Polypeptide coupling medicine as well as preparation method and application thereof

Abstract

The invention discloses a polypeptide coupling drug and a preparation method and application thereof, and belongs to the technical field of biological medicine, the polypeptide coupling drug is formed by bonding and connecting cyclic peptide molecules, connecting arms, spacers and antibiotic drugs through chemical bonds; aIP-III D4A amide and structural analogues of AIP-III D4A amide are selected as cyclic peptide molecules; the connecting arm selects a molecule which is sensitive to the specificity of cathepsin B in lysosome; and the spacer is a structural fragment capable of being automatically degraded. The polypeptide coupling drug has a good antibacterial effect, especially has an outstanding treatment effect on intracellular bacterial infection which is relatively difficult in current clinical treatment, and can be used for preparing efficient antibacterial drugs.

Description

Technical Field

[0001] The present invention belongs to the field of biomedicine technology, and relates to a class of polypeptide-coupled drugs, and pharmaceutically acceptable salts or pharmaceutical compositions thereof, and uses thereof in the preparation of antibacterial drugs. The present invention also relates to a method for preparing the polypeptide-coupled drugs. Background Art

[0002] Staphylococcus aureus (S.aureus, SA) is one of the important pathogens of humans and a type of Gram-positive bacteria with strong infectivity and pathogenicity. Studies have found that SA can enter cells within a few minutes after infection. SA that survives in cells can escape the killing of antibiotics and destroy the innate immune response, lyse host cells and spread, forming a vicious cycle of phagocytosis-host cell lysis and dissemination-re-phagocytosis, resulting in repeated attacks and prolonged infection. Therefore, the removal of intracellular bacteria is a key link in the success or failure of clinical anti-SA infection treatment. However, existing antibiotics are inefficient or even ineffective against intracellular SA due to low cell entry rates, intracellular inactivation or difficulty in effectively accumulating in the intracellular microenvironment. At present, long-term and high-concentration antibiotics are mainly used in clinical practice to eliminate intracellular bacterial infections, which not only aggravates the development of bacterial resistance, but also increases the economic and mental burden of patients. Therefore, it is particularly necessary to develop new strategies to effectively remove intracellular SA.

[0003] The strategy of designing conjugates or prodrugs can cleverly overcome the limitations of traditional small molecule antibiotics, such as difficulty in entering cells, easy cell excretion, and difficulty in effectively aggregating in the subcellular structure where bacteria are located. It has become a hot topic in the study of anti-intracellular bacteria. The strategies currently developed for anti-intracellular SA are very limited, mainly using some drug carriers, such as liposomes, nanoparticles, microspheres and exosomes to encapsulate antibiotics. Although this strategy can effectively increase the rate of antibiotic entry into cells, it generally has defects such as poor targeting specificity and bioincompatibility. In addition, researchers have also developed antibody-drug conjugates for anti-intracellular bacterial infections. By targeting bacteria, it cleverly solves the problem of co-localization of antibiotics and bacteria, and can effectively eliminate intracellular bacteria by locally aggregating antibiotics. However, its disadvantage is that the antibodies used have strong immunogenicity, multiple administrations are prone to off-target effects, and it is difficult to develop antibodies targeting pathogens.

[0004] In recent years, peptide-drug conjugates (PDC) have been widely valued and promoted. Compared with traditional antibody-drug conjugates, the core advantages of PDC are strong tissue penetration ability, low immunogenicity, easier chemical synthesis and lower production cost. At present, two PDC drugs have been approved by the FDA for the treatment of cancer. PDC usually consists of three parts: a peptide target head, a linker and a drug. The principle is to use the abnormally high expression of some receptors, proteins or enzymes in diseased tissues, and achieve targeting specificity through the high affinity and high specificity of the peptide ligand and the receptor. By designing a specific linker, the specific release of the drug can be achieved to achieve the effect of enhancing efficacy and reducing toxicity. The peptide target head of PDC is a key component in PDC drug design, which is responsible for accurately delivering the drug to the target site. Therefore, it is particularly important to find a suitable peptide target head.

