Sirna, sirna conjugate, and pharmaceutical composition and use thereof

Abstract

Provided is an siRNA, wherein a length and composition of an antisense strand of the siRNA enable the siRNA to inhibit expression of PKK mRNA by means of an RNAi mechanism; in a 3' to 5' direction, two nucleotides among the 11th to 13th nucleotides in a sense strand are fluorine-modified nucleotides, and the remaining nucleotide is an alkoxy-modified nucleotide; the antisense strand comprises 5 to 10 fluorine-modified nucleotides, wherein the 2nd and 14th nucleotides of the antisense strand, in the 3' to 5' direction, are fluorine-modified nucleotides, and one of the 6th to 8th nucleotides, one of the 15th to 17th nucleotides, and one of the 11th to 13th nucleotides are fluorine-modified nucleotides. Also provided are an siRNA conjugate, a pharmaceutically acceptable salt, a pharmaceutical composition, and the use thereof.

Description

A siRNA, siRNA conjugates, pharmaceutical compositions thereof, and uses Technical Field This disclosure relates to an siRNA, siRNA conjugates formed from the siRNA, pharmaceutically acceptable salts, pharmaceutical compositions thereof, and uses thereof, particularly to an siRNA capable of targeting PKK mRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions thereof, and their use in the treatment, prevention, or improvement of diseases related to PKK mRNA expression levels. Background Technology Bradykinin (BK) is a major regulator of vascular permeability. Excessive BK can increase vascular leakage, thereby exacerbating inflammation. Studies have shown that a genetic defect in C1-esterase inhibitors (C1-INH), the main natural inhibitor of BK, can lead to hereditary angioedema (HAE). Patients with the rare disease HAE often suffer from acute attacks of painful edema triggered by unknown factors, and attacks located in the throat can be life-threatening. Prokaryokinetic release enzyme (PKK) is a precursor of plasma kallikrein (PK). PKK is converted to PK upon activation by factor XIIa (FXIIa). PK cleaves high molecular weight kininogen, releasing bradykinin into the blood vessels. Therefore, by inhibiting PKK gene expression, excessive BK can be suppressed at the cellular level, thereby preventing and treating diseases or symptoms caused by excessive BK, such as inflammation, especially hereditary angioedema. Small interfering RNA (siRNA) can inhibit or block the expression of any target gene of interest in a sequence-specific manner based on the mechanism of RNA interference (RNAi), thereby achieving the purpose of treating diseases. In siRNA drugs, although a large number of siRNA modification schemes have been disclosed in the prior art, how to improve the modification of siRNA to obtain siRNAs with higher activity, higher stability, and / or longer-lasting effects remains a research direction in this field. Summary of the Invention This disclosure provides an siRNA, a conjugate containing the siRNA, a pharmaceutically acceptable salt, a pharmaceutical composition thereof, and its use. The siRNA, siRNA conjugate, and pharmaceutically acceptable salt provided in this disclosure have good pharmaceutical activity and long-lasting effects when targeting PKK mRNA. In one aspect, this disclosure provides an siRNA containing a sense strand and an antisense strand, each nucleotide in the siRNA being independently modified, the sense strand and the antisense strand being at least partially anticomplementary to form a double-stranded region, the length and composition of the antisense strand enabling the siRNA to inhibit PKK via an RNAi mechanism. The expression of mRNA, wherein the sense strand contains only two fluorinated nucleotides, and in the 3'-5' direction, two of the 11th-13th nucleotides of the sense strand are fluorinated nucleotides, and the remaining nucleotide is an alkoxylated nucleotide; the antisense strand contains 5-10 fluorinated nucleotides, and in the 5'-3' direction, the 2nd and 14th nucleotides of the antisense strand are fluorinated nucleotides, one of the 6th-8th nucleotides is a fluorinated nucleotide, one of the 15th-17th nucleotides is a fluorinated nucleotide, and one of the 11th-13th nucleotides is a fluorinated nucleotide, which is complementary to the alkoxylated nucleotide in the 11th-13th nucleotides of the sense strand in the 3'-5' direction to form a base pair. In another aspect, this disclosure provides an siRNA conjugate containing an siRNA group and a delivery group conjugated to the siRNA group, the siRNA group being a group formed by removing one or more atoms or groups of atoms from the siRNA of this disclosure. In another aspect, this disclosure also provides a pharmaceutically acceptable salt of the siRNA or siRNA conjugate described herein. In another aspect, this disclosure also provides a pharmaceutical composition comprising one or more of the siRNA, siRNA conjugates and pharmaceutically acceptable salts described in this disclosure, and pharmaceutically acceptable excipients. In another aspect, this disclosure also provides the use of the siRNA, siRNA conjugate, pharmaceutically acceptable salt and / or pharmaceutical composition described herein in the preparation of a medicament for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels. In another aspect, this disclosure also provides a method for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels, the method comprising administering to a subject in need an effective amount of one or more of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. In another aspect, this disclosure also provides a method for regulating the expression level of PKK mRNA in cells, the method comprising contacting the cells with an effective amount of one or more of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. In another aspect, this disclosure also provides a cell expressing PKK mRNA, said cell further comprising one or more of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. In addition, this disclosure also provides a kit comprising one or more of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. Incorporate by reference All publications, patents and patent applications mentioned in this specification are incorporated herein by reference to the same extent that each individual publication, patent or patent application is specifically and individually incorporated herein by reference. Beneficial effects The siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions disclosed herein exhibit high activity in regulating PKK mRNA and good long-lasting effects. The siRNA conjugates of this disclosure can effectively reach and enter the liver, exerting the regulatory activity of the siRNA and / or siRNA conjugates on PKK mRNA, thereby effectively treating diseases or symptoms related to PKK mRNA expression levels. On the one hand, the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions provided in this disclosure exhibit high PKK mRNA inhibitory activity in in vitro cell experiments. For example, the conjugates provided in this disclosure all showed high PKK mRNA inhibitory activity in primary mouse liver cells, with inhibition rates of over 70%, and even reaching 84.1%, at a concentration of 2 nM. Furthermore, the conjugates provided in this disclosure showed high IC50 in primary human liver cells. 50 The value of 1.1 nM indicates that the conjugate provided in this disclosure has a good inhibitory effect on the expression of PKK mRNA. On the other hand, the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions provided in this disclosure have shown highly effective and long-lasting PKK mRNA inhibitory effects in animal experiments. For example, C57BL / 6J mice administered the conjugates of this disclosure showed good PKK mRNA inhibitory effects in mice. Compared with the PBS blank control group, at a dose of 3 mg / kg and on day 8, the inhibition rate of PKK mRNA in mice was above 70%, and even reached above 90%. Furthermore, during a 57-day experimental period, hPKK transgenic mice administered the conjugates of this disclosure showed a high inhibition rate of hPKK protein expression. At doses of 3 mg / kg or 1 mg / kg, the inhibition rate of hPKK protein expression remained at 89.4% and 51.3% respectively on day 43, and at a dose of 3 mg / kg, the inhibition rate of hPKK protein expression was still 86.9% on day 57. For example, during an 8-day experimental period, hPKK transgenic mice administered the conjugate of this disclosure showed a high inhibition rate of hPKK protein expression. At a dosage of 3 mg / kg, the inhibition rate of hPKK protein expression remained above 75% on day 8, reaching a maximum of 84.7%. As another example, during a 43-day experimental period, hKLKB1 mice administered the conjugate of this disclosure showed a high inhibition rate of hPKK protein expression. At a dosage of 3 mg / kg, the inhibition rate of hPKK protein expression on day 43 was 70.26%, which is more than twice the inhibition rate of the preferred conjugates in the prior art. Therefore, the conjugates disclosed herein can stably and efficiently inhibit PKK mRNA expression over a long period of time, thereby reducing the level of PKK protein expression in subjects. The siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions disclosed herein possess excellent PKK mRNA regulatory activity and show great promise for the development of drugs for the treatment and / or prevention of diseases or symptoms related to PKK mRNA expression levels. Detailed Implementation The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure. In this disclosure, PKK mRNA refers to PKK mRNA expressed in mammals. In some embodiments, PKK mRNA refers to the mRNA with the sequence shown in Genbank accession numbers NM_008455.3, NM_001318394.1 or NM_001318396.1. definition In the context of this document, the terms "complementary" and "reverse complementary" are used interchangeably and have the meaning known to those skilled in the art: in a double-stranded nucleic acid structure, each base on one strand forms a hydrogen bond with a base on the other strand in a complementary manner, achieving base pairing and forming a Watson-Crick base pair. A "base pair" refers to the two bases that form a base pair. In DNA, the purine base adenine (A) always pairs with the pyrimidine base thymine (T) (or uracil (U) in RNA); the purine base guanine (G) always pairs with the pyrimidine base cytosine (C). Each base pair consists of one purine and one pyrimidine. When adenine on one strand always pairs with thymine (or uracil) on the other strand, and guanine always pairs with cytosine, the two strands are considered complementary, and the sequence of the complementary strand can be inferred from its sequence. When bases are modified, as long as the pairing relationship of purines and pyrimidines (including but not limited to the number and strength of hydrogen bonds between bases) is not affected, the modified bases are considered to be able to form complementary pairs. Correspondingly, "mismatch" or "base mismatch" in this field means that the bases at corresponding positions between the two single-stranded nucleic acids involved are not paired in a complementary manner; when the corresponding position includes a baseless nucleotide, it is also considered to have formed a mismatch with the bases on the other strand. In the preceding and following text, "at least partially anti-complementary," "substantially anti-complementary," "truly anti-complementary," and "completely anti-complementary" refer to the base pairing between the siRNA antisense strand and PKK mRNA, between the siRNA antisense strand and nucleotide sequence m, between the siRNA sense strand and antisense strand, and between any two nucleotide sequences. Unless otherwise specified, "at least partially anti-complementary" means that within a hypothetical or actual double-stranded region, there are no more than 50% base mismatches between the two nucleotide sequences capable of forming a double-stranded region; "substantially anti-complementary" means that within a hypothetical or actual double-stranded region, there are no more than 3 base mismatches between the two nucleotide sequences capable of forming a double-stranded region; "truly anti-complementary" means that within a hypothetical or actual double-stranded region, there are no more than 1 base mismatch between the two nucleotide sequences capable of forming a double-stranded region; and "completely anti-complementary" means that within a hypothetical or actual double-stranded region, there are no base mismatches between the two nucleotide sequences capable of forming a double-stranded region. When the two nucleotide sequences are “at least partially reverse complementary,” “substantially reverse complementary,” “truly reverse complementary,” or “completely reverse complementary,” they can form a double-stranded hybrid consisting of Watson-Crick base pairs after annealing. In the context of this disclosure, a "double-stranded region" is a double-stranded structure formed between the shortest nucleotide sequences comprising all base pairs on each single strand of a hypothetical or actual double-stranded nucleic acid structure. Therefore, a double-stranded region consists of all base pairs in the double-stranded nucleic acid structure and all base mismatches between those base pairs. In some embodiments, the double-stranded nucleic acid structure includes a double-stranded region and one or more overhanging ends, said overhanging ends consisting of all nucleotides outside the double-stranded region in one or both single strands of the double-stranded nucleic acid structure that have not formed base pairs. The two nucleotide sequences that can form a double-stranded region can be of the same or different lengths. In some embodiments, the double-stranded nucleic acid structure includes only the double-stranded region, in which case the two nucleotide sequences forming the double-stranded nucleic acid structure are of the same length. In some embodiments, the two nucleotide sequences forming the double-stranded nucleic acid structure are of the same length, the double-stranded nucleic acid structure includes a double-stranded region and one or both overhanging ends of the longer nucleotide sequence, and the overhanging ends of the two nucleotides are of the same length. In some embodiments, the two nucleotide sequences forming the double-stranded nucleic acid structure are of different lengths, the double-stranded nucleic acid structure includes a double-stranded region and one or both overhanging ends of the longer nucleotide sequence. For example, in some embodiments, the sense and antisense strands of siRNA are of different lengths, typically the sense strand is shorter (a shorter nucleotide sequence), and the antisense strand is longer (a longer nucleotide sequence), and the double-stranded nucleic acid structure includes a double-stranded region and one overhanging end of the antisense strand. In the preceding and following text, "there are X consecutive identical nucleotides between nucleotide sequence A and nucleotide sequence B, and the consecutive identical nucleotides include no more than Y base differences or have no base differences" means that nucleotide sequence A contains a continuous nucleotide sequence A' of length X, which is consecutively identical to a continuous nucleotide sequence B' of length X in nucleotide sequence B, and there are no more than Y base differences or have no base differences between nucleotide sequence A' and nucleotide sequence B'. In the preceding and following text, "nucleotide sequence A and nucleotide sequence B are substantially anticomplementary, substantially anticomplementary, or completely anticomplementary across a length of X nucleotides" means that there exists a continuous nucleotide sequence A' of length X in nucleotide sequence A, which is substantially anticomplementary, substantially anticomplementary, or completely anticomplementary to a continuous nucleotide sequence B' of length X in nucleotide sequence B. In the preceding and following text, "unmodified equivalent sequence" refers to the siRNA nucleotide sequence that does not contain any ribosome modifications, base modifications, or phosphate backbone modifications compared to the original sequence used as the basis for alignment. For example, the unmodified equivalent sequence of VPAmsCfsdTGmsUmia is ACUGUN, where N is A, C, G, or U. In the preceding and following text, "fluorinated nucleotides" refers to nucleotides formed by replacing the 2'-hydroxyl group of the ribosome with fluorine, and "non-fluorinated nucleotides" refers to nucleotides or nucleotide analogs formed by replacing the 2'-hydroxyl group of the ribosome with a non-fluorinated group. "Nucleotide analogs" refer to groups that can replace nucleotides in nucleic acids but whose structure differs from adenine ribonucleotides, guanine ribonucleotides, cytosine ribonucleotides, uracil ribonucleotides, or thymine deoxyribonucleotides, such as isonucleotides, bridged nucleic acids (BNAs), or acyclic nucleotides. "Methoxylated nucleotides" refers to nucleotides formed by replacing the 2'-hydroxyl group of the ribosome with a methoxy group. In the foregoing and hereinafter, particularly in the description of methods for preparing siRNA, pharmaceutical compositions, or siRNA conjugates of this disclosure, unless otherwise specified, the nucleoside monomer refers to the modified or unmodified RNA phosphoramidites (sometimes also called nucleoside phosphoramidites) used in phosphoramidite solid-phase synthesis, depending on the type and sequence of nucleotides in the siRNA or siRNA conjugate to be prepared. Phosphoramidite solid-phase synthesis is a method known to those skilled in the art for RNA synthesis. All nucleoside monomers used in this disclosure are commercially available. In the foregoing or hereinafter, "substituted" or "substituted group" includes, but is not limited to, substituted alkyl, substituted alkoxy, and substituted amino groups. Unless otherwise specified, "substituted" or "substituted group" refers to a group formed by replacing one or more hydrogen atoms in the group with one or more substituents. For example, "substituted alkoxy" refers to a group formed by replacing one or more hydrogen atoms in an alkoxy group with a substituent. Those skilled in the art will understand that compounds used in the application of this disclosure may contain various substituents, as long as the introduction of such substituents does not affect the function of this disclosure and achieves the purpose of this disclosure, it can be used in this disclosure. In some embodiments, the substituents are selected from the group consisting of C1-C1 groups. 