KR20220068111A - Composition for preventing or treating SARS-CoV-2 infection - Google Patents

Abstract

The present invention relates to a composition for preventing or treating an SARS-CoV-2 infectious disease capable of screening epigallocatechin gallate (EGCG), baicalin, or quercetin with a natural compound exhibiting inhibitory activity for Nsp15 of SARS-CoV-2; confirming antiviral effects of the EGCG, the baicalin, or the quercetin; and providing the EGCG, the baicalin, or the quercetin as an antiviral drug for the SARS-CoV-2 infectious disease.

Description

Composition for preventing or treating SARS-CoV-2 infection

The present invention relates to a composition for preventing or treating SARS-CoV-2 infection.

SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) is an acute severe respiratory disease coronavirus 2 first known in 2019 and is classified as a positive-sense single-stranded RNA virus. The disease infected by this virus was named Coronavirus disease 2019, abbreviated as COVID-19. The World Health Organization (WHO) has officially announced the coronavirus pandemic, and as of April 2021, the number of infected people in Korea is approaching 110,000, and about 130 million people around the world have been investigated. and continues to spread.

SARS-CoV-2 is a single-stranded (+) sensing RNA virus, in which the viral (+) sensing RNA genome is mainly used as mRNA in host cells to translate a large replicase composed of two polyproteins. Replicase uses the RNA genome as a template for replicating RNA. The viral proteases PLpro and 3CLpro break down polyproteins into 15-16 nonstructural proteins. Nonstructural proteins encode structural and nonstructural proteins by mediating whole genome and subgenomic mRNA replication.

Among the 16 nonstructural proteins, Nsp15 contains a uridylate-specific endoribonuclease (EndoU) in its catalytic C-terminal domain. Since the viral EndoU was found only in Nidovirales, it was named NendoU (nidovirus EndoU). The Nsp15 crystal structure of SARS-CoV-2 was identified with high resolution. Nsp15 is composed of three domains: an N-terminal oligomerization domain, an intermediate domain, and a C-terminal catalytic domain. The crystal structure of Nsp15 showed a hexameric assembly comprising two trimers.

NendoU hydrolyzes phosphodiester bonds at the uridine sites of single-stranded and double-stranded RNA to generate 2',3'-cyclic phosphodiester and 5'-hydroxyl termini. The host's innate immune system uses the pattern recognition receptor MDA5 to recognize polyU sequences from (-) sense viral RNA copied from polyA-viral RNA. Nsp15 evades the host's immune response by cleaving its own (-) sense RNA, limiting the accumulation of polyU sequences in cells. Nsp15 also has an essential role in the replication of coronaviruses by processing the viral genome. When Nsp15 was removed, viral replication was greatly reduced. Therefore, inhibition of Nsp15 activity could be a means of preventing and controlling viral infection in the asymptomatic stage by blocking the replication of the viral genome and activating the innate immune response of the host.

Korean Patent No. 10-2233689 (Announcement on March 30, 2021)

In order to solve the above problems, an object of the present invention is to provide a preventive or therapeutic agent for SARS-CoV-2 infection, a natural compound EGCG ( Epigallocatechin gallate), to provide a composition containing baicalin (baicalin) or quercetin (quercetin) as an antiviral component for SARS-CoV-2 infection.

The present invention provides a pharmaceutical composition for preventing or treating SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient.

In addition, the present invention provides a health food composition for preventing or improving SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient.

According to the present invention, EGCG (epigallocatechin gallate), baicalin or quercetin is screened as a natural compound showing the inhibitory activity of SARS-CoV-2 on Nsp15, and EGCG (epigallocatechin gallate), baicalin ( By confirming the antiviral effect of baicalin) or quercetin, epigallocatechin gallate (EGCG), baicalin or quercetin can be provided as antiviral agents for SARS-CoV-2 infection.

