A polypeptide degrading agent targeting degradation of CD26 and a preparation method and application thereof

Abstract

The application belongs to the technical field of biological medicine, and particularly relates to a polypeptide degradation agent for targeted degradation of CD26 and a preparation method and application thereof. The polypeptide degradation agent is obtained after coupling of a tetrapeptide and lenalidomide. The amino acid sequence of the tetrapeptide is any one of SEQ ID NO. 1 and SEQ ID NO. 2. The polypeptide degradation agent can specifically target and degrade DPP4, i.e. CD26, but cannot degrade DPP4 isozymes such as DPP7, DPP8 and DPP9, and thus has high selectivity. In addition, the polypeptide degradation agent has small molecular weight, one end is a natural short peptide, has good tissue compatibility, can quickly degrade target proteins in 6 hours, and thus has good tissue permeability.

Description

Technical Field

[0001] This invention belongs to the field of biomedical technology, specifically relating to a peptide degrader that targets and degrades CD26, its preparation method, and its application. Background Technology

[0002] CD26, also known as dipeptidyl peptidase 4 (DPP4), is a type II transmembrane glycoprotein dimer with a molecular weight of 110 kDa. Its extracellular region possesses serine protease activity, specifically recognizing the X-proline or X-alanine sequence at the N-terminus of peptides and catalyzing dipeptide cleavage. CD26 is highly expressed in immune cells such as the kidney, small intestine, endothelial cells, and T lymphocytes, participating in immune regulation, tumor metastasis, and metabolic disease processes through both enzyme-dependent and non-enzyme-dependent mechanisms. Notably, the interaction of CD26 with extracellular matrix proteins such as collagen and fibronectin has been shown to activate the integrin signaling pathway, promoting tumor cell migration.

[0003] Currently, clinical intervention strategies targeting CD26 mainly focus on small molecule enzyme activity inhibitors, such as alogliptin and sitagliptin, which inhibit dipeptide cleavage by competitively binding to catalytic pockets. However, these inhibitors have two major technical drawbacks: (1) they cannot block non-enzyme-dependent functions of CD26, such as the protein-protein interaction network between CD26 and CD45 and caveolin-1; (2) long-term use can easily lead to compensatory upregulation of the target and the development of drug resistance. In addition, although monoclonal antibodies such as Begelomab can clear CD26 from the membrane surface, they pose an immunogenic risk and are difficult to penetrate the solid tumor microenvironment.

[0004] In recent years, protein degradation-targeting chimeric technology has provided a new approach to overcome the limitations of traditional inhibitors by achieving specific degradation of target proteins through the ubiquitin-proteasome system. However, the development of existing CD26 degraders faces the following challenges: (1) small molecule PROTACs are limited by steric hindrance, resulting in insufficient binding efficiency to flat target sites; (2) antibody-based protein degraders AbTACs suffer from permeability limitations due to their large molecular weight. Therefore, the development of novel CD26 degraders that combine high selectivity and good tissue permeability is of great clinical significance. Summary of the Invention

[0005] To address the limitations of traditional CD26 inhibitors, this invention provides a peptide degrader that combines high selectivity and good tissue penetration for targeted CD26 degradation.

[0006] The technical solution adopted in this invention is: This invention provides a peptide degrader for targeted degradation of CD26, wherein the peptide degrader is obtained by coupling a tetrapeptide and lenalidomide; The amino acid sequence of the tetrapeptide is either one of those shown in SEQ ID NO.1 and SEQ ID NO.2.

[0007] A second aspect of the present invention provides a method for preparing the aforementioned polypeptide degrading agent, comprising the following steps: The tetrapeptide was synthesized in a solid phase according to the amino acid sequence shown in SEQ ID NO.1 or SEQ ID NO.2; The tetrapeptide is coupled with lenalidomide to obtain the polypeptide degrading agent.

[0008] Preferably, the coupling process is as follows: The tetrapeptide and lenalidomide were co-dissolved in N,N-dimethylformamide, and then a condensing agent was added. The mixture was reacted in an alkaline environment under nitrogen protection at 24°C~26°C in the dark for 11h~14h.

[0009] Preferably, the condensing agent is O-benzotriazole-N,N,N',N'-tetramethylurea tetrafluoroborate.

[0010] Preferably, the molar ratio of the tetrapeptide to lenalidomide is 5:6~8.

