl group, aralkyl group, functional group or ligand residue, optionally via a linking group; and wherein the oligonucleotide is an oligodeoxynucleotide containing 10-50 nucleotides.