1 is a list of natural compounds for screening Nsp15 inhibitors of SARS-CoV-2.
2 is a screening result of a natural compound for screening an Nsp15 inhibitor of SARS-CoV-2. The y-axis is the calculated relative enzyme activity (reaction rate) after 60 minutes of reaction, and the x-axis is a list of natural compounds in FIG. 1 .
3 is a molecular structure of epigallocatechin gallate (EGCG), baicalin and quercetin screened with an Nsp15 inhibitor of SARS-CoV-2.
Figure 4 is a result of analyzing the enzyme activity by pre-culturing the Nsp15 enzyme of baicalin (baicalin) and SARS-CoV-2. The y-axis represents relative fluorescence units (RFU), and the x-axis represents reaction time.
5 is a result of analyzing the Nsp15 inhibitory effect of green tea extract, EGCG, baicalin, and quercetin. The y-axis shows the calculated inhibition rate after 60 minutes of reaction, and the x-axis shows the concentration of each compound.
6 is a result of evaluating the antiviral effect of green tea extract, EGCG, and baicalin on the SARS-CoV-2 strain in vitro . The y-axis represents percent neutralization, and the x-axis represents concentration.
7 is a diagram illustrating a ligand docking model of Nsp15 and EGCG of SARS-CoV-2. The Nsp15 crystal structure of SARS-CoV-2 (PDB: 6VWW) is shown in blue, and EGCG is shown in orange.
8 is a diagram showing the interaction between Nsp15 (blue bar) and EGCG (orange bar), which have an active site of Nsp15. The gray dotted line represents the hydrophobic interaction, the blue straight line represents the hydrogen bonding, and the yellow dotted line represents the salt bridge.

The terms used in this specification have been selected as currently widely used general terms as possible while considering the functions in the present invention, but these may vary depending on the intention or precedent of a person skilled in the art, the emergence of new technology, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than the name of a simple term.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Numerical ranges are inclusive of the values defined in that range. Every maximum numerical limitation given throughout this specification includes all lower numerical limitations as if the lower numerical limitation were expressly written. Every minimum numerical limitation given throughout this specification includes all higher numerical limitations as if the higher numerical limitation were expressly written. All numerical limitations given throughout this specification shall include all numerical ranges that are better within the broader numerical limits, as if the narrower numerical limitations were expressly written.

Hereinafter, the present invention will be described in more detail.

The present invention provides a pharmaceutical composition for preventing or treating SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient.

The Nsp15 inhibitor is epigallocatechin gallate (EGCG), baicalin or quercetin.

The Nsp15 is a kind of endoribonuclease activated in the replication process of SARS-CoV-2 virus.

The epigallocatechin gallate (EGCG), also known as epigallocatechin-3-gallate, has a structure in which epigallocatechin and gallate are formed by an ester bond. It is a substance of catechins, a kind of polyphenol that gives green tea's astringent taste. Apple peels, plums, onions, hazelnuts, and pecans also contain epigallocatechin gallate. The EGCG (epigallocatechin gallate) is a compound represented by the following Chemical Formula 1, and may bind to the active site of Nsp15.

[Formula 1]

The baicalin (baicalin) is a compound of the flavonoid series contained in gold and the like, and is a compound represented by the following formula (2).

[Formula 2]

The quercetin (quercetin) is a compound represented by the following formula (3).

[Formula 3]

The pharmaceutical composition of the present invention is prepared in unit dose form or multi-dose by formulating using a pharmaceutically acceptable carrier according to a method that can be easily carried out by a person of ordinary skill in the art to which the present invention pertains. It can be prepared by introducing into a container.

The pharmaceutically acceptable carriers are those commonly used in formulation, and include lactose, dextrose, sucrose, sorbitol, mannitol, starch, acacia gum, calcium phosphate, alginate, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, water, syrup, methyl cellulose, methyl hydroxybenzoate, propylhydroxybenzoate, talc, magnesium stearate and mineral oil, and the like. The pharmaceutical composition of the present invention may further include a lubricant, a wetting agent, a sweetening agent, a flavoring agent, an emulsifying agent, a suspending agent, a preservative, and the like, in addition to the above components.

In the present invention, the content of the additive included in the pharmaceutical composition is not particularly limited and may be appropriately adjusted within the content range used for conventional formulation.

The pharmaceutical composition is an aqueous solution, a suspension, an injectable formulation such as an emulsion, a pill, a capsule, a granule, a tablet, a cream, a gel, a patch, a spray, an ointment, a warning agent, a lotion, a liniment agent, a pasta agent, and a cataplasma It may be formulated in the form of one or more external preparations selected from the group consisting of agents.