[0011] Preferably, the reaction conditions are 25°C and reaction in the dark for 12 hours.

[0012] A third aspect of the present invention provides an application of the aforementioned polypeptide degrading agent, wherein the polypeptide degrading agent is used in any of the following: 1) Preparation of drugs that target and degrade CD26; 2) Prepare drugs to enhance the killing effect of NK cells; 3) Prepare drugs to increase cytokine levels in NK cells; 4) Prepare drugs for treating tumors.

[0013] Preferably, the cytokines include at least one of interferon-γ and tumor necrosis factor-α.

[0014] Preferably, the tumor is esophageal cancer.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a peptide degrader for targeting and degrading CD26. The peptide degrader is obtained by coupling a tetrapeptide with lenalidomide; the amino acid sequence of the tetrapeptide is any one of the sequences shown in SEQ ID NO.1 and SEQ ID NO.2. The peptide degrader of this invention can specifically target and degrade DPP4, i.e., CD26; however, it cannot degrade DPP4 isoenzymes such as DPP7, DPP8, and DPP9, demonstrating its high selectivity. Furthermore, the peptide degrader of this invention has a small molecular weight, with one end being a natural short peptide. Its peptide backbone is more modifiable than that of smaller molecules, and high-affinity binding to the target site can be more easily achieved through flexible adjustment of the amino acid sequence. It also exhibits good tissue compatibility, rapidly degrading the target protein within 6 hours, demonstrating excellent tissue penetration.

[0016] This invention discovered and synthesized two short peptides containing four amino acids, finding that they possess excellent ability to target and bind to CD26 and inhibit CD26 enzyme activity. Based on these two short peptides, a PROTAC peptide degrader targeting CD26 was synthesized, demonstrating its good ability to degrade CD26 in various cell types. Simultaneously, in NK cells, its good ability to promote NK cell proliferation and purification was demonstrated. Attached Figure Description

[0017] Figure 1 The structure is LWWY-Lenalidomide.

[0018] Figure 2 The structure is LWWH-Lenalidomide.

[0019] Figure 3 To verify the degradation effects of PLY and PLH.

[0020] Figure 4 The effects of PLY and PLH on NK cell viability.

[0021] Figure 5 To evaluate the killing effect of NK cells.

[0022] Figure 6 Statistics on the levels of the cytokine INF-γ.

[0023] Figure 7 The degradation effect of PLH on DPP8 at different time points.

[0024] Figure 8 The degradation effect of PLY on DPP8 at different time points.

[0025] Figure 9The degradation effects of PLH and PLY on DPP7 and DPP9 at different time points are shown in Figure A: Degradation effect of PLH on DPP7 and DPP9 at different time points; Figure B: Degradation effect of PLY on DPP7 and DPP9 at different time points. Detailed Implementation

[0026] The present invention will be further illustrated below with specific embodiments, but these embodiments do not limit the scope of the invention. Modifications or substitutions to the details and form of the technical solutions of the present invention may be made without departing from the spirit and scope of the invention, but all such modifications or substitutions fall within the protection scope of the present invention.

[0027] The inventive concept of this invention is as follows: NK cells do not require recoding of antigen recognition receptor genes; instead, they primarily recognize the major histocompatibility complex (MHC) through a series of unique cell surface receptors. Receptor-ligand interactions activate NK cells to exert their corresponding biological functions. Based on domestic and international research, NK cell immunotherapy is safe and effective in treating and preventing malignant tumors. While NK cells have shown potential, their clinical application remains limited by several technical barriers, including: long culture cycles and insufficient expansion efficiency with conventional expansion protocols; functional exhaustion caused by the upregulation of NK cell inhibitory receptors, such as NKG2A; and the tumor microenvironment inhibiting NK cell killing. These systemic deficiencies severely restrict the production and clinical use of NK products, necessitating breakthroughs through technological innovation.

[0028] This invention addresses these problems by developing a peptide degrader that targets CD26. This drug can target and degrade CD26, and can also enhance the proliferative activity of NK cells. At the same time, it enhances the killing function of NK cells by promoting the secretion of cytokines such as interferon-γ and tumor necrosis factor-α during the killing process.

