[Title of Invention]

CHIMERIC DOUBLE-STRANDED NUCLEIC ACID

[Technical Field]

The present application relates to a double-stranded nucleic acid having an activity of suppressing the expression of a target gene by means of an antisense effect, and more particularly, to a double-stranded nucleic acid including an antisense nucleic acid that is complementary to the transcription product of a target gene and contains a region comprising four or more contiguous bases, and a nucleic acid that is complementary to the foregoing nucleic acid.

[Background Art]

In recent years, oligonucleotides have been a subject of interest in the on-going development of pharmaceutical products called nucleic acid drugs , and particularly, from the viewpoints of high selectivity of target gene and low toxicity, the development of nucleic acid drugs utilizing an antisense method is actively underway. The antisense method is a method of selectively inhibiting the expression of a protein that is encoded by a target gene, by introducing into a cell an oligonucleotide (antisense oligonucleotide (ASO) ) which is complementary to a partial sequence of the mRNA (sense strand) of a target gene.

As illustrated in FIG. 1 (upper portion) , when an oligonucleotide comprising an RNA is introduced into a cell as an ASO, the ASO binds to a transcription product (mRNA) of the target gene, and a partial double strand is formed. It is known that this double strand plays a role as a cover to prevent translation by a ribosome, and thus the expression of the protein encoded by the target gene is inhibited.

On the other hand, when an oligonucleotide comprising a DNA is introduced into a cell as an ASO, a partial DNA-RNA hetero-duplex is formed. Since this structure is recognized by RNase H, and the mRNA of the target gene is thereby decomposed, the expression of the protein encoded by the target gene is inhibited. (Fig. 1, lower portion). Furthermore, it has been also found that in many cases, the gene expression suppressing effect is higher in the case of using a DNA as an ASO (RNase H-dependent route) , as compared with the case of using an RNA.

On the occasion of utilizing an oligonucleotide as a nucleic acid drug, various nucleic acid analogs such as Locked Nucleic Acid (LNA) (registered trademark) , other bridged nucleic acids, and the like have been developed in consideration of an enhancement of the binding affinity to a target RNA, stability in vivo, and the like.

As illustrated in FIG .2, since the sugar moiety of a natural nucleic acid (RNA or DNA) has a five-membered ring with four carbon atoms and one oxygen atom, the sugar moiety has two kinds of conformations, an N-form and an S-form. It is known that these conformations swing from one to the other , and thereby, the helical structure of the nucleic acid also adopts different forms, an A-form and a B-form. Since the mRNA that serves as the target of the aforementioned ASO adopts a helical structure in the A-form, with the sugar moiety being mainly in the N-form, it is important for the sugar moiety of the ASO to adopt the N-form from the viewpoint of increasing the affinity to RNA. A product that has been developed under this concept is a modified nucleic acid such as a LNA (2 ' -0, 4 ' -C-methylene-bridged nucleic acid (2 ¹ , 4 ' -BNA) ) . For example, in the LNA, as the oxygen at the 2 '-position and the carbon at the 4 '-position are bridged by a methylene group, the conformation is fixed to the N-form, and there is no more fluctuation between the conformations. Therefore, an oligonucleotide synthesized by incorporating several units of LNAhas veryhighaffinityto RNA and very high sequence specificity, and also exhibits excellent heat resistance and nuclease resistance, as compared with oligonucleotides synthesized with conventional natural nucleic acids (see PTL 1) . Since other artificial nucleic acids also have such characteristics, much attention has been paid to artificial nucleic acids in connection with the utilization of an antisense method and the like (see PTLs 1 to 7) .

Furthermore, when n oligonucleotide is applied to a drug, it is important that the relevant oligonucleotide can be delivered to the target site with high specificity and high efficiency. In addition, as methods for delivering an oligonucleotide, a method of utilizing lipids such as cholesterol and vitamin E (NPLs 1 and 2) , a method of utilizing a receptor-specific peptide such as RVG-9R (NPL 3) , and a method of utilizing an antibody specific to the target site (NPL 4) have been developed.

[Citation List]

[Patent Literature]

[PTL 1]JP 10-304889 A

[PTL 2] WO 2005/021570

[PTL 3] JP 10-195098 A

[PTL 4] JP 2002-521310 W

[PTL 5] WO 2007/143315

[PTL 6] WO 2008/043753

[PTL 7] WO 2008/029619

[Non Patent Literature]

[NPL 1] Kazutaka Nishina et al., Molecular Therapy, Vol. 16 , 734-740 (2008)

[NPL 2]Jurgen Soutscheck et al., Nature, Vol. 432, 173-178 (2004)

[NPL 3]Kazutaka Nishina et al., Molecular Therapy, Vol. 16, 734-740 (2008)

[NPL 4]Dan Peer et al., Science, Vol. 319, 627-630 (2008) [Summary of Invention]

[Technical Problem]

In certain embodiments, a double-stranded nucleic acid complex comprises an antisense nucleic acid which suppresses the expression of a target gene, or more generally, suppresses the level of an RNA transcription product. It is a further object that the double-stranded nucleic acid complex delivers the antisense nucleic acid strand to a target site with high specificity and high efficiency.

[Solution to Problem]

For the purpose of studying how to enhance the stability of an ASO, the activity of suppressing the expression of a target gene in vivo (antisense effect), and the specificity and efficiency in the delivery of an ASO to a target site (delivery properties) in an antisense method, the inventors prepared an ASO comprising a LNA and a DNA (LNA/DNA gapmer) , to which a lipid (cholesterol) was directly bound, and the inventors evaluated the delivery properties and the antisense effect by intravenously administering this ASO to a mouse. As a result, it was found that when cholesterol is bound to the ASO, the delivery properties of the ASO to the liver are enhanced, however, the antisense effect was lost.

Thus, the inventors conducted thorough investigations in order to develop a nucleic acid which has a high antisense effect while increasing the delivery properties of an ASO, and asaresult, the inventors conceived of a new double-stranded nucleic acid complex produced, in one embodiment , by annealing a LNA/DNA gapmer to an RNA strand complementary to the gapmer, and first evaluated the antisense effect . Asaresult, it was found that the antisense effect of the double-stranded nucleic acid is typically better than that of a single-stranded LNA/DNA gapmer, and is rather enhanced depending on the strand length of the ASO used. The inventors also produced a double-stranded nucleic acid in which tocopherol is bound to the complementary strand comprising RNA, intravenously administered the double-stranded nucleic acid to a mouse, and evaluated its antisense effect. As a result, it was found that the double-stranded nucleic acid containing the complementary strand bound to tocopherol has a very high antisense effect. In addition, the inventors also found that the antisense effect of a LNA/DNA gapmer produced by annealing with a complementary strand comprising PNA (peptide nucleic acid) instead of RNA is at least similar to or better than that of a single-stranded LNA/DNA gapmer, and furthermore the PNA provides a way to indirectly associate the ASO with a peptide, protein, or antibody that can direct delivery of the ASO to a particular site .

That is, the application relates to a double-stranded nucleic acid having an activity of suppressing the expression of a target gene by means of an antisense effect.

In certain embodiments, the following are provided.

(1) A double-stranded nucleic acid having an activity of suppressing theexpressionofa target gene bymeans of an antisense effect, the double-stranded nucleic acid comprising nucleic acids of the following items (a) and (b) :

(a) an antisense nucleic acid that is complementary to the transcription product of the target gene and contains a region comprising a DNA of four or more contiguous bases, and

(b) a nucleic acid that is complementary to the nucleic acid of (a) .

(2) The double-stranded nucleic acid described in the item (1) , in which the nucleic acid of (a) further contains a region comprising a modified nucleic acid, which is disposed on at least any one of the 5 ' -terminal side and the 3 ¹ -terminal side of the region comprising a DNA of four or more contiguous bases.

(3) The double-stranded nucleic acid described in the item

(2) , in which the region comprising a modified nucleic acid of the nucleic acid of (a) is a region comprising a modified nucleic acid, whichisdisposedonthe5' -terminal side and the 3 ' -terminal side of the region comprising a DNA of four or more contiguous bases, and the modified nucleic acid is a LNA.

(4) The double-stranded nucleic acid described in any one of the items (1) to (3), in which the nucleic acid of (b) is an RNA or a PNA.

(5) The double-stranded nucleic acid described in any one of the items (1) to (3), in which the nucleic acid of (b) is an

RNA, the region complementary to the region comprising a modified nucleic acid of the nucleic acid of (a) is modified, and the modification has an effect of suppressing the decomposition caused by a ribonuclease (RNase).

(6) The double-stranded nucleic acid described in the item

(5), in which the modification is 2 ' -O-methylation and/or phosphorothioation.

(7) The double-stranded nucleic acid described in any one of the items (1) to (6), in which a functional moiety is bonded to the nucleic acid of (b) .

(8) The double-stranded nucleic acid described in any one of the items (1) to (7) , in which the strand lengths of the nucleic acids of (a) and (b) are the same.

(9) The double-stranded nucleic acid described in any one of the items (1) to (7) , in which the strand lengths of the nucleic acids of (a) and (b) are different.

(10) The double-stranded nucleic acid described in the item

(9) , further including a nucleic acid of the following item (c) :

(c) a nucleic acid that is complementary to a region in the nucleic acid having a longer strand length between the nucleic acids of (a) and (b) , which is protruding relative to the other nucleic acid.

( 11 ) The double-stranded nucleic acid described in the item

(10) , in which the nucleic acid of (c) is a PNA.

( 12 ) The double-stranded nucleic acid described in the item (10) or (11), in which a functional moiety is bonded to the nucleic acid of (c) .

(13) The double-stranded nucleic acid described in the item (7) or (12) , in which the functional moiety is a molecule having an activity of delivering the double-stranded nucleic acid to a target site.

( 14 ) A composition for suppressing the expression of a target gene by means of an antisense effect, the composition containing the double-stranded nucleic acid described in any one of the items (1) to (13) as an active ingredient.

(15) A method of reducing the level of a transcription product in a cell comprising contacting with the cell a composition comprising :

(a) a double-stranded nucleic acid complex comprising a first nucleic acid strand annealed to a second nucleic acid strand, wherein :

the first nucleic acid strand (i) comprises nucleotides and optionally nucleotide analogs, and the total number of nucleotides and optionally nucleotide analogs in the first nucleic acid strand is from 8 to 100, (ii) comprises at least 4 consecutive nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to the transcription product , and (iii) the first nucleic acid strand hybridizes to the transcription product; and

the second nucleic acid strand comprises nucleotides and optionally nucleotide analogs.

(16) A method of reducing the expression level of a gene in a mammal comprising the step of administering an effective amount to the mammal of a pharmaceutical composition comprising:

(a) a double-stranded nucleic acid complex comprising a first nucleic acid strand annealed to a second nucleic acid strand, wherein :

the first nucleic acid strand (i) comprises nucleotides and optionally nucleotide analogs, and the total number of nucleotides and optionally nucleotide analogs in the first nucleic acid strand is from 8 to 100, (ii) comprises at least 4 consecutive nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to a transcription product of the gene, and (iii) the first nucleic acid strand hybridizes to the transcription product; and

the second nucleic acid strand comprises nucleotides and optionally nucleotide analogs; and

(b) a pahrmaceutically acceptable carrier.

(17) A purified or isolated double stranded nucleic acid complex comprising a first nucleic acid strand annealed to a second nucleic acid strand, wherein:

the first nucleic acid strand (i) comprises nucleotides and optionally nucleotide analogs , and the total number of nucleotides and nucleotide analogs in the first nucleic acid strand is from 8 to 100, (ii) comprises at least 4 consecutive nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to a transcription product, (iii) comprises at least one non-natural nucleotide, and (iv) the first nucleic acid strand hybridizes to the transcription product; and

the second nucleic acid strand comprises nucleotides and optionally nucleotide analogs.

(18) A pharmaceutical composition for treating a mammal comprising the double stranded nucleic acid complex of item (17), wherein the transcription product is a mammalian transcription product, and a pharmaceutically acceptable carrier.

In other embodiments of the present invention, the following are provided.

<1> A purified or isolated double stranded nucleic acid com plex comprising a first nucleic acid strand annealed to a sec ond nucleic acid strand, wherein:

the first nucleic acid strand comprises DNA nucleotides and optionally nucleotide analogs, wherein a 5' wing region comprising one or more nuclease-resistant nucleotides is loca ted at the 5' terminus and/or a 3' wing region comprising one or more nuclease-resistant nucleotides is located at the 3' t erminus, the first nucleic acid strand includes at least 4 co nsecutive DNA nucleotides, and the total number of DNA nucleo tides and nucleotide analogs in the first nucleic acid strand is from 10 to 100 nucleotides;

the first nucleic acid strand further comprises a seque nee of at least 10 consecutive nucleotides complementary to a portion of a sequence of a transcription product; and

the second nucleic acid strand comprises:

(i) RNA nucleotides and optionally nucleotide analogs, and optionally a DNA nucleotide; or

(ii) DNA nucleotides and/or nucleotide analogs; or

(iii) PNA nucleotides;

wherein a 5' wing region comprising one or more nuclease-resi stant nucleotides is located at the 5' terminus and/or a 3' wi ng region comprising one or more nuclease-resistant nucleotid es is located at the 3' terminus, and where the total number o f RNA nucleotides, DNA nucleotides, nucleotide analogs, and P NA nucleotides in the second nucleic acid strand is from 10 t o 100 nucleotides.

<2> The double stranded nucleic acid complex of item <1>, w herein the transcription product is a protein-coding transcri ption product.

<3> The double stranded nucleic acid complex of <1>, wherei n the transcription product is a non-protein-coding transcrip tion product.

<4> The double stranded nucleic acid complex of any one of i terns <l>-<3>, wherein the number of nucleotides in the first nucleic acid strand and the second nucleic acid strand are th e same.

<5> The double stranded nucleic acid complex of any one of i terns <l>-<3>, wherein the number of nucleotides in the first nucleic acid strand and the second nucleic acid strand are di fferent .

<6> The double stranded nucleic acid complex of item <5>, w herein the number of nucleotides in the second nucleic acid s trand is greater than the number of nucleotides in the first nucleic acid strand.

<7> The double stranded nucleic acid complex of any one of i terns <l>-<6>, wherein the first nucleic acid strand comprises a total number of nucleotides ranging from 10 to 35 nucleoti des .

<8> The double stranded nucleic acid complex of any one of i terns <l>-<7>, wherein the nucleotides of the first nucleic ac id strand are all nuclease-resistant nucleotides.

<9> The double stranded nucleic acid complex of any one of i terns <l>-<8>, wherein the 5' wing region of the first nucleic acid strand comprises one or more nucleotide analogs and/or t he 3' wing region of the first nucleic acid strand comprises o ne or more nucleotide analogs located at the 3' terminus.

<10> The double stranded nucleic acid complex of any one of i terns <l>-<9>, wherein the first strand comprises a 5' wing re gion of at least 2 consecutive nucleotide analogs at the 5'-t erminus and a 3' wing region of at least 2 consecutive nucleot ide analogs at the 3' -terminus.

<11> The double stranded nucleic acid complex of item <10>, wherein the 5' wing region and the 3' wing region independentl y consist of 2 to 10 nucleotide analogs.

<12> The double stranded nucleic acid complex of claim 11, w herein the 5' wing region and the 3' wing region independently consist of 2-3 nucleotide analogs.

<13> The double stranded nucleic acid complex of any one of i terns <1>-<12>, wherein the first nucleic acid strand comprise s at least one nucleotide analog that is a bridged nucleotide s .

<14> The double stranded nucleic acid complex of any one of i terns <1>-<13>, wherein the nucleotide analogs contained in th e first nucleic acid strand are bridged nucleotides.

<15> The double stranded nucleic acid complex of item <14>, wherein the bridged nucleotides of the first nucleic acid str and are independently selected from LNA, cEt-BNA, amideBNA (A mNA) , and cMOE-BNA.

<16> The double stranded nucleic acid complex of claim <14>, wherein the bridged nucleotides of the second nucleic acid s trand are selected from a ribonucleotide in which the carbon atom at the 2' -position and the carbon atom at the 4'-positio n are bridged by 4 ' - (CH ₂ ) _p -0-2 ' , 4 ' - (CH ₂ ) _p -S-2 ' , 4 ' - (CH ₂ ) _p -OCO-2 1 , 4 ¹ - (CH ₂ ) _n -N (R ₃ ) -0- (CH ₂ ) _m -2 ' , where p, m and n represent an in teger from 1 to 4, an integer from 0 to 2, and an integer from

1 to 3, respectively, and R3 represents a hydrogen atom, an a lkyl group, an alkenyl group, a cycloalkyl group, an aryl gro up, an aralkyl group, an acyl group, a sulfonyl group, a fluo rescent or chemiluminescent label, a functional group with nu cleic acid cleavage activity, or an intracellular or intranuc lear localization signal peptide.