The pharmaceutical composition of the present invention may further include a pharmaceutically acceptable carrier and diluent for formulation. The pharmaceutically acceptable carriers and diluents include starch, sugar, and excipients such as mannitol, fillers and extenders such as calcium phosphate, cellulose derivatives such as carboxymethyl cellulose, hydroxypropyl cellulose, gelatin, alginate, and polyvinyl blood binders such as rolidone, lubricants such as talc, calcium stearate, hydrogenated castor oil and polyethylene glycol, disintegrants such as povidone and crospovidone, surfactants such as polysorbates, cetyl alcohol, and glycerol does not The pharmaceutically acceptable carrier and diluent may be biologically and physiologically compatible with the subject. Examples of diluents include, but are not limited to, saline, aqueous buffers, solvents, and/or dispersion media.

The pharmaceutical composition of the present invention may be administered orally or parenterally (eg, intravenously, subcutaneously, intraperitoneally or topically) according to a desired method. For oral administration, it may be formulated as tablets, troches, lozenges, aqueous suspensions, oily suspensions, prepared powders, granules, emulsions, hard capsules, soft capsules, syrups or elixirs, and the like. In the case of parenteral administration, it may be formulated as an injection, suppository, powder for respiratory inhalation, aerosol for spray, ointment, powder for application, oil, cream, etc.

The dosage of the pharmaceutical composition of the present invention depends on the patient's condition and weight, age, sex, health condition, dietary constitution specificity, the nature of the preparation, the degree of disease, the administration time of the composition, administration method, administration period or interval, excretion rate , and the range may vary depending on the drug form, and may be appropriately selected by those skilled in the art. For example, it may be in the range of about 0.1 to 10,000 mg/kg, but is not limited now, and may be administered in divided doses from once to several times a day.

The pharmaceutical composition may be administered orally or parenterally (eg, intravenously, subcutaneously, intraperitoneally or topically) according to a desired method. The pharmaceutically effective amount and effective dosage of the pharmaceutical composition of the present invention may vary depending on the formulation method, administration method, administration time and/or route of administration of the pharmaceutical composition, and those of ordinary skill in the art It is possible to easily determine and prescribe an effective dosage for treatment. Administration of the pharmaceutical composition of the present invention may be administered once a day, may be administered divided into several times.

In addition, the present invention provides a health food composition for preventing or improving SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient.

The present invention can be generally used as a commonly used food product.

The food composition of the present invention can be used as a health functional food. The term "health functional food" means a food manufactured and processed using raw materials or ingredients useful for the human body in accordance with the Health Functional Food Act, and "functionality" refers to the structure and function of the human body. It refers to ingestion for the purpose of obtaining useful effects for health purposes such as regulating nutrients or physiological effects.

The food composition of the present invention may contain conventional food additives, and the suitability as the "food additive" is determined according to the general rules and general test methods of food additives approved by the Ministry of Food and Drug Safety, unless otherwise specified. It is judged according to the standards and standards related to the item.

The items listed in the "Food Additives Code" include, for example, chemical compounds such as ketones, glycine, potassium citrate, nicotinic acid, and cinnamic acid; Mixed preparations such as sodium L-glutamate preparation, noodle-added alkali agent, preservative agent, and tar color agent can be mentioned.

The food composition of the present invention may be manufactured and processed in the form of tablets, capsules, powders, granules, liquids, pills, and the like.

For example, among the health functional foods in the form of capsules, hard capsules can be prepared by mixing and filling the composition according to the present invention with additives such as excipients in conventional hard capsules, and the soft capsule is the composition of the composition according to the present invention. It can be manufactured by mixing with additives such as excipients and filling in capsule bases such as gelatin. The soft capsule formulation may contain a plasticizer such as glycerin or sorbitol, a colorant, a preservative, and the like, if necessary.

The term definitions for the excipients, binders, disintegrants, lubricants, flavoring agents, and the like are described in documents known in the art and include those having the same or similar functions. The type of food is not particularly limited, and includes all health functional foods in the ordinary sense.