[0029] Addressing the current technological limitations of CD26-targeted therapies, this invention provides a peptide degrader for CD26 targeting. This peptide degrader is obtained by coupling a tetrapeptide with lenalidomide; the amino acid sequence of the tetrapeptide is any one of the sequences shown in SEQ ID NO. 1 and SEQ ID NO. 2. SEQ ID NO. 1: LWWY; SEQ ID NO. 2: LWWH. The tetrapeptide of this invention targets and recognizes the CD26 protein while simultaneously inhibiting enzyme activity, while lenalidomide recruits ubiquitination leading to protein degradation. The two peptides, when synthesized together, form a PROTAC drug to achieve the goal of targeted CD26 degradation.

[0030] This invention aims to develop a novel targeted degradation agent, which specifically addresses the following core issues: 1. Limitations of traditional small molecule inhibitors.

[0031] Incomplete inhibition of function: Existing DPP4 enzyme activity inhibitors, such as alogliptin, can only block the catalytic function of CD26 and cannot interfere with its non-enzymatic signaling pathways mediated by protein interactions, such as tumor metastasis driven by the integrin / FAK pathway.

[0032] Drug resistance risk: Long-term use can lead to compensatory upregulation of CD26 expression, reducing the effectiveness of treatment.

[0033] 2. Technical defects of antibody drugs.

[0034] Permeability limitation: Anti-CD26 monoclonal antibodies have a relatively large molecular weight of approximately 150 kDa, making it difficult to penetrate solid tumor tissue.

[0035] 3. Adaptability barriers of PROTAC technology Target binding challenge: CD26 lacks a flat surface structure with a deep binding pocket, which makes it difficult for traditional small molecule PROTAC warhead modules, such as those based on sitagliptin derivatives, to drive effective degradation.

[0036] 4. Application scenario expansion needs.

[0037] Currently, CD26-targeted agents are mainly focused on the treatment of type 2 diabetes, while their application in the regulation of the tumor immune microenvironment and drug-resistant tumors lacks systematic research.

[0038] This invention achieves the following breakthrough goals by designing peptide degraders targeting CD26: Dual-mechanism blockade: Simultaneously eliminating the enzymatic activity of CD26 and its protein-protein interaction-mediated non-enzymatic signal transduction.

[0039] Highly efficient permeability: It uses a polypeptide backbone of 4 amino acids with a molecular weight of less than 3kDa.

[0040] Advantages in resisting drug resistance: It completely degrades CD26 protein through the proteasome pathway, avoiding the risk of compensatory upregulation of the target.

[0041] Multifunctional applications: Expanding into the field of tumor immunotherapy, enhancing NK cell proliferation and killing. To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments. Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0042] The list of abbreviations for this invention is shown in Table 1.

[0043] Table 1. List of abbreviations for this invention Example 1 A method for preparing a peptide degrader that targets and degrades CD26 is as follows: 1. Solid-phase synthesis of tetrapeptide chain H-Leu-Trp-Trp-Tyr-OH.

[0044] 1.1 Loading of the starting amino acid Tyr.

[0045] 0.5 g of Fmoc-Tyr(tBu)-Wang resin with a loading of 0.3 mmol / g was placed in a 30 mL peptide synthesis reactor. 15 mL of dichloromethane was added, and the mixture was shaken at room temperature for 30 min to swell. The solvent was removed by filtration. The resin was washed with N,N-dimethylformamide in three 10 mL portions, filtering to dryness each time.

[0046] 1.2. Assemble the second tryptophan Trp.

[0047] Deprotection of Fmoc: Add 15 mL of v / v 20% piperidine / DMF solution, purge with nitrogen, and shake at room temperature for 15 min. Filter. Repeat the deprotection process once, shaking at room temperature for 10 min.

[0048] Washing test: Wash the resin 6 times with DMF, 10 mL each time; take 5 resin grains for ninhydrin test, confirming that the free amino group is dark blue.

[0049] Coupling reaction: Weigh 0.6 mmol of Fmoc-Trp(Boc)-OH and 0.6 mmol of condensing agent TBTU into a beaker, add 8 mL of DCM / DMF mixed solvent prepared at a 1:1 volume ratio, and then inject 1.2 mmol of N,N-diisopropylethylamine. After pre-activation for 5 min, transfer the solution to the reactor and react with shaking at room temperature for 2 h under nitrogen protection.

[0050] Post-treatment: Filter to remove the reaction solution, and wash the resin three times with 10 mL of DMF each time.

[0051] 1.3 Assemble the third tryptophan Trp.

[0052] The steps are the same as in 1.2, using the same equivalent amount of reagent.