[0005] The bacterial quorum sensing system (QS) is a "communication system" in which bacteria coordinate the expression of virulence genes by sensing their own population density. Agr is the most important QS system in SA. The system is regulated by anto-inducing peptide (AIP). Bacteria secrete AIP to the extracellular space. When the concentration of AIP reaches a critical threshold, AIP binds to the AgrC receptor on the bacterial surface, initiates AgrC autophosphorylation to activate the response regulator AgrA, and further initiates the expression of downstream virulence genes. Because the Agr system is closely related to the virulence of SA, and it only exists in bacteria but not in mammals, it has attracted much attention as a target for the development of anti-SA virulence drugs. Among them, designing and synthesizing AIP analogs to compete and antagonize the binding of bacteria's own AIP to AgrC is an important way to develop Agr quorum sensing inhibitors. Among the reported AIP analogs, AIP-IIID4A amides show a strong affinity for the AgrC receptor (IC 50 =55.1pM), and has good stability and water solubility, suggesting that it may be used as a target for the design of peptide-conjugated drugs.

[0006] After searching, there are no reports on the application of AIP-IIID4A amide structures and their analogs in conjugated drugs. Therefore, it is urgent to develop a new peptide conjugated drug with this type of cyclic peptide as the target to solve the problem that existing antibiotics cannot effectively eliminate intracellular bacterial infections. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a class of polypeptide conjugate drugs and their preparation methods and applications, so as to solve the technical problem that existing antibiotics cannot effectively eliminate intracellular bacterial infections. Compared with existing strategies, it can more accurately achieve the co-localization of antibiotics and bacteria in cells, and achieve the effect of efficiently eliminating intracellular bacteria through the release of local high-concentration antibiotics. At the same time, compared with antibody-conjugated drugs, the synthesis of polypeptide conjugates is simpler, and due to their small molecular weight, they have better bioavailability and can effectively avoid the generation of immunogenicity, and have good application prospects.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention discloses a class of polypeptide-coupled drugs, which are formed by connecting a cyclic peptide molecule, a connecting arm, a spacer and an antibiotic drug through chemical bonds;

[0010] The cyclic peptide molecule is selected from AIP-IIID4A amide and its structural analogs;

[0011] The linker arm selects a molecule that is specifically sensitive to cathepsin B in lysosomes;

[0012] The spacer is a self-degradable structural fragment.

[0013] Preferably, the cyclic peptide molecule, i.e. the polypeptide target head, of the present invention is a cyclic peptide molecule composed of 5 to 12 amino acids.

[0014] Further preferably, the representative structure is as follows:

[0015]

[0016] The linker described in the present invention refers to a dipeptide, a tetrapeptide, a hydrazone compound, etc. that can be specifically hydrolyzed under a specific intracellular microenvironment (such as acidity, specific enzymes).

[0017] Further preferably, the molecule comprises the following structure:

[0018]

[0019] The spacer described in the present invention refers to a self-degradable chemical structural unit that can connect the linker and the antibiotic drug.

[0020] Further preferably, the molecular fragment comprises the following structure:

[0021]

[0022] The antibiotics are various common antibiotics in clinical practice, such as rifamycin, rifamycin-type dmDNA31, vancomycin, daptomycin, linezolid, oxacillin, etc. The representative structures are as follows:

[0023]

[0024] The second object of the present invention is to provide salts of the above-mentioned polypeptide-conjugated drugs, including but not limited to salts formed by the polypeptide conjugate and the following acids: hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, acetic acid, tartaric acid, salicylic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, lactic acid, pyruvic acid, maleic acid, succinic acid, etc.

[0025] The third object of the present invention is to provide the use of the above-mentioned polypeptide-coupled drugs and / or salts in the preparation of antibacterial drugs.

[0026] Preferably, the antibacterial drug mainly targets intracellular bacteria, and in particular can effectively eliminate Staphylococcus aureus in macrophages and non-macrophages.