In the present invention, the term “prevention” refers to any act of inhibiting or delaying a disease by administering the composition according to the present invention. In the present invention, the term “treatment” refers to any action that improves or beneficially changes the symptoms of a disease by administration of the composition according to the present invention. In the present invention, "improvement" refers to any action that improves the bad state of a disease by administering or ingesting the composition of the present invention to an individual.

Hereinafter, experimental examples and examples will be described in detail to help the understanding of the present invention. However, the following experimental examples and examples are only to illustrate the content of the present invention, the scope of the present invention is not limited to the following experimental examples and examples. Experimental examples and examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

<Experimental example> Experimental material and method

The following experimental examples are intended to provide experimental examples commonly applied to each embodiment according to the present invention.

1. Plasmid Construction and Protein Purification

The gene encoding nsp15 of SARS-CoV-2 was obtained from Bioneer Corp. (Daejeon, Korea). The nsp15 gene was inserted into the pProEx-HTa vector (Thermo Fisher Scientific, MA, USA) together with a hexahistidine tag and a tobacco etch virus (TEV) cleavage site. The plasmid was transformed into E. coli BL21 (DE3) strain. Transformed cells were cultured in 4 L of Terrific Broth medium containing 100 μg/ml ampicillin at 37° C. until an OD ₆₀₀ of 1.0 was measured, and protein expression was 0.5 mM isopropyl β-D-1-thio-galactopyranoside. was induced at 16 °C for 20 hours. After harvesting the cells by centrifugation, they were resuspended in a lysis buffer containing 50 mM Tris-HCl (pH 8.0), 500 mM NaCl, 5% (v/v) glycerol, and 2 mM 2-mercaptoethanol. After destroying the cells by sonication, the cells were centrifuged at 19,000 g at 4° C. for 30 minutes to remove cell debris. Cell lysates were loaded onto Ni-NTA affinity agarose resin (GE Healthcare, IL, USA). The target protein was eluted with lysis buffer supplemented with 500 mM imidazole. Pooled proteins were collected and loaded onto a Superdex 200 pg HiLoad 26/600 size exclusion chromatography column (GE Healthcare). Prior to sample loading, the column was equilibrated with a buffer containing 50 mM Tris-HCl (pH 8.0), 150 mM NaCl, and 5 mM β-mercaptoethanol. The purified protein was concentrated and stored at -80°C.

2. Endoribonuclease Assay

Real-time endoribonuclease analysis was performed using an oligonucleotide substrate containing a carboxyfluorescein (FAM) fluorophore at the 5' end and tetramethylrhodamine (TAMRA) at the 3' end. The oligonucleotide substrate 5'-FAM-dArUdAdAdA-TAMRA-3' was obtained from Bioneer Corp. (Daejeon, Korea). 2 μM of the substrate was used together with 1 μM Nsp15 in a buffer containing 20 mM Tris-HCl (pH 8.0), 150 mM NaCl, 5 mM MnCl 2 , and 1 mM dithiothreitol (DTT). Initial screening was performed using a library of natural compounds purchased from several companies, and each compound was used at a concentration of 20 μM. Specifically, green tea extract from NOW Foods (IL, USA), >95% EGCG and baicalein from Sigma Aldrich (MO, USA), >95% pure baicalin from LiftMode (IL, USA), quercetin from Jarrow Formulas (CA) , USA). Natural compounds were dissolved in DMSO (baicalin, baicalein, quercetin) or distilled water (green tea, EGCG), and diluted to various concentrations for each reaction. The emission of the FAM fluorescence signal was detected with an excitation wavelength of 492 nm and an emission wavelength of 518 nm using a SpectraMax i3x (Molecular Devices, LLC., CA, USA) for 1 hour. Reaction rates and IC ₅₀ values were calculated using Prism 8 software (GraphPad, CA, USA).

3. Plaque Reduction Neutralization Test (PRNT) of SARS-CoV-2

SARS-CoV-2 (NCCP 43326) provided by the Korea Centers for Disease Control and Prevention (KDCA, former Centers for Disease Control and Prevention) was pre-incubated with green tea extract, EGCG, or serially diluted serum-free medium containing baicalin at 37°C for 30 minutes. . Then, Vero cells were infected with SARS-CoV-2 pre-incubated for 30 min at room temperature and covered with 0.8% low-melting agarose. 72 hours after SARS-CoV-2 infection, cells were fixed with 10% formalin and stained with 0.05% crystal violet to count viral plaques. All procedures were performed in a Biosafety Level 3 (BSL-3) facility.