10 Alkyl, C6-C 10 Aryl, C5-C 10 heteroaryl, C1-C 10 Haloalkyl, -OC1-C 10 Alkyl, -OC1-C 10 Alkylphenyl, -C1-C 10 Alkyl-OH, -OC1-C 10 Halogenated alkyl, -SC1-C10 Alkyl, -SC1-C 10 Alkylphenyl, -C1-C 10 Alkyl-SH, -SC1-C 10 Halogenated alkyl groups, halogenated substituents, -OH, -SH, -NH2, -C1-C 10 Alkyl-NH2,-N(C1-C) 10 Alkyl) (C1-C 10 alkyl), -NH(C1-C 10 Alkyl), -N(C1-C 10 Alkyl) (C1-C 10 alkylphenyl), -NH(C1-C 10 Alkylphenyl), -CN, -NO2, -CO2H, -C(O)O(C1-C 10 Alkyl), -CON (C1-C) 10 Alkyl) (C1-C 10 Alkyl), -CONH (C1-C) 10 Alkyl group), -CONH2, -NHC(O) (C1-C 10 alkyl), -NHC(O)(phenyl), -N(C1-C 10 Alkyl)C(O)(C1-C 10 Alkyl), -N(C1-C 10 alkyl)C(O)(phenyl), -C(O)C1-C 10 Alkyl, -C(O)C1-C 10 Alkylphenyl, -C(O)C1-C 10 Haloalkyl, -OC(O)Cl-C 10 Alkyl group, -SO2 (C1-C) 10 alkyl), -SO2 (phenyl), -SO2 (C1-C 10 Halogenated alkyl groups), -SO2NH2, -SO2NH (C1-C 10 alkyl), -SO2NH (phenyl), -NHSO2 (C1-C 10 Alkyl), -NHSO2 (phenyl) and -NHSO2 (C1-C) 10 (Halogenated alkyl). In some embodiments, the substituent is one of C1-C3 alkyl, C6-C8 aryl, -OC1-C3 alkyl, -OC1-C3 alkylphenyl, halogen, -OH, -NH2, -CN, or -NO2. Those skilled in the art will understand that for any group containing one or more substituents, these groups are not intended to introduce any substitution or substitution pattern that is spatially impractical, synthetically infeasible, and / or inherently unstable. As used herein, “alkyl” refers to a saturated straight-chain and / or branched hydrocarbon group having a specified number of carbon atoms, typically from 1 to 20 carbon atoms, such as from 1 to 10 carbon atoms, or from 1 to 8 or 1 to 6 carbon atoms. For example, C1-C6 alkyl comprises straight-chain and branched alkyl groups having 1 to 6 carbon atoms. When referring to an alkyl residue having a specific number of carbons, it is intended to cover all branched and straight-chain forms having that number of carbons; thus, for example, “butyl” means including n-butyl, sec-butyl, isobutyl, and tert-butyl; “propyl” includes n-propyl and isopropyl. Alkylenes are subsets of alkyl, referring to residues that are identical to alkyl but have two connection sites. As used herein, "alkoxy" refers to an alkyl group with a specified number of carbon atoms connected by oxygen bridges, such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, pentooxy, 2-pentoxy, isopentoxy, neopentoxy, hexoxy, 2-hexoxy, 3-hexoxy, 3-methylpentoxy, etc. Alkoxy groups typically have 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms connected by oxygen bridges. As used herein, "alkenyl" refers to an unsaturated branched or straight-chain hydrocarbon group having at least one carbon-carbon double bond obtained by removing a hydrogen molecule from an adjacent carbon atom of a parent alkyl group. The group can be in either a cis or trans configuration of the double bond. Typical alkenyl groups include, but are not limited to: vinyl; propenyl, such as propyl-1-en-1-yl, propyl-1-en-2-yl, propyl-2-en-1-yl (allyl), propyl-2-en-2-yl; butenyl, such as buten-1-en-1-yl, buten-1-en-2-yl, 2-methylpropen-1-en-1-yl, buten-2-en-1-yl, buten-2-en-2-yl, buten-1,3-dien-1-yl, buten-1,3-dien-2-yl, etc. In some embodiments, the alkenyl group has 2 to 20 carbon atoms, while in other embodiments, it has 2 to 10, 2 to 8, or 2 to 6 carbon atoms. Subalkenyl groups are a subset of alkenyl groups, referring to residues that are identical to alkenyl groups but have two connection points. As used herein, "alkynyl" refers to an unsaturated branched or straight-chain hydrocarbon group having at least one carbon-carbon triple bond obtained by removing two hydrogen molecules from adjacent carbon atoms of a parent alkyl group. Typical alkynyl groups include, but are not limited to: ethynyl; propynyl, such as prop-1-yn-1-yl, prop-2-yn-1-yl; butynyl, such as but-1-yn-1-yl, but-1-yn-3-yl, but-3-yn-1-yl, etc. In some embodiments, the alkynyl group has 2 to 20 carbon atoms, while in other embodiments, it has 2 to 10, 2 to 8, or 2 to 6 carbon atoms. Ionynyl is a subset of alkynyl, referring to residues that are identical to alkynyl but have two connection sites. As used herein, "aryl" refers to a group derived from an aromatic monocyclic or polycyclic hydrocarbon ring system by removing a hydrogen atom from a ring carbon atom. This aromatic monocyclic or polycyclic hydrocarbon ring system contains only hydrogen and carbon atoms of 6 to 18, wherein at least one ring in the ring system is fully unsaturated, i.e., contains a cyclic, delocalized (4n+2)π-electron system according to Hückel's theory. Aryl groups include, but are not limited to, phenyl, fluorenyl, and naphthyl groups. Alearyl groups are a subset of aryl groups, referring to residues identical to aryl groups but with two connection points. As used herein, a "heterocyclic group" refers to a group derived from a monocyclic saturated or partially unsaturated, non-aromatic or bicyclic saturated or partially unsaturated heterocyclic hydrocarbon group, wherein the bicyclic ring system is non-aromatic, the monocyclic or bicyclic ring has, for example, 3 to 10 members or 5 to 10 members, wherein at least one member and up to five members, particularly one, two or three ring members, are heteroatoms selected from N, O and S, and the remaining ring atoms are carbon atoms in a stable combination known to those skilled in the art. The heterocyclic nitrogen and sulfur atoms are optionally oxidized, and the nitrogen atom is optionally quaternized. As used herein, the heterocycle can form a bicyclic ring with another ring system, i.e., one or two of the atoms constituting the heterocycle are shared with another ring system. The heterocyclic group can be linked to the rest of the molecule via carbon or heteroatoms; and, in the case of a bicyclic group, the above-mentioned linking can be made via a ring containing heteroatoms or a fused ring. Examples of heterocyclic groups include, but are not limited to: aziridine, pyrrolidinyl, piperidinyl, aziridine-heptyl, diaziridine-heptyl, dihydrofuranyl (e.g., 2,3-dihydrofuranyl, 2,5-dihydrofuranyl), dioxacyclopentyl, morpholinyl, oxazolyl, oxazinyl, indololinyl, isoindolinyl, piperazinyl, tetrahydrofuranyl, thiomorpholinyl, and dihydropyranyl (e.g., 3,4-dihydropyranyl). 3,6-dihydropyranyl), piperazineyl, dioxane, hexahydropyrimidinyl, pyrazolinyl, pyrazolylylene, 4H-quinazinyl, quininecycloyl, tetrahydropyranyl, tetrahydropyridinyl, tetrahydropyrimidinyl, tetrahydrothiopheneyl, thiazolyl, benzopyranyl, tetrahydroquinolinyl, dihydropyrrolopyridinyl, dihydrobenzoxazinyl, pyrrolopyridinyl, dihydronaphthidinyl, dihydroisoquinolinyl, and tetrahydroisoquinolinyl. Subheterocyclic groups are a subset of heterocyclic groups, referring to residues identical to heterocyclic groups but with two connection sites. As used herein, "heteroaryl" refers to a group derived from a 3- to 18-membered aromatic ring radical, comprising 2 to 17 carbon atoms and 1 to 6 heteroatoms selected from nitrogen, oxygen, and sulfur. As used herein, a heteroaryl can be a monocyclic, bicyclic, tricyclic, or tetracyclic system, wherein at least one ring in the ring system is fully unsaturated, i.e., comprising a cyclic delocalized (4n+2) π-electron system according to Hückel's theory. Heteroaryls include fused ring or bridged ring systems. In some embodiments, the heteroatoms in the heteroaryl are oxidized heteroatoms. In some embodiments, the heteroaryl contains one or more nitrogen atoms. In some embodiments, one or more of the nitrogen atoms in the heteroaryl are quaternized nitrogen atoms. The heteroaryl is attached to the remainder of the molecule via any ring atom. Examples of heteroaryl groups include, but are not limited to: 1,2,3-triazolyl, aziridine, benzimidazolyl, benzoindolyl, 1,3-benzodioxazolyl, benzofuranyl, benzooxazolyl, benzo[d]thiazolyl, benzo[d]thiadiazolyl, benzo[b][1,4]dioxepinyl, benzo[b][1,4]oxazinyl, 1,4-benzodioxalkyl (1,4-benzyl) zodioxanyl), benzonaphthofuranyl, benzoxazolyl, benzodioxolyl, benzodioxinyl, benzopyranyl, benzopyranoneyl, benzofuranyl, benzofuranoneyl, benzothiophenyl, benzothiophene[3,2-d]pyrimidinyl, benzotriazolyl, benzo[4,6]imidazo[1,2-a]pyridyl, carbazoleyl, cinnolinyl, cyclopentano[d]pyrimidinyl, 6,7- Dihydro-5H-cyclopentano[4,5]thieno[2,3-d]pyrimidinyl, 5,6-dihydrobenzo[h]quinazolinyl, 5,6-dihydrobenzo[h]cinnolinyl, 6,7-dihydro-5H-benzo[6,7]cycloheptano[1,2-c]pyridazinyl, dibenzofuranyl, dibenzothienoyl, furanyl, furanoneyl, furan[3, 2-c]pyridyl, 5,6,7,8,9,10-hexahydrocyclooctano[d]pyrimidinyl, 5,6,7,8,9,10-hexahydrocyclooctano[d]pyridazinyl, 5,6,7,8,9,10-hexahydrocyclooctano[d]pyridyl, isothiazolyl, imidazolyl, indazolyl, indole, isoindole, dihydroindole, isodihydroindole, isoquinolinyl, indolizinyl, isoxazolyl, 5,8-methanol-5,6,7,8-tetrahydroquinazolinyl (5,8-methano-5,6,7,8-tetrahydroquinazolinyl), naphthyridinyl, 1,6-naphthyridinonyl, oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl, 5,6,6a,7,8,9,10,10a-octahydrobenzo[H]quinazolinyl, 1-phenyl-1H-pyrroleyl, phenazinyl, phenothiazinyl, phenotoxazinyl, phthalazinyl, pteridinyl, purine, pyrroleyl, pyrazolyl, pyrazolo[3,4-d]pyrimidinyl, pyridinyl, pyrido[3,2-d]pyrimidinyl, pyridinyl Pyridinyl[3,4-d]pyrimidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrroloyl, quinoxalinyl, quinolinyl, tetrahydroquinolinyl, 5,6,7,8-tetrahydroquinazalinyl, 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidinyl, 6,7,8,9-tetrahydro-5H-cycloheptano[4,5]thieno[2,3-] [d]pyrimidinyl, 5,6,7,8-tetrahydropyrido[4,5-c]pyridazinyl, thiazolyl, thiadiazolyl, triazolyl, tetrazolyl, triazinyl, thieno[2,3-d]pyrimidinyl, thieno[3,2-d]pyrimidinyl, thieno[2,3-c]pyridinyl (thieno[2,3-c]pridinyl), and thiophenyl / thienyl. Heteroaryl groups are a subset of heteroaryl groups, referring to residues identical to heteroaryl groups but with two linkage sites. As used herein, “halogenated” or “halogenated” refers to fluorinated, chlorinated, bromine, and iodinated substances, and the term “halogen” includes fluorine, chlorine, bromine, and iodine. As used herein, “haloalkyl” means an alkyl group as defined above in which a specified number of carbon atoms are replaced by one or more, up to a maximum permissible number of halogen atoms. Examples of haloalkyl groups include, but are not limited to, trifluoromethyl, difluoromethyl, 2-fluoroethyl, and pentafluoroethyl. Various hydroxyl protecting groups, such as hydroxyl or amino protecting groups, may be used in this disclosure. Generally, protecting groups insensitize chemical functional groups to specific reaction conditions and can be added to and removed from the functional group in a molecule without substantially impairing the rest of the molecule. Representative hydroxyl protecting groups are disclosed in Beaucage et al., Tetrahedron 1992, 48, 2223-2311, and Peter GMWuts, Greene's Protective Groups in Organic Synthesis, Chapter 2, 5th edition, John Wiley & Sons, Inc., New Jersey, 2014, all of which are incorporated herein by reference in their entirety. In some embodiments, the protecting group is stable under basic conditions but can be removed under acidic conditions. In some embodiments, non-exclusive examples of hydroxyl protecting groups that may be used herein include 9-phenyloxanthracene-9-yl (Pixyl) and 9-(p-methoxyphenyl)oxanthracene-9-yl (Mox). In some embodiments, non-exclusive examples of hydroxyl protecting groups that may be used herein include Tr (triphenylmethyl), MMTr (4-methoxytriphenylmethyl), DMTr (4,4'-dimethoxytriphenylmethyl), and TMTr (4,',4”-trimethoxytriphenylmethyl). The term “subject” as used herein refers to any animal, such as a mammal or marsupial. Subjects in this disclosure include, but are not limited to, humans, non-human primates (e.g., rhesus monkeys or other types of macaques), mice, pigs, horses, donkeys, cattle, rabbits, sheep, rats, and any kind of poultry. In some embodiments, “subject” refers to a mammal, such as a rodent or primate. In some embodiments, “subject” refers to a mouse, rat, or non-human primate. In some embodiments, “subject” refers to a human subject. As used herein, “treatment” refers to a method of achieving a beneficial or desired outcome, including but not limited to treatment benefits. A “treatment benefit” means the eradication or improvement of the underlying disorder being treated. Furthermore, a treatment benefit is achieved by eradicating or improving one or more physical symptoms associated with the underlying disorder, thereby observing improvement in the subject, even though the subject may still be suffering from the underlying disorder. As used herein, “prevention” refers to methods for obtaining a beneficial or desired outcome, including but not limited to preventive benefits. To obtain a “preventive benefit,” siRNA, siRNA conjugates, or pharmaceutical compositions may be administered to subjects at risk of developing a specific disease, or to subjects reporting one or more physiological symptoms of a disease, even if a diagnosis of the disease may not have been made. In some embodiments, “prevention” includes reducing or eliminating the risk of a specific disease by intervening in the levels of PKK mRNA or PKK protein in subjects at risk of developing the specific disease before the risk progresses to a defined disease course. Unless otherwise specified, in the context of any reference to the siRNA and / or siRNA conjugates described in the applications or methods provided in this disclosure, including but not limited to any siRNA and / or siRNA conjugates represented by any structural formula described in the applications or methods provided in this disclosure, the reference may also refer to a pharmaceutically acceptable salt of the siRNA and / or the conjugate, depending on the context. This disclosed siRNA The mechanism of action of siRNA is to silence the expression of specific genes through RNA interference. Therefore, if it can be effectively delivered to hepatocytes, siRNA targeting PKK can inhibit the expression of PKK mRNA in the liver. In one aspect, this disclosure provides an siRNA containing a sense strand and an antisense strand, each nucleotide in the siRNA being independently modified, the sense strand and the antisense strand being at least partially anticomplementary to form a double-stranded region, the length and composition of the antisense strand enabling the siRNA to inhibit PKK via an RNAi mechanism. The expression of mRNA, wherein the sense strand contains only two fluorinated nucleotides, and in the 3'-5' direction, two of the 11th-13th nucleotides of the sense strand are fluorinated nucleotides, and the remaining nucleotide is an alkoxylated nucleotide; the antisense strand contains 5-10 fluorinated nucleotides, and in the 5'-3' direction, the 2nd and 14th nucleotides of the antisense strand are fluorinated nucleotides, one of the 6th-8th nucleotides is a fluorinated nucleotide, one of the 15th-17th nucleotides is a fluorinated nucleotide, and one of the 11th-13th nucleotides is a fluorinated nucleotide, which is complementary to the alkoxylated nucleotide in the 11th-13th nucleotides of the sense strand in the 3'-5' direction to form a base pair. The inventors unexpectedly discovered that the siRNA and siRNA conjugates described in this disclosure have good stability and PKK mRNA inhibitory activity in cells and / or in subjects, and can treat and / or prevent diseases and / or symptoms related to PKK mRNA expression level and / or PKK protein expression level by regulating / altering the expression level of PKK mRNA, thus showing good application prospects. In the siRNA disclosed herein, the sense and antisense strands may be of the same or different lengths. In some embodiments, the lengths of the sense and antisense strands are 19-26 nucleotides. In some embodiments, the length difference between the sense and antisense strands is 0-5 nucleotides. In some embodiments, the length of the sense strand is not greater than the length of the antisense strand. In some embodiments, the length of the sense strand is 19-23 nucleotides, and the length of the antisense strand is 19-26 nucleotides. Therefore, the ratio of the lengths of the sense and antisense strands in the siRNA of this disclosure can be 19 / 19, 19 / 20, 19 / 21, 19 / 22, 20 / 20, 20 / 21, 20 / 22, 20 / 23, 21 / 21, 21 / 22, 21 / 23, 21 / 24, 22 / 22, 22 / 23, 22 / 24, 22 / 25, 23 / 23, 23 / 24, 23 / 25, or 23 / 26. In some embodiments, for ease of synthesis, the length of the sense strand is 19-21 nucleotides, and the length of the antisense strand is 19-23 nucleotides. In some embodiments, the sense strand and antisense strand are of the same length, each independently being 19, 20, or 21 nucleotides. In some embodiments, the length of the sense strand is 19-21 nucleotides, and the length of the antisense strand is 20-24 nucleotides, with the antisense strand being 1-3 nucleotides longer than the sense strand. In some embodiments, the length of the antisense strand is 2 nucleotides longer than the sense strand. In some embodiments, the length of the sense strand is 19 nucleotides, and the length of the antisense strand is 20-24 nucleotides. In some embodiments, the length of the sense strand is 20 nucleotides, and the length of the antisense strand is 21-24 nucleotides. In some embodiments, the length of the sense strand is 21 nucleotides, and the length of the antisense strand is 22-24 nucleotides. In some embodiments, the length of the sense strand is 19 nucleotides, and the length of the antisense strand is 21 nucleotides. In some embodiments, the sense strand is 21 nucleotides long and the antisense strand is 21 nucleotides long. In some embodiments, the sense strand is 21 nucleotides long and the antisense strand is 23 nucleotides long. In this case, the siRNA and conjugates containing the siRNA described in this disclosure have a better balance between synthetic cost, stability, and RNAi activity. As previously stated, each nucleotide in the siRNA provided in this disclosure is independently a modified nucleotide, and the antisense strand contains 5-10 fluorinated nucleotides. In some embodiments, the antisense strand contains 5-8 fluorinated nucleotides. In some embodiments, the 2nd and 14th nucleotides of the antisense strand are fluorinated nucleotides along the 5'-3' direction, the 4th or 5th nucleotide is a fluorinated or alkoxy-modified nucleotide, one of the 6th-8th nucleotides is a fluorinated nucleotide, one of the 15th-17th nucleotides is a fluorinated nucleotide, the 18th or 19th nucleotide is a fluorinated or alkoxy-modified nucleotide, and one of the 11th-13th nucleotides is a fluorinated nucleotide, which forms a base pair complementary to the alkoxy-modified nucleotides in the 11th-13th nucleotides of the sense strand along the 3'-5' direction. In some embodiments, each nucleotide other than the fluorinated nucleotide in the siRNA is independently selected from one of alkoxy-modified nucleotides, substituted alkoxy-modified nucleotides, alkyl-modified nucleotides, substituted alkyl-modified nucleotides, amine-modified nucleotides, heat-labile nucleotides, BNA, or reverse debased deoxynucleotides. In some embodiments, the alkoxy-modified nucleotides are independently selected from C1-C3 alkoxy-modified nucleotides. In some embodiments, the substituted alkoxy-modified nucleotides are independently selected from substituted C1-C3 alkoxy-modified nucleotides. In some embodiments, the alkyl-modified nucleotides are independently selected from C1-C3 alkyl-modified nucleotides. In some embodiments, the substituted alkyl-modified nucleotides are independently selected from substituted C1-C3 alkyl-modified nucleotides. In this disclosure, "modified nucleotide" refers to a nucleotide in which the hydroxyl group at the 2' position of the ribose is replaced by another atom or group, or a nucleotide analogue. In some embodiments, the total number of substituted alkoxy-modified nucleotides, alkyl-modified nucleotides, substituted alkyl-modified nucleotides, amine-modified nucleotides, heat-labile nucleotides, BNA, or reverse debasedoxynucleotides does not exceed four. In some embodiments, the total number of substituted alkoxy-modified nucleotides, alkyl-modified nucleotides, substituted alkyl-modified nucleotides, amine-modified nucleotides, heat-labile nucleotides, or BNA does not exceed two. In some embodiments, the total number of substituted alkoxy-modified nucleotides, alkyl-modified nucleotides, substituted alkyl-modified nucleotides, amine-modified nucleotides, heat-labile nucleotides, or BNA does not exceed one. In some embodiments, each nucleotide other than the fluorinated nucleotide is independently selected from alkoxy-modified nucleotides or reverse debasedoxynucleotides, and the number of reverse debasedoxynucleotides does not exceed three. In some embodiments, the number of reverse debasedoxynucleotides does not exceed two. In some embodiments, the number of reverse debasedoxynucleotides is one. In some embodiments, the siRNA does not contain reverse debasedoxynucleotides. In some embodiments, the siRNA contains 1-3 inverted abasic deoxyribonucleotides (abbreviated as invab or ia, having the structure shown in formula (35) below). In some embodiments, the 3' terminal nucleotide and / or 5' terminal nucleotide of the positive strand are the inverted abasic deoxyribonucleotides. In some embodiments, the 3' terminal nucleotide of the positive strand is the inverted abasic deoxyribonucleotide. In some embodiments, the oxygen atom directly attached to the ribose ring as shown in formula (35) may be attached to the 3' phosphate group of the penultimate nucleotide of the positive strand. In some embodiments, the oxygen atom directly attached to the ribose ring as shown in formula (35) may be attached to the 3' phosphate group of the 3' terminal nucleotide of the positive strand, and the oxygen atom attached to the ribose ring via a methylene group as shown in formula (35) may be attached to a hydrogen atom, a hydroxyl protecting group, or a delivery group as described below. In some embodiments, the oxygen atom in Formula (35) that is connected to the ribose ring via a methylene group may be attached to the 5' phosphate group of the penultimate nucleotide at the 5' end of the positive strand. In some embodiments, the oxygen atom in Formula (35) that is connected to the ribose ring via a methylene group may be attached to the 5' phosphate group of the penultimate nucleotide at the 5' end of the positive strand, and the oxygen atom in Formula (35) that is directly attached to the ribose ring may be attached to a hydrogen atom, a hydroxyl protecting group, or a delivery group as described below. In the preceding and following text, “fluorinated nucleotides”, “2'-fluorinated nucleotides”, “nucleotides in which the 2'-hydroxyl group of the ribose group is replaced by fluorine” and “nucleotides with a 2'-fluorinated ribose group” have the same meaning, all referring to compounds in which the 2'-hydroxyl group of the nucleotide is replaced by fluorine, resulting in a compound with the structure shown in formula (7) below. Here, Base represents a nucleic acid base, such as A, U, G, C, or T. In this context, "thermally unstable nucleotide" refers to a nucleotide with a thermally unstable modification, wherein the thermally unstable modification is a modification that lowers the thermal dissociation temperature of the siRNA double strand by at least 0.5 °C compared to the siRNA double strand with an unmodified nucleotide at the corresponding position. Exemplary thermally unstable modifications can be found in the specification in PCT Publication WO2018 / 098328A1.