[0027] Further preferably, the polypeptide-conjugated drug targets bacteria extracellularly, and after the bacteria enter the cell, it is specifically hydrolyzed in a specific subcellular organelle and releases a high concentration of antibiotics, thereby exerting anti-intracellular bacterial activity.

[0028] The fourth object of the present invention is to provide an antibacterial drug, comprising the above-mentioned polypeptide conjugate or its hydrate or pharmaceutically acceptable salt, and a pharmaceutically acceptable carrier. The pharmaceutical composition is prepared into a dosage form such as injection, capsule, syrup, aerosol, gel, cream, pill or transdermal patch.

[0029] Furthermore, the antibacterial drug of the present invention can be used alone or in combination with other drugs.

[0030] The fifth object of the present invention is to provide a method for synthesizing the above-mentioned polypeptide-coupled drug or a pharmaceutically acceptable salt thereof, wherein a linker arm with a spacer is connected to a cyclic peptide molecule through a click chemistry reaction under copper catalysis, and then conjugated according to the structural unit in the antibiotic drug to obtain the drug.

[0031] Specifically, the connection between the linker arm and the peptide and the drug is achieved by copper-catalyzed click reaction and formation of quaternary ammonium salt or esterification reaction, respectively, to prepare the desired peptide-coupled drug. The reaction equation involved is as follows:

[0032]

[0033] Among them, the linker I modified with an azide group and the cyclic peptide modified with a carbon-terminal alkynyl group are connected by a copper-catalyzed click reaction to obtain II. Then, according to the structural characteristics of antibiotic drugs, the conjugation of antibiotics is mainly achieved in two ways: ① For antibiotics containing tertiary amine fragments, the hydroxyl group in compound II is halogenated to obtain the corresponding halide, which then undergoes an electrophilic substitution reaction with the tertiary amine group in the drug to achieve the connection of the drug by forming a quaternary ammonium salt structure (Formula A); ② For antibiotics containing fragments such as carboxyl and sulfonic acid groups, the connection of the drug is achieved by esterification of the hydroxyl group in II with the carboxyl group (Formula B).

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The peptide conjugate drug disclosed in the present invention focuses on the problem of intracellular bacterial treatment. On the one hand, the design of AIP-IIID4Aamide and its analogs as peptide target heads can not only effectively achieve bacterial targeting, but also inhibit bacterial Agr and reduce its pathogenicity; on the other hand, given that SA mainly survives in phagolysosomes in cells, in the design of the PDC drug linker, the linker that is specifically sensitive to cathepsin B in lysosomes is mainly selected to ensure the stability of the designed PDC drug outside the cell and the specific hydrolysis and release of antibiotics in the lysosome. That is, the present invention realizes the design of bacterial-targeted peptide conjugate drugs through a strategy similar to the "Trojan horse". The peptide conjugate targets bacteria, enters the cell with the bacteria, and hydrolyzes and releases antibiotics in a specific intracellular environment, thereby achieving co-localization of antibiotics and bacteria in the cell, and reaching a local high concentration, effectively removing intracellular bacteria. The technical route described in the present invention provides a feasible new strategy for the treatment of intracellular bacteria. At the same time, the peptide conjugate drug synthesis route of the present invention is simple and the synthesis method is mature.

[0036] The polypeptide-coupled drug of the present invention has a good antibacterial effect, especially for intracellular bacterial infections, which are more difficult to treat in current clinical treatment, and can be used to prepare highly effective antibacterial drugs. The present invention also discloses a method for preparing such polypeptide-coupled drugs, and discloses for the first time the function and application of bacterial quorum sensing signal molecule peptide analogs as targeted drug carriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The structural schematic diagram of the polypeptide-coupled drug of the present invention;

[0038] Figure 2 The diagram is a graph showing the inhibitory effect of QSI-A synthesized in Example 1 of the present invention on the bacterial quorum sensing system; wherein A is a graph showing the effect of QSI-A on bacterial RNA III mRNA; and B is a graph showing the effect of QSI-A on bacterial agrA mRNA;