4. Molecular docking studies

Molecular docking of epigallocatechin gallate (EGCG) and Nsp15 was performed with AutoDock Vina. The Nsp15 crystal structure of SARS-CoV-2 (PDB: 6VWW) was used as a search model, and a grid box of ligand docking sites covered the active site pocket and adjacent regions. The most suitable form with the lowest RMSD (root mean square deviation) value was selected to calculate the binding energy between Nsp15 and EGCG using the same software. The interaction between Nsp15 and EGCG was analyzed using the protein-ligand interaction profiler (PLIP) web server.

Example 1. Inhibitor screening for Nsp15 endoribonuclease in natural compound library

The Nsp15 gene was synthesized from SARS-CoV-2 through a customized gene synthesis service, and the protein was overproduced in the Escherichia coli expression system. When E. coli was induced at 16°C, the protein was expressed in a soluble form. When the previously established assay was applied using 5'-FAM-dArUdAdAdA-TAMRA-3 ' as a substrate, the purified protein exhibited endonuclebonuclease activity. When the synthetic substrate was cleaved at the rU site by Nsp15, FAM liberated from TAMRA emitted a fluorescence signal at 512 nm. As shown in FIG. 1 , a complex library composed of edible natural compounds was used for screening. As shown in FIGS. 2 and 3 , water-soluble green tea extract, baicalin, and quercetin were identified as inhibitor candidates in the initial screening. In particular, as shown in FIG. 4 , pre-incubation of baicalin with Nsp15 enzyme doubled the inhibitory effect, resulting in a slow binding pattern. The structural flexibility of the Nsp15 enzyme may be correlated with the pre-culture effect of the inhibitor.

Example 1-1. Epigallocatechin gallate (EGCG)

The green tea extract used for screening contained epigallocatechin gallate (EGCG), epigallocatechin, and catechin gallate. EGCG is the most abundant catechin in green tea extract. As shown in FIG. 5 , the green tea extract strongly inhibited the Nsp15 enzyme of SARS-CoV-2 with an IC ₅₀ value of 2.54 μg/ml. To analyze whether EGCG is an inhibitory compound of Nsp15, pure EGCG (>95% purity) was used in the same Nsp15 ribonuclease assay. The pure EGCG compound strongly inhibited the Nsp15 enzyme, and the IC ₅₀ value was measured to be about 0.78 μg/ml or 1.70 μM. When the same mass was used, pure EGCG showed more than 3 times higher inhibitory activity than green tea extract. Since EGCG accounts for about 50% of green tea, the inhibitory effect of green tea extract can be explained by the inhibitory activity of EGCG. Therefore, it was confirmed that the inhibitory effect of green tea extract was due to EGCG.

Example 1-2. baicalin, baicalein, and quercetin

Baicalin is a glucuronide of the flavonoid baicalein, and is widely found in the leaves of Scutellaria baicalensis , S. lateriflora , and S. galericulata . Baicalin and baicalein are well known proline endopeptidase inhibitors. In particular, it has been reported that baicalin and baicalein exhibit an inhibitory effect on the protease 3CLpro of SARS-CoV-2. The high-resolution structure of the coronavirus protease complexed with baicalein showed that the baicalin aglycone moiety tightly binds to the active site of the protease.

As shown in FIG. 5 , both baicalin and baicalein showed a significant inhibitory effect at less than 10 μM (IC ₅₀ of baicalin was 7.98 μM (3.56 μg/ml), and that of baicalin was IC ₅₀ is 8.61 μM (2.33 μg/ml). According to the previous study, in the cytotoxicity assay, baicalin had a higher 50% cytotoxic concentration (CC ₅₀ ) value than baicalein (188.4 μg/ml for baicalin and 8.9 μg/ml for baicalein). ml), which means that the cytotoxicity of baicalin is low.