<17> The double stranded nucleic acid complex of any one of i terns <1>-<16>, wherein the DNA nucleotides in first nucleic a cid strand are phosporothioated .

<18> The double stranded nucleic acid complex of any one of i terns <1>-<17>, wherein the nucleotide analogs in the first nu cleic acid strand are phosphorothioated .

<19> The double stranded nucleic acid complex of any one of i terns <1>-<18>, wherein the first nucleic acid strand includes a segment of 4-20 consecutive DNA nucleotides.

<20> The double stranded nucleic acid complex of any one of i terns <1>-<19>, wherein the first strand comprises (i) a 5' wi ng region of at least 2 consecutive nucleotide analogs at the 5' -terminus, (ii) a 3' wing region of at least 2 consecutive nucleotide analogs at the 3' -terminus, and (iii) at least 4 c onsecutive DNA nucleotides.

<21> The double stranded nucleic acid complex of any one of i terns <1>-<19>, wherein the first strand comprises (i) a 5' wi ng region of at least 2 consecutive nucleotide analogs at the 5' -terminus, (ii) a 3' wing region of at least 2 consecutive nucleotide analogs at the 3' -terminus, wherein said nucleotid e analogs in the 5' wing region and 3' wing region are bridged nucleotides; and (iii) at least 4 consecutive DNA nucleotide s; wherein said bridged nucleotides and said DNA nucleotides are phosphorothioated .

<22> The double stranded nucleic acid of any one of items <1> -<21>, wherein the first nucleic acid strand has a length of 12-25 nucleotides.

<23> The double stranded nucleic acid complex of any one of i terns <l>-<22>, wherein the second nucleic acid strand compris es RNA nucleotides and/or nucleotide analogs, and optionally a DNA nucleotide.

<24> The double stranded nucleic acid complex of item <23>, wherein the 5' wing region of the second nucleic acid strand c omprises at least one nucleotide analog, the 3' wing region o f the second nucleic acid strand comprises at least one nucle otide analog, and the second nucleic acid strand comprises at least 4 consecutive RNA nucleotides.

<25> The double stranded nucleic acid complex of item <23>, wherein the 5' wing region of the second nucleic acid strand c omprises at least one phosphorothioated nucleotide, the 3' wi ng region of the second nucleic acid strand comprises at leas t one phosphorothioated nucleotide, and the second nucleic ac id strand comprises at least 4 consecutive RNA nucleotides. <26> The double stranded nucleic acid complex of item <24> o r <25>, wherein all nucleotides of the 5' wing and the 3' wing region of the second nucleic acid strand are phosphorothioat ed.

<27> The double stranded nucleic acid complex of any one of c laims <24>-<26>, wherein the nuclease-resistant nucleotides o f the second nucleic acid strand are independently selected f rom a bridged nucleotide and a 2 ' -O-methylated RNA.

<28> The double stranded nucleic acid complex of item <27>, wherein the bridged nucleotides of the second nucleic acid st rand are independently selected from LNA, cEt-BNA, amideBNA ( AmNA) , and cMOE-BNA.

<29> The double stranded nucleic acid complex of item <27>, wherein the bridged nucleotides of the second nucleic acid st rand are selected from a ribonucleotide in which the carbon a torn at the 2 '-position and the carbon atom at the '-position are bridged by 4 ' - (CH ₂ ) _p -0-2 ' , 4 ' - (CH ₂ ) _p -S-2 ' , 4 ' - (CH ₂ ) _p -OCO-2 '

, 4 ¹ - (CH ₂ ) _n -N (R3) -0- (CH ₂ ) m-2 ' , where p, m and n represent an int eger from 1 to 4, an integer from 0 to 2, and an integer from 1 to 3, respectively, and R3 represents a hydrogen atom, an a lkyl group, an alkenyl group, a cycloalkyl group, an aryl gro up, an aralkyl group, an acyl group, a sulfonyl group, a fluo rescent or chemiluminescent label, a functional group with nu cleic acid cleavage activity, or an intracellular or intranuc lear localization signal peptide.

<30> The double stranded nucleic acid complex of item <24>, wherein the second nucleic acid strand comprises (i) a 5' win g region of at least 2 phosphorothioated, 2 ' -O-methylated RNA nucleotides at the 5' -terminus, (ii) a 3' ^' wing region of at 1 east 2 phosphorothioated, 2 ' -O-methylated RNA nucleotides at the 3' -terminus, and (iii) at least 4 consecutive natural RNA nucleotides that, independently, are optionally phophorothio ated.

<31> The double stranded nucleic acid complex of item <24>, wherein the second nucleic acid strand comprises (i) a 5' win g region of at least 2 phosphorothioated, bridged nucleotides at the 5' -terminus, (ii) a 3' wing region of at least 2 phosp horothioated, bridged nucleotides at the 3' -terminus, and (ii i) at least 4 consecutive natural RNA nucleotides that, indep endently, are optionally phophorothioated .

<32> The double stranded nucleic acid complex of any of item s <l>-<22>, wherein the second nucleic acid strand comprises PNA nucleotides .

<33> The double stranded nucleic complex of any of items <23 >-<32>, wherein the second nucleic acid strand further compri ses a functional moiety having a function selected from a lab eling function, a purification function, and a targeted deliv ery function.

<34> The double stranded nucleic acid complex according to a ny one of items <1> to <3> and <5> to <33>, wherein the double stranded nucleic acid complex further comprises a third nucl eic acid strand annealed to the second nucleic acid strand. <35> The double stranded nucleic acid according to item <34> , wherein the third nucleic acid strand comprises DNA nucleot ides and optionally nucleotide analogs, and includes at least 4 consecutive DNA nucleotides, where the total number of nuc leotides is from 10 to 100 nucleotides, said third nucleic ac id strand further comprising a sequence of at least 10 consec utive nucleotides complementary to a portion of a sequence of a transcription product.

<36> The double stranded nucleic acid according to item <35> , wherein the third strand comprises (i) a 5' wing region of a t least 2 consecutive nucleotide analogs at the 5' -terminus, (ii) a 3' wing region of at least 2 consecutive nucleotide ana logs at the 3' -terminus, wherein said nucleotide analogs in t he 5' wing region and 3' wing region are bridged nucleotides; and (iii) at least 4 consecutive DNA nucleotides; wherein sai d bridged nucleotides and said DNA nucleotides are phosphorot hioated.

<37> The double stranded nucleic acid according to item <34> , wherein the third nucleic acid strand comprises PNA nucleot ides .

<38> The double stranded nucleic complex of any of items <34 >-<37>, wherein the third nucleic acid strand further compris es a functional moiety having a function selected from a labe ling function, a purification function, and a targeted delive ry function.

<39> The double stranded nucleic acid complex according to i tern 33 or 38, wherein said functional moiety is a molecule se lected from a lipid, a peptide, and a protein.

<40> The double stranded nucleic acid complex according to i tern <39>, wherein the functional moiety is joined to the 3'-t erminal nucleotide or the 5' -terminal nucleotide.

<41> The double stranded nucleic acid complex according to i tern <39> or <40>, wherein the functional moiety is a lipid.

<42> The double stranded nucleic acid complex according to i tern <41>, wherein the functional moiety is a lipid selected f rom cholesterol, a fatty acid, a lipid-soluble vitamin, a gly colipid, and a glyceride.

<43> The double stranded nucleic acid complex according to i tern <41>, wherein the functional moiety is a lipid selected f rom cholesterol, a tocopherol, and a tocotrienol.

<44> The double stranded nucleic acid complex according to i tern <39> or <40>, wherein the functional molecule is a peptid e or protein selected from a receptor ligand and an antibody.

<45> A pharmaceutical composition comprising a pharmaceutica lly acceptable carrier and the double stranded nucleic acid c omplex of any one of items <1> to <44>.

<46> Use of the double stranded nucleic acid complex of any one of items <1> to <44> for the preparation of a medicament f or reducing the expression of a gene in a mammal. <47> Use of the double stranded nucleic acid complex of any o ne of items <1> to <44> for reducing expression of a gene in a mammal.

<48> A method of reducing expression of a gene in a mammal co mprising the step of administering an effective amount to the mammal of a pharmaceutical composition comprising:

a purified or isolated double stranded nucleic acid complex c omprising a first nucleic acid strand annealed to a second nu cleic acid strand, wherein:

the first nucleic acid strand comprises DNA nucleotides and o ptionally nucleotide analogs, and includes at least 4 consecu tive DNA nucleotides, where the total number of DNA nucleotid es and nucleotide analogs in the first nucleic acid strand is from 10 to 100 nucleotides;

the first nucleic acid strand further comprises a sequence of at least 10 consecutive nucleotides complementary to a porti on of a sequence of a mammalian transcription product; and the second nucleic acid strand comprises:

(i) RNA nucleotides and optionally nucleotide analogs, and op tionally a DNA nucleotide; or

(ii) DNA nucleotides and/or nucleotide analogs; or

(iii) PNA nucleotides;

where the total number of RNA nucleotides, DNA nucleotides, n ucleotide analogs, and PNA nucleotides in the second nucleic acid strand is from 10 to 100 nucleotides; and

a pharmaceutically acceptable carrier. <49> The method of item <48>, wherein the route of administr ation is enteral.

<50> The method of item <48>, wherein the route of administr ation is parenteral.

<51> The method of any one of items <48>-<50>, wherein the do sage ranges from 0.001 mg/kg/day to 50 mg/kg/day of the doubl e stranded nucleic acid complex.

<52> The method of any one of items <48>-<51>, wherein the mammal is a human.

[Advantageous Effects of Invention]

According to certain embodiments, an antisense nucleic acid can be delivered in a double-stranded complex and the expression of a target gene or the level of a transcription product can be selectively and very effectively suppressed by the antisense nucleic acid. In some embodiments, the double-stranded complex can be delivered to a target site with high specificity and high efficiency by associating a delivery moiety with the complex.

[Brief Description of Drawings]

[Fig.1] FIG.1 is a diagram illustrating the general mechanisms of certain antisense methods. As illustrated in the diagram, when an oligonucleotide ( antisense oligonucleotide (ASO) ) ("DNA" in the diagram) that is complementary to a partial sequence of the mRNA of a target gene is introduced into a cell, the expression of a protein that is encoded by the target gene is selectively inhibited. In the dashed box, a degradation mechanism is shown in which RNase H cleaves mRNA at a location at which it is hybridized to an ASO. As a result of RNase H cleavage, the mRNA generally will not be translated to produce a functional gene expression product .

[Fig. 2] FIG. 2 is a schematic diagram illustrating the structures of RNA, DNA, and an LNA nucleotide.

[Fig. 3] FIGS. 3A-B are schematic diagrams illustrating ex amples of suitable embodiments of double-stranded nucleic aci d complexes. The 5 ' -LNA-DNA-LNA-3 ' strands are antisense nucl eic acids complementary to the targeted transcription product . In the diagram, "(s)" represents nucleic acids with phosph orothioate linkages; "(o)" represents nucleic acids with natu ral phosphorothioate linkages; and "(m/s)" represents RNA tha t has been phosphorothioated and 2 ' -O-methylated . Furthermor e, "X" represents a functional moiety, and may independently represent a lipid (for example, cholesterol or tocopherol), a sugar or the like, or a protein, a peptide (for example, an a ntibody) or the like.

[Fig. 4] FIGS. 4A-B are schematic diagrams illustrating ex amples of suitable embodiments of a double-stranded nucleic a cid complexes that contain three strands: a first ASO nucleic acid strand and a second complementary nucleic acid strand, that have different strand lengths, and a third nucleic acid strand comprising a PNA to which is bound a functional molecu le such as a peptide, an antibody, or the like. Symbols in th e diagram have the same meanings as those defined in FIG. 3.

[Fig. 5] FIGS. 5A-B are schematic diagrams illustrating ex amples of suitable embodiments of a double-stranded nucleic a cid complex that have at least a first ASO nucleic acid stran d and a second complementary nucleic acid strand that have di fferent chain lengths. In these embodiments, either (A) the nucleic acid further comprises a third nucleic acid strand co mplementary to the second nucleic acid strand or (B) the seco nd nucleic acid strand further comprises a self-complementary region of phosphorothioated DNA attached to the second nucle ic acid strand by a hairpin linker. Furthermore, in the diag ram, " (m) " represents a 2 ' -O-methylated RNA. Other symbols h ave the same meanings as those defined in FIG. 3.

[Fig. 6] FIG. 6A is a schematic diagram illustrating a nucl eic acid having the structure of 5 ' -LNA-DNA-LNA-3 ' that is la beled at the 5' terminus with the fluorescent dye Cy3. FIG. 6 B is a schematic diagram illustrating a nucleic acid having t he structure of 5 ' -LNA-DNA-LNA-3 ' that is labeled at the 5' t erminus with the fluorescent dye Cy3 and is labeled at the 3'- terminus with cholesterol ("Choi"),

"(s)" represents a phosphorothioated nucleic acid.

[Fig. 7] FIG. 7 is a fluorescence microscopic photograph il lustrating the results of observing the liver of a mouse to w hich fluorescently ( Cy3 ) -labeled "LNA" (in accordance with FI G. 6A) or fluorescently ( Cy3 ) -labeled "chol-LNA" (in accordan ce with FIG. 6B) has been administered.

[Fig. 8] FIG. 8 is a graph illustrating the results obtaine d by administering to mice "12-mer Cy3-Chol-LNA (ApoBl ) " (in a ccordance with FIG . 6B) , "20-mer Cy3-Chol-LNA (ApoBl ), " or "2 9-mer Cy3-Chol-LNA (ApoBl ) , " or "12-mer Cy3-LN (ApoBl ) " (in ac cordance with FIG. 6A) , all of which have a sequence compleme ntary to the base sequence of ApoBl gene, and analyzing the a mount of expression of ApoBl gene in the livers of these mice by quantitative PCR.

[Fig. 9] FIG. 9 is a schematic diagram illustrating certain embodiments of a double-stranded nucleic acid. Symbols have the same meanings as those defined in FIG. 3-6.

[Fig. 10] FIG. 10 is a schematic diagram illustrating the a ntisense strand (ASO) and its complementary strands (cRNA(o), cRNA(G), and cRNA(m/s)), which were used to evaluate the ant isense effect of a double-stranded nucleic acid complex accor ding to one embodiment. Symbols have the same meanings as th ose defined in FIG. 3-6 and 9.

[Fig. 11] FIG. 11 shows photographs illustrating the result s obtained by analyzing the presence or absence of annealing of the antisense strand and its complementary strands illustr ated in FIG. 10 by electrophoresis. Panel A indicates the re suits of taking a photograph under UV illumination, and panel

B shows a photograph of the gel.

[Fig. 12] FIG. 12 is a photograph taken under UV illuminati on illustrating the results obtained by annealing the antisen se strand and its complementary strands illustrated in FIG. 1 0, treating the strands with RNase H, and analyzing the react ion products by electrophoresis. [Fig. 13] FIG. 13 is a graph illustrating the results obtai ned by introducing the antisense strand illustrated in FIG. 1 0 or double-stranded nucleic acid complexes (at concentration s of 0.4 nM or 10 nM) composed of the antisense strand and one of the complementary strands illustrated in FIG. 10, into ce lis. The amount of expression of ApoBl gene, whose transcript ion product is targeted by the antisense strand, in the cells was analyzed by quantitative PCR.

[Fig. 14] FIG. 14 is a graph illustrating the results obtai ned by analyzing the amount of expression of ApoBl gene in ce lis into which the antisense strand illustrated in FIG. 10 or double-stranded nucleic acid complexes composed of the antis ense strand and one of the complementary strands illustrated in FIG. 10, normalized to the amount of expression obtained i n the cells where only the antisense strand was introduced.

[Fig. 15] FIG. 15 is a schematic diagram illustrating an an tisense strand, a complementary strand (cRNA(G)), and a compl ementary strand with a tocopherol functional moiety (Toc-cRNA (G) ) , which were used to evaluate the antisense effect of a d ouble-stranded nucleic acid complex. "Toe" represents tocoph erol. Other symbols have the same meanings as those defined in FIG. 3-6, 9, and 10.

[Fig. 16] FIG. 16 is a graph illustrating the results obtai ned by administering the antisense strand illustrated in FIG. 15 or double-stranded nucleic acids composed of the antisens e strand and one of the complementary strands illustrated in FIG. 15, to mice, and analyzing the amounts of expression of ApoBl gene, whose transcription product is targeted by the an tisense strand, in the mice.