[0236] -

[0251] The thermal instability modification described in the paragraph. In some embodiments, the heat-labile nucleotide is a type of acyclic nucleotide or heteronucleotide. Acyclic nucleotides are a class of nucleotides formed by opening the sugar ring of a nucleotide. In some embodiments, acyclic nucleotides can be unblocking nucleic acids (UNA) or glycerol nucleic acids (GNA), wherein UNA is shown in formula (15) and GNA is shown in formula (16): In formulas (15) and (16) above, R is selected from H, OH or alkoxy (O-alkyl). Isonucleotides are compounds formed by altering the position of a base on the ribose ring in a nucleotide. In some embodiments, an isonucleotide can be a compound formed by moving a base from the 1'-position to the 2'-position or 3'-position on the ribose ring, as shown in formula (17) or (18). In the compounds of formulas (17)-(18) above, Base represents a nucleic acid base, such as A, U, G, C or T; R is selected from H, OH, F or non-fluorine groups as described above. In some embodiments, the heat-labile nucleotide is selected from one of the following: GNA as shown in formula (27A), 2'-OMe abasic nucleotide as shown in formula (27B), 3'-OMe modified nucleotide as shown in formula (27C), 5'-Me modified nucleotide as shown in formula (27D), SNA as shown in formula (27E), hGNA as shown in formula (27F), hhGNA as shown in formula (27G), mGNA as shown in formula (27H), TNA as shown in formula (27I), h'GNA as shown in formula (27J), UNA as shown in formula (27K), or a hyperspacer as shown in formula (27L). In the compounds of formulas (27A)-(27L) above, Base represents a nucleic acid base, such as A, U, G, C, or T; R 27 Selected from H, OH, F, alkoxy, alkyl, or substituted alkoxy groups. * indicates that the carbon atom is chiral, and the compound can be an R configuration, an S configuration, or a racemic mixture of R and S configurations. In some embodiments, each thermally unstable nucleotide is independently a GNA as shown in formula (27A). BNA refers to a restricted or inaccessible nucleotide. BNA can contain a five-, six-, or seven-membered ring with a bridging structure of a fixed C3'-endoglycan condensation. This bridge is typically incorporated into the 2'-, 4'-position of the ribose to provide a 2',4'-BNA nucleotide. In some embodiments, BNA can be LNA or cET BNA, where LNA is shown in formula (12) and cET BNA is shown in formula (13). In some embodiments, each BNA in the siRNA described in this disclosure refers to an LNA or cET BNA. In some embodiments, each modified nucleotide other than the fluorinated nucleotide in the siRNA provided in this disclosure is independently selected from alkoxy-modified nucleotides or reverse debased deoxynucleotides. In some embodiments, for ease of synthesis, each alkoxy-modified nucleotide is independently a 2'-methoxy-modified nucleotide, and the 2'-methoxy-modified nucleotide (2'-OMe) has the structure shown in formula (8). In some implementations, the sense strand is 19 nucleotides long and the antisense strand is 21 nucleotides long. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 6th, 12th, 14th, and 16th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 16th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 8th, 12th, 14th, and 16th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 12th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 7th, 11th, 14th, and 16th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 12th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 7th, 13th, 14th, and 16th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently a methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 15th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 17th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 5th, 7th, 12th, 14th, 16th, and 19th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 5th, 7th, 12th, 14th, 16th, and 18th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. In some embodiments, in the siRNA provided in this disclosure, along the 3'-5' direction, the first nucleotide of the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide; along the 5'-3' direction, the 2nd, 4th, 7th, 12th, 14th, 16th, and 18th nucleotides of the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently alkoxylated nucleotide. In some embodiments, each alkoxylated nucleotide is independently methoxylated nucleotide. The inventors have specifically discovered that the siRNA with the above-mentioned modification provided in this disclosure can effectively maintain the high inhibitory activity of siRNA and siRNA conjugate against PKK mRNA while maintaining stability. In some embodiments, in the siRNA provided in this disclosure, each of 1-4 of the linking groups between adjacent nucleotides in the 5' ends of the first to fifth nucleotides of the sense and antisense strands is independently a phosphate ester group with a modifying group. In some embodiments, in the siRNA provided in this disclosure, each of the linking groups between adjacent nucleotides in the 5' ends of the first to third nucleotides of the sense and antisense strands is independently a phosphate ester group with a modifying group. In some embodiments, in the siRNA provided in this disclosure, each of 1-4 of the linking groups between adjacent nucleotides in the 3' ends of the first to fifth nucleotides of the sense and antisense strands is independently a phosphate ester group with a modifying group. In some embodiments, in the siRNA provided in this disclosure, each of the linking groups between adjacent nucleotides in the 3' ends of the first to third nucleotides of the sense and antisense strands is independently a phosphate ester group with a modifying group. In some embodiments, the linking group between every two adjacent nucleotides in the 5' and / or 3' ends of the first-2, 1-3, 1-4, or 1-5 nucleotides of the sense and antisense strands is a thiophosphate group, and the remaining adjacent nucleotides are linked by phosphate groups. In some embodiments, the linking group between every two adjacent nucleotides in the 5' ends of the first-2, 1-3, 1-4, or 1-5 nucleotides of the sense and antisense strands is a thiophosphate group, and the remaining adjacent nucleotides are linked by phosphate groups. In some embodiments, the linking group between every two adjacent nucleotides in the 3' ends of the first-2, 1-3, 1-4, or 1-5 nucleotides of the sense and antisense strands is a thiophosphate group, and the remaining adjacent nucleotides are linked by phosphate groups. In some embodiments, all adjacent nucleotides in the sense strand are linked by phosphate groups. Without being theoretically limited, the modified phosphate ester group can enhance the resistance of the siRNA disclosed herein to exonuclease activity and improve the stability of the siRNA in the subject's body. In some embodiments, the siRNA of the present disclosure containing the modified phosphate ester group and the siRNA conjugates exhibit better PKK mRNA inhibitory activity and / or longer duration of action. In some embodiments, each phosphate group having a modifying group is independently a thiophosphate group having the structure shown in formula (28): In some embodiments, the 5'-terminal nucleotide of the antisense strand is a 5'-hydroxynucleotide, a 5'-phosphate nucleotide, or a 5'-phosphate analog-modified nucleotide, wherein the 5'-hydroxynucleotide has the structure shown in formula (29); the 5'-phosphate nucleotide has the structure shown in formula (30); and the 5'-phosphate analog-modified nucleotide has a structure selected from those shown in formulas (31) to (34). R is selected from H, OH, OCH3 and F; Base represents a nucleic acid base, selected from A, U, C, G or T. In some embodiments, the 5'-phosphate nucleotide is a nucleotide containing a 5'-phosphate modification as shown in formula (30), the 5'-phosphate analog modified nucleotide is a nucleotide containing a vinyl phosphate (5'-(E)-vinylphosphonate, E-VP) modification as shown in formula (31), or a phosphate thioester modified nucleotide as shown in formula (33). In some embodiments, the 5'-terminal nucleotide of the antisense strand is a 5'-hydroxy nucleotide or a nucleotide containing a vinyl phosphate (5'-(E)-vinylphosphonate, E-VP) modification. In some embodiments, the 5'-terminal nucleotide being a vinyl phosphate (5'-(E)-vinylphosphonate, E-VP) modified nucleotide can further increase one or more of the stability, in vivo pharmacodynamic activity, and long-lasting effect of the siRNA and siRNA conjugates described in this disclosure. The siRNA disclosed herein, through the aforementioned modification scheme, achieves a good balance between gene expression regulatory activity and in vivo stability. In the context of this disclosure, "modification scheme" refers to a combination of nucleotide ribose modifications, phosphate modifications, 5' end modifications, and / or base modifications of different numbers, positions, and types that are unrelated to or weakly related to a specific sequence. In some embodiments, the siRNA of this disclosure, through the aforementioned modification scheme, can maintain excellent stability without significantly reducing the original drug activity of the siRNA, thereby achieving a good balance between gene expression regulatory activity and in vivo stability. In some embodiments, the siRNA of this disclosure, through the aforementioned modification scheme, can maintain excellent stability without significantly reducing the original RNAi activity of the siRNA, thereby achieving a good balance between PKK mRNA inhibitory activity and in vivo stability. As previously described, the length and composition of the antisense strand of the siRNA disclosed herein enable the siRNA to inhibit PKK mRNA expression via RNAi mechanism. In some embodiments, the antisense strand of the siRNA disclosed herein is sufficiently complementary to the PKK mRNA. In the context of this disclosure, "sufficiently complementary" means that the complementarity between the antisense strand of the siRNA disclosed herein and the PKK mRNA is sufficient to reduce or eliminate the production of the protein encoded by the PKK mRNA through RNAi action. In some embodiments, "sufficiently complementary" means that the antisense strand of the siRNA disclosed herein is substantially anticomplementary, substantially anticomplementary, or completely anticomplementary to the PKK mRNA across at least 16 nucleotides, for example, across 16-25 nucleotides, across 18-23 nucleotides, or across 19-21 nucleotides. In some embodiments, the nucleotide sequence of the antisense strand other than position 1 is completely anticomplementary to the PKK mRNA along the 5'-3' direction. In some embodiments, all nucleotides of the antisense strand are completely anticomplementary to the PKK mRNA. In some embodiments, the two nucleotide sequences that are “fully complementary” may include completely anticomplementary internal regions (e.g., completely anticomplementary across a length of at least 6, 8, or 10 nucleotides). In some embodiments, the antisense strand of the siRNA described herein is completely anticomplementary to the PKK mRNA at least within a seed region. The “seed region” refers to the region of nucleotides 2-8 of the antisense strand of the siRNA described herein, where the antisense strand of the siRNA can better mediate RNAi action and suppress PKK mRNA levels. In some embodiments, the antisense strand is substantially anticomplementary, substantially anticomplementary, or completely anticomplementary to a continuous nucleotide sequence m in the PKK mRNA; the length of the nucleotide sequence m is not greater than the length of the antisense strand, and the length of the nucleotide sequence m is the same as or differs from the length of the antisense strand by no more than 8 nucleotides, or by 1-5 nucleotides. As previously stated, nucleotide sequence m is a continuous nucleotide sequence in PKK mRNA. In some embodiments, nucleotide sequence m is a segment of the nucleotide sequence shown in SEQ ID NO:3 or SEQ ID NO:4 below: 5'-AATTATACTGAATTCCAAAAACCAATATGCC-3'(SEQ ID NO:3) In some embodiments, the nucleotide sequence m of 5'-AATTACACTGAATTCCAAAAACCAATATGCC-3' (SEQ ID NO:4) has a length of at least 16 nucleotides, or 16-25 nucleotides, or 18-23 nucleotides, or 19-21 nucleotides. In some embodiments, the length of the nucleotide sequence m is 19, 21, or 23 nucleotides. In some embodiments, the antisense strand is the same length as the nucleotide sequence m, and at least the nucleotide sequence of the antisense strand other than the terminal nucleotide is completely anticomplementary to the nucleotide sequence m. Thus, the siRNA of this disclosure can further improve the inhibitory effect on PKK mRNA. In some embodiments, the nucleotide sequence of the antisense strand other than position 1 is completely anticomplementary to the nucleotide sequence m in the 5'-3' direction. In some embodiments, all nucleotides of the antisense strand are completely anticomplementary to the nucleotide sequence m. In the siRNA described in this disclosure, the sense strand and the antisense strand are at least partially anticomplementary to form a double-stranded region. In some embodiments, the length of the double-stranded region formed by the sense strand and the antisense strand is at least 16 nucleotides. In some embodiments, the length of the double-stranded region formed by the sense strand and the antisense strand is 16-23 nucleotides. In some embodiments, the length of the double-stranded region formed by the sense strand and the antisense strand is 18, 19, 20, or 21 nucleotides. In some embodiments, the sense strand and the antisense strand are substantially anticomplementary, substantially anticomplementary, or completely anticomplementary. In some embodiments, the sense strand and the antisense strand are substantially anticomplementary or completely anticomplementary within the double-stranded region. In some embodiments, along the 5'-3' direction, at least the nucleotide sequence of the sense strand other than the first and last positions is substantially anticomplementary or completely anticomplementary to the antisense strand. In some embodiments, along the 5'-3' direction, the nucleotide sequence of the sense strand other than the last position is completely anticomplementary to the antisense strand; or all nucleotides of the sense strand are completely anticomplementary to the antisense strand. In some embodiments, the unmodified equivalent sequence of the positive strand of the siRNA described herein comprises a nucleotide sequence of the same length as the nucleotide sequence m, and differing by no more than 3 bases, no more than 1 base, or having no base difference. The definition and selection of the nucleotide sequence m are as described above. In the preceding and following text, a "base difference" between one nucleotide sequence and another means that the base type of the nucleotide at the same position has changed compared to the latter. For example, if a nucleotide base in the latter is A, and the corresponding nucleotide base at the same position in the former is U, C, G, or T, then a base difference exists between the two nucleotide sequences at that position. When bases are modified, as long as the purine-pyrimidine pairing relationship used to form the siRNA structure is not affected, it is also considered that there is no base difference between the modified base and the original base. In some embodiments, it is considered that there is no base difference between U and T. In some embodiments, it is considered that there is no base difference between C and 5-methylcytosine (5mC). In some implementations, a base difference at a given position can also be considered to have occurred when a baseless nucleotide or its equivalent is replaced. When comparing two nucleotide sequences to determine the number of base differences, alignment is performed using the method that minimizes the number of base differences among all alignment methods, and the base differences are determined based on this alignment. In this case, "identical positions" refers to the corresponding positions between the two nucleotide sequences in that alignment. For example, when positions 1-5 of nucleotide sequence A are aligned with positions 2-6 of nucleotide sequence B in the same direction, the number of base differences is minimized compared to other alignment methods. Therefore, "identical positions" means that position 1 of nucleotide sequence A is aligned with position 2 of nucleotide sequence B, position 2 of nucleotide sequence A is aligned with position 3 of nucleotide sequence B, and so on. In some embodiments, the number of base differences between two nucleotide sequences of different lengths refers to the number of base differences calculated from the first nucleotide without a base difference to the last nucleotide without a base difference in the alignment with the minimum number of base differences. In some embodiments, the number of base differences between two nucleotide sequences of the same length refers to the total number of base differences between the first to last nucleotides of one nucleotide sequence and the first to last nucleotides of the other nucleotide sequence, in the same direction. In some embodiments, the absence of base differences between two nucleotide sequences of different lengths means that, in the same direction, there are no base differences between the first to last nucleotides of the shorter nucleotide sequence and each nucleotide at the same position in the other nucleotide sequence. In some embodiments, the absence of base differences between two nucleotide sequences of the same length means that, in the same direction, there are no base differences between the first to last nucleotides of one nucleotide sequence and the first to last nucleotides of the other nucleotide sequence. In some embodiments, the siRNA of this disclosure contains a sense strand and an antisense strand. The sense strand contains a nucleotide sequence I, and the antisense strand contains a nucleotide sequence II. Both nucleotide sequences I and II are 19 nucleotides in length. Nucleotide sequences I and II are substantially anticomplementary, substantially anticomplementary, or completely anticomplementary to form a double-stranded region. Nucleotide sequence I is the same length as the nucleotide sequence shown in SEQ ID NO:1, and differs by no more than 3 bases. Nucleotide sequence II is the same length as the nucleotide sequence shown in SEQ ID NO:2, and differs by no more than 3 bases. 