[0039] Figure 3 This is a graph showing the antibiotic release characteristics of QSI-A synthesized in Example 1 of the present invention under the action of Cathepsin enzyme;

[0040] Figure 4 The results of the in vitro anti-intracellular bacterial activity test of QSI-A synthesized in Example 1 of the present invention are shown; wherein A is a graph showing the killing effect of QSI-A on intracellular bacteria in macrophage Raw264.7 cells; BE are graphs showing the killing effect of QSI-A on intracellular bacteria in non-macrophage A549, IEC-6, HacaT and MG63 cells, respectively;

[0041] Figure 5 The results of the in vivo anti-intracellular bacterial activity test of QSI-A synthesized in Example 1 of the present invention are shown in Figure 1; wherein A is a bacterial count in mouse kidney under the action of QSI-A; and B is a HE staining image of mouse lung, liver, kidney and other organ tissues under the action of QSI-A;

[0042] Figure 6 LC-MS spectrum of the Peptide-Linker coupling substance II synthesized in Example 1;

[0043] Figure 7 LC-MS spectrum of the hydroxyl halogenated product III synthesized in Example 1;

[0044] Figure 8 This is the LC-MS spectrum of the target product QSI-A synthesized in Example 1. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0048] See also Figure 1 , which is a class of polypeptide-coupled drugs or pharmaceutically acceptable salts thereof disclosed in the present invention. In the general formula I, Peptide represents a polypeptide target head, which is a cyclic peptide molecule composed of 5 to 12 amino acids. Linker represents a connecting arm, which refers to a dipeptide, a tetrapeptide, a hydrazone compound, etc. that can be specifically hydrolyzed under a specific intracellular microenvironment (such as acidity, specific enzymes). Spacer represents a spacer, which refers to a self-degradable chemical structural unit that can connect the linker and the corresponding drug. Drug is a variety of common clinical antibiotics, such as rifamycin, rifamycin-like dmDNA31, vancomycin, daptomycin, linezolid, benzylpenicillin, etc.

[0049] Preferably, the polypeptide-conjugated drug disclosed in the present invention specifically includes compounds with the following structures:

[0050]

[0051]

[0052] The present invention also provides a method for preparing the polypeptide conjugate or its hydrate or pharmaceutically acceptable salt, wherein the method comprises connecting the azido-modified linker and the carbon-terminal alkynyl-modified cyclic peptide through a copper-catalyzed click reaction, and then performing drug conjugation according to the specific structural units contained in different antibiotics. For the connection of antibiotics containing tertiary amine fragments, the hydroxyl group in the above-mentioned linker is halogenated to obtain the corresponding halide, and then an electrophilic substitution reaction is carried out with the tertiary amine group in the antibiotic to achieve drug connection and obtain a polypeptide-conjugated drug, as shown in reaction formula (A):

[0053]

[0054] For antibiotics containing carboxylic acid fragments, the coupling of antibiotics is achieved by forming an ester between the hydroxyl group in the connecting arm and the carboxylic acid, as shown in reaction formula (B):

[0055]

[0056] The following is a specific embodiment to illustrate the steps of the synthesis method of the present invention:

[0057] Example 1 Synthesis of Peptide Conjugate QSI-A-1

[0058] 1. Synthesis of Peptide-Linker Couplings

[0059] The reaction equation is as follows:

[0060]

[0061] Add azido Val-Cit-PABOH I (68 mg, 0.147 mmol) and polypeptide (90 mg, 0.147 mmol) to the reaction bottle, add methanol (6 mL), add water (0.5 mL), add VcNa (58 mg, 0.295) and CuSO4 (11.7 mg, 0.073 mmol), stir and react at room temperature for 1 hour, LCMS shows that the reaction is complete. Add water (10 mL) to the reaction solution, extract with EA:IPA=4:1 (20 mL×3), wash the organic phase with water (10 mL×2), combine the organic phases, dry with anhydrous sodium sulfate, and remove the solvent by rotary evaporation to obtain Peptide-Linker coupling II, which is an off-white solid, a total of 150 mg. LC-MS (ESI) m / z: 1073.4 [Μ+H] + LC-MS spectrum see Figure 6 .