[Fig. 17] FIG. 17 is a graph illustrating the results obtai ned by evaluating the specificity of the antisense effect of a double-stranded nucleic acid complex composed of the antise nse strand and a complementary strand having tocopherol bound thereto as illustrated in FIG. 15.

[Fig. 18] FIG. 18 is a graph illustrating the results obtai ned by evaluating the dose dependency of the antisense effect of a double-stranded nucleic acid complex composed of the an tisense strand and a complementary strand having tocopherol b ound thereto as illustrated in FIG. 15.

[Fig. 19A] FIG. 19A is a graph illustrating the results obt ained by evaluating sustainability of the antisense effect of double-stranded nucleic acid complexes composed of the antis ense strand and complementary chains having tocopherol bound thereto as illustrated in FIG. 15. In the diagram, "d" repre sents the number of days passed after the relevant double-str anded nucleic acid was administered.

[Fig. 19B] FIG. 19B is a graph- illustrating the results obt ained by evaluating sustainability of the antisense effect of double-stranded nucleic acid complexes composed of the antis ense strand and complementary chains having tocopherol bound thereto as illustrated in FIG. 15. In the diagram, "d" repre sents the number of days passed after the relevant double-str anded nucleic acid was administered.

[Fig. 20A] FIG. 20A is a schematic diagram illustrating an antisense oligonucleotide and complementary strands accordin g to certain embodiments.

[Fig. 20B] FIG. 20B is a graph comparing the results obtain ed by evaluating the antisense effect of the double-stranded nucleic acid complex (LNA/cRNA (G) -OM) according to one embodi ment of the present invention, which has a complementary stra nd comprising RNA that is entirely 2 ' -O-methylated .

[Fig. 21] FIG. 21 is a schematic diagram illustrating suita ble embodiments of a double-stranded nucleic acid that can be used to incorporate a peptide, protein, or the like as a fun ctional moiety. The symbols in the diagram have the same mea nings as those defined in FIG. 3 and FIG. 4.

[Fig. 22] FIG. 22 is a graph illustrating the results obtai ned by evaluating the antisense effect of the double-stranded nucleic acid complex composed of three strands: the antisens e strand, a complementary strand comprising RNA, and a PNA st rand for binding to a peptide or the like.

[Fig. 23] FIG. 23 is a graph illustrating the results obtai ned by evaluating the antisense effect of double-stranded nuc leic acid complexes composed of an antisense strand and a com plementary strand comprising PNA.

[Fig. 24] FIG. 24 is a schematic diagram illustrating an an tisense oligonucleotide and complementary strands according t o certain embodiments. [Fig. 25A] FIG. 25A is a graph illustrating the results obtai ned for double-stranded nucleic acid complexes prepared with the strands shown in Fig. 24.

[Fig. 25B] FIG. 25B is a graph illustrating the results obta ined for double-stranded nucleic acid complexes prepared with the strands shown in Fig. 24.

[Fig. 26] FIG. 26 is a graph illustrating the results obtaine d in Example 11 for suppression of expression using double-st randed nucleic acid complexes.

[Fig. 27A] FIGS. 27A is a graph illustrating the results obta ined in Example 12 evaluating the suppression of expression o f hTTR with double-stranded nucleic acid complexes of differe nt length.

[Fig. 27B] FIGS. 27B is a graph illustrating the results obta ined in Example 12 evaluating the suppression of expression o f hTTR with double-stranded nucleic acid complexes of differe nt length.

[Fig. 28] FIG. 28 is a graph illustrating the results obtaine d in Example 12 evaluating the serum protein level for a prot ein targeted by a double-stranded nucleic acid complex before and after treatment.

[Fig. 29] FIG. 29 is a fluorescent image showing the results obtained in Example 13 showing localization of a double-stran ded nucleic acid complex comprised of three strands.

[Fig. 30] FIG. 30 is a graph illustrating the results of Exam pie 13 showing suppression of expression caused by a double-s tranded nucleic acid complex comprised of three strands.

[Fig. 31] FIG. 31 is a graph illustrating the results of Exam pie 14 showing suppression of the level of an miRNA.

[Fig. 32] FIG. 32 is a graph illustrating the results obtaine d in Example 15 demonstrating suppression of expression using a double-stranded nucleic acid complex containing an ASO tha t includes amideBNA (AmNA) nucleotide analog.

[Description of Embodiments]

Double-stranded nucleic acid complexes including an ant isense nucleic acid and a nucleic acid complementary to the a ntisense nucleic acid.

Certain embodiments include a purified or isolated doub le-stranded nucleic acid complex comprising a first nucleic a cid annealed to a second nucleic acid, which has an activity of suppressing the expression of a target gene or more genera lly the level of a transcription product, by means of an anti sense effect.

The first nucleic acid strand (i) comprises nucleotides and optionally nucleotide analogs, and the total number of n ucleotides and nucleotide analogs in the first nucleic acid s trand is from 8 to 100, (ii) comprises at least 4 consecutive nucleotides that are recognized by RNase H when the first nuc leic acid strand is hybridized to a transcription product, (i ii) comprises at least one non-natural nucleotide, and (iv) t he first nucleic acid strand hybridizes to the transcription product; and the second nucleic acid strand comprises nucleotides an d optionally nucleotide analogs, and

the second nucleic acid strand can anneal to the first nuclei c acid strand

The second nucleic acid strand comprises:

(i) an RNA nucleotide and optionally a nucleotide analog, and optionally a DNA nucleotide; or

(ii) a DNA nucleotide and/or a nucleotide analog; or

(iii) PNA nucleotides.

The "antisense effect" means suppressing the expression of a target gene or the level of a targeted transcription pro duct, which occurs as a result of hybridization of the target ed transcription product (RNA sense strand) with, for example , a DNA strand, or more generally strand designed to cause th e antisense effect, complementary to a partial sequence of th e transcription product or the like, wherein in certain insta nces inhibition of translation or a splicing function modifyi ng effect such as exon skipping (see the description in the u pper part outside the area surrounded by dotted lines in FIG. 1) may be caused by covering of the transcription product by the hybridization product, and/or decomposition of the transc ription product may occur as a result of recognition of the h ybridized portion (see the description within the area surrou nded by dotted lines in FIG. 1) .

The "target gene" or "targeted transcription product" w hose expression is suppressed by the antisense effect is not particularly limited, and examples thereof include genes hos e expression is increased in various diseases. Also, the "tr anscription product of the target gene" is a mRNA transcribed from the genomic DNA that encodes the target gene, and also i ncludes a mRNA that has not been subjected to base modificati on, a mRNA precursor that has not been spliced, and the like.

More generally, the "transcription product" may be any RNA s ynthesized by a DNA-dependent RNA polymerase.

The term "purified or isolated double-stranded nucleic acid complex" as used herein means, a nucleic acid complex tha t comprises at least one nucleic strand that does not occur i n nature, or is essentially free of naturally occurring nucle ic acid materials.

The term "complementary" as used herein means a relatio nship in which so-called Watson-Crick base pairs (natural typ e base pair) or non-Watson-Crick base pairs (Hoogsteen base p airs and the like) can be formed via hydrogen bonding. It is not necessary that the base sequence of the targeted transcri ption product, e.g., the transcription product of a target ge ne, and the base sequence of the first nucleic acid strand be perfectly complementary, and it is acceptable if the base seq uences have a complementary of at least 70% or higher, prefer ably 80% or higher, and more preferably 90% or higher (for ex ample, 95%, 96%, 97%, 98%, or 99% or higher) . The complement ary of sequences can be determined by using a BLAST program o r the like. A first strand can be "annealed" to a second stran d when the sequences are complementary. A person of ordinary skill in the art can readily determine the conditions (tempe rature, salt concentration, etc.) under which two strands can be annealed. Also, a person having ordinary skill in the art can easily design an antisense nucleic acid complementary to the targeted transcription product based on the information of the base sequence of, e.g., the target gene.

The first nucleic acid strand according to certain embo diments is an antisense nucleic acid complementary to a trans cription product, such as that of a target gene, and is a nucl eic acid containing a region comprising at least 4 consecutiv e nucleotides that are recognized by RNase H when the first n ucleic acid strand is hybridized to the transcription product

As used herein, the term "nucleic acid" may refer to a m onomeric nucleotide or nucleoside, or may mean an oligonucleo tide consisting of plural monomers. The term "nucleic acid s trand" is also used herein to refer to an oligonucleotide. Nu cleic acid strands may be prepared in whole or in part by chem ical synthesis methods, including using a automated synthesiz er or by enzymatic processes, including but not limited to po lymerase, ligase, or restriction reactions.

The strand length of the first nucleic acid strand is no t particularly limited, but the strand length is usually at 1 east 8 bases, at least 10 bases, at least 12 bases, or at leas t 13 bases. The strand length may be up to 20 bases, 25 bases , or 35 bases. The strand length may even be as long as about 100 bases. Ranges of the length may be 10 to 35 bases, 12 to 25 bases, or 13 to 20 bases. In certain instances, the choic e of length generally depends on a balance of the strength of the antisense effect with the specificity of the nucleic acid strand for the target, among other factors such as cost, syn thetic yield, and the like.

The "at least four consecutive nucleotides that are rec ognized by RNase H" is usually a region comprising 4 to 20 con secutive bases, a region comprising 5 to 16 consecutive bases

, or a region comprising 6 to 12 consecutive bases. Furtherm ore, nucleotides that may be used in this region are those th at, like natural DNA, are recognized by RNase H when hybridiz ed to RNA nucleotides, wherein the RNase H cleaves the RNA st rand. Suitable nucleotides, such as modified DNA nucleotides and other bases are know in the art. Nucleotides that contai n a 2' -hydroxy group, like an RNA nucleotide are known to not be suitable. One of skill in the art can readily determine th e suitability of a nucleotide for use in this region of "at le ast four consecutive nucleotides."

In certain embodiments, the first nucleic acid strand c omprises "nucleotides and optionally nucleotide analogs." Th is term means that the first strand includes DNA nucleotides, RNA nucleotides, and optionally may further include nucleoti de analogs in the strand.

As used herein, "DNA nucleotide" means a naturally occur ring DNA nucleotide, or a DNA nucleotide with a modified base , sugar, or phosphate linkage subunit. Similarly, "RNA nucle otide" means a naturally occurring RNA nucleotide, or an RNA nucleotide with a modified base, sugar, or phosphate linkage subunit. A modified base, sugar, or phosphate linkage subuni t is one in which a single substituent has been added or subst ituted in a subunit, and the subunit as a whole has not been r eplaced with a different chemical group. From the viewpoint that a portion or the entirety of the region comprising the n ucleotide has high resistance to deoxyribonuclease and the li ke, the DNA may be a modified nucleotide. Examples of such mo dification include 5-methylation , 5-fluorination, 5-brominat ion, 5-iodination, and N4-methylation of cytosine; 5-demethyl ation, 5-fluorination, 5-bromination, and 5-iodination of thy midine; N6-methylation and 8-bromination of adenine; N2-methy lation and 8-bromination of guanine; phosphorothioation, meth ylphosphonation, methylthiophosphonation, chiral methylphosp honation, phosphorodithioation , phosphoroamidation, 2 ' -O-met hylation, 2 ' -methoxyethyl (MOE) at ion, 2 ' -aminopropyl (AP ) ation , and 2 ' -fluorination . However, from the viewpoint of having excellent pharmacokinetics, phosphorothioation is preferred Such modification may be carried out such that the same DNA may be subjected to plural kinds of modifications in combina tion. And, as discussed below, RNA nucleotides may be modifi ed to achieve a similar effect.

In certain instances, the number of modified DNA ' s and the position of modification may affect the antisense effect and the like provided by the double-stranded nucleic acid of the as disclosed herein. Since these embodiments may vary wi th the sequence of the target gene and the like, it may depend on cases, but a person having ordinary skill in the art can d etermine suitable embodiments by referring to the description s of documents related to antisense methods. Furthermore, wh en the antisense effect possessed by a double-stranded nuclei c acid complex after modification is measured, if the measure d value thus obtained is not significantly lower than the mea sured value of the double-stranded nucleic acid complex befor e modification (for example, if the measured value obtained a fter modification is lower by 30% or more than the measured v alue of the double-stranded nucleic acid complex before modif ication) , the relevant modification can be evaluated. The me asurement of the antisense effect can be carried out, as indi cated in the Examples below, by introducing a nucleic acid co mpound under test into a cell or the like, and measuring the a mount of expression (amount of mRNA, amount of cDNA, amount o f a protein, or the like) of the target gene in the cell in wh ich the expression is suppressed by the antisense effect prov ided by the nucleic acid compound under test, by appropriatel y using known techniques such as Northern Blotting, quantitat ive PCR, and Western Blotting.

As used herein, "nucleotide analog" means a non-natural ly occurring nucleotide, wherein the base, sugar, or phosphat e linkage subunit has more than one substituent added or subs tituted in a subunit, or that the subunit as a whole has been replaced with a different chemical group. An example of an a nalog with more than one substitution is a bridged nucleic ac id, wherein a bridging unit has been added by virtue of two su bstitutions on the sugar ring, typically linked to the 2' and 4' carbon atoms. In regard to the first nucleic acid strand a ccording to certain embodiments, from the viewpoint of increa sing the affinity to a partial sequence of the transcription product of the target gene and/or the resistance of the targe t gene to a nuclease, the first nucleic acid strand further c omprises a nucleotide analog. The "nucleotide analog" may be any nucleic acid in which, owing to the modifications (bridg ing groups, substituents , etc.), the affinity to a partial se quence of the transcription product of the target gene and/or the resistance of the nucleic acid to a nuclease is enhanced , and examples thereof include nucleic acids that are disclos ed to be suitable for use in antisense methods, in JP 10-3048 89 A, WO 2005/021570, JP 10-195098 A, JP 2002-521310 W, WO 20 07/143315, WO 2008/043753, WO 2008/029619, and WO 2008/049085

(hereinafter, these documents will be referred to as "docume nts related to antisense methods"). That is, examples thereo f include the nucleic acids disclosed in the documents descri bed above: a hexitol nucleic acid (HNA) , a cyclohexane nuclei c acid (CeNA) , a peptide nucleic acid (PNA), a glycol nucleic acid (GNA) , a threose nucleic acid (TNA) , a morpholino nucle ic acid, a tricyclo-DNA (tcDNA) , a 2 ' -O-methylated nucleic ac id, a 2 ' -MOE ( 2 ' -O-methoxyethyl ) lated nucleic acid, a 2 ' -AP ( 2 ' -O-aminopropyl ) lated nucleic acid, a 2 ' -fluorinated nuclei c acid, a 2 ' -F-arabinonucleic acid (2'-F-ANA), and a BNA (bri dged nucleic acid) .

The BNA according to certain embodiments may be any rib onucleotide or deoxyribonucleotide in which the 2' carbon ato m and 4' carbon atom are bridged by two or more atoms. Exampl es of bridged nucleic acids are known to those of skill in the art. One subgroup of such BNA' s can be described as having t he carbon atom at the 2 '-position and the carbon atom at the 4 '-position bridged by 4 ' - (CH ₂ ) _p -0-2 ' , 4 ' - (CH ₂ ) _p -S-2 ' , 4 ' - (CH ₂ ) _p - OCO-2 ' , 4 ' - (CH ₂ ) _n -N ( R ₃ ) -0- (CH ₂ ) _m -2 ' (here, p, m and n represent an integer from 1 to 4, an integer from 0 to 2, and an intege r from 1 to 3 , respectively; and R3 represents a hydrogen ato m, an alkyl group, an alkenyl group, a cycloalkyl group, an a ryl group, an aralkyl group, an acyl group, a sulfonyl group, and a unit substituent (a fluorescent or chemiluminescent la beling molecule, a functional group having nucleic acid cleav age activity, an intracellular or intranuclear localization s ignal peptide, or the like)) . Furthermore, in regard to the BNA according certain embodiments, in the 0R ₂ substituent on the carbon atom at the 3 '-position and the ORi substituent on the carbon atom at the 5 '-position, Ri and R ₂ are typically hy drogen atoms, but may be identical with or different from eac h other, and may also be a protective group of a hydroxyl grou p for nucleic acid synthesis, an alkyl group, an alkenyl grou p, a cycloalkyl group, an aryl group, an aralkyl group, an ac yl group, a sulfonyl group, a silyl group, a phosphoric acid group, a phosphoric acid group protected by a protective grou p for nucleic acid synthesis, or -P(R ₄ )R ₅ (here, R ₄ and R ₅ , whi ch may be identical with or different from each other, each r epresent a hydroxyl group, a hydroxyl group protected by a pr otective group for nucleic acid synthesis, a mercapto group, a mercapto group protected by a protective group for nucleic acid synthesis, an amino group, an alkoxy group having 1 to 5 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, a cyanoalkoxy group having 1 to 6 carbon atoms, or an amino gr oup substituted with an alkyl group having 1 to 5 carbon atom s) . Non-limiting examples of such a ΒΝΆ include a-L-methylen eoxy (4 ' -CH ₂ -O-2 ' ) BNA or β-D-methyleneoxy (4 ' -CH ₂ -O-2 ¹ ) BNA, whi ch are also known as LNA (Locked Nucleic Acid (registered tra demark) , 2 ' , 4 ¹ -BNA) , ethyleneoxy (4 ' -CH ₂ ) 2-0-2 ^» ) BNA which is a lso known as ENA, β-D-thio ( ' -CH ₂ -S-2 ' ) BNA, aminooxy ( 4 ' -CH ₂ -0 -N (R ₃ ) -2 ' ) BNA, oxyamino (4 ' -CH ₂ - (R ₃ ) -0-2 ' ) BNA which is also k nown as 2 ' , 4 ' -BNANC , 2 ' , 4 ' -BNACOC , 3 ' -amino-2 ' , ' -BNA, 5 ' -met hyl BNA, ( 4 ' -CH (CH ₃ ) -0-2 ' ) BNA, which is also known as cEt-BNA, (4' -CH (CH ₂ OCH ₃ ) -0-2' ) BNA, which is also known as cMOE-BNA, am ideBNA ( 4 ' -C (O) - (R) -2' ) BNA (R=H, Me), which is also known as AmNA, and other BNA' s known to those of skill in the art.