5'-CUGAAUUCCAAAAACCAAZ1-3' (SEQ ID NO: 1); 5'-Z2UUGGUUUUUGGAAUUCAG-3'(SEQ ID NO:2), Wherein, Z1 is A, U or reverse debased deoxynucleotide, Z2 is U or A, the nucleotide sequence I contains nucleotide Z3 corresponding to Z1, the nucleotide sequence II contains nucleotide Z4 corresponding to Z2, and Z4 is the first nucleotide at the 5' end of the antisense strand, wherein Z3 and Z4 are selected from A, U, C, G, T or reverse debased deoxynucleotide, respectively. In the preceding and following text of this disclosure, "positional correspondence" means that the nucleotides are located at the same position in the nucleotide sequence, starting from the same end. For example, the first nucleotide Z3 at the 3' end of nucleotide sequence I is the nucleotide that corresponds to the first nucleotide Z1 at the 3' end of SEQ ID NO:1, and the first nucleotide Z4 at the 5' end of nucleotide sequence II is the nucleotide that corresponds to the first nucleotide Z2 at the 5' end of SEQ ID NO:2. In some embodiments, the sense strand contains only nucleotide sequence I, and the antisense strand contains only nucleotide sequence II. In some embodiments, there is one base difference or no base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1, and / or there is one base difference or no base difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2. The base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1 may include a difference at position Z3 and / or a base difference at any other nucleotide position in nucleotide sequence I. In some embodiments, the base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1 may include a base difference at position Z3 and / or a base difference at a nucleotide position adjacent to Z3. In some embodiments, the base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1 is a base difference at position Z3. In some embodiments, Z3 is G or C. In some embodiments, there is no base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1. In some embodiments, Z3 is an alkoxy-modified nucleotide or a reverse-deoxy-debased nucleotide. In some embodiments, the difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2 includes a difference at the Z4 position, where Z4 is selected from C or G. In some embodiments, the difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2 is a difference at the Z4 position, where Z4 is selected from C or G. In some embodiments, there is no base difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2. In some embodiments, Z4 is an alkoxy-modified nucleotide or a 5'-vinyl phosphate-modified nucleotide. In some embodiments, nucleotides 3-19 of nucleotide sequence II are completely anticomplementary to PKK mRNA in the 5'-3' direction. In some embodiments, nucleotide sequence II is completely anticomplementary to nucleotide sequence I. Alternatively, a base mismatch exists between the second nucleotide of nucleotide sequence II in the 5'-3' direction and the second nucleotide of nucleotide sequence I in the 3'-5' direction. By including this base mismatch, high PKK mRNA inhibitory activity can be achieved while maintaining low off-target effects. In some embodiments, the sense strand further contains nucleotide sequence III, and the antisense strand further contains nucleotide sequence IV, each nucleotide of nucleotide sequence III and nucleotide sequence IV being independently a non-fluorinated nucleotide, the length of nucleotide sequence III being 1, 2, 3, or 4 nucleotides, the length of nucleotide sequence IV being equal to that of nucleotide sequence III, nucleotide sequence III being attached to the 5' end of nucleotide sequence I, and nucleotide sequence IV being attached to the 3' end of nucleotide sequence II, and nucleotide sequence IV and nucleotide sequence III being substantially anticomplementary or completely anticomplementary, wherein substantially anticomplementary means that there is no more than one base mismatch between the two nucleotide sequences; and completely anticomplementary means that there is no mismatch between the two nucleotide sequences. In some embodiments, nucleotide sequences III and IV are both 1 nucleotide in length along the 5'-3' direction, with bases A in nucleotide sequence III and U in nucleotide sequence IV; in this case, the length ratio of the positive and negative strands is 20 / 20. Alternatively, nucleotide sequences III and IV are both 2 nucleotides in length, with bases UA in nucleotide sequence III and UA in nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 21 / 21. Alternatively, nucleotide sequences III and IV are both 3 nucleotides in length, with bases AUA in nucleotide sequence III and UAU in nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 22 / 22. Alternatively, nucleotide sequences III and IV are both 4 nucleotides in length, with bases UAUA in nucleotide sequence III and UAUA in nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 23 / 23. In some embodiments, nucleotide sequences III and IV are 2 nucleotides in length, with the base composition of nucleotide sequence III being UA and the base composition of nucleotide sequence IV being UA in the 5'-3' orientation; in this case, the length ratio of the sense strand to the antisense strand is 21 / 21. In some embodiments, each nucleotide of nucleotide sequence III and nucleotide sequence IV is independently a methoxylated nucleotide. In some embodiments, nucleotide sequences III and IV are both 1 nucleotide in length along the 5'-3' direction, with bases A for nucleotide sequence III and U for nucleotide sequence IV; in this case, the length ratio of the positive and negative strands is 20 / 20. Alternatively, nucleotide sequences III and IV are both 2 nucleotides in length, with bases CA for nucleotide sequence III and UG for nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 21 / 21. Alternatively, nucleotide sequences III and IV are both 3 nucleotides in length, with bases ACA for nucleotide sequence III and UGU for nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 22 / 22. Alternatively, nucleotide sequences III and IV are both 4 nucleotides in length, with bases UACA for nucleotide sequence III and UGUA for nucleotide sequence IV along the 5'-3' direction; in this case, the length ratio of the positive and negative strands is 23 / 23. In some embodiments, nucleotide sequences III and IV are 2 nucleotides in length, with the base composition of nucleotide sequence III being CA and the base composition of nucleotide sequence IV being UG in the 5'-3' orientation; in this case, the length ratio of the sense strand to the antisense strand is 21 / 21. In some embodiments, each nucleotide of nucleotide sequence III and nucleotide sequence IV is independently a methoxylated nucleotide. In some embodiments, the antisense strand of this disclosure further includes a nucleotide sequence V, each nucleotide of which is independently a non-fluorinated nucleotide, the nucleotide sequence V being 1 to 3 nucleotides in length and attached to the 3' end of the antisense strand, forming a 3' overhanging end of the antisense strand after siRNA formation. In some embodiments, the nucleotide sequence V is 1 to 3 nucleotides in length and attached to the 3' end of nucleotide sequence II or IV. In some embodiments, the nucleotide sequence V is 2 to 3 nucleotides in length, each nucleotide in the nucleotide sequence V being independently a methoxylated nucleotide. In some embodiments, to obtain good pharmaceutical activity, the nucleotide sequence V is 2 nucleotides in length and, in the 5'-3' orientation, consists of two consecutive thymine deoxyribonucleotides, two consecutive uracil ribonucleotides, or is completely reverse complementary to PKK mRNA. In some embodiments, the nucleotide sequence V is attached to the 3' end of nucleotide sequence II, and, in the 5'-3' orientation, the base composition of the nucleotide sequence V is UU, UA, or UG. In some embodiments, the nucleotide sequence V is attached to the 3' end of the nucleotide sequence II, and the base composition of the nucleotide sequence V is UU, UA, or UG in the 5'-3' orientation, wherein U is a methoxy-modified nucleotide or GNA, and A or G is a methoxy-modified nucleotide. In some embodiments, the sense strand of the siRNA contains a nucleotide sequence as shown in SEQ ID NO:5, and the antisense strand contains a nucleotide sequence as shown in SEQ ID NO:6. 5'-CUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO:5); 5'-Z4UUGGUUUUUGGAAUUCAGUA-3' (SEQ ID NO: 6); Wherein, Z4 is the first nucleotide at the 5' end of the antisense strand, Z3 is selected from A, U or reverse debased deoxynucleotide, and Z4 is selected from A or U. In some embodiments, the sense strand of the siRNA contains a nucleotide sequence as shown in SEQ ID NO:7, and the antisense strand contains a nucleotide sequence as shown in SEQ ID NO:8. 5'-UACUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO:7); 5'-Z4UUGGUUUUUGGAAUUCAGUAUA-3' (SEQ ID NO:8); Wherein, Z4 is the first nucleotide at the 5' end of the antisense strand, Z3 is selected from A, U or reverse debased deoxynucleotide, and Z4 is selected from A or U. In some embodiments, the sense strand of the siRNA contains a nucleotide sequence as shown in SEQ ID NO:41, and the antisense strand contains a nucleotide sequence as shown in SEQ ID NO:42. 5'-CACUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO: 41); 5'-Z4UUGGUUUUUGGAAUUCAGUGUA-3' (SEQ ID NO: 42); Wherein, Z4 is the first nucleotide at the 5' end of the antisense strand, Z3 is selected from A, U or reverse debased deoxynucleotide, and Z4 is selected from A or U. In some implementations, the siRNA is siPKK1, siPKK2, or siPKK3: siPKK1 Chain of Justice: 5'-CUGAAUUCCAAAAACCAAia-3'(SEQ ID NO:9) Antonym: 5'-AUUGGUUUUUGGAAUUCAGUA-3' (SEQ ID NO:10) siPKK2 Justice chain: 5'-UACUGAAUUCCAAAAACCAAia-3' (SEQ ID NO:11) Antisense chain: 5'-AUUGGUUUUUGGAAUUCAGUAUA-3' (SEQ ID NO:12) siPKK3 Chain of Justice: 5'-CACUGAAUUCCAAAAACCAAia-3'(SEQ ID NO:43) Antonym: 5'-AUUGGUUUUUGGAAUUCAGUGUA-3' (SEQ ID NO:44) Wherein, ia refers to the reverse debased deoxynucleotide. In some embodiments, the sense strand of the siRNA described herein is identical to the sense strand of any one of siPKKa1-siPKKa10 listed in Table 1 for at least 15, at least 16, at least 17, at least 18, or 19 consecutive nucleotides, respectively, with no more than 3 base differences, no more than 1 base difference, or no base differences. The antisense strand of the siRNA described herein is identical to the antisense strand of any one of siPKKa1-siPKKa10 for at least 17, at least 18, at least 19, at least 20, or 21 consecutive nucleotides, respectively, with no more than 3 base differences, no more than 1 base difference, or no base differences. In some embodiments, the siRNA described herein is any one of siPKKa1, siPKKa2, siPKKa3, siPKKa4, siPKKa5, siPKKa6, siPKKa7, siPKKa8, siPKKa9, and siPKKa10 shown in Table 1 below. Table 1. siRNA sequences disclosed herein. In this context, uppercase letters C, G, U, A, and T represent the base composition of the nucleotide; lowercase letter o indicates that the nucleotide represented by the uppercase letter to the left of o is alkoxy-modified; lowercase letter f indicates that the nucleotide represented by the uppercase letter to the left of f is fluorinated; lowercase letter s indicates that the two nucleotides represented by the uppercase letters to its left and right are linked by a thiophosphate group; ia indicates a reverse debased deoxynucleotide; P1 indicates that the nucleotide represented by the uppercase letter to its right is a 5'-hydroxy nucleotide, a 5'-phosphate nucleotide, a 5'-thiophosphate modified nucleotide, or a 5'-vinylphosphate (5'-(E)-vinylphosphonate, E-VP) modified nucleotide. In some embodiments, each alkoxy-modified nucleotide is independently methoxy-modified. The siRNA provided in this disclosure can be obtained using conventional siRNA preparation methods in the art (e.g., solid-phase synthesis and liquid-phase synthesis). Solid-phase synthesis is already available as a commercially available custom service. Modified nucleotide groups can be introduced into the siRNA described in this disclosure using appropriately modified nucleoside monomers. Methods for preparing appropriately modified nucleoside monomers and for introducing modified nucleotide groups into siRNA are well known to those skilled in the art. All modified nucleoside monomers are commercially available or prepared using known methods. The siRNA provided in this disclosure can be used alone, or combined with a delivery group to form an siRNA conjugate, or combined with a pharmaceutically acceptable carrier to form a pharmaceutical composition, or used in any other suitable form. Contacting cells with an effective amount of the siRNA, siRNA conjugate, pharmaceutically acceptable salt, or one or more of the pharmaceutical composition can regulate PKK mRNA levels, or administering an effective amount of the siRNA, siRNA conjugate, pharmaceutically acceptable salt, or pharmaceutical composition to a subject can regulate PKK mRNA expression levels to achieve the purpose of treating pathological conditions or diseases associated with PKK mRNA expression levels. The siRNA conjugate disclosed herein In another aspect, this disclosure provides an siRNA conjugate containing an siRNA group and a delivery group conjugated to the siRNA group, the siRNA group being independently formed by removing one or more atoms or groups of atoms from the siRNA provided in this disclosure. In the context of this disclosure, unless otherwise stated, "conjugation" refers to the covalent connection between two or more chemical parts, each having a specific function; correspondingly, "conjugate" refers to a compound formed by the covalent connection of the respective chemical parts. Further, "siRNA conjugate" refers to a compound formed by the covalent connection of one or more conjugating groups and an siRNA group. The siRNA group refers to the chemical part formed by removing one or more atoms from an siRNA molecule. Those skilled in the art will understand that the RNAi activity of the siRNA group formed by this removal is at least the same as or equivalent to the RNAi activity of the siRNA itself. In some embodiments, the removal of one or more atoms or groups does not impair the inhibitory activity or stability of the siRNA against the target mRNA. In some embodiments, the siRNA group is a group formed by removing one atom or group (e.g., a hydrogen atom, a hydroxyl group, or a phosphate ester group) from the siRNA provided in this disclosure. For example, the siRNA group can be a chemical part formed by removing a hydrogen atom from the phosphate ester bond of siRNA, or a chemical part formed by removing a hydrogen atom from the 5' hydroxyl group of the 5' terminal nucleotide of the sense or antisense strand of siRNA, or a chemical part formed by removing a hydrogen atom from the 3' hydroxyl group of the 3' terminal nucleotide of the sense or antisense strand of siRNA. siRNA conjugates should be understood, depending on the context, as a collective term for multiple siRNA conjugates or a siRNA conjugate represented by a specific chemical formula. The delivery group is a group for delivering the siRNA group into cells expressing PKK mRNA. The delivery group in the siRNA conjugates disclosed herein can be any of the various delivery groups known to those skilled in the art of siRNA pharmacology. In some embodiments, the delivery group comprises a linker group and a pharmaceutically acceptable targeting group, and the siRNA group, the linker group, and the targeting group are sequentially covalently or non-covalently linked, each of the targeting groups being selected from ligands capable of binding to receptors on the surface of hepatocytes. In some embodiments, the number of targeting groups is 1-6. In one embodiment, the number of targeting groups is 2-4. The siRNA group is capable of regulating the expression level of PKK mRNA in the liver and can be non-covalently or covalently conjugated to the delivery group, for example, it can be covalently conjugated to the delivery group. The conjugation site between the siRNA group and the delivery group can be at the 3' or 5' end of the sense strand of the siRNA group, or at the 5' end of the antisense strand, or within the internal sequence of the siRNA group. In some embodiments, the conjugation site between the siRNA group and the delivery group is at the 3' end of the sense strand of the siRNA group. In some embodiments, the delivery group can be attached to any position on the nucleotide, such as a phosphate group, a 2', 3', or 5'-hydroxyl group of the ribose, or a base. When the delivery group is attached to the 3' or 5' end of the sense or antisense strand, it is typically attached to the oxygen atom formed by removing a hydrogen atom from the 3' or 5'-hydroxyl group of the nucleotide; when the delivery group is attached to an inner sequence of the sense or antisense strand, it is typically attached to a phosphate group, a ribose ring, or a base. In some embodiments, the delivery group can be attached to the 3'-hydroxyl group of an inner sequence nucleotide of the sense or antisense strand, in which case the nucleotides are linked by a 2'-5' phosphodiester bond. Various connection methods can be found in the following non-patent literature: Muthiah Manoharan et al. siRNA conjugates carrying sequentially assembled trivalent N-acetylgalactosamine linked through nucleosides elicit robust gene silencing in vivo in hepatocytes. ACS Chemical biology, 2015, 10(5): 1181-7. The entire contents of this article are incorporated herein by reference. In some embodiments, the siRNA group and the delivery group are linked by acid-labile or reducible chemical bonds. These bonds can degrade in the acidic environment of the endosome, thereby converting the siRNA group into free siRNA. For non-degradable conjugations, the delivery group can be attached to the positive strand of the siRNA group to minimize the impact of the conjugation on the activity of the siRNA group. The targeting group can be linked to the siRNA group via a suitable linker. Those skilled in the art can select a suitable linker based on the specific type of the targeting group. For example, when the targeting group is a group that targets receptors on the surface of hepatocytes, the types of these linkers, the types of targeting groups, and the way they are linked to the siRNA can be found in the disclosure of WO2015006740A2, the entire disclosure of which is incorporated herein by reference. In some embodiments, the targeting group can be a ligand commonly used in the field of siRNA drug delivery. For example, when the targeting group is a group that targets receptors on the surface of hepatocytes, various ligands can be seen, for example, described in WO2009082607A2, the disclosure of which is incorporated herein by reference in its entirety. In some embodiments, at least one or each of the target groups is selected from any ligand capable of binding to cell surface receptors of cells expressing PKK mRNA. In some embodiments, at least one or each of the target groups is independently selected from ligands capable of binding to receptors on the surface of mammalian liver cells. In some embodiments, at least one or each of the target groups is independently selected from small molecule ligand groups capable of affinity for desialylate glycoprotein receptors on the surface of hepatocytes. In some embodiments, at least one or each of the target groups is selected from ligands capable of binding to receptors on the surface of mammalian hepatocytes. In some embodiments, at least one or each of the target groups is independently a ligand with affinity for desialyl glycoprotein receptors on the surface of mammalian hepatocytes. In some embodiments, each of the target groups is independently a desialyl glycoprotein or a sugar. In some embodiments, each of the target groups is independently selected from D-mannose pyranoyl ... D-Furfuranose, β-D-Furfuranose, α-D-Fructose, α-D-Fructose, α-D-Galactopyranose, β-D-Galactopyranose, α-D-Galactopyranose, β-D-Galactopyranose, Glucosamine, Sialic acid, Galactosamine, N-acetylgalactosamine, N-trifluoroacetylgalactosamine, N-propionylgalactosamine, N-butyrylgalactosamine, N-isobutyrylgalactosamine, 2-Amino-3-O -[(R)-1-carboxyethyl]-2-deoxy-β-D-glucopyranose, 2-deoxy-2-methylamino-L-glucopyranose, 4,6-dideoxy-4-carboxamido-2,3-di-O-methyl-D-mannopyranose, 2-deoxy-2-sulfonamido-D-glucopyranose, N-ethanolyl-α-neuraminic acid, 5-thio-β-D-glucopyranose, 2,3,4-tri-O-acetyl-1- The target group is one of the following: thio-6-O-triphenylmethyl-α-D-glucopyranoside methyl ester, 4-thio-β-D-galactopyranose, 3,4,6,7-tetra-O-acetyl-2-deoxy-1,5-dithio-α-D-glucopyranoside ethyl ester, 2,5-dehydrated-D-alosulfonyl, ribose, D-ribose, D-4-thioribose, L-ribose, or a group formed by removing an atom or group from L-4-thioribose. In some embodiments, at least one or each of the target groups is a galactose group or an N-acetylgalactosamine group formed by removing an atom or group from galactose or N-acetylgalactosamine. In some embodiments, each of the target groups is an N-acetylgalactosamine group. In some embodiments, the linker group in the siRNA conjugate of this disclosure has a structure as shown in formula (301): Where k is an integer from 1 to 5, Indicates the site of covalent linkage of groups; all L A Connect to L C The same atom in; or, each L A Independently connected to L C Different atoms in it. In some implementations, L C It has -NH-C(H) n301 (CH2O-) k The structure shown is such that k is an integer from 1 to 3, and n301 = 3 - k; L B The length is 5-20 atoms. In some implementations, each L A Independently, it is a straight-chain alkylene group with a length of 5-20 carbon atoms, wherein one or more methylene groups are optionally replaced by any one or more groups selected from the group consisting of: C(O), NH, O, S, 1,2,3-triazole subunit, succinimide subunit. In some implementations, L A Having a structure containing amide bonds as shown in formula (302), L B It has a structure as shown in equation (303): Where, n 302 q 302 and p 302 Each is an independent integer from 2 to 6; optionally, n 302 q 302 and p 302 Each can be 2 or 3 independently; n 303 n is an integer between 4 and 16, optionally n 303 For integers between 8 and 12, This indicates the site where the group is covalently linked. In some embodiments, the linking group has a structure as shown in formula (304) or formula (305): In the linking group, each L A Each of the target groups is connected via an ether bond and via L C The oxygen atom of the hydroxyl group in some parts is related to L. C Partially linked by ether bonds; L B Through the carbonyl group in formula (303) and L CThe nitrogen atom of the amino group in some of them forms an amide bond and is connected to the siRNA group through the oxygen atom in formula (303) by forming a phosphate ester bond or a thiophosphate ester bond. In some embodiments, the siRNA conjugates provided in this disclosure have a structure as shown in formula (305A): Wherein, Nu represents the siRNA group formed by the siRNA provided in this disclosure. In some embodiments, the linker group in the siRNA conjugate of this disclosure has the structure shown in formula (306): Where, n 306 For each p, the integer is between 0 and 3. 