[0053] 1.4 Assemble the fourth leucine (Leu).

[0054] Removal of Fmoc protecting groups: Same as the removal of Fmoc protecting groups in 1.2, perform Fmoc group removal.

[0055] Coupling optimization: Dissolve 0.6 mmol Fmoc-Leu-OH in 8 mL of pure DMF solvent, add 0.6 mmol TBTU condensing agent, and pre-activate with 1.2 mmol DIEA for 5 min. Transfer the activated solution to the resin from the previous step and react with shaking under nitrogen protection for 3 h.

[0056] N-terminal deprotection and verification: The resin was washed twice with 15 mL v / v 20% piperidine / DMF, 15 min each time. The elution from washing the resin with pure DMF eight times was neutral, and ninhydrin detection confirmed the presence of free amino groups.

[0057] The final product is a resin peptide.

[0058] 1.5. Cleavage and crude peptide purification.

[0059] The cutting fluid is prepared using the following formula: Trifluoroacetic acid:triisopropylsilane:water = 95:2.5:2.5, v / v / v. In this example, 10 mL of cutting fluid was prepared for cutting.

[0060] Add the cutting fluid to the reactor and cut at room temperature with shaking under light-protected conditions for 2.5 h. Collect the filtrate by suction filtration, wash the resin three times with fresh TFA, 2 mL each time, and combine the filtrates.

[0061] The filtrate was slowly added dropwise to 50 mL of pre-cooled diethyl ether at -20 °C, and the mixture was allowed to stand in an ice bath for 30 min to precipitate the tetrapeptide.

[0062] The precipitate was collected by centrifugation at 3000 rpm for 5 min, washed three times with cold ether, and dried under vacuum for 4 h to obtain crude peptide LWWY. In this example, approximately 120 mg of crude peptide LWWY was obtained.

[0063] 2. LWWY is coupled with lenalidomide.

[0064] 2.1 Activation condensation reaction.

[0065] 0.15 mmol of crude peptide LWWY and 0.18 mmol of lenalidomide were dissolved in 10 mL of anhydrous DMF. The mixture was cooled to 4 °C in an ice bath, and 0.18 mmol of condensing agent TBTU and 0.54 mmol of base DIEA were added sequentially. The ice bath was removed, and the mixture was reacted at 25 °C in the dark under nitrogen protection for 12 h.

[0066] Process monitoring: Samples were taken every 2 hours for HPLC analysis. During HPLC analysis: C18 column, gradient elution with acetonitrile / 0.1% v / v TFA aqueous solution, detection at 280 nm, the retention time of the target product was approximately 18.5 min.

[0067] 2.2 Post-processing purification.

[0068] The reaction solution was concentrated to 3 mL under reduced pressure at 30 °C. 10 mL of a 1:1 v / v TFA / DCM mixture was added, and the mixture was stirred at room temperature for 30 min to quench byproducts. The mixture was then added dropwise to 50 mL of pre-cooled methyl tert-butyl ether at 0 °C, ultrasonically dispersed for 1 min, and then allowed to stand in an ice bath for 1 h. The precipitate was collected by centrifugation at 4000 rpm for 10 min and dried under vacuum to obtain the crude conjugate.

[0069] 2.3 High-performance liquid chromatography (HPLC) purification.

[0070] The crude conjugate was dissolved in 500 μL DMSO and 1.5 mL of aqueous solution containing 0.1% TFA (v / v), and then loaded onto a preparative HPLC system. The parameters of the preparative HPLC system are as follows: Chromatographic column: Kromasil C18 20mm×250mm; mobile phase: phase A - v / v 0.1% TFA aqueous solution, phase B - v / v 0.1% TFA acetonitrile solution; gradient program: 0min~5min 20% phase B → 30min~40min 60% phase B; flow rate: 8mL / min, detection wavelength 280nm.

[0071] Collect the fraction with a retention time of 17.5 min to 19.5 min, and perform the operation in an ice bath in the dark. Combine the fractions and freeze-dry to obtain a white powder of LWWY-Lenalidomide. Approximately 10 mg of LWWY-Lenalidomide was prepared in this example. See the detailed structure below. Figure 1 .

[0072] Example 2 A method for preparing a peptide degrader that targets and degrades CD26 is as follows: 1. Solid-phase synthesis of tetrapeptide chain H-Leu-Trp-Trp-His-OH.