Furthermore, in the nucleotide analog, according to cer tain embodiments, a base moiety may be modified. Examples of the modification at a base moiety include 5-methylation, 5-f luorination, 5-bromination, 5-iodination, and N4-methylation of cytosine; 5-demethylation, 5-fluorination, 5-bromination , and 5-iodination of thymidine; N6-methylation and 8-bromina tion of adenine; and N2-methylat ion and 8-bromination of guan ine. Furthermore, in the modified nucleic acid according to certain embodiments, a phosphoric acid diester binding site m ay be modified. Examples of the modification of the phosphor ic acid diester binding site include phosphorothioation, meth ylphosphonation , methylthiophosphonation, chiral methylphosp honation, phosphorodithioation, and phosphoroamidat ion . How ever, from the viewpoint of having excellent pharmacokinetics , phosphorothioation may be used. Also, such modification of a base moiety or modification of a phosphoric acid diester b inding site may be carried out such that the same nucleic aci d may be subjected to plural kinds of modifications in combin ation .

Generally, modified nucleotides and modified nucleotide analogs are not limited to those exemplified herein. Numero us modified nucleotides and modified nucleotide analogs are k nown in art, such as, for example those disclosed in U.S. Pat ent No. 8,299,039 to Tachas et al., particularly at col. 17-2 2, and may be used in the embodiments of this application.

A person having ordinary skill in the art can appropria tely select and use a nucleotide analog among such modified n ucleic acids while taking consideration of the antisense effe ct, affinity to a partial sequence of the transcription produ ct of the target gene, resistance to a nuclease, and the like However, the nucleotide analog in some embodiments is a LN A represented by the following formula (1) :

[Chem. 1]

Base

In formula (1), "Base" represents an aromatic heterocyc lie group or aromatic hydrocarbon ring group which may be sub stituted, for example, a base moiety (purine base or pyrimidi ne base) of a natural nucleoside, or a base moiety of a non-na tural (modified) nucleoside, while examples of modification o f the base moiety include those described above; and

Ri and ϊ½, which may be identical with or different from each other, each represent a hydrogen atom, a protective gro up of a hydroxyl group for nucleic acid synthesis, an alkyl g roup, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an acyl group, a sulfonyl group, a silyl grou p, a phosphoric acid group, a phosphoric acid group protected by a protective group for nucleic acid synthesis, or -P(R ₄ )R ₅ [here, R ₄ and R5, which may be identical or different from ea ch other, each represent a hydroxyl group, a hydroxyl group p rotected by a protective group for nucleic acid synthesis, a mercapto group, a mercapto group protected by a protective gr oup for nucleic acid synthesis, an amino group, an alkoxy gro up having 1 to 5 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, a cyanoalkoxy group having 1 to 6 carbon atom s, or an amino group substituted with an alkyl group having 1 to 5 carbon atoms.

The compounds shown by the above chemical formulas are represented as nucleosides, but the "LNA" and more generally, the BNA according to certain embodiments include nucleotide forms in which a phosphoric acid derived group is bound to th e relevant nucleoside (nucleotide) . In other words, BNA's, s uch as LNA, are incorporated as nucleotides in the nucleic st rands that comprise the double stranded nucleic acid complex.

The "wing region comprising one or more nucleotide anal ogs" according to certain embodiments is located on the 5 ¹ -te rminal side and/or the 3 ' -terminal side of the region compris ing at least four consecutive DNA nucleotides (hereinafter, a lso called "DNA gap region") .

The region comprising a nucleotide analog that is dispo sed to the 5 ' -terminus of the DNA gap region (hereinafter, al so called "5 ¹ wing region") and the region comprising a nucle otide analog that is disposed to the 3' -terminus of the DNA g ap region (hereinafter, also called "3' wing region") may eac h independently comprise at least one kind of a nucleotide an alog that is discussed in the documents related to antisense methods, and may further comprise a natural nucleic acid (DNA or RNA) in addition to such a nucleotide analog. Furthermor e, the strand lengths of the 5' wing region and the 3' wing re gion are independently usually 1 to 10 bases, 1 to 7 bases, or 2 to 5 bases.

Furthermore, there are suitable embodiments of the numb er of kinds and position of the nucleotide analog and the nat ural nucleotide in the 5' wing region and the 3' wing region, since the number and the position of those nucleic acids may affect the antisense effect and the like provided by the doub le-stranded nucleic acid complex in certain embodiments. Sin ce these suitable embodiments may vary with the sequence and the like, it may depend on cases, but a person having ordinar y skill in the art can determine the suitable embodiments by referring to the descriptions of documents related to antisen se methods. Furthermore, when the antisense effect possessed by a double-stranded nucleic acid after modification is meas ured in the same manner as in the case of the region comprisin g "at least four consecutive DNA nucleotides," if the measure d value thus obtained is not significantly lower than that of a double-stranded nucleic acid before modification, the rele vant modification can be evaluated as a preferred embodiment.

Meanwhile, antisense methods involving an RNA or a LNA only that have been traditionally attempted have suppressed t ranslation through binding to a target mRNA; however, their e ffects are typically insufficient. On the other hand, in ant isense methods involving a DNA only, since a double-stranded structure composed of a DNA and an RNA is obtained once the DN A binds to a target gene transcript, a strong target gene exp ression suppressing effect could be expected to be obtained b y making the DNA-RNA heteroduplex a target of RNase H and the reby cleaving the mRNA. However, since the binding of DNA it self to the target RNA is weak, the actual effect has also typ ically been insufficient.

Therefore, when a DNA having a strand length of at least four or more bases is disposed at the center of a first nucle ic acid strand, and a LNA (or other BNA) having a strong bindi ng affinity to RNA (i.e., to the targeted transcription produ ct) is disposed at both ends of this first strand, such a comp osite strand thereby promotes cleavage of the target RNA by R Nase H. The "DNA having a strand length of four" is not howeve r limited to just DNA nucleotides. It is contemplated that t he first nucleic acid strand comprises at least 4 consecutive nucleotides that are recognized by RNase H when the first nu cleic acid strand is hybridized to a transcription product. From the viewpoint that the antisense effect occurring as a r esult of heteroduplex formation with the targeted transcript! on product is excellent, the optional inclusion of nucleotide analogs according to certain embodiments in regions comprisi ng a modified nucleic acid disposed on the 5' side and the 3' side of the region comprising at least four consecutive nucle otides that are recognized by RNase H when the first nucleic acid strand is hybridized to a transcription product, is desi rable. The nucleotide analog may be a BNA, such as, e.g., LNA The second nucleic acid strand according to some embodi ments of is a nucleic acid complementary to the first nucleic acid strand described above. It is not necessary that the ba se sequence of the second nucleic acid strand and the base se quence of the first nucleic acid strand be perfectly compleme ntary to each other, and the base sequences may have a comple mentary of at least 70% or higher, preferably 80% or higher, and more preferably 90% or higher (for example, 95%, 96%, 97% , 98%, 99% or higher) .

The second nucleic acid strand is an oligonucleotide co mprising at least one kind of nucleic acid selected from RNA, DNA, PNA (peptide nucleic acid) and BNA (e.g., LNA) . More sp ecifically, the second strand comprises (i) an RNA nucleotide and optionally a nucleotide analog, and optionally a DNA nuc leotide; or

(ii) a DNA nucleotide and/or a nucleotide analog; or

(iii) PNA nucleotides.

The term "RNA nucleotides and optionally nucleotide ana logs, and optionally a DNA nucleotide" means that the second strand includes RNA nucleotides, and optionally may further i nclude nucleotide analogs in the strand, and optionally may f urther include DNA nucleotides in the strand. The term "DNA n ucleotides and/or nucleotide analogs" means that the second s trand may include either DNA nucleotides or nucleotide analog s, or may include both DNA nucleotides and nucleotide analogs The term "PNA nucleotides" means that the second strand may be composed of PNA nucleotides.

However, as will be described in the Examples that foil ow, from the viewpoint that when the double-stranded nucleic acid complex of certain embodiments is recognized by RNase H in the cell and the second nucleic acid strand is decomposed, the antisense effect of the first nucleic acid strand is rea dily exhibited, the second nucleic acid strand comprises RNA nucleotides. Furthermore, from the viewpoint that a function al molecule such as a peptide can be easily bound to the doubl e-stranded nucleic acid complex of some embodiments, the seco nd nucleic acid strand is a PNA.

As used herein, "RNA nucleotide" means a naturally occur ring RNA nucleotide, or an RNA nucleotide with a modified bas e, sugar, or phosphate linkage subunit. A modified base, sug ar, or phosphate linkage subunit is one in which a single sub stituent has been added or substituted in a subunit, and the subunit as a whole has not been replaced with a different che mical group.

In regard to the second nucleic acid strand, a portion o r the entirety of the nucleic acid may be a modified nucleoti de, from the viewpoint of having high resistance to a nucleas e such as a ribonuclease (RNase) . Examples of such modificat ion include 5-methylat ion, 5-fluorination, 5-bromination, 5- iodination and N4-methylation of cytosine; 5-demethylation, 5 -fluorination, 5-bromination, and 5-iodination of thymidine; Νβ-methylation and 8-bromination of adenine; N2-methylation a nd 8-bromination of guanine; phosphorothioation, methylphosp honation, methylthiophosphonation, chiral methylphosphonatio n, phosphorodithioation, phosphoroamidat ion, 2 ' -O-methylat io n, 2 ' -methoxyethyl ( OE ) ation, 2 ' -aminopropyl (AP) lation, and 2 ' -fluorination . Also, an RNA nucleotide with a thymidine ba se substituted for a uracil base is also contemplated. Howev er, from the viewpoint of having excellent pharmacokinetics, phosphorothioation is used. Furthermore, such modification m ay be carried out such that the same nucleic acid may be subje cted to plural kinds of modifications in combination. For ex ample, as used in the Examples described below, the same RNA may be subjected to phosphorothioation and 2 ' -O-methylation i n order to provide resistance to enzymatic cleavage. However , where it is expected or desired for an RNA nucleotide to be cleaved by RNase H, then only either phosphorothioation or 2' -O-methylation can be applied.

There are suitable embodiments of the number of nucleot ide analogs and the position of modification with regard to t he second nucleic acid strand, since the number and the posit ion of modification may affect the antisense effect and the 1 ike provided by the double-stranded nucleic acid complex in c ertain embodiments. Since these suitable embodiments may var y with the type, sequence and the like of the nucleic acid to be modified, it may depend on cases, but the type, sequence a nd the like can be characterized by measuring the antisense e ffect possessed by the double-stranded nucleic acid after mod ification in the same manner as in the case of the first nucle ic acid strand described above. According to such a suitable embodiment, from the viewpoint that while the decomposition by a ribonuclease such as RNase A is suppressed until the sec ond nucleic acid strand is delivered into the nucleus of a pa rticular cell, the second nucleic acid strand can easily exhi bit the antisense effect by being decomposed by RNase H in th e particular cell, the second nucleic acid strand is an RNA, a region complementary to the region of the first nucleic aci d strand comprising a nucleotide analog (i.e., 5' wing region and/or 3' wing region) is a modified nucleic acid or is a nuc leotide analog, and the modification or the analog has an eff ect of suppressing decomposition by enzymes, such as a ribonu clease. According to certain embodiments, the modification i s 2 ' -O-methylation and/or phosphorothioation of RNA. Further more, in this case, the entire region that is complementary t o the region of the first nucleic acid strand comprising a nu cleotide analog may be modified, or a portion of the region t hat is complementary to the region comprising a modified nucl eic acid of the first nucleic acid strand may be modified. In addition, the region that is modified may be longer than the region comprising a modified nucleic acid of the first nuclei c acid strand, or may be shorter, as long as the region that i s modified comprises that portion.

In the double-stranded nucleic acid complex of certain embodiments, a functional moiety may be bonded to the second nucleic acid strand. The bonding between the second nucleic acid strand and the functional moiety may be direct bonding, or may be indirect bonding mediated by another material. How ever, in certain embodiments, it is preferable that a functio nal moiety be directly bonded to the second nucleic acid stra nd via covalent bonding, ionic bonding, hydrogen bonding or t he like, and from the viewpoint that more stable bonding may be obtained, covalent bonding is more preferred.

There are no particular limitations on the structure of the "functional moiety" according to certain embodiments, pr ovided it imparts the desired function to the double-stranded nucleic acid complex and/or the strand to which it is bound. The desired functions include a labeling function, a purific ation function, and a delivery function. Examples of moietie s that provide a labeling function include compounds such as fluorescent proteins, luciferase, and the like. Examples of moieties that provide a purification function include compoun ds such as biotin, avidin, a His tag peptide, a GST tag peptid e, a FLAG tag peptide, and the like.

Furthermore, from the viewpoint of delivering the first nucleic acid strand to a target site with high specificity a nd high efficiency, and thereby suppressing very effectively the expression of a target gene by the relevant nucleic acid, it is preferable that a molecule having an activity of deliv ering the double-stranded nucleic acid complex of some embodi ments to a "target site" within the body, be bonded as a funct ional moiety to the second nucleic acid strand.

The moiety having a "targeted delivery function" may be , for example, a lipid, from the viewpoint of being capable o f delivering the double-stranded nucleic acid complex of cert ain embodiments to the liver or the like with high specificit y and high efficiency. Examples of such a lipid include lipi ds such as cholesterol and fatty acids (for example, vitamin E (tocopherols, tocotrienols ) , vitamin A, and vitamin D) ; lip id-soluble vitamins such as vitamin K (for example, acylcarni tine) ; intermediate metabolites such as acyl-CoA; glycolipids , glycerides, and derivatives thereof. However, among these, from the viewpoint of having higher safety, in certain embod iments, cholesterol and vitamin E (tocopherols and tocotrieno Is) are used. Furthermore, from the viewpoint of being capab le of delivering the double-stranded nucleic acid complex of certain embodiments to the brain with high specificity and hi gh efficiency, examples of the "functional moiety" according to the certain embodiments include sugars (for example, gluco se and sucrose) . Also, from the viewpoint of being capable o f delivering the double-stranded nucleic acid complex of cert ain embodiments to various organs with high specificity and h igh efficiency by binding to the various proteins present on the cell surface of the various organs, examples of the "func tional moiety" according to certain embodiments include pepti des or proteins such as receptor ligands and antibodies and/o r fragments thereof.

In regard to the double-stranded nucleic acid complex o f certain embodiments, the strand length of the first nucleic acid strand and the strand length of the second nucleic acid strand may be identical or may be different. As the double-s tranded nucleic acid complex of some embodiments in which the first and second nucleic acid strands have the same strand 1 ength, for example, the double-stranded nucleic acids illustr ated in FIG. 3 are an example of such embodiments.

Furthermore, as the double-stranded nucleic acid of som e embodiments in which the first and second nucleic acid stra nds have different strand lengths, for example, the double-st randed nucleic acids illustrated in FIG. 4 and FIG. 5 are exa mples of such embodiments. That is, some embodiments can pro vide a double-stranded nucleic acid which further comprises a third nucleic acid strand in addition to the first and secon d nucleic acid strands described above.