[0062] 2. Hydroxyl halogenation reaction in peptide-linker coupling

[0063] The reaction equation is as follows:

[0064]

[0065] At room temperature, HCl / EA (5 mL) was added to the peptide-linker coupling product II (130 mg, 0.12 mmol), and the reaction was stirred at room temperature for 3 hours. The reaction solution was concentrated and the residual HCl was removed with DCM (5 times) to obtain the hydroxyl halogenated product III (140 mg, light yellow solid). LC-MS (ESI) m / z: 1091.6 [Μ+H] + LC-MS spectrum see Figure 7 .

[0066] 3. Synthesis of target product QSI-A-1

[0067] The reaction equation is as follows:

[0068]

[0069] Under ice bath, add dmDNA31 (30 mg, 0.0324 mmol) in DMF (1 mL) to the solution of III (105 mg, 0.0972 mmol) in DMF (3 mL) obtained above, and stir the reaction solution at room temperature for 30 minutes. Then add DIEA (21.3 mg, 0.162 mmol) in DMF (1 mL) to the reaction system, and stir the reaction at 60°C for 16 hours. The reaction solution is directly separated by reverse phase preparative separation (MeCN / H2O with 0.1% FA) and freeze-dried to obtain the target product QSI-A-1 (14 mg, yield: 15.4%, dark blue solid). LC-MS (ESI) m / z: 1982.8 [Μ] + LC-MS spectrum see Figure 8 .

[0070] The following is an antibacterial activity test experiment using the polypeptide conjugate synthesized in Example 1 as an example:

[0071] 1. QSI-A bacterial targeting evaluation method

[0072] The targeting of QSI-A to bacteria was investigated by detecting the expression level of Agr effector molecule RNAIII: QSI-A at different concentrations (0.01 μM, 0.1 μM, 1 μM) was co-incubated with SA strain for 5 h. Total bacterial RNA was extracted using the trizol method and reverse transcribed into cDNA according to the instructions of the Takara reverse transcription kit. Real-time quantitative PCR was performed using the SYBR Green method and the results were analyzed according to the Takara ( Premix Ex Taq TM II) and perform the reaction according to the instructions. Each reaction was repeated twice. Finally, the ΔCT method was used to compare the expression of RNAIII in each group relative to the internal reference gene 16S. The results are shown in Figure 2 The experimental results showed that under the action of QSI-A, the expression level of bacterial Agr effector molecule RNAIII decreased significantly, suggesting that it can effectively target bacteria, inhibit the bacterial quorum sensing system, and achieve the effect of reducing bacterial virulence.

[0073] 2. Evaluation of QSI-A antibiotic release characteristics

[0074] QSI-A was diluted to 200 μg / mL with Cathepsin B buffer (20 mM sodium acetate, 1 mM EDTA, 5 mM L-cysteine, pH 5.0). 10 μg / mL Cathepsin B (CTSB) was added to the diluted QSI-A, and after incubation at 37°C for 1 h, 9 volumes of TSB medium were added to terminate the reaction. The buffer without Cathepsin B was used as a control group, and the obtained reaction solution was diluted 2-fold in a 96-well plate, and 5×10 5 CFU of SA strain, after being cultured at 37℃ overnight. Use a microplate reader to detect the absorbance at 630nm to reflect the bacterial growth. Figure 3 The experimental results showed that compared with the control group, the growth of bacteria in the Cathepsin B buffer incubation group was significantly inhibited, indicating that under the action of this enzyme, the Linker in QSI-A was hydrolyzed, resulting in a sharp increase in the content of rifamycin in the system, effectively killing the bacteria.