306 Independently, integers from 1 to 6. The site indicates a covalently linked group; the linking group is connected to the target group by an ether bond formed by an oxygen atom marked with *; the linking group is connected to the siRNA by at least one of the oxygen atoms marked with # forming a phosphate ester bond or a thiophosphate ester bond, and the remaining oxygen atoms marked with # are connected to hydrogen atoms to form hydroxyl groups, or connected to C1-C3 alkyl groups to form C1-C3 alkoxy groups; In some embodiments, the siRNA conjugates of this disclosure have a structure as shown in formula (307): Wherein, Nu represents the siRNA group formed by the siRNA provided in this disclosure. In some embodiments, the siRNA conjugates of this disclosure have the structure shown in formula (308): in, n 308 The integers are selected from 2 to 4; Each m 308 Independently selected as an integer from 2 to 5; Each R 308 Independently, it can be a hydrogen atom, a methyl group, or an ethyl group, or two R atoms attached to the same carbon atom. 308 Together with this carbon atom, they form a carbonyl group; One of the groups represented by A0 is an siRNA group, which is the group formed by removing an atom or group of atoms from the siRNA described in this disclosure; each of the remaining A0 groups is an independent targeting group, and each targeting group may be the same or different, and their definition and selection range are as described above. In some embodiments, each targeting group is independently selected from a ligand that has an affinity for the desialylate glycoprotein receptor on the surface of mammalian hepatocytes. Each L1 is independently a divalent linker with a length of 1-70 atoms; This indicates the site where the group is covalently linked. In some embodiments, each L1 is independently a straight-chain alkylene group with a length of 1-70 carbon atoms, wherein one or more carbon atoms are optionally replaced by any one or more groups selected from the group consisting of: C(O), NH, O, S, CH=N, S(O)2, OP(O)2, OP(O)(S), C2-C 10 alkenyl, C2-C 10 Ethyne group, C6-C 10 Aromatic, C3-C 18 Heterocyclic groups and C5-C 10 Heteroaryl; and the linear alkylene group may optionally have substituents of any one or more of the group consisting of: C1-C 10 Alkyl, C6-C 10 Aryl, C5-C 10 heteroaryl, C1-C 10 Haloalkyl, -OC1-C 10 Alkyl, OC1-C 10 Alkylphenyl, -C1-C 10 Alkyl-OH, -OC1-C 10 Halogenated alkyl, -SC1-C 10 Alkyl, -SC1-C 10 Alkylphenyl, -C1-C 10 Alkyl-SH, -SC1-C 10 Halogenated alkyl groups, halogenated substituents, -OH, -SH, -NH2, -C1-C 10 Alkyl-NH2,-N(C1-C) 10 Alkyl) (C1-C 10 alkyl), -NH(C1-C 10 Alkyl), N(C1-C) 10 Alkyl) (C1-C 10 alkylphenyl), NH(C1-C 10 Alkylphenyl), cyano, nitro, -CO2H, -C(O)O(C1-C 10 Alkyl), -CON (C1-C) 10 Alkyl) (C1-C 10 Alkyl), -CONH (C1-C) 10 Alkyl groups, -CONH2, -NHC(O) (C1-C) 10 alkyl), -NHC(O)(phenyl), -N(C1-C 10 Alkyl)C(O)(C1-C10 Alkyl), -N(C1-C 10 alkyl)C(O)(phenyl), C(O)C1-C 10 Alkyl, C(O)C1-C 10 Alkylphenyl, C(O)C1-C 10 Haloalkyl, -OC(O)Cl-C 10 Alkyl group, -SO2 (C1-C) 10 alkyl), -SO2 (phenyl), -SO2 (C1-C 10 Halogenated alkyl groups), -SO2NH2, -SO2NH (C1-C 10 alkyl), -SO2NH (phenyl), -NHSO2 (C1-C 10 Alkyl), -NHSO2 (phenyl) and -NHSO2 (C1-C) 10 (Halogenated alkyl groups). Those skilled in the art will understand that, although for convenience, L1 is defined as a linking group formed by substitution or substitution of a linear alkylene group, it may not be a linear group or may have a different name, such as an amine or alkenyl group resulting from the aforementioned substitution and / or substitution. Unless otherwise stated, in the chemical structural formulas described in this disclosure, the “length” of any group refers to the number of atoms in the longest atomic chain of that group, excluding hydrogen atoms; in the calculation of group length, when multiple connections are involved between two atoms (e.g., two atoms belong to the same cyclic group, and thus at least two atomic chains contain the two atoms), the length is calculated according to the shortest atomic chain between the two atoms. For example, 1,4-cyclohexanediyl, 1,4-piperidinediyl, 1,4-phenylene, and 1,4-piperazindiyl are all calculated as having a length of 4 atoms, while 1,2-cyclopentadiyl is calculated as having a length of only 2 atoms. The function of L1, covalently linked to A0 representing the siRNA group, is to covalently link the siRNA group to the target group. This allows the siRNA conjugate containing the siRNA group to enter cells expressing PKK mRNA through the targeting effect of the target group, without affecting the regulatory effect of the siRNA group on PKK mRNA expression after entry into the cells. Therefore, in some embodiments, the length of L1 covalently linked to A0 representing the siRNA group is 3-20 atoms, 4-15 atoms, or 5-12 atoms. In some embodiments, L1 covalently linked to A0 representing the siRNA group is selected from one or more of A1, A2, A4, A5, A10, A16, A18, and A19, combined with a phosphate ester group or a modified phosphate ester group. Where j1 is an integer between 2 and 10; This indicates the site where the group is covalently linked. In some embodiments, R2 is selected from at least two of A1, A2, A4, A10 and A16 connected with a phosphate ester group or a modified phosphate ester group; in some embodiments, R2 is selected from at least two of A1, A2, A10 connected with a phosphate ester group or a modified phosphate ester group. In some embodiments, L1, covalently linked to A0 representing the siRNA group, has a structure as shown in formulas (B1), (B2), (B3), or (B4): in, L represents the site where groups are covalently linked. B1 and L B2 Whether identical or different, independently selected from one of the following groups or any combination thereof: -(CH2) q1 -、-CH(OH)-、-CH(CH2OH)-、-NH-、-O-、-S-、1,4-cyclohexanediyl、1,4-piperidinidyl、1,4-phenylene、1,4-piperazinidyl、pyrrolidinediyl、where q1 is an integer from 1 to 6, L B1 and L B2 The length of each is independently 1-20 atoms. In some embodiments, L B1 and L B2 The length of each is independently 1-10 atoms. In some embodiments, L B1 and L B2 The length of each atom is independently 1-6 atoms. L B3 A group selected from phosphate ester groups, thiophosphate ester groups, and dithiophosphate ester groups is covalently linked to the 5' hydroxyl group at the 5' position of the ribose of the 5' terminal nucleotide of the sense or antisense strand of the siRNA group, or the oxygen atom remaining after removing one hydrogen atom from the 3' hydroxyl group of the ribose of the 3' terminal nucleotide. In some embodiments, L B3 It is a phosphate ester group, covalently linked to the 5' hydroxyl group of the ribose at the 5' end of the positive strand of the siRNA group, or the oxygen atom remaining after removing one hydrogen atom from the 3' hydroxyl group of the ribose at the 3' end of the siRNA group. In some embodiments, when the siRNA conjugates of this disclosure are prepared by a solid-phase synthesis process, L1, covalently linked to A0 representing the siRNA group, needs to simultaneously contain a linking site for N-linking to the nitrogen-containing backbone, a linking site for linking to the siRNA group, and a functional group capable of linking to a solid-phase support. In some embodiments, the N-linking site on the nitrogen-containing backbone in L1, covalently linked to A0 representing the siRNA group, forms an amide bond with N, is covalently linked to the siRNA group via a phosphate ester bond, and the functional group capable of linking to the solid-phase support is a hydroxyl or amino group. In some embodiments, R2 is B5, B6, B5', or B6'. in, This indicates the site where a group is covalently bonded. The value of q2 can be an integer from 1 to 10. In some implementations, q2 is an integer from 1 to 5. The function of L1 covalently linked to A0, representing the target group, is to position the target group in a suitable spatial location, thereby better binding to receptors on the surface of mammalian hepatocytes, and thus specifically targeting and entering the hepatocytes. Therefore, any L1 covalently linked to A0, representing the target group, can be used in this disclosure as long as it has an appropriate length and its chemical properties do not significantly affect delivery. In some embodiments, each L1 covalently linked to the target group is independently a divalent linker with a length of 3-25 atoms. In some embodiments, each L1 covalently linked to A0, representing the target group, has an independent length of 4-15 atoms. In some embodiments, each L1 covalently linked to A0, representing the target group, has a length of 5-10 atoms. In some embodiments, the length of each L1 covalently linked to A0, representing the target group, is the same. In some embodiments, each L1 covalently linked to A0 representing a target group may be the same or different, and is independently selected from the group consisting of groups represented by formulas (L3)-(L18) and any combination thereof: Where each j1 is an integer from 2 to 10; each R' is independently a hydrogen atom or a C1-C3 alkyl group. This indicates the site where the group is covalently linked. For ease of synthesis and / or chemical stability, in some embodiments, each L1 covalently linked to A0 representing a target group is independently a combination of at least two linking units, each linking unit independently having a structure shown in any one of formulas (L3)-(L7). In some embodiments, each linking unit independently has a structure shown in any one of formulas (L3), (L4), and (L7). For ease of synthesis, in some embodiments, each L1 covalently linked to A0 representing a target group includes a carbonyl group bonded to a nitrogen atom shown in formula (308). In some embodiments, each L1 covalently linked to A0 representing a target group independently has the structure shown in formula (L20) or (L21): Where j2 is an integer from 4 to 9, and j3 is 1 or 2. In some embodiments, j2 is 5, 6, or 7, and j3 is 1. In some embodiments, each L1 covalently linked to A0 representing the target group is identical. In the conjugates disclosed herein, the number of targeting groups and the spacing between them are the number and spacing that provide a suitable spatial configuration of multiple targeting groups. For this purpose, n308 and each m308 are independently integers selected from 2 to 4. In some embodiments, n308 is 3 or 4, so that the number of targeting groups in the conjugates of this disclosure is 3 or 4, which enables better binding to hepatocyte surface receptors. In some embodiments, n308 is 3, and each m308 is independently 3 or 4. Those skilled in the art will understand that each R 308 When the individual atoms are hydrogen atoms, methyl groups, or ethyl groups, the delivery efficiency of the siRNA conjugate is not affected, and the objectives of this disclosure can still be achieved. In some embodiments, for ease of synthesis, each R... 308 Each is an independent hydrogen atom. In some embodiments, the siRNA conjugates of this disclosure have the structure shown in formula (403): Wherein, Nu represents the siRNA group. In some embodiments, the P atom shown in the above structural formula is covalently linked to the 3' terminal nucleotide of the positive strand of the siRNA group. In some embodiments, the 3' terminal nucleotide of the positive strand of the siRNA group is a reverse debased deoxynucleotide, and the P atom shown in the above structural formula is covalently linked to the siRNA group by substituting a hydrogen atom in the hydroxyl group of the reverse debased deoxynucleotide of the positive strand of the siRNA group represented by Nu, which is connected to the ribose ring via a methylene group. In some embodiments, the P atom shown in formula (403) is covalently linked to the oxygen atom remaining after removing a hydrogen atom from the 3' position of the ribose hydroxyl group of the 3' terminal nucleotide of the positive strand of the siRNA group represented by Nu. In some embodiments, the P atom shown in formula (403) is covalently linked to the oxygen atom of the reverse debased deoxynucleotide ia shown in formula (35) at the 3' terminal of the positive strand of the siRNA group represented by Nu, which is connected to the ribose ring via a methylene group, thereby covalently linking to the positive strand of the siRNA group. In some embodiments, the siRNA conjugates of this disclosure may independently contain siRNA groups formed from, for example, the siRNAs listed in Table 1. siRNA conjugates containing these siRNA groups exhibit excellent stability and high PKK mRNA inhibitory activity. In some embodiments, the siRNA conjugates of this disclosure are one of conjugate 1-conjugate 4, conjugate 7-conjugate 16 shown in Table 2A. This disclosure relates to the preparation of siRNA conjugates. The aforementioned siRNA conjugates can be synthesized using methods already described in detail in the prior art. For example, WO2015006740A2 describes in detail various methods for preparing siRNA conjugates. In some embodiments, the siRNA conjugates disclosed herein can also be obtained using methods well known to those skilled in the art. For instance, WO2014025805A1 describes a method for preparing the structure shown in formula (305A), and Rajeev et al. describe a method for preparing the structure shown in formula (307) in ChemBioChem 2015, 16, 903-908. Chinese patent application CN110959011A also discloses in detail a method for preparing the siRNA conjugate shown in formula (308). The contents of the above-mentioned documents are incorporated herein by reference in their entirety. The pharmaceutically acceptable salts disclosed herein In another aspect, this disclosure also provides pharmaceutically acceptable salts of the siRNA or siRNA conjugates described herein. Pharmaceutically acceptable salts are known to those skilled in the art. By forming salts, the pharmaceutically acceptable salts of the siRNA or siRNA conjugates described herein may exhibit better solubility, bioavailability, or stability than the siRNA or siRNA conjugates themselves. In the siRNA or siRNA conjugates described in this disclosure, each adjacent nucleotide is linked by a phosphodiester bond or a phosphothiodiester bond. The non-bridging oxygen or sulfur atom in the phosphodiester bond or phosphothiodiester bond carries a negative charge and can exist in the form of a hydroxyl or mercapto group. The hydrogen ion in the hydroxyl or mercapto group can also be partially or completely replaced by a cation. The cation can be any cation, such as a metal cation, ammonium ion (NH4+). + The siRNA is one of the organic ammonium cations. Further, the delivery group may also contain a salt-forming group. For improved solubility and / or bioavailability, in some embodiments, the pharmaceutically acceptable salt is a partial or complete water-soluble salt of the siRNA or the siRNA conjugate. In some embodiments, the water-soluble salt may be an amine salt, an alkali metal salt, or an alkaline earth metal salt. In some embodiments, the amine salt is selected from one or more of ammonium salts, methylamine salts, tertiary amine salts, and quaternary ammonium salts; the alkali metal salt is selected from potassium salts or sodium salts; and the alkaline earth metal salt is selected from calcium salts or magnesium salts. In some embodiments, the tertiary amine salt is a triethylamine salt, a triisopropylamine salt, or an N,N-diisopropylethylamine salt. In some embodiments, the pharmaceutically acceptable salt of the siRNA or the siRNA conjugate is a salt or a partial salt of the siRNA or the siRNA conjugate, wherein the salt or partial salt is selected from one or more of ammonium salts, methylamine salts, and sodium salts. In some embodiments, the pharmaceutically acceptable salt is a sodium salt or a partial sodium salt of the siRNA or the siRNA conjugate. In some embodiments, the pharmaceutically acceptable salt is a mixture of a methylamine salt and an ammonium salt of the siRNA or the siRNA conjugate. The pharmaceutical compositions disclosed herein In another aspect, this disclosure also provides a pharmaceutical composition comprising one or more of the siRNA, siRNA conjugates and pharmaceutically acceptable salts provided in this disclosure, and pharmaceutically acceptable excipients. Pharmaceutically acceptable excipients are one or more of the various components commonly used in the art, such as solvents, protectants, osmotic pressure regulators, and one or more other pharmaceutically acceptable carriers. For example, when the pharmaceutical composition is an injection solution, the pharmaceutically acceptable excipient is a solvent, such as one or more of deionized water, water for injection, pH buffer, physiological saline, ethanol, and aqueous ethanol solution. The pH buffer may be a tris(hydroxymethyl)aminomethane hydrochloride buffer with a pH of 7.5-8.5 and / or a phosphate buffer with a pH of 5.5-8.5, for example, a phosphate buffer with a pH of 5.5-8.5. The amount of solvent used is adjusted according to the required solution concentration. The concentration of siRNA conjugate in the injection solution can be 0.01 mg / mL-20 mg / mL, 0.1 mg / mL-10 mg / mL, or 0.5 mg / mL-5 mg / mL (calculated as siRNA). The protective agent may be at least one selected from inositol, sorbitol, sucrose, trehalose, mannose, maltose, lactose, and glucose. Based on the total weight of the pharmaceutical composition, the content of the protective agent may be 0.01-30% by weight. The osmotic pressure regulator may be sodium chloride and / or potassium chloride. The content of the osmotic pressure regulator results in an osmotic pressure of 200-700 milliosm / kg (mOsm / kg) for the pharmaceutical composition. The content of the osmotic pressure regulator can be readily determined by those skilled in the art based on the desired osmotic pressure. In some embodiments, the dosage of the formulation made from the pharmaceutical composition may be adjusted during administration depending on the route of administration. In some embodiments, the pharmaceutical composition may be a liquid formulation, such as an injection; or it may be a lyophilized powder for injection, which is mixed with liquid excipients to form a liquid formulation for administration. The liquid formulation may be administered subcutaneously, intramuscularly, or intravenously, or may be delivered via a spray to the lungs, or via a spray to other organs (such as the liver), or orally. In some embodiments, the pharmaceutical composition is administered via subcutaneous injection. Other pharmaceutically acceptable carriers may be those conventionally used in the field of siRNA delivery, such as, but not limited to, magnetic nanoparticles (e.g., Fe3O4 or Fe2O3-based nanoparticles), carbon nanotubes, mesoporous silicon, calcium phosphate nanoparticles, polyethylenimine (PEI), polyamidoamine (PAMAM) dendrimer, poly(L-lysine) (PLL), chitosan, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), poly(D&L-lactic / glycolic acid) copolymer (PLGA), and poly(2-aminoethyl ethylene phosphate). One or more of the following: phosphate), PPEEA, and poly(2-dimethylaminoethyl methacrylate), PDMAEMA, and their derivatives. In some embodiments, there are no particular requirements for the content of siRNA and pharmaceutically acceptable carrier in the pharmaceutical composition. In some embodiments, the weight ratio of siRNA to pharmaceutically acceptable carrier can be 1:(1-500), and in some embodiments, the weight ratio is 1:(1-50). In some embodiments, the pharmaceutical composition may be in the form of a liposomal formulation. In some embodiments, the pharmaceutically acceptable carrier used in the liposomal formulation comprises an amine-containing transfection compound (hereinafter also referred to as an organic amine), a cofactor lipid, and / or a polyethylene glycol-modified lipid. The organic amine, cofactor lipid, and polyethylene glycol-modified lipid may be selected from one or more of the amine-containing transfection compounds or their pharmaceutically acceptable salts or derivatives, cofactor lipids, and polyethylene glycol-modified lipids described in Chinese patent application CN103380113A (which is incorporated herein by reference in its entirety). In some embodiments, the organic amine may be a compound of formula (201) as described in Chinese patent application CN103380113A, or a pharmaceutically acceptable salt thereof: in: X 101 and X 102 Each can be independently O, S, NA, or CA, where A is hydrogen or C1-C. 20 hydrocarbon chain; Y 101 and Z 101 Each can be independently C=O, C=S, S=O, CH-OH, or SO2; R 101 R 102 R 103 R 104 R 105 R 106 and R 107 Each is independently hydrogen, cyclic or acyclic, substituted or unsubstituted, branched or straight aliphatic group, cyclic or acyclic, substituted or unsubstituted, branched or straight heteroaliphatic group, substituted or unsubstituted, branched or straight acyl group, substituted or unsubstituted, branched or straight aryl group, substituted or unsubstituted, branched