The third nucleic acid strand is complementary to a reg ion of whichever is the longer of the first and second nuclei c acid strands, which region is protruding relative to the ot her nucleic acid.

The third nucleic acid strand according to some embodim ents can serve as an antisense oligonucleotide, like the firs t nucleic acid strand. As such, the third strand can target t he same sequence or a different sequence than the first stran d. Thus the structure and nucleotide composition discussed i n relation to the first strand can be similarly applied to th e structure and composition of the third strand. Furthermore , similarly to the second nucleic acid strand, by causing the functional moieties described above to be directly or indire ctly bonded to the third nucleic acid strand, various functio ns can be imparted to the third nucleic acid strand, for exam pie, it can be made to function as a delivery agent of the com plex.

For example, as illustrated in FIG. 4, when a PNA is use d as the third nucleic acid strand, since the PNA and a protei n (amino acid) can be bonded through a peptide bond, a double -stranded nucleic acid complex of some embodiments having a f unctional moiety comprising a protein or the like can be easi ly prepared. Furthermore, since the PNA of the double-strand ed nucleic acid illustrated in FIG. 4 has a shorter strand le ngth than that of the RNA of the double-stranded nucleic acid of some embodiments illustrated in the lower part of FIG. 3, and there is no need to match the PNA to the base sequence of the target gene, mass production can be achieved. Generally, since synthesis of a PNA is a cost-consuming process, the do uble-stranded nucleic acid illustrated in FIG. 4 is a preferr ed embodiment from the viewpoint that a relatively inexpensiv e double-stranded nucleic acid can be provided. Particularly , since the double-stranded nucleic acid illustrated in the 1 ower part of FIG. 4 has not only a first functional moiety com prising a protein or the like, but also a second functional m oiety, which may comprise a lipid or the like, the double-str anded nucleic acid complex can be delivered to a target site with higher specificity and higher efficiency.

Furthermore, in general, when a compound is enterally a dministered (peroral administration or the like) , the compoun d is diffused in the body not through the blood vessels but th rough the lymphatic vessels. However, in order to reach the lymphatic vessels, the molecular weight of the compounds typi cally should be 11,000 Daltons to 17,000 Daltons or more. Fu rthermore, since an enterally administered compound is expose d to RNase A in the intestinal tube, it is typically preferab le that a nucleic acid drug containing RNA have all the porti ons of RNA modified by 2 ' -O-methylation or the like. Therefo re, the double-stranded nucleic acid illustrated in FIG. 5, w hich has a molecular weight of about 18,000 Daltons and has a

11 the RNA parts 2 ' -O-methylated, can be suitably used for pe renteral administration. Furthermore, the double-stranded nu cleic acid illustrated in the lower part of FIG. 5 has a DNA s trand (third nucleic acid strand) and a hairpin loop nucleic acid (preferably, a nucleic acid comprising 4 to 9 bases) tha t links the DNA strand and a complementary strand comprising RNA (second nucleic acid strand) .

Thus, some suitable exemplary embodiments of the double -stranded nucleic acid complex of some embodiments have been described, but the double-stranded nucleic acid of some embod iments is not intended to be limited to the exemplary embodim ents described above. Furthermore, any person having ordinar y skill in the art can produce the first nucleic acid strand, the second nucleic acid strand, and the third nucleic acid st rand according to some embodiments by appropriately selecting a known method. For example, the nucleic acids according to some embodiments can be produced by designing the respective base sequences of the nucleic acids on the basis of the infor mation of the base sequence of the targeted transcription pro duct (or, in some cases, the base sequence of a targeted gene ) , synthesizing the nucleic acids by using a commercially ava ilable automated nucleic acid synthesizer (products of Applie d Biosystems, Inc.; products of Beckman Coulter, Inc.; and th e like) , and subsequently purifying the resulting oligonucleo tides by using a reverse phase column or the like. Nucleic ac ids produced in this manner are mixed in an appropriate buffe r solution and denatured at about 90°C to 98°C for several mi nutes (for example, for 5 minutes), subsequently the nucleic acids are annealed at about 30°C to 70°C for about 1 to 8 hour s, and thus the double-stranded nucleic acid complex of some embodiments can be produced. Furthermore, a double-stranded nucleic acid complex to which a functional moiety is bonded c an be produced by using a nucleic acid species to which a func tional moiety has been bonded in advance, and performing synt hesis, purification and annealing as described above. Numero us methods for joining functional moieties to nucleic acids a re well-known in the art. Thus, suitable exemplary embodiments of the double-stra nded nucleic acids of the present invention have been describ ed, but as will be disclosed in the following Examples, the " second nucleic acid strand" according to some embodiments is excellent from the viewpoint that an antisense nucleic acid c an be delivered to a target site with high efficiency, withou t causing a decrease in the antisense effect. Therefore, the double-stranded nucleic acids of some embodiments are not in tended to be limited to the exemplary embodiments described a bove, and for example, an embodiment that includes the follow ing antisense nucleic acid instead of the first nucleic acid strand described above, can also be provided:

A double-stranded nucleic acid complex having an activi ty of suppressing the expression of a target gene by means of the antisense effect, the double-stranded nucleic acid comple x comprising (i) an antisense nucleic acid that is complement ary to the transcription product of the target gene, wherein the nucleic acid does not comprise DNA, and (ii) a nucleic ac id that is complementary to the foregoing nucleic acid (i) .

That is, in certain embodiments, an antisense nucleic a cid has a non-RNase H-dependent antisense effect. The "non-R Nase H-dependent antisense effect" means an activity of suppr essing the expression of a target gene that occurs as a resul t of inhibition of translation or a splicing function modifyi ng effect such as exon skipping when a transcription product of the target gene (RNA sense strand) and a nucleic acid stra nd that is complementary to a partial sequence of the transcr iption product are hybridized (see the description of the upp er part outside the area surrounded by dotted lines in FIG. 1 ) .

The "nucleic acid that does not comprise DNA" means an a ntisense nucleic acid that does not comprise natural DNA and modified DNA, and an example thereof may be a PNA or a nucleic acid comprising morpholino nucleic acid. Furthermore, in re gard to the "nucleic acid that does not comprise DNA, " simila rly to the first nucleic acid strand or the second nucleic ac id strand, a portion or the entirety of the nucleic acid may b e composed of modified nucleotides, from the viewpoint that t he resistance to nucleases is high. Examples of such modific ation include those described above, and the same nucleic aci d may be subjected to plural kinds of modifications in combin ation. Furthermore, preferred embodiments related to the num ber of modified nucleic acids and the position of modificatio n can be characterized by measuring the antisense effect poss essed by the double-stranded nucleic acid after modification, as in the case of the first nucleic acid strand described abo ve .

It is not necessary that the base sequence of the "nucle ic acid that does not comprise DNA" and the base sequence of a nucleic acid that is complementary to the nucleic acid or th e base sequence of the transcription product of a target gene be perfectly complementary to each other, and the base seque nces may have a complementarity of at least 70% or higher, pr eferably 80% or higher, and more preferably 90% or higher (fo r example, 95%, 96%, 97%, 98%, 99% or higher) .

There are no particular limitations on the strand lengt h of the "nucleic acid that does not comprise DNA, " but the st rand length is as described above in regard to the first nucl eic acid, and is usually 8 to 35 bases, 10 to 35 bases, 12 to 25 bases, or 13 to 20 bases.

The "nucleic acid that is complementary to a nucleic ac id that does not comprise DNA" according to some embodiments is the same as the second nucleic acid strand described above Furthermore, in the case where the strand length of the nuc leic acid that does not comprise DNA and the strand length of the nucleic acid that is complementary to the nucleic acid ar e different, this embodiment may also comprise a third nuclei c acid strand. Furthermore, this embodiment may also have th e functional moieties described above bonded to the "nucleic acid that is complementary to the nucleic acid that does not comprise DNA" and/or the third nucleic acid strand.

Composition for suppressing expression of target gene o r level of targeted transcription product by means of antisen se effect.

The double-stranded nucleic acid complex of some embodi ments can be delivered to a target site with high specificity and high efficiency and can very effectively suppress the ex pression of a target gene or the level of a transcription pro duct, as will be disclosed in the Examples described below. Therefore, some embodiments can provide a composition which c ontains the double-stranded nucleic acid complex of some embo diments as an active ingredient and is intended to suppress, e.g., the expression of a target gene by means of an antisens e effect. Particularly, the double-stranded nucleic acid com plex of some embodiments can give high efficacy even when adm inistered at a low concentration, and by suppressing the dist ribution of the antisense nucleic acid in organs other than t he delivery-targeted area, adverse side effects can be reduce d. Therefore, some embodiments can also provide a pharmaceut ical composition intended to treat and prevent diseases that are associated with, e.g., increased expression of a target g ene, such as metabolic diseases, tumors, and infections.

The composition containing the double-stranded nucleic acid complex of some embodiments can be formulated by known p harmaceutical methods. For example, the composition can be u sed enterally (perorally or the like) in the form of capsules , tablets, pills, liquids, powders, granules, fine granules, film-coating agents, pellets, troches, sublingual agents, pep tizers, buccal preparations, pastes, syrups, suspensions, eli xirs, emulsions, coating agents, ointments, plasters, catapla sms, transdermal preparations, lotions, inhalers, aerosols, i njections and suppositories, or non-enterally .

In regard to the formulation of these preparations, pha rmacologically acceptable carriers or carriers acceptable as food and drink, specifically sterilized water, physiological saline, vegetable oils, solvents, bases, emulsifiers, suspend ing agents, surfactants, pH adjusting agents, stabilizers, fl avors, fragrances, excipients, vehicles, antiseptics, binder s, diluents, isotonizing agents, soothing agents, extending a gents, disintegrants , buffering agents, coating agents, lubri eating agents, colorants, sweetening agents, thickening agent s, corrigents, dissolution aids, and other additives can be a ppropriately incorporated.

On the occasion of formulation, as disclosed in Non-Pat ent Document 1, the double-stranded nucleic acid complex of s ome embodiments to which a lipid is bound as a functional moi ety may be caused to form a complex with a lipoprotein, such a s chylomicron or chylomicron remnant. Furthermore, from the viewpoint of increasing the efficiency of enteral administrat ion, complexes (mixed micelles and emulsions) with substances having a colonic mucosal epithelial permeability enhancing a ction (for example, medium-chain fatty acids, long-chain unsa turated fatty acids, or derivatives thereof (salts, ester for ms or ether forms)) and surfactants (nonionic surfactants and anionic surfactants) may also be used, in addition to the li poproteins .

There are no particular limitations on the preferred fo rm of administration of the composition of some embodiments, and examples thereof include enteral (peroral or the like) or non-enteral administration, more specifically, intravenous a dministration , intraarterial administration, intraperitoneal administration, subcutaneous administration, intracutaneous administration, tracheobronchial administration, rectal adm inistration, and intramuscular administration, and administr ation by transfusion.

The composition of some embodiments can be used for ani mals including human beings as subjects. However, there are no particular limitations on the animals excluding human bein gs, and various domestic animals, domestic fowls, pets, exper imental animals and the like can be the subjects of some embo diments .

When the composition of some embodiments is administere d or ingested, the amount of administration or the amount of ingestion may be appropriately selected in accordance with th e age, body weight, symptoms and health condition of the subj ect, type of the composition (pharmaceutical product, food an d drink, or the like), and the like. However, the effective a mount of ingestion of the composition according to the certai n embodiments is 0.001 mg/kg/day to 50 mg/kg/day of the doubl e stranded nucleic acid complex.

The double-stranded nucleic acid complex of some embodi ments can be delivered to a target site with high specificity and high efficiency, and can suppress the expression of a ta rget gene or the level of a transcription product very effect ively, as will be disclosed in the Examples that follow. The refore, some embodiments can provide a method of administerin g the double-stranded nucleic acid complex of some embodiment s to a subject, and suppressing the expression of a target ge ne or transcription product level by means of an antisense ef feet. Furthermore, a method of treating or preventing variou s diseases that are associated with, e.g., increased express! on of target genes, by administering the composition of some embodiments to a subject can also be provided.

[Examples]

Hereinafter, some embodiments will be described more specifically by way of Examples and Comparative Examples, but the embodiments not intended to be limited to the following Examples. Meanwhile, the mice supplied to the experiments described below were 4 to 6-week old female ICR mice with body weights of 20 to 25 g. Unless particularly stated otherwise, the experiments using mice were all carried out with n = 3 to

4. Furthermore, the BNA used in the present Examples was a LNA represented by the above formula (1) . In addition, Sequences described in Comparative Example 1 and Examples 1-15 are presented in Tables 1-3.

[Table 2]

[Table 3]

(Comparative Example 1)

The stability of an antisense oligonucleotide (ASO) in an antisense method, the activity of suppressing the expression of a target gene in vivo (antisense effect), and the delivery properties and antisense effect in vivo were evaluated for an

ASO comprising LNA nucleotides and DNA nucleotides ("LNA/DNA gapmer") to which cholesterol had been directly bound so as to enhance the delivery properties.

Two ASO' s, having the LNA/DNA gapmer structures schematically illustrated in Fig. 6, were prepared. Cy3-ASO, in which a fluorescent dye Cy3 was covalently bonded to the 5 ' -terminus of an LNA/DNA gapmer ASO (Fig. 6A) , and Cy3-Chol-ASO, in which cholesterol was covalently bonded to the 3 ' -terminus of the Cy3-ASO (FIG. 6B) , were prepared. The target gene of these ASO's is apolipoprotein B (ApoB) gene, and its sequence is shown below. These ASO's were produced by commissioning Gene Design, Inc. with the synthesis.

GCattggtatTC (upper case: LNA, lower case: DNA, between nucleic acids: phosphorothioate bond) (SEQ ID N0:1)

Meanwhile, Cy3 and the ASO were bonded to each other by a phosphorothioate bond according to a known technique, and cholesterol and the ASO were bonded to each other through tetraethylene glycol linker.

These ASO's were respectively intravenously injected in an amount of 10 mg/kg through the mouse tail vein, and after one hour, the mice were dissected to extract the livers. The livers thus obtained were fixedwitha 4% formalin solution, subsequently the solution was replaced with a 30% sucrose solution, the livers were embedded in OCT Compound, and then sections having a thickness of 10 m were produced therefrom. Subsequently, the sections were nucleus stained by using DAPI , and then the signal intensities of Cy3 in the sections were observed using a confocal microscope. The results thus obtained are presented in FIG. 7.

Furthermore, Cy3-ASO and Cy3-Chol-ASO were intravenously injected to three mice each through the tail vein, and after three days, the second administration of ASO was carried out . The amount of ASO administered was set to 10 mg/kg. Furthermore, mice of a negative control group were also prepared by administering PBS only instead of the ASO. The day after the second administration, the mice were perfused with PBS, and then the mice were dissected to extract the livers. 1 ml of a nucleic acid extracting reagent (Isogen, manufactured by Gene Design, Inc.) was added to 80 mg of the liver thus extracted, and mRNA was extracted according to the protocol attached to the reagent. Subsequently, the concentrations of mRNA of these mice were measured, and cDNA was synthesized from a certain amount of mRNA by using Superscript III (manufactured by Invitrogen, Inc.) according to the protocol attached thereto. The cDNA thus produced was used as a template, and quantitative RT-PCR was carried out using a TaqMan System (manufactured by Roche Applied Bioscience Corp.). Meanwhile, the primers used in the quantitative RT-PCR were products designed and produced by Life Technologies Corp. based on the various gene numbers. Furthermore, the conditions for temperature and time were as follows: 15 seconds at 95°C, 30 seconds at 60°C, and 1 second at 72°C were designated as one cycle, and 40 cycles thereof were carried out. Based on the results of the quantitative RT-PCR thus obtained, the amount of expression of mApoB/amount of expression of mGAPDH (internal standard gene) were respectively calculated, and the calculation results for the negative control group and the calculation results for the ASO-administered groups were compared and evaluated byat-test. The results thus obtained are presented in FIG. 8.

As is obvious from the results presented in FIG. 7, the LNA/DNA gapmer to which cholesterol had been directly bound was accumulated in the liver in a much larger amount than the LNA/DNA gapmer without cholesterol bound thereto.

However, as presented in FIG. 8, it was found that when cholesterol is directly bound to the LNA/DNA gapmer and used, the antisense effect was lost.

(Example 1)

Since it was found that the antisense effect is impaired when a functional moiety such as cholesterol is directly bound to the LNA/DNA gapmer (antisense strand) , the inventors conceived of using a double-stranded nucleic acid complex where the complementary strand to the ASO carries a functional moiety to direct delivery of the ASO. FIG. 9 schematically illustrates one embodiment of such a complex.