[0075] 3. QSI-A in vitro anti-intracellular bacteria activity test

[0076] Macrophage RAW264.7 and non-macrophage A549, GM63, HacaT, and IEC-6 cells were cultured at 5×10 6 Each well was inoculated in a 24-well plate. SA in the logarithmic growth phase was collected and resuspended in the cell culture medium for later use. The prepared SA was added to the cell wells at a ratio of 10:1 (bacteria / cell), and five groups were set up in parallel. The drug-treated groups were given QSI-A, rifamycin antibiotics dmDNA31, corresponding AIP-III derivatives, and a 1:1 mixture of dmDNA31 and AIP-III derivatives (three concentration gradients were set, 10μM, 20μ, and 50μM, respectively), and the control group was given normal saline. After centrifugation at 250g for 7min, it was placed in a cell culture incubator and incubated for 30min. Then 50μg / ml of gentamicin was added to the culture medium, the supernatant was removed after 30min of action, washed twice with cell culture medium without antibiotics, and cultured in cell culture medium without antibiotics for 2h. Finally, 0.1% Triton X-100 was added to the cells to lyse the cells and release the bacteria. The lysate was diluted in multiples and evenly spread on TSA agar plates. The plates were incubated in a 37°C constant temperature incubator overnight. Finally, CFU counts were performed to calculate the number of colonies in the cells. Figure 4The experimental results showed that QSI-A can effectively eliminate intracellular Staphylococcus aureus in both macrophages and non-macrophages tested, while the first-line clinical drug vancomycin has a poor effect on the elimination of intracellular bacteria, or even no ability to eliminate them. At the same time, different cells present different specific situations, which may be related to factors such as the intracellular survival mechanism of Staphylococcus aureus.

[0077] 4. QSI-A in vivo anti-intracellular bacterial activity test

[0078] 100 μl of SA bacterial solution (1×10 9 CFU / mL) were injected into seven-week-old Balb / c mice via the tail vein. Between 6h and 24h after infection, 10mg / kg vancomycin was injected intraperitoneally twice a day to establish an intracellular SA infection model. 16 Balb / c mice were randomly divided into four groups, 4 mice in each group, three treatment groups and one control group. The treatment groups were given vancomycin, rifamycin antibiotics dmDNA31 and QSI-A, respectively, and the control group was treated with normal saline. Drugs were administered 12 hours after infection, with the dosages of vancomycin 110 mg / Kg, dmDNA31 0.5 mg / Kg, and QSI-A 10 mg / Kg, respectively. Four days after administration, all infected mice were killed, and the liver, kidney, and spleen were collected. These organs were placed in PBS for homogenization, and the homogenate of each organ was diluted 10 times. The dilution was evenly spread on TSA agar plates and placed in a 37°C constant temperature incubator for overnight incubation. CFU counts were performed, and the colony counts of each organ of mice under treatment with each drug group and the control group were calculated to evaluate the anti-intracellular SA infection effect of QSI-A in vivo, and the pathological level of mouse organs was evaluated by HE staining. Figure 5 , the experimental results show that ( Figure 5 Middle A), after QSI-A treatment, the kidney counts of mice were almost gone, and the effect was significantly better than vancomycin and rifamycin antibiotics dmDNA31. In addition, HE staining results showed ( Figure 5 In the middle B), the drug-treated group was able to significantly reduce the degree of damage to the lungs, liver, kidneys and other organs of infected mice. In summary, QSI-A exhibited good anti-intracellular bacterial activity in vivo.

[0079] In summary, in view of the high affinity of AIP-IIID4A amide and its analogs to the AgrC receptor on the bacterial surface, the present invention uses them as the target head of drug design, which can not only achieve bacterial targeting, but also inhibit the bacterial quorum sensing system, reduce bacterial pathogenicity, and is conducive to the development of antibacterial agents with synergistic antibacterial functions. The polypeptide conjugate drug of the present invention can solve the bottleneck problem that existing antibiotics cannot effectively remove intracellular bacteria. At the same time, compared with the existing cell-targeted anti-intracellular bacteria strategy, the polypeptide conjugate described in this study targets bacteria outside the cell, enters the cell with the bacteria, and specifically hydrolyzes and releases high-concentration antibiotics inside the cell, thereby achieving co-localization of bacteria and antibiotics inside the cell, thereby effectively enhancing the intracellular bacteria removal effect. Compared with the existing antibody-conjugated drugs, the present invention uses polypeptide conjugates, which makes drug synthesis simpler and easier to obtain, and the resulting drug molecular structure is smaller, which is conducive to the improvement of drug bioavailability, and can effectively avoid immunogenicity and off-target effects. What is more worth mentioning is that the PDC drug described in the present invention uses the bacterial quorum sensing self-inducing peptide analog AIP-IIID4A amide as the target head, which can not only achieve the bacterial targeting of the drug, but also reduce the bacterial pathogenicity by inhibiting the bacterial quorum sensing system, thereby exerting a dual-functional antibacterial effect.