In addition, the same Nsp15 assay was performed with the flavonoid quercetin. Quercetin (3,3',4',5,7-pentahydroxyflavone) is very abundant in onion peels, apples, red grapes and green leafy vegetables. Quercetin (quercetin) has high antioxidant properties among similar flavonoids, and is attracting attention as a potential anticancer and antiviral agent. As shown in FIG. 5 , in the SARS-CoV-2 Nsp15 enzyme assay, quercetin exhibited inhibitory activity against Nsp15 with an IC ₅₀ of about 13.79 μM (4.17 μg/ml). The structural similarity of the flavonoids quercetin and baicalin means that the binding mode may be shared at the active site of Nsp15. However, since the chemical structure of EGCG is significantly different from that of baicalin and quercetin, the binding mode of EGCG may not be shared with baicalin and quercetin.

Example 2. Antiviral activity of green tea extract, EGCG, and baicalin against intracellular SARS-CoV-2

Quercetin and baicalein also showed inhibitory activity on the Nsp15 enzyme, but were excluded from the antiviral activity experiment due to their relatively low inhibitory activity and insoluble properties in water. To evaluate the antiviral activity of green tea extract, EGCG, and baicalin, a plaque reduction neutralization test was performed using SARS-CoV-2 isolated from COVID-19 patients. PRNT is a standard method for quantifying circulating levels of antiviral neutralizing antibodies. Vero cells were pre-incubated with various concentrations of green tea extract, EGCG, or baicalin, and infected with SARS-CoV-2 virus. Viral plaques were counted to determine live virus titer.

As shown in FIG. 6 , green tea extract and EGCG exhibited anti-neutralizing effects (PRNT ₅₀ ) of 0.24 μg/ml and 0.20 μM (0.092 μg/ml), respectively. As shown in the results of Nsp15 analysis, considering the content of EGCG in green tea extract, it can be seen that EGCG is a major component of antiviral activity of green tea extract. Baicalin showed limited antiviral activity compared to EGCG (PRNT ₅₀ = 83.3 μM (37.2 μg/ml)). This can be explained by the characteristics of baicalin showing low solubility in the medium used for the experiment.

Example 3. Docking model of Nsp15 and EGCG

To gain molecular insight into Nsp15 binding, a docking model was generated using the Nsp15 crystal structure of SARS-CoV-2 (PDB: 6VWW). When using AutoDock Vina software, the docking model ranked EGCG binding to the active site of Nsp15 as the top priority. The binding energy of this molecular docking was calculated to be -6.9 kcal/mol.

As shown in FIG. 7 , the EGCG molecule was found to be tightly bound to the active site of Nsp15. According to the docking model, many hydroxyl groups of EGCG interact with all major residues in the active site of Nsp15. EGCG-Nsp15 interaction was analyzed in the docking model using the PLIP web server.

As shown in FIG. 8 , the bound EGCG molecule had hydrophobic interactions with Lys290, Val292, Tyr343, and Leu346 at the Nsp15 active site, and hydrogen bonds with His235, Gly248, His250, Lys290, Ser294, and Thr341 at the active site. formed. The carbonyl group of EGCG has a polar interaction with Lys290. The gallate rings of EGCG were stacked by a pi interaction with the phenyl ring (B-ring), and the two stacked rings fit well into the active site. This docking model indicates that the gallate ring of EGCG is important in inhibiting the activity of the Nsp15 enzyme.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. do. That is, the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

A pharmaceutical composition for preventing or treating SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient. The pharmaceutical composition according to claim 1, wherein the Nsp15 inhibitor is epigallocatechin gallate (EGCG), baicalin, or quercetin. The pharmaceutical composition according to claim 2, wherein the epigallocatechin gallate (EGCG) is a compound represented by the following formula (1).
[Formula 1]

The pharmaceutical composition according to claim 2, wherein the baicalin is a compound represented by the following formula (2).
[Formula 2]

The pharmaceutical composition according to claim 2, wherein the quercetin is a compound represented by the following formula (3).
[Formula 3]

The pharmaceutical composition according to claim 2, wherein the epigallocatechin gallate (EGCG) binds to the active site of Nsp15. A health food composition for preventing or improving SARS-CoV-2 infection comprising an Nsp15 inhibitor as an active ingredient. The health food composition according to claim 7, wherein the Nsp15 inhibitor is epigallocatechin gallate (EGCG), baicalin or quercetin.

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