or straight heteroaryl group; x is an integer from 1 to 10; n is an integer from 1 to 3, m is an integer from 0 to 20, and p is 0 or 1; where, if m = p = 0, then R 102 It is hydrogen; Furthermore, if at least one of n or m is 2, then R 103 The nitrogen in formula (201) forms a structure as shown in formula (202) or formula (203): In this context, g, e, and f are each an integer from 1 to 6, "HCC" represents a hydrocarbon chain, and each *N represents a nitrogen atom in formula (201). In some implementations, R 103 It is a polyamine. In other embodiments, R 103 It is a ketal. In some embodiments, R in formula (201) 101 and R 102 Each of them is independently an arbitrary substituted or unsubstituted, branched or straight-chain alkyl or alkenyl group having 3 to 20 carbon atoms, such as 8 to 18 carbon atoms, and 0 to 4 double bonds, such as 0 to 2 double bonds. In some implementations, if each of n and m independently has a value of 1 or 3, then R 103 It can be any one of the following equations (204)-(213): In equations (204)-(213), g, e, and f are each independent integers from 1 to 6, each "HCC" represents a hydrocarbon chain, and each * indicates R.103 Possible connection points with nitrogen atoms in equation (201), wherein each H at any * position can be replaced to achieve connection with nitrogen atoms in equation (201). Those skilled in the art can obtain the compound represented by formula (201) by any reasonable method. In some embodiments, the compound represented by formula (201) can be prepared according to the description in Chinese patent application CN103380113A. In some embodiments, the organic amine is an organic amine as shown in formula (214) and / or an organic amine as shown in formula (215): The auxiliary lipid is cholesterol, cholesterol analogues and / or cholesterol derivatives; The PEGylated lipid is 1,2-dipalmitoyl-sn-glycerol-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)]-2000. In some embodiments, the molar ratio of the organic amine, the auxiliary lipid, and the polyethylene glycol-modified lipid in the pharmaceutical composition is (19.7-80):(19.7-80):(0.3-50), for example, (50-70):(20-40):(3-20). In some embodiments, the pharmaceutical composition particles formed from the siRNA of this disclosure and the above-mentioned amine-containing transfection reagent have an average diameter of about 30 nm to about 200 nm, typically about 40 nm to about 135 nm, and more typically, the average diameter of the liposome particles is about 50 nm to about 120 nm, about 50 nm to about 100 nm, about 60 nm to about 90 nm, or about 70 nm to about 90 nm. For example, the average diameter of the liposome particles is about 30, 40, 50, 60, 70, 75, 80, 85, 90, 100, 110, 120, 130, 140, 150, or 160 nm. In some embodiments, in the pharmaceutical composition formed by the siRNA or siRNA conjugate of this disclosure and the above-mentioned amine-containing transfection reagent, the weight ratio (weight / weight ratio) of siRNA to all lipids (e.g., organic amines, auxiliary lipids and / or polyethylene glycol-modified lipids) is in the range of about 1:1 to about 1:50, about 1:1 to about 1:30, about 1:3 to about 1:20, about 1:4 to about 1:18, about 1:5 to about 1:17, about 1:5 to about 1:15, about 1:5 to about 1:12, about 1:6 to about 1:12 or about 1:6 to about 1:10. For example, the weight ratio of siRNA to all lipids of this disclosure is about 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17 or 1:18. In some embodiments, the components of the pharmaceutical composition may exist independently when sold, and may be in liquid form when used. In some embodiments, the pharmaceutical composition formed by the siRNA or siRNA conjugate provided in this disclosure and the pharmaceutically acceptable carrier described above can be prepared according to various known methods, simply by replacing existing siRNAs with the siRNA provided in this disclosure; in some embodiments, it can be prepared according to the following method: An organic amine, auxiliary lipid, and polyethylene glycol-modified lipid are suspended in an alcohol at the above molar ratio and mixed to obtain a lipid solution. The amount of alcohol used is such that the total mass concentration of the resulting lipid solution is 2-25 mg / mL, for example, 8-18 mg / mL. The alcohol is selected from pharmaceutically acceptable alcohols, such as alcohols that are liquid near room temperature, for example, one or more of ethanol, propylene glycol, benzyl alcohol, glycerol, polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400, for example, ethanol. The siRNA provided in this disclosure is dissolved in a buffer salt solution to obtain an aqueous siRNA solution. The concentration of the buffer salt solution is 0.05-0.5M, for example, 0.1-0.2M. The pH of the buffer salt solution is adjusted to 4.0-5.5, for example, 5.0-5.2. The amount of buffer salt solution used is such that the concentration of siRNA does not exceed 0.6 mg / mL, for example, 0.2-0.4 mg / mL. The buffer salt is selected from one or more of soluble acetate and soluble citrate, for example, sodium acetate and / or potassium acetate. The lipid solution and siRNA aqueous solution are mixed, and the resulting product is incubated at 40-60°C for at least 2 minutes, for example, 5-30 minutes, to obtain the incubated liposome formulation. The volume ratio of lipid solution to siRNA aqueous solution is 1:(2-5). The incubated liposome formulation is concentrated or diluted, impurities are removed, and sterilization is performed to obtain the pharmaceutical composition provided in this disclosure. Its physicochemical parameters are: pH value of 6.5-8, encapsulation efficiency of not less than 80%, particle size of 40-200 nm, polydispersity index of not more than 0.30, and osmotic pressure of 250-400 mOsm / kg; for example, the physicochemical parameters can be: pH value of 7.2-7.6, encapsulation efficiency of not less than 90%, particle size of 60-100 nm, polydispersity index of not more than 0.20, and osmotic pressure of 300-400 mOsm / kg. Concentration or dilution can be performed before, after, or simultaneously with impurity removal. Impurity removal can be achieved using various existing methods, such as ultrafiltration at 100 kDa using a tangential flow system or hollow fiber column, with the ultrafiltration exchange solution being phosphate-buffered saline (PBS) at pH 7.4. Sterilization can be achieved using various existing methods, such as filtration sterilization through a 0.22 μm filter. Applications of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions disclosed herein This disclosure also provides for the use of one or more of the siRNAs, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions of this disclosure in medicaments for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels. In some embodiments, the disease or symptom associated with PKK mRNA expression levels is an inflammatory disease and / or embolic disease, particularly hereditary angioedema. This disclosure also provides a method for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels, the method comprising administering to a subject in need an effective amount of one or more of the disclosed siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions. In addition, this disclosure also provides a method for regulating the expression level of PKK mRNA in cells, the method comprising contacting cells expressing PKK mRNA with an effective amount of one or more of the disclosed siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions. As used herein, the term "administration" refers to the delivery of one or more of siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions into a subject by means of a method or route that at least partially targets one or more of siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions to a desired site to produce a desired effect. Routes of administration suitable for the methods of this disclosure include local administration and systemic administration. Generally, local administration results in the delivery of more of one or more of siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions to a specific site compared to the entire body of the subject; while systemic administration results in the delivery of one or more of said siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions to substantially the entire body of the subject. The medication may be administered to the subject via any suitable route known in the art, including but not limited to: oral or parenteral routes, such as intravenous administration, intramuscular administration, subcutaneous administration, transdermal administration, airway administration (aerosol), pulmonary administration, nasal administration, rectal administration, and local administration (including oral and sublingual administration). Administration frequency may be once or more daily, weekly, bi-weekly, bi-weekly, monthly, or annually. The dosages of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure are conventional dosages in the art, determined based on various parameters, particularly the age, weight, and sex of the subject. Toxicity and efficacy can be determined in cell culture or laboratory animals using standard pharmaceutical procedures, such as determining the LD50 (the dose that causes 50% of the population to die) and ED50 (the dose that elicits 50% of the maximum response intensity in a quantitative response, and the dose that elicits a positive response in 50% of the subjects in a qualitative response). Ranges of human dosages can be derived based on data obtained from cell culture analysis and animal studies. When administering the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure, for example, to male or female C57BL / 6J or PKKH / HeNCrlVr mice, aged 6-12 weeks and weighing 18-25 g, the amount of siRNA in the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions is as follows: for the siRNA conjugates, the siRNA dosage can be 0.001-100 mg / kg body weight, in some embodiments 0.01-50 mg / kg body weight, in further embodiments 0.05-20 mg / kg body weight, in even further embodiments 0.1-15 mg / kg body weight, and in still further embodiments 0.1-10 mg / kg body weight. The above dosages are preferred when administering the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. In another aspect, this disclosure also provides one or more of the disclosed siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions for use as medicaments. In some embodiments, this disclosure also provides one or more of the disclosed siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions for use as medicaments for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels. In some embodiments, the diseases or symptoms associated with PKK mRNA expression levels are selected from inflammatory diseases and / or thromboembolic diseases, particularly hereditary angioedema. In another aspect, this disclosure also provides a cell expressing PKK mRNA, said cell further comprising one or more of the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions described in this disclosure. The methods provided in this disclosure for inhibiting PKK mRNA expression in cells involve siRNA, siRNA conjugates, pharmaceutically acceptable salts, and / or pharmaceutical compositions in which the amount of siRNA is readily determined by those skilled in the art based on the desired effect. For example, in some embodiments, the amount of siRNA in the siRNA conjugate is sufficient to reduce PKK mRNA levels and result in an extracellular concentration of 1 pM to 1 μM, or 0.01 nM to 100 nM, or 0.05 nM to 50 nM, or about 5 nM at the surface of target cells. The amount required to achieve this local concentration will vary depending on various factors, including the delivery method, delivery site, the number of cell layers between the delivery site and the target cells or tissue, and whether the delivery is local or systemic. The concentration at the delivery site can be significantly higher than the concentration at the surface of the target cells or tissue. The reagent kit disclosed herein This disclosure provides a kit comprising one or more of the following: siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions provided in this disclosure. In some embodiments, the kit described herein may provide one or more of siRNA, siRNA conjugates, pharmaceutically acceptable salts, and pharmaceutical compositions in a single container. In some embodiments, the kit described herein may include a container providing pharmaceutically acceptable excipients. In some embodiments, the kit may also contain other components, such as stabilizers or preservatives. In some embodiments, the kit described herein may contain at least one other therapeutic agent in a container other than the container providing the siRNA, siRNA conjugates, pharmaceutically acceptable salts, and / or pharmaceutical compositions described herein. In some embodiments, the kit may include instructions for mixing siRNA, siRNA conjugates, pharmaceutically acceptable salts and / or pharmaceutical compositions with pharmaceutically acceptable carriers and / or excipients or other ingredients (if any). In the kits disclosed herein, siRNA, siRNA conjugates, pharmaceutically acceptable salts and / or pharmaceutical compositions, and / or pharmaceutically acceptable excipients may be provided in any form, such as liquid, dry, or lyophilized. In some embodiments, the siRNA, siRNA conjugates, pharmaceutically acceptable salts and / or pharmaceutical compositions, and optional pharmaceutically acceptable excipients are substantially pure and / or sterile. In some embodiments, sterile water may be provided in the kits disclosed herein. The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto. Example Unless otherwise specified, the reagents, culture media, and consumables used in the following examples are all commercially available products, and the nucleic acid electrophoresis, real-time PCR, and other operations used are all performed in accordance with the methods described in Molecular Cloning (Cold Spring Harbor Laboratory Press (1989)). Preparation Example 1: Synthesis of the siRNA conjugates disclosed herein Following the preparation method described in Example 14 of CN110959011A, conjugates 1-4 and 7-16 as shown in Table 2A were prepared, differing only in that the sense and antisense strand sequences of the siRNA groups contained in the siRNA conjugates are as shown in Table 2A, respectively. Nucleoside phosphoramidide monomers were sequentially linked to nucleic acid sequences according to the sense and antisense strand sequences in Table 2A to synthesize the sense and antisense strands of the siRNA conjugates. After synthesis, conjugates 1-4, 7-12, and 16 were purified by centrifugation and ultrafiltration using 3K (MWCO) ultrafiltration tubes; conjugates 13-15 were first purified by self-packed column ionization using strong anion exchange packing material, and then purified by desalting using a HiPrep 26 / 13 Desalting pre-packed column. Among them, conjugates 1-4, 7-12, and 16 are mixtures of methylamine and ammonium salts of compounds having the structure shown in formula (403), and conjugates 13-15 are sodium salts of compounds having the structure shown in formula (403). The P atom shown in formula (403) is covalently linked to the reverse debased deoxynucleotide ia (as shown in formula (35)) at the 3' end of the positive strand of the siRNA group represented by Nu, and to the oxygen atom connected to the ribose ring via a methylene group, thereby covalently linking it to the positive strand of the siRNA group. Furthermore, the siRNA groups contained in these siRNA conjugates respectively have the siRNA sequences corresponding to conjugates 1-4 and 7-16 in Table 2A. The sequences and structures of conjugates 1, 13, 14, and 15 are the same as those of conjugates 16, 12, 2, and 3, respectively. The only difference is that the antisense strand of the siRNA is attached to the 5' end with a vinyl phosphate (VP). Each siRNA conjugate was diluted to a concentration of 0.2 mg / mL (based on siRNA) using ultrapure water (Milli-Q ultrapure water system, resistivity 18.2 MΩ*cm (25℃)). Molecular weight was then determined using liquid chromatography-mass spectrometry (LC-MS, Agilent Technologies, model: 1290-6135B). The molecular weight data for conjugates 1-4 and 7-15 are shown in Table 2 below. Table 2 shows the molecular weight determination data of conjugates 1-15. As shown in Table 2, the measured molecular weights of the sense and antisense strands of the siRNA conjugates are consistent with the theoretical values, indicating that the synthesized conjugates 1-4 and 7-15 have the double-stranded nucleic acid sequences required by the target design. Comparative Preparation Example 1: Synthesis of Reference Conjugate 1 Referring to the procedures of Examples 1-3 in WO2023143483A1, reference conjugate 1 was prepared as shown in Table 2A below. The sense and antisense strand sequences of the siRNA group contained in reference conjugate 1 are shown in Table 2A, respectively. This reference conjugate is a sodium salt having the structure shown in formula (501) below: The helical structure indicates that the reference conjugate 1 contains siRNA groups other than ia. In formula (501), the P atom in the phosphate group linked to the N-containing six-membered ring is covalently linked to the oxygen atom directly linked to the ribose ring at the 5' end of the positive strand of the siRNA group, as shown in formula (35), and thus covalently linked to the positive strand of the siRNA. Furthermore, the siRNA contained in this siRNA conjugate has the siRNA sequence corresponding to reference conjugate 1 in Table 2A. Table 2A siRNA sequences in siRNA conjugates In this context, uppercase letters C, G, U, A, and T represent the base composition of a nucleotide; lowercase letter m indicates that the nucleotide adjacent to the left of m is 2'-methoxy modified; lowercase letter f indicates that the nucleotide adjacent to the left of f is 2'-fluorinated modified; lowercase letter s indicates that the two nucleotides to the left and right of s are linked by a thiophosphate group; the letter combination VP indicates that the nucleotide adjacent to the right of VP is vinyl phosphate modified; and ia represents a reverse debased deoxynucleotide. Experimental Example 1: In vitro inhibitory activity of the disclosed conjugate. This experiment investigated the inhibition of PKK mRNA in primary mouse liver cells by conjugates 1-4 and 7-12. [1] Cell culture Primary hepatocytes were obtained from fresh liver tissue of C57BL / 6J mice (6 weeks old, purchased from Spifort (Beijing) Biotechnology Co., Ltd.). The density of the primary hepatocytes was adjusted to 1×10⁻⁶ cells in Opti-MEM (1×) medium (GIBCO, catalog number 31985-70). 