[0080] It can be seen that the polypeptide conjugate drug described in the present invention focuses on the difficult problem of treating intracellular bacteria. For the first time, the bacterial population-sensing self-inducing peptide molecules are used as targeting carriers. Through the "Trojan Horse" strategy, the design of bacteria-targeted polypeptide conjugate drugs is realized. The polypeptide conjugate drug synthesis route is simple and the synthesis method is mature. The polypeptide conjugate targets bacteria, enters the cell with the bacteria, and hydrolyzes and releases antibiotics in a specific intracellular environment, thereby achieving co-localization of antibiotics and bacteria in the cell, and reaching local high concentrations, effectively eliminating intracellular bacteria. The technical route described in the present invention provides a feasible new strategy for the treatment of intracellular bacteria, and is expected to develop a class of PDC drugs with synergistic antibacterial functions.

[0081] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A polypeptide-conjugated drug or a pharmaceutically acceptable salt thereof, characterized in that: It is composed of cyclic peptide molecules, connecting arms, spacers and antibiotic drugs connected by chemical bonds; The cyclic peptide molecule is selected from AIP-IIID4A amide and its structural analogs; The linker arm selects a molecule that is specifically sensitive to cathepsin B in lysosomes; The spacer is a self-degradable structural fragment.

2. A peptide-conjugated drug according to claim 1, characterized in that: The AIP-IIID4A amide and its structural analogs include cyclic peptide molecules with the following structures:

3. The polypeptide-conjugated drug or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: The connecting arm includes a molecule with the following structure:

4. The polypeptide-conjugated drug or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: The spacer includes a molecular fragment of the following structure:

5. The polypeptide-conjugated drug or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: The antibiotic drugs include rifamycin, rifamycin-like dmDNA31, vancomycin, daptomycin, linezolid and oxacillin.

6. A polypeptide-conjugated drug or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 5, characterized in that: Includes any of the following compounds:

7. Use of a polypeptide-coupled drug or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 6 in the preparation of an antibacterial drug, characterized in that: The antibacterial drug is a drug against intracellular bacteria.

8. An antibacterial drug, characterized in that: The polypeptide-coupled drug according to any one of claims 1 to 6 is prepared into an injection, capsule, syrup, aerosol, gel, cream, pill or transdermal patch with or without the addition of a pharmaceutically acceptable carrier.

9. A method for preparing a polypeptide-coupled drug or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 6, characterized in that: include: Under copper catalysis, the linker with the spacer is connected to the cyclic peptide molecule through a click chemistry reaction, and then conjugated according to the structural unit in the antibiotic drug; wherein: For the connection of antibiotic drugs containing tertiary amine fragments: the hydroxyl group in the connecting arm is halogenated to obtain a halide, which then undergoes an electrophilic substitution reaction with the tertiary amine group in the antibiotic drug to achieve connection; For the connection of antibiotic drugs containing carboxylic acid fragments: the hydroxyl group in the connecting arm is reacted with the carboxylic acid to form an ester to achieve coupling with the antibiotic drug; Furthermore, the polypeptide-coupled drug is prepared by reacting with an acid to obtain a pharmaceutically acceptable salt thereof.

10. Use of AIP-IIID4A amide and its structural analogs as polypeptide targets in the preparation of antibacterial drugs, characterized in that: The AIP-IIID4A amide and its structural analogs are used as targeted drug carriers for preparing anti-intracellular bacteria drugs.

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