For example, in the case of using an RNA strand as the complementary strand to an antisense LNA/DNA gapmer (ASO comprising a LNA and a DNA) and further binding a functional moiety to the RNA, the complex of the ASO and the complementary RNA strand (cRNA) is specifically and efficiently delivered to the target site by the functional moiety bonded to the cRNA. Further, when the complex is delivered into the nucleus of the cell at the target site, since the cRNA is itself an RNA- DNA hetero-oligonucleotide , it is believed that the cRNA is cleaved by RNase H present in the nucleus, thereby exposing the ASO as a single strand. Subsequently, this ASO binds to mRNA of the target gene and forms a new RNA-DNA heteroduplex, wherein the mRNA is decomposed by RNase H to achieve an antisense effect.

That is, the inventors conceived that by conducting cleavage of a cRNA having a functional moiety bonded thereto and decomposition of mRNA of a target gene by using RNase H, a LNA/DNA gapmer (ASO comprising a LNA and a DNA) can be delivered to a target site with high specificity and high efficiency, and the expression of the target gene can be very effectively suppressed without the antisense effect of the ASO being inhibited by the functional moiety.

Then, in order to demonstrate such conception, the inventors first produced a double-stranded DNA of a LNA/DNA gapmer and a cRNA by the method described below, and evaluated the properties .

As the LNA/DNA gapmer, a Cy3-ASO produced in the same manner as in Comparative Example 1 was used. Also, as the cRNA, three different complementary strand structures were prepared. The three structures are schematically illustrated in FIG. 10. One structure comprises conventional RNA (natural RNA) only ( cRNA ( o ) ) , in a second structure, two bases each at end of the cRNA strand were chemically modified ( 2 ' -O-methylated and phosphorothioated) to have RNase resistance (cRNA(G)), and in the third structure, all the bases in the cRNA strand were chemically modified ( 2 ' -O-methylated and phosphorothioated) to be resistant to cleavage by RNase (cRNA(m/s) ) . The probes were produced on commission by Hokkaido System Science Co. , Ltd. The sequences of the cRNA strands were as follows:

cRNA(o): 5 * -GAAUACCAAUGC-3 ' (SEQ ID NO : 2 )

cRNA(G): 5 ' -g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 3)

cRNA(m/s): 5 ' -g _s a _s a _s u _s a _s c _s C _s a _s a _s u _s g _s c-3 ' (SEQ ID NO: 4) (Upper case: RNA, lower case: 2'-OMe-RNA, s: phosphorothioate bonds between the nucleic acids)

The LNA/DNA gapmer and the respective cRNA's were mixed in equimolar amounts, and the mixtures were heated at 95°C for 5 minutes and then were kept warm at 37°C for one hour to thereby anneal these nucleic acid strand and form double-stranded nucleic acid complexes. The annealed nucleic acids were stored at 4°C or on ice.

Subsequently, the Cy3-ASO's that had been annealed with the respective cRNA' s, and Cy3-ASO were applied to 15% acrylamide gel in an amount of 100 pmol each in terms of the amount of LNA, and electrophoresis was carried out at 100 V for one hour. After the electrophoresis, a photograph of the gel was taken directly, and then a photograph was taken under UV light. The results thus obtained are presented in FIG. 11A, B.

Furthermore, the Cy3-AS0 ' s that had been annealed with the respective cRNA's, and the Cy3-ASO were treated with RNase H, subj ected to elect rophoresis as described above , and a photograph of the gel was taken under UV illumination. The results thus obtained are presented in FIG. 12.

The results presentedin FIG. 11 demonstrate that the product obtained by annealing Cy3-ASO and cRNA(o) together, the product obtained by annealing Cy3-ASO and cRNA(G) together, and the product obtained by annealing Cy3-ASO and cRNA (m/s ) together all had slower migration rates as compared with Cy3-ASO (Lane 1) , which was a single-stranded ASO, confirming that the annealed products respectively formed double-stranded nucleic acids.

Furthermore, although not illustrated in the drawings, a complementary strand comprising DNA (cDNA) and Cy3-ASO were mixed and annealed as described above, and the product was analyzed by electrophoresis; however, the product had the same band height as that of Cy3-ASO. It was confirmed that cDNA and Cy3-ASO cannot form a double-stranded nucleic acid under the conditions employed .

Meanwhile, the seguences and modifications of the cDNA's that were evaluated were the same as those of cRNA(o), cRNA(G) and cRNA (m/s ) , except that uracil was changed to thymine (hereinafter, the same) .

Also, as is obvious from the results illustrated in FIG.

12, even though a RNase H treatment was applied, the duplex of Cy3-ASO and cRNA (m/s ) maintained the double-stranded nucleic acid structure. On the other hand, since treatment of the cRNA(o) and cRNA(G) duplexes yielded a product having the same migration rate as that of Cy3-AS0, it was confirmed that the complementary RNA strand of these duplexes was decomposed by RNase H and thus the single-stranded Cy3-AS0 nucleic acids were released from the duplex and could migrate as a single strand.

Subsequently, in addition to the electrophoresis described above, the melting point (Tm) of a double-stranded nucleic acid composed of the LNA/DNA gapmer and cRNA was evaluated by the method described below.

Sample solutions (100 yL) in which the final concentrations were adjusted to 100 mM for sodium chloride, 10 mM for a sodium phosphate buffer solution (pH 7.2) , and 2 μΜ for the respective oligonucleotide strands were placed in a boiling water bath, and the sample solutions were cooled to room temperature over 12 hours and were left to stand for 2 hours at 4°C. Under a nitrogen gas stream, the sample solutions were cooled to 5°C, and after the samples were maintained at 5°C for 15 minutes, the analysis was commenced. For the melting point analysis, the temperature was increased to 90°C at a rate of 0.5°C /min, and the absorbance at 260 nm was plotted at an interval of 0.5°C. The Tm values were calculated by a differential method. The measurement was carried out by using Shimadzu UV-1650PC spectrophotometer. The results thus obtained are presented in Table 4.

[Table 4] Nucleic Acid Modification Tm(°C)

o 45.32

CRNA G 47.65

m/ s 41.17

o 37.51

cDNA G 34.33

m/s 26.45

As shown by the results presented in Table 4, the melting temperature (Tm) of duplexes formed between the LNA/DNA gapmer and the cDNA strands was lower than the body temperature in all cases. On the contrary, the melting temperature (Tm) of the duplex of LNA/DNA gapmer and cRNA was maintained in the range of 40°C in all cases, and thus it was found that the relevant double-stranded nucleic acids do not undergo dissociation at room temperature or the body temperature.

(Example 2)

A complementary strand comprising conventional RNA only (cRNA(o) ) (SEQ ID NO: 2) ; a complementary strand in which all the RNA's were subjected to 2 ' -OMe (2 ' -O-methylation) modification and phosphorothioate binding ( S-conversion) between the nucleic acids (cRNA(m/s)) (SEQ ID NO: 4); and a complementary strand in which only the two terminal RNA bases were subjected to 2 ' -OMe modification and S-conversion between the nucleic acids, and the 8 bases at the center were conventional RNA's (cRNA(G)) (SEQ ID NO: 3) were provided in the same manner as in Example 1. These complementary strands were all annealed with the LNA/DNA gapmer (SEQ ID NO: 1), and thus double-stranded nucleic acids were produced. The target gene of the LNA/DNA gapmer was the rat apolipoprotein B (rApoB) gene. The ASO was produced by commissioning Gene Design, Inc. with the synthesis.

The LNA/DNA gapmer was transfected alone and as part of a double-stranded complex with each of the cRNA strands described above to rat liver cell culture systems (McA-RH7777 ) , by using Lipofectamine 2000 (manufactured by Invitrogen, Inc.) according to the usage protocol provided with the reagent. The concentration of the gapmer that was added to the medium at the time of the transfection was set to 0.4 nM or 10 nM. Furthermore, controls in which no nucleic acid strands were added to cells were also prepared. Subsequently, 24 hours after the transfection, the cells were collected by using Isogen, andmRNA's were collected according to the manufacturer's usage protocol.

The concentrations of these mRN ' s were measured, and cDNA ' s were synthesized from certain amounts of the mRNA's by using Superscript III according to the manufacturer's protocol. Subsequently, the cDNA's thus produced were used as templates, and quantitative RT-PCR was carried out by using a TaqMan system. Meanwhile, for the primers used in the quantitative RT-PCR, those designed and produced by Life Technologies Corp. based on the various gene numbers. Furthermore, the conditions for temperature and time were as follows : 15 seconds at 95°C, 30 seconds at 60°C, and 1 second at 72°C were designated as one cycle, and 40 cycles thereof were carried out. Based on the results of the quantitative RT-PCR thus obtained, the amount of expression of rApoB/amount of expression of rGAPDH (internal standard gene) were respectively calculated, and the calculation results for the control group and the calculation results for the nucleic acid-administered groups were compared and evaluated by a t-test .

The results thus obtained are presented in FIG. 13. In addition, for the transfections made with 10 nM concentration, the results for the double-stranded nucleic acid complexes were normalized to the results for the LNA/DNA gapmer (ASO) alone and evaluated by the t-test. The results thus obtained are presented in FIG.

14.

As shown by the results presented in FIG. 13, the antisense effect of the double-stranded nucleic acid comprising the LNA/DNA gapmer and cRNA (o) (LNA/cRNA (o ) ) and the double-stranded nucleic acid comprising the LNA/DNA gapmer and cRNA (G) (LNA/cRNA ( G) ) is similar to that caused by the LNA/DNA gapmer (ss-ASO) when administered at the lower concentration of 0.4 nM. However, as shown in FIG. 14, when administered at the higher concentration of 10 nM, the results suggest that the double-stranded complexes in which the complementary strand is susceptible to cleavage

(LNA/cRNA (o) and LNA/cRNA ( G ) ) improve the antisense effect by about 20% compared to the gapmer ASO administered as a single strand.

Therefore, it was found that even if a LNA/DNA gapmer is annealed with a complementary strand comprising RNA to obtain a double-stranded nucleic acid complex, the target gene expression suppressing effect (antisense effect ) in the cell was maintained . Furthermore, when a complementary RNA strand susceptible to RNase H was used, the antisense effect in the cell was further increased. Such an increase in the antisense effect is believed to be caused by the cleavage of the complementary strand RNA in the nucleus. (Example 3)

Next, as illustrated schematically in FIG. 15, a complementary RNA strand in which tocopherol (Toe) was bound to the 5 ' -terminus of the cRNA(G) (Toc-cRNA (G) ) was produced, and this was annealed with the LNA/DNA gapmer (antisense strand) . Thereby, indirect binding of tocopherol to an antisense strand was successfully achieved. The sequence, composition, and strand length of the LNA/DNA gapmers and the complementary strands (cRNA) used in the Examples were as follows.

Antisense LNA/DNA gapmer strands

1. ASO 12-mer: 5 ' -GCattggtatTC-3 ' (SEQ ID NO:l)

2. ASO 13-mer: 5 ' -GCattggtatTCA-3 ' (SEQ ID N0:5)

3. ASO 14-mer: 5 ' -AGCattggtatTCA-3 ' (SEQ ID NO: 6) (Upper case: LNA, lower case: DNA, between nucleic acids: phosphorothioate bond at all sites)

Complementary strands

1. cRNA 12-mer: 5 ' -g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 2)

2. cRNA 13-mer: 5 ' -u _s g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 7)

3. cRNA 14-mer: 5 ' -u _s g _s a _s AUACCAAU _s g _s c _s u-3 ' (SEQ ID NO: 8) (Upper case: RNA, lower case: 2 ' -OMe-RNA, s: phosphorothioate bonds between the nucleic acids) The binding between tocopherol and the cRNA was carried out according to a known technique, by preparing tocopherol amidite in which the hydroxyl group at the 6-position of the chromane ring of tocopherol was joined to the phosphoramidite , and then the tocopherol amidite was coupled to the 5 ' -terminus of the RNA by standard coupling methods.

Next, the LNA/DNA gapmer (ss-ASO) , the double-stranded nucleic acid complex comprising a LNA/DNA gapmer and cRNA(G) (LNA/cRNA (G) ) , and the double-stranded nucleic acid complex comprising a LNA/DNA gapmer and Toc-cRNA(G) (LNA/Toc-cRNA (G) ) , pairing in each complex strands that have the same strand length of 12 bases, 13 bases, or 14 bases, respectively, were intravenously injected to a mouse in an amount of 0.75 mg/kg each through the tail vein. Also, as a negative control group, mice to which only PBS was injected instead of the single-stranded

ASO or double-stranded nucleic acid complex were also prepared. Seventy-two hours after the injection, the mice were perfused with PBS, and then the mice were dissected to extract the liver. Subsequently, extraction of mRNA, synthesis of cDNA, and quantitative RT-PCR were carried out by the same methods as the methods described in Comparative Example 1, the amount of expression of mApoB/amount of expression of mGAPDH (internal standard gene) was calculated, and comparisons were made between the group administered with PBS (PBS only) and the groups administered with a nucleic acid. The results thus obtained are presented in FIG. 16. As illustrated in FIG. 16, it was found that by binding tocopherol to a complementary strand, ASO/Toc-cRNA (G) is delivered to and accumulated in the liver with high specificity and high efficiency, and a marked antisense effect was exhibited as compared with ASO/cRNA(G) . As shown, the effect exhibited by the ASO/Toc-cRNA having a strand length of 13 bases was particularly large.

(Example 4)

The specificity of ASO/Toc-cRNA complex for its target gene was evaluated by the same method as the method described in Example

3. That is, a double-stranded nucleic acid comprising a LNA/DNA gapmer having a strand length of 13 bases and the complementary strand Toc-cRNA(G) (ASO/Toc-cRNA (G) ) was prepared, and intravenously injected to a mouse, and by using the liver-derived cDNA obtained from the mouse, the expression of the target gene

(mApoBgene) in the liver and endogenous control genes (mTTRgene, mSODl gene, and mGAPDH gene) was evaluated by quantitative PCR. Meanwhile, regarding the primers used in the quantitative RT-PCR, primers designed and produced by Life Technologies Corp. based on the various gene numbers were used. The results thus obtained are presented in FIG. 17.

As shown by the results graphed in FIG. 17, in the liver of the mouse to which ASO/Toc-cRNA 13-mer was administered, a significant decrease in the expression was observed only in the mApoB gene, which was the gene transcription product targeted by the LNA/DNA gapmer (ASO) . Therefore, it was found that the double-stranded nucleic acid complex comprising the LNA/DNA gapmer and Toc-cRNA(G) has a high specificity for the targeted gene .

(Example 5)

The dose-dependency of the antisense effect by

ASO/Toc-cRNA (G) was evaluated by the same method as the method described in Example 3 using the 13-mer strands. That is, ASO/Toc-cRNA (G) 13-mer double-stranded complex was intravenously injectedtomice in an amount of 0 mg/kg, 0.02 mg/kg, 0.05mg/kg, 0.09 mg/kg or 0.75 mg/kg, and by using the liver-derived cDNA obtained from the mice, expression of mApoB gene was evaluated by quantitative PCR. The results thus obtained are presented in FIG. 18.

As shown by the results illustrated in FIG. 18, it was found that the antisense effect of ASO/Toc-cRNA (G) exhibited a dose-dependent effect. Also, it was found from these results that the amount of ASO/Toc-cRNA (G) required to suppress the expression of the target gene by half (ED50) was calculated to be about 0.036 mg/kg, which is a low concentration for achieving 50% suppression.

(Example 6)

The sustainability of the antisense effect by ASO/cRNA and ASO/Toc-cRNA was evaluated by the same method as the method described in Example 3. That is, a LNA/DNA gapmer (ss-ASO) , the double-stranded nucleic acid comprising a LNA/DNA gapmer and cRNA-G (ASO/cRNA (G) ) , or the double-stranded nucleic acid comprising a LNA/DNA gapmer and Toc-cRNA (ASO/Toc-cRNA (G) ) was intravenously injected into a mouse. The strand length of all the nucleic acid strands was 13 bases. Controls werealso included in which just PBS solution and no nucleic acids were injected. In a first experiment, after the intravenous injection, liver was extracted after 1 day, after 3 days, after 7 days, after 14 days, and after 28 days, and by using the liver-derived cDNA, the expression of mApoB gene was evaluated by quantitative PCR. The results thus obtained are presented in FIG. 19A. The experiment was repeated using a PBS solution control, single-stranded LNA only, and the double-stranded complex ASO/Toc-cRN (G) , and resulting expression levels of mApoB was evaluated by the same method, after 1 day, 3 days, 7 days, 14 days, 28 days, and 42 days post-injection. The results obtained are presented in FIG. 19B.