5 To obtain a suspension of primary mouse liver cells, the concentration was 1 × 10⁶ cells / mL. 5 Cells were seeded into 12-well plates with 1 mL of cell culture per well. [2] Transfection For each analyte conjugate, a 20 μM (based on the amount of siRNA in the conjugate) stock solution was prepared using PBS, and then diluted to a 0.8 μM working solution. The analytes used were conjugates 1-4 and conjugates 7-12. For each conjugate to be tested, prepare a 1A solution, each 1A solution containing 3 μL of the conjugate working solution and 97 μL of Opti-MEM medium (purchased from GIBCO, catalog number 31985-070). For each analyte, prepare a 1B solution, each 1B solution containing 3 μL of Lipofectamine. TM RNAiMAX (purchased from Invitrogen, catalog number: 13778150) and 97 μL of Opti-MEM medium. After mixing, let stand at room temperature for 5 min. For each conjugate to be tested, one portion of solution 1A and one portion of solution 1B were mixed and incubated at room temperature for 20 min to obtain transfection complex X1. Transfection complex X1 of each conjugate was added to each well, mixed thoroughly, at a volume of 200 μL / well, to obtain a transfection mixture with a concentration of 2 nM (based on the amount of siRNA). Transfection complex X1 of each siRNA conjugate was transfected into 3 wells, designated as test groups X1-X10. One portion of solution 1B was mixed with 100 μL of Opti-MEM medium to obtain blank transfection mixture B. Blank transfection mixture B was then added to three other wells at a volume of 200 μL / well to obtain transfection mixtures without conjugates, which were designated as the blank control group. The test groups X1-X10 and the blank control group were placed in an incubator containing 5% CO2 and cultured at 37°C for 4 hours. Then, 1 mL of complete culture medium containing 20% ​​FBS was added to each well, and the cells were collected after culturing for another 24 hours. [3] Detection After culture, total RNA was extracted from each well using the MagaBio plus Total RNA Purification Kit II (purchased from Hangzhou Bori Technology Co., Ltd., catalog number: BSC69) according to the method described in its instructions, using a fully automated nucleic acid extraction and purification instrument (purchased from Hangzhou Bori Technology Co., Ltd., model: NPA-96). For each well of cells, 1 μg of total RNA was taken and transduced using the reagents provided in the reverse transcription kit (Promega, catalog number: A3500), with Goldenstar selected as the primary RNA source. TM Oligo(dT) 17 As primers, a 20 μL reverse transcription reaction system was prepared according to the reverse transcription procedure in the kit instructions to reverse transcribe the total RNA from the cells in each well. The reverse transcription conditions were as follows: for each reverse transcription reaction system, the system was incubated at 70°C for 10 min, then at 42°C for 30 min, and finally at 95°C for 5 min. After the reaction was completed, 60 μL of DEPC water was added to the reverse transcription reaction system to obtain a solution containing cDNA. For each reverse transcription reaction system, 5 μL of the above-mentioned cDNA-containing solution was used as a template. A 20 μL qPCR reaction system was prepared using the reagents provided in the SYBR Select Master Mix kit (Applied Biosystems, catalog number 4472908). The PCR primer sequences for amplifying the target gene PKK and the internal reference gene GAPDH are shown in Table 3, with a final concentration of 10 μM for each primer. Each qPCR reaction system was placed on an ABI StepOnePlus Real-Time PCR instrument and amplified using a three-step method. The amplification program was: 95℃ pre-denaturation for 10 min, followed by 95℃ denaturation for 30 s, 60℃ annealing for 30 s, and 72℃ extension for 30 s. This denaturation, annealing, and extension process was repeated 40 times to obtain product W1 containing amplified target gene PKK and internal reference gene GAPDH. Product W1 was then subjected to a gradient temperature increase to 95℃ for 15s, 60℃ for 1min, and then to 95℃ with fluorescence signals collected every 0.3℃. After 15s at 95℃, the melting curves of the target gene and the internal reference gene GAPDH in product W1 were collected by a real-time quantitative PCR instrument to obtain the Ct values ​​of the target gene PKK and the internal reference gene GAPDH. Table 3 Primer Information The relative quantitative calculation of the expression level of the target gene PKK mRNA in each test group was performed using the Ct(ΔΔCt) method. The calculation method is as follows: ΔΔCt=(Ct 测试组目标基因 -Ct 测试组内参基因 )-(Ct 空白对照组目标基因-Ct 空白对照组内参基因 mean Relative expression level = 2 -ΔΔCt ×100% mRNA inhibition rate = (blank control group 2) -ΔΔCt Mean - Test Group 2 -ΔΔCt ) / Blank control group 2 -ΔΔCt Mean × 100% The experimental results are shown in Table 4 below. Table 4. Inhibition rate of PKK mRNA in primary mouse liver cells As shown in Table 4, the conjugates 1-4 and 7-12 provided in this disclosure both exhibited high inhibitory effects on PKK mRNA in primary mouse liver cells. At a concentration of 2 nM, the inhibition rates of conjugates 1-4 and 7-12 on PKK mRNA were both above 70%, and the inhibition rate of conjugate 12 on PKK mRNA reached 84.1%, indicating that the conjugates provided in this disclosure have a good inhibitory effect on PKK mRNA expression. Experiment 2: Determination of the activity of the conjugate in C57BL / 6J mice (in vivo) C57BL / 6J mice were randomly divided into groups of five (all males). Each group was administered conjugates 1-4, 7-10, 12, and 16, respectively. Dosage was calculated based on body weight, and all mice were given a single subcutaneous injection. Each conjugate was administered in a 0.3 mg / mL solution of 0.9 wt% sodium chloride, at a volume of 10 mL / kg body weight (3 mg / kg for each conjugate), designated as the test group. Ten male C57BL / 6J mice served as the control group, receiving PBS at a volume of 10 mL / kg body weight. On day 8 post-administration, mice were sacrificed, and plasma was collected. To prevent clotting, 3.2 wt% (0.109 mol / L) sodium citrate dihydrate solution was added at a volume ratio of 1:9 (v / v) to prevent coagulation. The plasma was then separated by centrifugation. Approximately 100 mg / mouse of the left lobe of the liver was collected and stored using RNA later (Sigma Aldrich). Subsequently, liver tissue from each mouse was homogenized using a tissue homogenizer, and total RNA was extracted from the liver tissue using the Trizol method (BioFlux). The extracted total RNA was reverse transcribed using a reverse transcription kit (Promega, catalog number A3500) according to the manufacturer's instructions. Goldenstar RNA was selected as the target RNA. TM Oligo(dT) 17As primers, the reverse transcription conditions were as follows: the reverse transcription reaction system was incubated at 70℃ for 10 min, then at 42℃ for 30 min, and finally at 95℃ for 5 min. After the reaction, 80 μL of DEPC water was added to the reverse transcription reaction system to obtain a solution containing cDNA. The expression level of PKK mRNA in liver tissue was detected according to the qPCR detection method in Experiment Example 1. For the same test group, the average relative expression level of PKK mRNA at each concentration was the arithmetic mean of the relative expression levels of five mice at that concentration. Data analysis was performed using Graphpad Prism 8.0 statistical analysis software. The PKK mRNA expression level in the control group was recorded as 100%, and correspondingly, the PKK mRNA expression inhibition rate was recorded as 0%. The test results were standardized with respect to the PKK mRNA expression level in the control group, and the results are shown in Table 5. In Table 5, the PKK mRNA inhibition rate is the average PKK mRNA inhibition rate of a group of mice treated with the corresponding conjugate. Table 5. Inhibition rate of conjugates on PKK mRNA in mice. As shown in Table 5, the conjugates provided in this disclosure exhibited good inhibitory effects on PKK mRNA in C57BL / 6J mice. Compared with the PBS blank control group, the conjugates provided in this disclosure showed an inhibition rate of over 70% on PKK mRNA in mice at a dose of 3 mg / kg and on day 8 of administration. The inhibition rate of conjugate 1 on PKK mRNA reached over 90%. Experimental Example 3: Activity test of conjugate 1 in mice (in vivo) The conjugate 1 disclosed herein was dissolved in PBS to obtain a solution of conjugate 1 with a concentration of 0.5 mg / mL (based on the amount of siRNA). Male human PKK transgenic mice (grade: SPF; age: 6-8 weeks, purchased from Shanghai Southern Model Biotechnology Co., Ltd.) were randomly divided into 3 groups of 5 mice per group: test group 1, test group 2, and blank control group. Each mouse in test group 1 was administered 0.5 mg / mL of conjugate 1 solution via subcutaneous abdominal injection, with a single dose of 6 mL / kg mouse body weight. Each mouse in test group 2 was administered 0.5 mg / mL of conjugate 1 solution, with a single dose of 2 mL / kg mouse body weight. Mice in the blank control group were administered PBS solution. For each group, mice were weighed and their body weight was recorded before administration, and the dosage was administered according to body weight. Using the drug administration time point as day 1, blood samples were collected from mice via the orbital sinus on days 15, 22, 29, 43, and 57 after drug administration. The hPKK protein content in the serum of mice in the test group and the blank control group was measured using the Prekallikrein and Kallikrein Human ELISA kit (purchased from Abcam, catalog number: ab171015) according to the instructions. The pre-drug hPKK protein expression level was normalized to 100%, and the decrease rate of hPKK protein expression in mouse serum was calculated. The baseline value of the hPKK protein inhibition rate in the serum of each test group and the blank control group was 0%. The hPKK protein inhibition rate for each mouse at different blood collection times was calculated using the formula: hPKK protein inhibition rate = (1 - protein content after drug administration / protein content before drug administration) × 100%. The serum hPKK protein inhibition rate of each test group is shown as the average value. The results are shown in Table 6. Table 6. hPKK protein inhibition rate in mice As shown in Table 6, during the 57-day experimental period, mice given the conjugate 1 of this disclosure exhibited a high inhibition rate of hPKK protein expression. For the test group with a dose of 3 mg / kg mouse body weight, the inhibition rate of hPKK protein expression was still as high as 86.9% at the 57th day of administration. It can be seen that the conjugate provided by this disclosure can inhibit the expression of PKK mRNA for a long time, thereby reducing the level of hPKK protein expression in serum, showing significant and long-lasting pharmaceutical activity and excellent development prospects. Experiment 4: Activity test of the conjugate in mice (in vivo) The conjugates 13-15 and reference conjugate 1 of this disclosure were dissolved in PBS to prepare conjugate solutions with a concentration of 0.5 mg / mL (based on the amount of siRNA). Male human PKK transgenic mice from the same source as in Experiment 3 were randomly divided into 9 groups of 5 mice each: test group 1, test group 2, test group 3, test group 4, test group 5, test group 6, control group 1, control group 2, and blank control group. Each mouse in test group 1 was administered 0.5 mg / mL of conjugate 13 solution via subcutaneous abdominal injection (2 mL / kg body weight per dose); each mouse in test group 2 was administered 0.5 mg / mL of conjugate 13 solution (6 mL / kg body weight per dose); each mouse in test group 3 was administered 0.5 mg / mL of conjugate 14 solution (2 mL / kg body weight per dose); and each mouse in test group 4 was administered 0.5 mg / mL of conjugate 14 solution. The following treatments were administered: 1. Mice in test group 5 were given 0.5 mg / mL of conjugate 15 solution at a single dose of 2 mL / kg body weight; 2. Mice in test group 6 were given 0.5 mg / mL of conjugate 15 solution at a single dose of 6 mL / kg body weight; 3. Mice in control group 1 were given 0.5 mg / mL of reference conjugate 1 solution at a single dose of 2 mL / kg body weight; 4. Mice in control group 2 were given 0.5 mg / mL of reference conjugate 1 solution at a single dose of 6 mL / kg body weight; 5. Mice in the blank control group were given PBS solution at a dose of 6 mL / kg body weight. Mice in all groups were weighed and their body weight was recorded before administration, and the dosage was determined by body weight. Using the drug administration point as day 1, blood samples were collected from mice via the orbital cavity before administration and on day 8 after administration. The expression levels of hPKK protein in the serum of mice in each test group, control group, and blank control group were detected according to the instructions using the Prekallikrein and Kallikrein Human ELISA kit (purchased from Abcam, catalog number: ab171015). Normalization was performed with the pre-administration hPKK protein expression level as 100%, and the decrease rate of hPKK protein expression in mouse serum was calculated. The calculation method was the same as in Experiment 3, and the results are shown in Table 7. Table 7. Inhibition rate of hPKK protein in mice As shown in Table 7, within an 8-day experimental period, the conjugates disclosed herein exhibited an inhibition rate of approximately 50% on hPKK protein expression in mice at a dose of 1 mg / kg body weight. In the test group with a dose of 3 mg / kg body weight, the inhibition rate reached over 75%, with conjugate 14 achieving an inhibition rate of 84.7%. All these results were significantly higher than the inhibition rate of the reference conjugate 1. The conjugates disclosed herein demonstrate good hPKK protein expression inhibition rates in mice, exhibiting excellent pharmaceutical activity. Experiment 5: Activity test of the conjugate in mice (in vivo) The conjugate 14 and reference conjugate 1 of this disclosure were dissolved in PBS to prepare conjugate solutions with a concentration of 0.5 mg / mL (based on the amount of siRNA). hKLKB1 mice (grade: SPF; age: 13-15 weeks, purchased from Shanghai Southern Model Biotechnology Co., Ltd.) were randomly divided into 3 groups of 5 mice per group: test group, control group, and blank control group. The test group was administered 0.5 mg / mL of conjugate 14 solution to each mouse via subcutaneous abdominal injection, with a single dose of 6 mL / kg mouse body weight (3 mg / kg). The control group was administered 0.5 mg / mL of reference conjugate 1 solution to each mouse, with a single dose of 6 mL / kg mouse body weight (3 mg / kg). The blank control group was administered PBS solution to each mouse, with a dose of 6 mL / kg mouse body weight. Mice in all groups were weighed and their weight recorded before administration, and the dosage was administered according to body weight. Taking the time of drug administration as day 1, blood was collected from each mouse via the orbital sinus before drug administration and on days 8, 15, 29, and 43 after drug administration. The expression level of hPKK protein in the serum of mice in each test group, control group, and blank control group was detected using the Prekallikrein and Kallikrein Human ELISA kit (purchased from Abcam, catalog number: ab171015) according to the instructions. The formula for calculating the hPKK protein inhibition rate is: hPKK protein inhibition rate = (1 - protein expression level after drug administration / protein expression level before drug administration) × 100%. The calculation method is the same as in Experiment 3. The results are shown in Table 8. Table 8. Inhibition rate of hPKK protein in mice As shown in Table 8, during the 43-day experimental period, the test group administered conjugate 14 exhibited a significantly higher inhibition rate of hPKK protein expression in mice compared to the control group administered reference conjugate 1. On day 8, conjugate 14 showed a maximum inhibition rate of 84.72% against serum hPKK protein, while reference conjugate 1 showed a maximum inhibition rate of 61.64%. Furthermore, the test group administered conjugate 14 maintained a 70.26% inhibition rate against serum hPKK protein on day 43, more than twice that of reference conjugate 1. Therefore, the conjugates disclosed in this invention demonstrate good hPKK protein expression inhibition rates in mice, exhibiting long-lasting and excellent pharmaceutical activity. Inhibitory activity of conjugate in human primary liver cells (Example 6) This experiment investigated the inhibitory activity of conjugate 14 on PKK mRNA in primary human liver cells. Human liver primary cells (purchased from BioIVT, catalog number M00995-SCERT) were thawed according to the manufacturer's instructions using the provided culture medium and reagents. 5 mL of plating medium (purchased from BioIVT, catalog number Z990033) was preheated to 37°C. The cryovials containing the cells were placed in a 37°C water bath and gently inverted until the contents were completely thawed. The cell suspension was poured into the preheated plating medium, the cryovials were rinsed, and the cell suspension was mixed thoroughly. The cells were gently inverted to ensure complete resuscitation. After cell counting, the cells were plated. The cell suspension was prepared at a concentration of 5.925 × 10⁻⁶ cells / mL. 4 Cells were seeded in 96-well plates (purchased from Corning, catalog number CORN4442), with 200 μL of plating medium added to each well. For the conjugates to be tested, a conjugate stock solution with a concentration of 200 μM (based on the amount of siRNA in the conjugate) was prepared using PBS. The conjugate stock solution was then serially diluted with hepatocyte maintenance medium (BioIVT, catalog number Z990034), with each concentration added to three wells to obtain mixtures with final concentrations of 5000 nM, 500 nM, 50 nM, 5 nM, 0.5 nM, 0.05 nM, and 0.005 nM. The group containing conjugate 14 was designated as the test group, and the group containing hepatocyte maintenance medium was designated as the blank control group. The test groups and blank control groups were cultured at 37°C in an incubator containing 5% CO2 / 95% air for 7 days. During this period, 50% of the maintenance medium was replaced every 48 hours, maintaining a constant 200 μL of medium per well. Cells were collected on day 7 for RNA extraction. Cells were lysed using Buffer RLT (Qiagen, catalog number 79216), and total RNA was extracted from each well using the Rneasy 96kit (Qiagen, catalog number 74181) according to the manufacturer's instructions. For each well, 0.1 μg of total RNA was extracted and processed using a High-Capacity cDNA Reverse Transcription Kit (Applied Biosystems). TM (Catalog number 4368814) was reverse transcribed according to its instructions to obtain 20 μL of a solution containing cDNA. The reverse transcription conditions were as follows: for each reverse transcription reaction system, the system was incubated at 25°C for 10 min, then at 37°C for 120 min, and finally at 85°C for 5 min. For each reverse transcription reaction system, 2 μL of the above-mentioned cDNA-containing solution was used as a template. A 10 μL qPCR reaction system was prepared using reagents provided by SsoAdvanced Universal Probes Supermix (supplier: Bio-Rad, catalog number: 1725280). PCR primers for amplifying the target gene PKK were prepared using FAM as a reporter dye (purchased from Applied Biosystems, catalog number: 4331182, assay: Hs00168478_m1). PCR primers for amplifying the internal reference gene GAPDH were prepared using HEX as a reporter dye (purchased from Bio-Rad, catalog number: 10031230, assay: qHsaCEP0041396). The final concentration of each primer was 1×. The following procedure was used to perform qPCR reactions on a real-time PCR system (Bio-Rad, model: CFX Opus 96): 95℃ for 30 seconds, followed by 95℃ for 10 seconds and 60℃ for 20 seconds, for a total of 40 cycles, to obtain the Ct values ​​of the target gene PKK and the internal reference gene GAPDH. Following the Ct(ΔΔCt) method in Experiment Example 1, the relative quantitative calculation of the expression level of the target gene PKK mRNA in the test group and the blank control group was performed to obtain the relative expression level of PKK mRNA in the test group at different concentrations. Based on the relative mRNA expression levels measured in the test groups at different concentrations, nonlinear regression analysis was performed using GraphPad Prism 10.2.2 software. A log(inhibitor) vs. response-variable slope (four parameters) model was selected to fit the dose-response curve. The IC50 of the test conjugate in primary human liver cells was calculated based on the function corresponding to the dose-response curve. 50 The value, the function is as follows, In the formula: Y represents the relative expression level of mRNA. X is the logarithm of the transfection conjugate concentration. Bot is the Y value corresponding to the bottom of the steady-state period. Top is the Y value corresponding to the peak of the steady-state period. LogIC50 is the value of X when Y is halfway between the bottom and the top, while HillSlope is the slope of the curve at X'. Based on the dose-response curve and the corresponding function, X is read from the software. 50 The IC50 of conjugate 14 in primary human liver cells was obtained. 50 The value is 1.1 nM, indicating that the conjugate provided in this disclosure has a strong inhibitory effect on PKK mRNA expression. Some embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure. It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately. Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. An siRNA comprising a sense strand and an antisense strand, each nucleotide in the siRNA being independently a modified nucleotide, the sense strand and the antisense strand being at least partially anticomplementary to form a double-stranded region, the length and composition of the antisense strand being such that the siRNA can inhibit the expression of PKK mRNA via an RNAi mechanism, wherein, The positive strand contains only two fluorinated nucleotides, and in the 3'-5' direction, two of the 11th-13th nucleotides in the positive strand are the fluorinated nucleotides, and the remaining nucleotide is an alkoxylated nucleotide. The antisense strand contains 5-10 fluorinated nucleotides, and in the 5'-3' direction, the 2nd and 14th nucleotides of the antisense strand are fluorinated nucleotides, one of the 6th-8th nucleotides is a fluorinated nucleotide, one of the 15th-17th nucleotides is a fluorinated nucleotide, and one of the 11th-13th nucleotides is a fluorinated nucleotide. The fluorinated nucleotides are complementary to the alkoxylated nucleotides in the 11th-13th nucleotides of the sense strand in the 3'-to-5' direction to form a base pair.

2. The siRNA as described in claim 1, wherein, The lengths of the sense strand and the antisense strand may be the same or different, the length of the sense strand is 19-23 nucleotides, and the length of the antisense strand is 19-26 nucleotides; Alternatively, the length difference between the sense and antisense strands may be 0-5 nucleotides. Alternatively, the length of the justice chain is not greater than the length of the antisense chain; Alternatively, the sense and antisense strands may be of the same length, either 19, 20, or 21 nucleotides. Alternatively, the length of the sense strand is 19-21 nucleotides, the length of the antisense strand is 20-24 nucleotides, and the length of the antisense strand is 1-3 nucleotides longer than the length of the sense strand; or the length of the antisense strand is 2 nucleotides longer than the length of the sense strand. Alternatively, the length of the sense strand is 19 nucleotides and the length of the antisense strand is 21 nucleotides; or the length of the sense strand is 21 nucleotides and the length of the antisense strand is 21 nucleotides; or the length of the sense strand is 21 nucleotides and the length of the antisense strand is 23 nucleotides.

3. The siRNA as described in claim 1 or 2, wherein, The antisense strand contains 5-8 fluorinated nucleotides.

4. The siRNA according to any one of claims 1-3, wherein, In the 5'-3' orientation, the 2nd and 14th nucleotides of the antisense strand are fluorinated nucleotides, the 4th or 5th nucleotide is a fluorinated or alkoxylated nucleotide, one of the 6th-8th nucleotides is a fluorinated nucleotide, one of the 15th-17th nucleotides is a fluorinated nucleotide, the 18th or 19th nucleotide is a fluorinated or alkoxylated nucleotide, and one of the 11th-13th nucleotides is a fluorinated nucleotide, which forms a base pair complementary to the alkoxylated nucleotide in the 11th-13th nucleotides of the sense strand in the 3'-5' orientation.

5. The siRNA according to any one of claims 1-4, wherein, In the siRNA, each nucleotide other than the fluorinated nucleotide is independently selected from one of the following: alkoxy-modified nucleotides, substituted alkoxy-modified nucleotides, alkyl-modified nucleotides, substituted alkyl-modified nucleotides, amine-modified nucleotides, heat-labile nucleotides, BNA, or reverse debased deoxynucleotides.

6. The siRNA according to any one of claims 1-5, wherein, The positive strand contains 1-3 reverse debased deoxynucleotides, wherein the 3' terminal nucleotide and / or 5' terminal nucleotide of the positive strand is the reverse debased deoxynucleotide, or the 3' terminal nucleotide of the positive strand is the reverse debased deoxynucleotide.

7. The siRNA as described in claim 5 or 6, wherein, In the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 6th, 12th, 14th and 16th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 16th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 8th, 12th, 14th, and 16th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 12th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 7th, 11th, 14th, and 16th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 12th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 7th, 13th, 14th, and 16th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 15th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 7th, 12th, 14th, and 17th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 5th, 7th, 12th, 14th, 16th, and 19th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 5th, 7th, 12th, 14th, 16th, and 18th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide. Alternatively, in the 3'-5' direction, the first nucleotide in the sense strand is a reverse debased deoxynucleotide, the 11th and 13th nucleotides are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide; in the 5'-3' direction, the 2nd, 4th, 7th, 12th, 14th, 16th, and 18th nucleotides in the antisense strand are fluorinated nucleotides, and each of the remaining nucleotides is independently an alkoxylated nucleotide.

8. The siRNA according to any one of claims 1-7, wherein, Each alkoxy-modified nucleotide is independently a methoxy-modified nucleotide.

9. The siRNA according to any one of claims 1-8, wherein, Each of 1-4 of the linking groups between adjacent nucleotides in the 5' end of the sense and antisense strands, and / or 1-4 of the linking groups between adjacent nucleotides in the 3' end of the sense and antisense strands, is independently a phosphate ester group with a modifying group. Alternatively, each of the linking groups between adjacent nucleotides in the first to third nucleotides at the 5' end of the sense and antisense strands, and / or between adjacent nucleotides in the first to third nucleotides at the 3' end, is independently a phosphate ester group with a modifying group.

10. The siRNA as described in claim 9, wherein, The phosphate group with the modifying group is a thiophosphate group having the structure shown in formula (28):

11. The siRNA according to any one of claims 1-10, wherein, The 5' terminal nucleotide of the antisense strand is a 5'-hydroxy nucleotide, a 5'-phosphate nucleotide, or a 5'-phosphate analog modified nucleotide, wherein the 5'-hydroxy nucleotide has the structure shown in formula (29); the 5'-phosphate nucleotide has the structure shown in formula (30); and the 5'-phosphate analog modified nucleotide has a structure selected from the structures shown in formulas (31) to (34). R is selected from H, OH, OCH3 and F; Base represents a nucleic acid base, selected from A, U, C, G or T.

12. The siRNA according to any one of claims 1-11, wherein, The antisense strand is substantially anticomplementary, substantially anticomplementary, or completely anticomplementary to a continuous nucleotide sequence m in the PKK mRNA; the length of the nucleotide sequence m is not greater than the length of the antisense strand, and the length of the nucleotide sequence m is the same as the length of the antisense strand, or differs from it by no more than 8 nucleotides, or differs from it by 1-5 nucleotides. Alternatively, the length of the nucleotide sequence m is at least 16 nucleotides, or 16-25 nucleotides, or 18-23 nucleotides, or 19-21 nucleotides; or, the length of the nucleotide sequence m is 19, 21, or 23 nucleotides. Alternatively, the antisense strand has the same length as the nucleotide sequence m, and at least the nucleotide sequence other than the terminal nucleotide of the antisense strand is completely anticomplementary to the nucleotide sequence m; Alternatively, in the 5'-3' direction, the nucleotide sequence other than position 1 of the antisense strand is completely anticomplementary to the nucleotide sequence m; or all nucleotides of the antisense strand are completely anticomplementary to the nucleotide sequence m.

13. The siRNA according to any one of claims 1-12, wherein, The justice chain and the antisense chain are essentially opposite complementary, substantially opposite complementary, or completely opposite complementary. Alternatively, in the 5'-3' direction, at least the nucleotide sequence other than the first and last positions of the sense strand is substantially anticomplementary or completely anticomplementary to the antisense strand; Alternatively, in the 5'-3' direction, the nucleotide sequence of the sense strand except the last nucleotide is completely anticomplementary to the antisense strand; or all nucleotides of the sense strand are completely anticomplementary to the antisense strand. Alternatively, the unmodified equivalent sequence of the positive strand may contain a nucleotide sequence that is the same length as the nucleotide sequence m and has no more than 3 base differences, no more than 1 base difference, or no base differences.

14. The siRNA as described in claim 12 or 13, wherein, The sense strand contains a nucleotide sequence I, and the antisense strand contains a nucleotide sequence II. Both nucleotide sequences I and II are 19 nucleotides in length. They are substantially anticomplementary, substantially anticomplementary, or completely anticomplementary, forming a double-stranded region. Nucleotide sequence I is the same length as the nucleotide sequence shown in SEQ ID NO:1, with no more than 3 base differences. Nucleotide sequence II is the same length as the nucleotide sequence shown in SEQ ID NO:2, with no more than 3 base differences. 5'-CUGAAUUCCAAAAACCAAZ1-3' (SEQ ID NO: 1); 5'-Z2UUGGUUUUUGGAAUUCAG-3'(SEQ ID NO:2), Wherein, Z1 is A, U or reverse debased deoxynucleotide, Z2 is U or A, the nucleotide sequence I contains nucleotide Z3 corresponding to Z1, the nucleotide sequence II contains nucleotide Z4 corresponding to Z2, and Z4 is the first nucleotide at the 5' end of the antisense strand, wherein Z3 and Z4 are selected from A, U, C, G, T or reverse debased deoxynucleotide, respectively.

15. The siRNA as described in claim 14, wherein, There is a 1-base difference or no base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1, and / or there is a 1-base difference or no base difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2; Alternatively, the base difference between nucleotide sequence I and the nucleotide sequence shown in SEQ ID NO:1 includes a difference at position Z3, where Z3 is selected from G or C, and / or the base difference between nucleotide sequence II and the nucleotide sequence shown in SEQ ID NO:2 includes a difference at position Z4, where Z4 is selected from C or G.

16. The siRNA as described in claim 14 or 15, wherein, The sense strand further contains nucleotide sequence III, and the antisense strand further contains nucleotide sequence IV. Nucleotide sequence III and nucleotide sequence IV are each independently 1-4 nucleotides in length. Nucleotide sequence III is attached to the 5' end of nucleotide sequence I, and nucleotide sequence IV is attached to the 3' end of nucleotide sequence II. Nucleotide sequence III and nucleotide sequence IV are of equal length and are substantially anticomplementary or completely anticomplementary. "Substantially anticomplementary" means that there is no more than one base mismatch between the two nucleotide sequences; "completely anticomplementary" means that there is no mismatch between the two nucleotide sequences. Alternatively, the nucleotide sequence I is the nucleotide sequence shown in SEQ ID NO:1, the nucleotide sequence II is the nucleotide sequence shown in SEQ ID NO:2, the length of nucleotide sequences III and IV is 1 nucleotide, and the base of nucleotide sequence III is A; Alternatively, both nucleotide sequences III and IV are 2 nucleotides in length, and the base composition of nucleotide sequence III is UA or CA in the 5'-3' direction; Alternatively, both nucleotide sequences III and IV are 3 nucleotides in length, and the base composition of nucleotide sequence III is AUA or ACA in the 5'-3' direction; Alternatively, both nucleotide sequences III and IV are 4 nucleotides in length, and the base composition of nucleotide sequence III is UAUA or UACA in the 5'-3' orientation.

17. The siRNA according to any one of claims 14-16, wherein, The antisense strand also contains a nucleotide sequence V, which is 1 to 3 nucleotides in length, and is attached to the 3' end of the antisense strand to form the 3' overhang of the antisense strand. Alternatively, the length of the nucleotide sequence V is 2 nucleotides; Alternatively, the nucleotide sequence V may be two consecutive thymine deoxyribonucleotides or two consecutive uracil ribonucleotides, or the nucleotide sequence V may be completely inversely complementary to PKK mRNA.

18. The siRNA according to any one of claims 14-17, wherein, The sense strand of the siRNA contains the nucleotide sequence shown in SEQ ID NO:5, and the antisense strand contains the nucleotide sequence shown in SEQ ID NO:

6. 5'-CUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO:5); 5'-Z4UUGGUUUUUGGAAUUCAGUA-3' (SEQ ID NO: 6); Alternatively, the sense strand of the siRNA contains a nucleotide sequence as shown in SEQ ID NO:7, and the antisense strand contains a nucleotide sequence as shown in SEQ ID NO:

8. 5'-UACUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO:7); 5'-Z4UUGGUUUUUGGAAUUCAGUAUA-3' (SEQ ID NO:8); Alternatively, the sense strand of the siRNA may contain a nucleotide sequence as shown in SEQ ID NO:41, and the antisense strand may contain a nucleotide sequence as shown in SEQ ID NO:

42. 5'-CACUGAAUUCCAAAAACCAAZ3-3' (SEQ ID NO: 41); 5'-Z4UUGGUUUUUGGAAUUCAGUGUA-3' (SEQ ID NO:42); wherein, Z4 is the first nucleotide at the 5' end of the antisense strand, Z3 is selected from A, U or reverse debased deoxynucleotide, and Z4 is selected from A or U; Alternatively, the siRNA may be siPKK1, siPKK2, or siPKK3: siPKK1 Chain of Justice: 5'-CUGAAUUCCAAAAACCAAia-3'(SEQ ID NO:9) Antonym: 5'-AUUGGUUUUUGGAAUUCAGUA-3' (SEQ ID NO:10) siPKK2 Justice chain: 5'-UACUGAAUUCCAAAAACCAAia-3' (SEQ ID NO:11) Antisense chain: 5'-AUUGGUUUUUGGAAUUCAGUAUA-3' (SEQ ID NO:12) siPKK3 Justice chain: 5'-CACUGAAUUCCAAAAACCAAia-3' (SEQ ID NO:43) Antisense chain: 5'-AUUGGUUUUUGGAAUUCAGUGUA-3' (SEQ ID NO:44) Wherein, ia refers to the reverse debased deoxynucleotide.

19. The siRNA according to any one of claims 14-18, wherein, The sense strand is identical to the sense strand of any one of siPKKa1-siPKKa10 listed in Table 1 in at least 15, at least 16, at least 17, at least 18, or 19 consecutive nucleotides, respectively, with no more than 3 base differences, no more than 1 base difference, or no base differences; the antisense strand is identical to the antisense strand of any one of siPKKa1-siPKKa10 in at least 17, at least 18, at least 19, at least 20, or 21 consecutive nucleotides, respectively, with no more than 3 base differences, no more than 1 base difference, or no base differences. Alternatively, the siRNA may be any one of siPKKa1, siPKKa2, siPKKa3, siPKKa4, siPKKa5, siPKKa6, siPKKa7, siPKKa8, siPKKa9 and siPKKa10 shown in Table 1.

20. An siRNA conjugate, wherein, The siRNA conjugate contains an siRNA group and a delivery group conjugated to the siRNA group, wherein the siRNA group is independently formed by removing one or more atoms or groups of atoms from the siRNA of any one of claims 1-19.

21. The siRNA conjugate of claim 20, wherein, The delivery group comprises a linker group and a pharmaceutically acceptable target group, and the siRNA group, the linker group and the target group are covalently or non-covalently linked in sequence, and at least one or each of the target groups is independently selected from ligands capable of binding to receptors on the surface of hepatocytes; Alternatively, the siRNA conjugate has the structure shown in formula (403); Alternatively, the siRNA conjugate may contain an siRNA group formed from any one of the siPKKa1, siPKKa2, siPKKa3, siPKKa4, siPKKa5, siPKKa6, siPKKa7, siPKKa8, siPKKa9 and siPKKa10 listed in Table 1. Alternatively, the siRNA conjugate is one of conjugate 1-conjugate 4, conjugate 7-conjugate 16 shown in Table 2A.

22. A pharmaceutically acceptable salt of the siRNA as described in any one of claims 1-19 or the siRNA conjugate as described in 20 or 21; Alternatively, the pharmaceutically acceptable salt is a partial or complete water-soluble salt of the siRNA or the siRNA conjugate; Alternatively, the water-soluble salt is an amine salt or an alkali metal salt; Alternatively, the amine salt is selected from one or more of ammonium salts, methylamine salts, tertiary amine salts, and quaternary ammonium salts, and the alkali metal salt is selected from potassium salts or sodium salts; Alternatively, the tertiary amine salt is a triethylamine salt, a triisopropylamine salt, or an N,N-diisopropylethylamine salt; Alternatively, the pharmaceutically acceptable salt is a salt or a portion of the siRNA or the siRNA conjugate, wherein the salt is one or more of a methylamine salt, a triethylamine salt, and a sodium salt.

23. A pharmaceutical composition comprising one or more of the following: siRNA as described in any one of claims 1-19, siRNA conjugate as described in claim 20 or 21, and pharmaceutically acceptable salt as described in claim 22, and pharmaceutically acceptable excipients; Alternatively, the pharmaceutically acceptable excipient is one or more of solvents, preservatives, osmotic pressure regulators, and other pharmaceutically acceptable carriers; Alternatively, the solvent is one of deionized water, water for injection, pH buffer, physiological saline, ethanol, or an aqueous solution of ethanol.

24. Use of the siRNA of any one of claims 1-19, the siRNA conjugate of claim 20 or 21, the pharmaceutically acceptable salt of claim 22, and / or the pharmaceutical composition of claim 23 in the preparation of a medicament for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels.

25. The use as described in claim 24, wherein, The diseases or symptoms associated with PKK mRNA expression levels are inflammatory diseases and / or thromboembolic diseases; or, the diseases or symptoms associated with PKK mRNA expression levels are hereditary angioedema.

26. A method for treating and / or preventing diseases or symptoms associated with PKK mRNA expression levels, the method comprising administering to a subject in need an effective amount of one or more of the following: siRNA of any one of claims 1-19, siRNA conjugate of claim 20 or 21, pharmaceutically acceptable salt of claim 22, and pharmaceutical composition of claim 23.

27. A method for regulating PKK mRNA expression levels in cells, the method comprising contacting the cells with an effective amount of one or more of the following: siRNA of any one of claims 1-19, siRNA conjugate of claim 20 or 21, pharmaceutically acceptable salt of claim 22, and pharmaceutical composition of claim 23.

28. A cell expressing PKK mRNA, and the cell comprising one or more of the following: siRNA of any one of claims 1-19, siRNA conjugate of claim 20 or 21, pharmaceutically acceptable salt of claim 22, and pharmaceutical composition of claim 23.

29. A kit comprising one or more of the following: siRNA according to any one of claims 1-19, siRNA conjugate according to claim 20 or 21, pharmaceutically acceptable salt according to claim 22, and pharmaceutical composition according to claim 23.

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