As shown by the results illustrated in FIG. 19A, the maximum antisense effect was exhibited on the third day after administration in all of the tested nucleic acids. Furthermore, the same degree of antisense effect as was observed on the first day after administration was exhibited even 7 days after administration. Furthermore, it was shown that the expression of the target gene was suppressed to an extent of 60% even 14 days after administration, and to an extent of 20% even 28 days after administration, suppression levels that are measurably significant compared to the single-stranded ASO . In the second experiment, the same general trend was observed, as shown by FIG. 19B. The maximum antisense effect was observed 3 days post-injection, and the level of suppression observed on the first day was exhibited 7 days post-injection. The suppression 14 and 28 days later was observed to be 80% and 50%, respectively, and a measurable effect was observed even 42 days post-injection.

Therefore, it was also found that the double-stranded nucleic acids of some embodiments have high sustainability in connection with the antisense effect.

(Example 7)

The antisense effect of the double-stranded nucleic acid complex of another embodiment was evaluated. The composition of the nucleic acid strands compared is schematically illustrated in FIG. 20A. Whereas previous experiments used cRNA(G) (SEQ ID NO: 3) , which has a central region of natural RNA bases with 2' -OMe modified, phosphorothioated 5' and 3' wing regions, here, a complementary strand contained the same 5' and 3' wings (two terminal 2 ' -OMe modified RNA bases and phosphorothioate links), but the central 8 bases were 2 ' -OMe modified RNA with a natural phosphodiester link between the nucleotides (cRNA (G) -OM) (SEQ ID NO: 9) .

That is, the 12-mer LNA/DNA gapmer against mouse apolipoprotein B (mApoB) , and 12-mer complementary strands incorporating modified RNA bases to different degrees were designed and produced.

Antisense LNA/DNA gapmer strand ASO 12-mer:

5 ' -GCattggtatTC-3 ' (SEQ ID NO: 1) (Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strands

1. cRNA(G) : 5 ' -g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 3)

2. cRNA(G)-0M: 5 ' -g _s a _s auaccaau _s g _s c-3 ' (SEQ ID NO: 9)

(Upper case: RNA, lower case: 2 ' -O e-RNA, s: phosphorothioate bonds between nucleic acids)

Regarding the LNA/DNA gapmer, a product produced by commissioning Gene Design, Inc. was used. Regarding the complementary strands, products produced by commissioning

Hokkaido System Science Co., Ltd. were used.

Further, the LNA/DNA gapmer and each of the complementary strands were mixed in equimolar amounts , and the mixture was heated at 95°C for 5 minutes. Subsequently, the mixture was left to stand at a constant temperature of 37°C for one hour to anneal the strands . Also, if any product was not to be used immediately, the product was stored at 4°C thereafter.

Subsequently, the double-stranded nucleic acid comprising LNA 12-mer and cRNA 12-mer (AS0/cRNA(G) ) , or the double-stranded nucleic acid comprising LNA 12-mer and cRNA(G)-OM 12-mer

(ASO/cRNA (G) -0M) was intravenously injected through the tail vein of a mouse in an amount of 0.75 mg/kg. Control mice receiving administrations of PBS only were also prepared. Three days after the intravenous injection, the mice were perfused with PBS, and then the livers were extracted. Subsequently, extraction of mRNA, synthesis of cDNA, and quantitative RT-PCR were carried out by the same methods as the methods described in Comparative Example 1 , the amount of expression of mApoB/amount of expression of mGAPDH (internal standard gene) was calculated, and a comparison was made between the group administered with PBS only (PBS only) and the groups administered with a nucleic acid. The results thus obtained are presented in FIG. 20B.

As shown by the results illustrated in FIG. 20B, even when cRNA(G)-0M was used instead of cRNA(G) in the double-stranded nucleic acid complex embodiment of the present invention, the antisense effect was not lost.

Generally, when a pharmaceutical product is enterally administered (oral administration, or the like), since the pharmaceutical product is exposed to RNase A in the intestinal tract, it is highly preferable that a nucleic acid drug containing RNA have all the relevant parts of RNA modified by 2 ¹ -OMe or the like.

Therefore, since an RNA strand that is entirely modified by 2 ' -OMe can also be used as a complementary strand for the double-stranded nucleic acid of some embodiments, it was found that the double-stranded nucleic acid of some embodiments can be applied to embodiments of enteral administration.

(Example 8)

In regard to a double-stranded nucleic acid complex comprising a LNA/DNA gapmer and Toc-cRNA, it was found as discussed above that the double-stranded nucleic acid has a high antisense effect and can be delivered to the liver or the like with high specificity and high efficiency.

As such, it is known that when a lipid such as tocopherol is bound, the delivery properties to the liver or the like are dramatically increased, but the delivery to other organs is on the contrary difficult . Currently, a method for delivery to other organs that is most effectively used is a method of utilizing a kind of target peptide that binds to various proteins on the cell surface of various organs. In some embodiments, it is contemplated to directly bind a peptide as a delivery moiety to a nucleic acid, and thereby utilize a targeting peptide in a double-stranded nucleic acid complex containing a complementary strand comprising RNA such as described above.

In other embodiments, such as demonstrated by the example described below, a peptide nucleic acid (PNA) , which can readily be joined to peptide or antibody-based functional moieties, was used as the complementary strand in the double-stranded nucleic acid complex of some embodiments. As shown in the following formula, a PNA does not have phosphate bonds like conventional nucleic acids, but instead had the useful characteristic of having peptide linkages, so that joining a peptide to a PNA strand is made easy. In addition, PNA is characterized by having a high Tm value as in the case of a LNA, so that the double strand is not likely to dissociate, and by having a strong resistance to cleavage by RNase.

[Chem. 2] [ RNA ] [ PNA]

5' terminal N terminal

inal

In regard to the demonstration, several embodiments for binding a targeting peptide or the like (peptide-binding strand) to a nucleic acid strand, which is part of the double-stranded nucleic acid complex but where the targeting peptide functional moiety is not directly bound to the LNA/DNA gapmer are contemplated . Examples of such embodiments are shown in FIG. 21A-C. In FIG. 21A, the functional moiety is bound to the complementary RNA strand . In FIG. 21B, three strands are used to form the double-stranded nucleic acid complex. Here, the complementary RNA anneals with both the LNA/DNA antisense strand and a PNA strand. Joining a peptide-based functional moiety to the PNA strands results in a complex carrying a delivery functional moiety, but the moiety is not directly bound to the ant isense oligonucleotide . The third strand does not have to be PNA, but could comprise DNA, RNA, and/or nucleotide analogs. Generally, this embodiment provides that a functional moiety can be indirectly associated with the antisense strand by using a complementary strand that is longer than the antisense strand, and preparing a third strand that anneals to the complementary strand in the overhanging portion. Also, as shown in FIG. 21C, the complementary strand can itself be prepared with a functional moiety. The functional moieties shown in FIG. 21C can be independently chosen.

Next, based on this concept, the inventors designed and produced a LNA/DNA gapmer against mouse apolipoprotein B (mApoB) , a complementary strand comprising RNA, and a peptide-binding strand as shown below.

Antisense LNA/DNA gapmer strand

ASO 12-mer: 5 ' -GCattggtatTC-3 ' (SEQ ID NO: 1)

(Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strand

cRNA21-mer: 5 ' -u _s u _s cGCACCAGAAUACCAAu _s g _s c-3 ' (SEQIDNO:10) (Upper case: RNA, lower case: 2'-OMe-RNA, s: phosphorothioate bonds between nucleic acids) Third (peptide) strand

PNA 9-mer: N ' -TGGTGCGAA-C ' (SEQ ID NO: 11)

(Underlined: PNA)

Regarding the LNA/DNA gapmer, a product produced by commissioning Gene Design, Inc. was used. Regarding the complementary strand, a product produced by commissioning Hokkaido System Science Co., Ltd. was used. Furthermore, regarding the peptide-binding strand, a product produced by commissioning Fasmac Co., Ltd. was used.

The LNA/DNA gapmer, the complementary strand, and the peptide-based strand were mixed in equimolar amounts, and the mixture as heated at 95 °C for 5 minutes . Subsequently, themixture was left to stand at a constant temperature of 37°C for one hour to anneal the strands. Also, if the strands were not to be used immediately, the strands were stored at 4°C thereafter.

Subsequently, ASO 12-mer (ss-ASO) or a double-stranded nucleic acid complex comprising (1) ASO 12-mer, (2) cRNA(G) 21-mer, and (3) PNA 9-mer (ASO, PNA/cRNA (G) ) was intravenously injected to a mouse through the tail vein in an amount of 0.75 mg/kg. Furthermore, a mouse to which PBS only was administered was also prepared as a control . Three days after the intravenous injection, themicewereperfusedwithPBS, andthentheliverswere extracted. Subsequently, extraction of mRNA, synthesis of cDNA, and quantitative RT-PCR were carried out by the same methods as the methods described in Comparative Example 1, the amount of expression of mApoB/amount of expression of mGAPDH (internal standard gene) was calculated, and a comparison was made between the group administered with PBS only (PBS only) and the groups

0

administered with nucleic acids. The results thus obtained are presented in FIG. 22.

As is obvious from the results illustrated in FIG. 22, the antisense effect of ASO, PNA/cRNA (G) complex was not reduced as compared with the effect of LNA 12-mer.

(Example 9)

The following example demonstrates that a PNA strand can be used as the complementary strand in the double-stranded nucleic acid complex as an embodiment.

That is, it is contemplated that a PNA strand can be used as the complementary strand, instead of RNA, as illustrated in FIG. 3B. This arrangement also provides an embodiment of a double-stranded nucleic acid complex in which a functional moiety such as a targeting peptide is not directly bound to the antisense strand (e.g., LNA/DNA gapmer) but is indirectly associated with it .

Based on this concept, a LNA/DNA gapmer against mouse apolipoprotein B (mApoB) , and a complementary strand comprising

PNA were designed and produced as shown below.

Antisense LNA/DNA gapmer strand

ASO 12-mer: 5 ' -GCattggtatTC-3 " (SEQ ID NO: 1)

(Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strands 1. cPNA 12-mer: ' -GAAUACCAAUGC-C ' (SEQ ID NO: 12)

2. cPNA 10-mer: ' -GAAUACCAAU-C ' (SEQ ID NO: 13)

3. cPNA 8-mer: ' -GAAUACCA-C ' (SEQ ID NO: 14)

(underlined: PNA)

Regarding the LNA/DNA gapmer, a product produced by commissioning Gene Design, Inc. was used. Regarding the complementary strand, a product produced by commissioning Fasmac Co., Ltd. was used.

The LNA/DNA gapmer and each of the complementary strands were mixed in equimolar amounts, and the mixture as heated at 95°C for 5 minutes. Subsequently, the mixture was left to stand at a constant temperature of37°Cfor one hour to anneal the strands . Also, if the strands were not to be used immediately, the strands were stored at 4°C thereafter.

Subsequently, ASO 12-mer . (ss-ASO), a double-stranded nucleic acid comprising ASO 12-mer and cPNA 12-mer (ASO/cPNA 12-mer) , a double-stranded nucleic acid comprising ASO 12-mer and cPNA 10-mer (ASO/cPNA 10-mer) , or a double-stranded nucleic acid comprising ASO 12-mer and cPNA 8-mer (ASO/cPNA 8-mer) were intravenously injected to a mouse through the tail vein in an amount of 0.75 mg/kg. Furthermore, a mouse to which PBS only was administered was also prepared as a control . Three days after the intravenous injection, the mice were perfused with PBS, and then the livers were extracted. Subsequently, extraction of mRNA, synthesis of cDNA, and quantitative RT-PCR were carried out by the same methods as the methods described in Comparative Example 1 , the amount of expression of mApoB/amount of expression of mGAPDH (internal standard gene) was calculated, and a comparison was made between the group administered with PBS only (PBS only) and the groups administered with nucleic acids. The results thus obtained are presented in FIG. 23.

As shown by the results illustrated in FIG .23, theantisense effect of any of the ASO/cPNA complexes was at least as strong as the effect observed for the ss-ASO 12-mer.

(Example 10)

This example demonstrated that various structures for the complementary strand that comprise "RNA nucleotides and optionally nucleotide analogs" can be used in the double-stranded nucleic acid complex and will yield an antisense effect. Four types of complementary strand structures were designed and prepared. The structures are schematically illustrated in FIG.

24. As the figure shows, two types of 5' and 3' wing regions were combined with two types of central regions . The wing regions comprise either 2 ' -OMe modified RNA with phosphorothioate links , or the nucleotide analog LNA, with phosphorothioate links. The central region comprises either natural phosphodiester-linked

RNA, or phosphorothioate-linked RNA.

The following 13-mer nucleic strands were produced and tested :

Antisense LNA/DNA gapmer strand

ASO 13-mer: 5 ' -GCattggtatTCA-3 ' (SEQ ID NO: 5)

(Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strands

1. Toc-cRNA(G) : 5 ' -u _s g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 7)

2. Toc-cLNA(G): 5 ' -u _s g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO: 15) 3. Toc-cLNA(s) : 5 ' -u _s g _s a _s A _s U _s A _s C _s C _s A _s A _s U _s g _s c-3 ' (SEQ ID NO:

16)

4. Toc-cRNA(s) : 5 ' -u ₃ g _s a _s A _s U _s A _s C _s C _s A _s A _s U _s g _s C-3 ' (SEQ ID NO:

17)

(Uppercase: RNA, lowercase: 2 ¹ -OMe-RNA, underlined lower case: LNA, s: phosphorothioate bonds between nucleic acids)

The LNA/DNA gapmer and each of the complementary strands were mixed in equal molar amounts and annealed as described above in Example 7. Next, the annealed double-stranded nucleic acid complexes were intravenously injected through the tail vein of a mouse in an amount of 0.75 mg/kg. A control mouse was also prepared by injecting PBS solution through the tail vein. Three days after the injection, the mice were perfused with PBS, the livers extracted, and subsequently mRNA extraction, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative mApoB expression level compared to mGAPDH (internal standard gene) was calculated, and the results are presented in FIGS. 25A-B.

As shown by FIG. 25A, comparing the results of Toc-cRNA(G) with Toc-cLNA(G) , the 5' and 3' wing regions of the complementary strand can be prepared using bridged nucleic acids as well as

RNA, and a similarly large antisense effect can be obtained. The data further show that for either of these types of wing regions, the central RNA portion of the nucleic acid strand can phosphorothioated, and the antisense effect remains as large as that observed with natural RNA in the central portionofthestrand. Compare Toc-cLNA(s) and Toc-cRNA(s) in relation to the effect observed for Toc-cRNA(G), in FIGS 25A and 25B, respectively.

As discussed in conjunction with Example 7, this example further shows other embodiments in which the nuclease resistance of the complementary strand can be increased without lose of the antisense effect. Specifically, the full length of the strand can be phosphorothioated and yet where central region comprises phosphorothioate-modified RNA, the antisense strand can still be released and suppress level of the mRNA transcript.

(Example 11)

This example demonstrated that even if the first and second strands (antisense and complementary strands) have different lengths the antisense effect is still obtained. Here, a 13-mer LNA/DNA gapmer was annealed with a 31-mer complementary RNA-based strand and tested for suppression of expression of ApoB gene in mice. Furthermore, the 31-mer was prepared with a 5' wing comprising three 2'-OMe modified, phosphorothioated RNA nucleotides, a 3' wing comprising twenty 2'-OMe modified, phosphorothioated RNA nucleotides, and a central region comprising eight RNA nucleotides that have a phosphorothioate link. The activity of the 13-mer/31-mer complex was compared with the activity of a 13-mer/13-mer complex. Antisense LNA/DNA gapmer strand

LNA 13-mer: 5 ' -GCattggtatTCA-3 ' (SEQ ID NO: 5)

(Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strands

1. 13-mer Toc-cRNA (G) : 5 ' -u _s g _s a _s AUACCAAU _s g _s c-3 ' (SEQ ID NO:

7)

2. 31-mer Toc-cRNA(s) : 5 " -u _s g _s a _s AUACCAAUgcuacgcauacgcacca _s C _s C _s a-3 ' (SEQ ID NO: 18)

(Upper case: RNA, lower case: 2'-OMe-RNA, s: phosphorothioate bonds between nucleic acids)

The LNA/DNA gapmer and each of the complementary strands were mixed in equal molar amounts and annealed as described above in Example 7. Next, the annealed double-stranded nucleic acid complexes were intravenously injected through the tail vein of a mouse in an amount of 0.75 mg/kg. A control mouse was also prepared by injecting PBS solution through the tail vein. Three days after the injection, the mice were perfused with PBS, the livers extracted, and subsequently mRNA extraction, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative mApoB expression level compared to mGAPDH (internal standard gene) was calculated, and the results are presented in FIG. 26.

As shown by FIG. 26, comparing the suppression achieved with double-stranded complexes having a 31-mer Toc-cRNA (s) complementary strand versus those having a 13-mer Toc-cLNA(G) complementary strand shows that a similarly large antisense effect was obtained. The data further show that the central RNA portion of the nucleic acid strand can phosphorothioated and the antisense effect remains as large as that observed with natural RNA in the central portion of the strand, even if the complementary strands also differ in length.

(Example 12)

To demonstrate the sequence-specificity and the universal applicability of the antisense effect provided by the double-stranded nucleic acids complexes disclosed herein, antisense probes targeting the transcription product of a different gene, human transthyretin (hTTR) were prepared. The experiments were performed using transgenic mice, altered to contain hTTR. (The mice thus contain both hTTR and mTTR. ) The antisense and complementary strands were prepared in two lengths, as 13-mer and 20-mer strands, and they were tested as the 13-mer/13-mer and 20-mer/20-mer double-stranded complexes. Also, the complementary strand was prepared with a 5' -tocopherol functional moiety to direct the complex to the liver . Furthermore , because hTTR expression ultimately yields a protein observable in the blood, the serum concentration of the expressed protein was analyzed, and was found to decrease following injection of the double-stranded nucleic acid complex. The sequence and composition of the various strands designed, produced, and tested ■ are shown below.

Antisense LNA/DNA gapmer strands 1. ASO 13-mer: 5'- TGtctctgccTGG-3 ¹ (SEQ ID NO: 19)

2. ASO 20-mer: 5'- TTATTgtctctgcctGGACT-3 ' (SEQ ID NO: 21)

(Upper case: LNA, lower case: DNA, phosphorothioate bonds between nucleic acids at all sites)

Complementary strands

1. 13-mer Toc-cRNA(G) : 5 ' - cscsasGGCAGAGAscsa-3 ' (SEQ ID NO: 20)

2. 20-mer Toc-cRNA(G): 5'- asgsuscscsAGGCAGAGACsasasusasa-3 ¹ (SEQ ID NO: 22)

(Upper case: ^' RNA, lower case: 2 ' -OMe-RNA, s: phosphorothioate bonds between nucleic acids)

The 13-mer antisense and complementary strands and the 20-mer antisense and complementary strands, respectively, were mixed in equal molar amounts and annealed as described above in Example 7. Next, 13-mer single stranded antisense strand and the 13-mer annealed double-stranded nucleic acid complex were intravenously inj ected through the tail vein of a transgenic mouse inanamount of 0.75mg/kg. Similarly, the 20-mer antisense single and 20-mer double-stranded complex were injected in an amount of 6 mg/kg. Control mice were also prepared by injecting PBS solution through the tail vein. Three days after the injection, the mice were perfused with PBS, the livers extracted, and subsequently mRNA extraction, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative hTTR expression levels compared to mGAPDH (internal standard gene) were calculated, and the results are presented in FIG.27Aand 27B for the 13-mer and 20-mer strands, respectively. hTTR that is synthesized in the liver is secreted into the blood. Thus, if antisense probes can be delivered to the liver and are effective in suppressing the expression of hTTR, then the result of the suppression should be the lowering of the blood serum concentration of the protein. Blood serum concentration levels were measured before the injection treatment with the 13-mer nucleic acid strands and again three days post-injection at a commercial lab. The serum concentrations observed are presented in FIG. 28.

As shown by FIG. 27A, the 13-mer double-stranded complex was effective in suppressing the mRNA transcript by more than 95%. In comparison, the single-stranded ASO only yielded a suppression of about 50%. The 20-mer complex also yielded a similar level of suppression of about 50%, whereas the single-stranded 20-mer had essentially no suppression, as illustrated in FIG. 27B. This falloff in the ability to suppress expression is commonly observed as the oligonucleotide increases in length. However, the longer oligonucleotides also are more selective and thus may be more safe. The efficacy of a treatment can be tailored by adjusting, for example, the dosage amount, dosing regimen, and the length, sequence, and composition of the antisense strand. However, as shown by these examples, delivering the antisense strand as a double-stranded nucleic acid complex according to the various embodiments of the present invention yields a significantly greater degree of suppression than when the same antisense strand isdeliveredasasingle strand .

The pre- and post-treatment serum concentration levels are shown in FIG. 28, and the results show a significant reduction in hTTR caused by the 13-mer double-stranded complex from -40 mg/dl to <5 mg/dl, compared with the single-stranded 13-mer (-44 mg/dl to ~28 mg/dl ) and the PBS control ( approximately no change ) . (Example 13)

This example demonstrated the delivery of a double-stranded nucleic acid complex to cells of the nervous systemusing a peptide as the delivery functional moiety. A double-stranded complex comprising three strands, an antisense strand, a complementary strand, and a PNA strand, having the general structure illustrated in FIG. 21B was used. A dodecapeptide , DRG1, was joined to the N-terminal of a 9-mer PNA strand to act as a delivery agent to localize the complex in dorsal root ganglia (DRG) cells. This

9-mer PNA was annealed with a 13-mer antisense strand and a 22-mer complementary strand, which are described below, to form the double-stranded complex used in the experiment. The gene targeted by the antisense strand was TRPV1.

Antisense LNA/DNA gapmer strand

ASO 13-mer: 5 ' -TAgtccagttCAC-3 ' (SEQ ID NO: 23)

(Upper case: LNA; lower case: DNA; phosphorothioate bonds between nucleic acids at all sites)

Complementary strand

cRNA(G) 22-mer: 5 ' -g _s u _s g _s AACUGGACuauacgcac _s c _s a-3 ' (SEQ ID

NO: 24) (Upper case: RNA; lower case: 2'-OMe-RNA; s: phosphorothioate bonds between nucleic acids)

Third (peptide) strand

pep-PNA 9-mer: N ' -SPGARAFGGGGS-tggtgcgta-C ' (SEQ ID NOs : 25 and 31)

(Upper case: amino acid; Underlined, lower case: PNA) The LNA/DNA gapmer, the complementary strand, and the peptide-PNA strand were mixed in equimolar amounts, and the mixture as heated at 95°C for 5 minutes . Subsequently, themixture was left to stand at a constant temperature of 37°C for one hour to anneal the three strands ("ts-TRPVl") . Also, if the strands were not to be used immediately, the strands were stored at 4°C. Also, a double-stranded complex comprising just the antisense strand and the complementary strand ("ds-TRPVl") was prepared the same way.

Mice were obtained from Sankyo Lab (Tokyo, Japan) , kept within a pathogen-free animal facility and provided food and water ad libitum. Eight-week old female ICR mice weighing on average 27 g received 2.66 ug intra-thecal injections of PBS, ds-TRPVl, or ts-TRPVl. Animal procedures were performed by a physician licensed for animal experimentation, in accordance with ethical and safety protocols approved by the Animal Experiment Committee of Tokyo Medical and Dental University. Intra-thecal injection was administered following induction of anaesthesia via intra-peritoneal injection of chloral hydrate (0.5 mg/g body weight) and ketamine hydrochloride (0.05 mg/g body weight) . All mice were placed in the prone position and underwent partial laminectomy of the second and third lumbar vertebrae (L2-L3) . Once exposed, the duramater between these vertebrae was punctured using s 27-gauge needle; subsequently, a PE-10 catheter connected to a 10 uL Hamilton syringe was inserted caudally into the subarachnoid space to approximately the level of L5 and a 10 uL volume was steadily administered over a 1 -minute period. After the removal of the catheter, the fascia and skin were sutured with 4-0-nylon thread and treated with antibiotic solution. The animals were then positioned in the head-up position and allowed to recover on a heated pad.

Histological analysis was performed as follows . Mice were euthanized 2 days after injection via 3 mg chloral hydrate intra-peritoneal injection and transcardial fixation with PFA (4% paraformaldehyde in PBS) following PBS perfusion. DRG

(unilteral L6) were harvested. The DRG thus obtained were fixed with a 4% formalin solution, subsequently the solution was replaced with a 30% sucrose solution, the livers were embedded in OCT Compound, and then sections having a thickness of lOym were produced therefrom. Subsequently, the sections were nucleus stained by using DAPI, and then the signal intensities of Cy3 in the sections were observed using a confocal microscope. The confocal imaging analysis is shown in FIG. 29.

Relative expression level analysis of TRPV1 was performed as follows. Mice were sacrificed 7 days after injection via induction of anaesthesia and transcardial PBS perfusion. Three unilateral DRG were harvested from each mouse: lumbar spinal DRG (LSD) L4, L5, andL6. Thereafter, mRNA extract ion, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative mTRPVl expression levels compared to mGAPDH ( internal standard gene ) were calculated, and the results are presented in FIG. 30.

The histological analysis, shown in FIG. 29, reveals that the Cy3-labeled antisense strand localized to the nucleus of DRG cells. This is evidenced by the coincident fluorescent signals of the nuclear stain the fluorescent label on the antisense strand .

Again, this experiment demonstrated that the double-stranded complex comprising three strands remained intact and the delivery moiety on the third strand directed the complex, and thereby the antisense strand, to the cell of interest.

The antisense effect is observed, as shown in FIG. 30 by the suppression of the expression of mTRPVl. The complex, ts-PRPVl, which contains the peptide-PNA strand and thus can guide the complex to DRG cells, demonstrated a suppression of about 40%. In contrast, the ds-TRPVl complex, which lacked the peptide-PNA strand suppressed the gene expression, but only by about 20% . This example again demonstrated the ability to deliver an antisense strand to a specific cell type using complexes comprising three st rands . Furthermore, this example illustrates the use of a peptide to guide the delivery, and achieves this in a cell type (DRG) and organ different from that illustrated in other examples (nervous system instead of the liver) . (Example 14)

This example demonstrated an antisense effect by the double-stranded nucleic acid complex against non-protein encoding RNA transcript products, namely, against an miRNA. In a mouse liver, miR-122, an miRNA, is known to be expressed. A

15-mer anti-miR strand was designed and prepared with a 5' wing and a 3' wing comprising three nucleotides analogs (bridged nucleic acid, LNA) , and a 9 base central region comprising DNA, wherein all the links were phosphorothioated . A complementary strand with 5' and 3' wings comprising 2 ' -OMe, phosphorothioated

RNA and a central region comprising natural RNA was prepared.

Anti-miR LNA/DNA gapmer strand

ASO 15-mer: 5'- CCAttgtcacacTCC-3 ' (SEQ ID NO: 26) (Upper case: LNA; lower case: DNA; phosphorothioate bonds between nucleic acids at all sites)

Complementary strand

Toc-cRNA(G) 15-mer: 5 ' -Toc-g _s g _s a _s GUGUGACCA _s u _s g _s g-3 ' ( SEQ ID NO: 27)

(Upper case: RNA; lower case: 2 ' -OMe-RNA; s: phosphorothioate bonds between nucleic acids)

The anti-miR LNA/DNA gapmer and the complementary strand were mixed in equal molar amounts and annealed as described above in Example 7. Next, the single-stranded anti-miR strand and the annealed double-stranded nucleic acid complexes were intravenously injected through the tail vein of a mouse in an amount of 0.75 mg/kg. A control mouse was also prepared by injecting PBS solution through the tail vein. Three days after the injection, the mice were perfused with PBS, the livers extracted, and subsequently mRNA extraction, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative mApoB expression level compared to mGAPDH (internal standard gene) was calculated, and the results are presented in FIG. 31.

As shown by FIG. 31, the double-stranded complex provides nearly a 50% reduction in the level of miR- 122, whereas the single stranded anti-miR oligonucleotide provided justa~20% reduction . It is also noteworthy that the typical methods for reducing miRNA levels use a mixmer type probe structure, and the probe needs to be delivered at a dose of -10 mg/kg to achieve a 50% reduction (ED50) . As illustrated, the double-stranded complex according to some embodiments that is presented in this example achieves ED50 at a considerably lower dosage amount.

(Example 15)

This example used an antisense strand comprising "amideBNA" amido-bridged nucleic acids to achieve an antisense effect. Amido-bridged nucleic acids (also referred to as "AmNAs") are analogs of LNAs that have a cyclic amide bridge (4' -C (0) -N (R) -2' ; R=H, Me) joining the 2' and 4' -carbons of the sugar ring. The synthesis of AmNAs, their incorporation into oligonucleotides and the properties thereof, such as binding affinity and nuclease resistance, were recently disclosed by A. Yahara et al., in ChemBioChem 2012, 13, 2513-2516, the disclosure of which is incorporated by reference. As disclosed by Yahara et al. , AmNAs exhibit excellent binding affinities toward complementary strands and a high degree of nuclease resistance, thus making them suitable for use in antisense oligonucleotides. A 13-mer antisense strand was designed and prepared with a 5' wing and a 3' wing comprising, respectively, two and three nucleotides analogs (amideBNA, AmNA) , and an 8 base central region comprising DNA, wherein all the links were phosphorothioated. A complementary strand with 5' and 3' wings comprising 2'-OMe, phosphorothioated RNA and a central region comprising natural RNA was prepared.

Antisense amideBNA (AmNA) /DNA gapmer strand

ASO 13-mer: 5 ' -GCattggtatTCA-3 ¹ (SEQ ID NO: 28)

(Upper case: N-methyl amideBNA (AmNA) , lower case: DNA, phosphorothioate bonds between nucleic acids at all sites) Complementary strand

1. 13-mer Toc-cRNA (G) : 5 ' -u _s g _s a _s AUACCAAU _s g _s c-3 · (SEQ ID NO:

7)

(Upper case: RNA, lower case: 2'-OMe-RNA, s: phosphorothioate bonds between nucleic acids)

The antisense amidoBNA/DNA gapmer (ASO) and the complementary strand were mixed in equal molar amounts and annealed as described above in Example 7. Next, the single-stranded ASO and the annealed double-stranded nucleic acid complex were intravenously injected through the tail vein of a mouse in various amounts (ss-ASO: 0.75 mg/kg; 2.25 mg/kg; Toc-ASO/cRNA (G) : 0.33 mg/kg; 1.0 mg/kg) . A control mouse was also prepared by injecting PBS solution through the tail vein. Seven days or fourteen days after the injection, the mice were perfused with PBS, the livers extracted, and subsequently mRNA extraction, cDNA synthesis, and quantitative RT-PCR was carried out as described in Comparative Example 1. The relative mApoB expression level compared to mGAPDH (internal standard gene) was calculated, and the results are presented in FIG. 32.

As shown by FIG .32, the double-stranded nucleic acid complex that incorporates amideBNA (AmNA) into the 5' wing and 3' wing regions of the first nucleic acid (antisense oligonucleotide) generates an antisense effect in vivo. The graphs shows that even when the double-stranded complex is injected into mice in lower amounts than the single-stranded ASO a greater degree of suppression is achieved with the double-stranded complex. For example, the ASO/Toc-cRNA (G) complex inj ected at 1.0 mg/kg yielded a suppression by approximately 55%, which was significantly lower than the result of just 20% suppression with ss-ASO at 2.25 mg/kg dose when measured 7 days post-injection. As demonstrated by this embodiment, a greater degree of suppression of expression is achieved with less reagent by practicing the method and using the double-stranded complex disclosed herein.

[Industrial Applicability]

As discussed above, using a double-stranded nucleic aci d complex according to embodiments of the present invention, in some embodiments an antisense nucleic acid can be delivere d to a particular organ (cells) with high specificity and hig h efficiency, and the expression of a target gene or the leve 1 of a transcription product can be very effectively suppress ed by the antisense nucleic acid. Furthermore, since various molecules such as lipids (for example, tocopherol and choles terol), sugars (for example, glucose and sucrose), proteins, peptides, and antibodies can be applied to the double-strande d nucleic acid of some embodiments as functional moieties for the delivery to particular organs, the double-stranded nucle ic acid complex of some embodiments can be targeted to variou s organs, tissues and cells. Also, since the antisense effec t is not reduced even if the double-stranded nucleic acid of some embodiments is subjected to modification for imparting r esistance to RNase or the like, the double-stranded nucleic a cid of some embodiments can also be used in embodiments of en teral administration.

Therefore, the double-stranded nucleic acid of some emb odiments can provide high efficacy even when administered at a low concentration, and is also excellent from the viewpoint of reducing adverse side effects by suppressing the distribu tion of antisense nucleic acids in organs other than the targ et organ. Therefore, the double-stranded nucleic acid is use ful as a pharmaceutical composition or the like for treating and preventing diseases that are associated with increased ex pression of target genes, such as metabolic diseases, tumors, and infections and/or increased level of a transcription pro duct .