[0073] 1.1 Loading of initial amino acids.

[0074] Take 0.5 g of Fmoc-His(Trt)-Wang Resin resin with a loading of 0.3 mmol / g, which is 0.15 mmol; protect His imidazole nitrogen with triphenylmethyl, swell in DCM for 30 min, and wash three times with DMF, 10 mL each time.

[0075] 1.2. Assemble the second tryptophan Trp.

[0076] Remove Fmoc protecting group: v / v 20% piperidine / DMF 15mL, shake twice, 15min each time.

[0077] Washing test: After washing with DMF 6 times, ninhydrin test showed a deep blue color.

[0078] Coupling reaction: Trp was coupled to the product in 1.1 using the following reagent system: Fmoc-Trp(Boc)-OH: 0.6 mmol, TBTU: 0.6 mmol, DIEA: 1.2 mmol, solvent: DCM / DMF at a volume ratio of 1:1, prepare 8 mL.

[0079] The coupling process is exactly the same as 1.2 in Example 1.

[0080] Removal of Fmoc protecting groups: Same as 1.1 in Example 1.

[0081] 1.3 Assemble the third tryptophan Trp.

[0082] Same as 1.2 in this embodiment, using the same equivalent reagent.

[0083] 1.4 Assemble the fourth leucine (Leu).

[0084] As in section 1.4 of Example 1, the resin peptide was finally obtained.

[0085] 1.5. Cleavage and crude peptide purification.

[0086] A step-by-step cutting strategy is adopted to avoid His side reactions: First, shake with 10 mL of v / v 1% TFA / DCM for 10 min, filter, and remove the Trt protecting group of His; then replace with standard cleavage buffer → shake for 2 h to lyse the peptide chain and remove Boc → add 50 mL of -20℃ diethyl ether dropwise to precipitate → centrifuge → wash 3 times with cold diethyl ether → vacuum dry → crude peptide LWWH. The crude peptide LWWH obtained in this example is approximately 115 mg, a light yellow solid.

[0087] The standard cutting fluid formula is as follows: TFA:TIS:H2O:phenyl sulfide = 90:2.5:2.5:5. In this example, 10 mL was prepared for cutting.

[0088] 2. LWWH is coupled with lenalidomide.

[0089] 2.1 Activation condensation reaction.

[0090] Crude peptide LWWH and lenalidomide were dissolved in anhydrous DMF. Condensing agent TBTU and base DIEA were added sequentially in an ice bath at 4°C; the ice bath was removed, and the reaction was carried out at 25°C in the dark for 12 hours under nitrogen protection. The material ratios are shown in Table 2.

[0091] Table 2 Material Proportions Process monitoring: Samples were taken every 2 hours for HPLC analysis. HPLC analysis: C18 column, gradient elution with acetonitrile / 0.1% v / v TFA aqueous solution, detection at 280 nm, target product retention time approximately 17.8 min.

[0092] 2.2 Post-processing and purification.

[0093] Same as 2.2 of Example 1.

[0094] 2.3 High-performance liquid chromatography (HPLC) purification.

[0095] The crude conjugate was dissolved in 500 μL DMSO and 1.5 mL of aqueous solution containing 0.1% TFA (v / v), and then loaded onto a preparative HPLC system. The parameters of the preparative HPLC system are as follows: Column: Kromasil C18 20mm×250mm; Mobile phase: Phase A - v / v 0.1% TFA aqueous solution, Phase B - v / v 0.1% TFA acetonitrile solution; Gradient program: 0min~5min 15% Phase B → 30min 50% Phase B; Flow rate: 8mL / min, Detection wavelength: 280nm.

[0096] The fractions retained for 17.5 to 18.2 minutes were collected and subjected to an ice bath in the dark. The combined fractions were freeze-dried to obtain LWWH-Lenalidomide. Approximately 10 mg of LWWH-Lenalidomide was prepared in this example. See the detailed structure below. Figure 2 .

[0097] Example 3 The application of a peptide degrader that targets and degrades CD26 is as follows: The effects of LWWY-Lenalidomide prepared in Example 1 and LWWH-Lenalidomide prepared in Example 2 were verified. For ease of description, LWWY-Lenalidomide will be abbreviated as PLY and LWWH-Lenalidomide as PLH in the following text.

[0098] 1. Evaluation of degradation effect.

[0099] The PLH and PLY prepared in this invention, along with the first-generation CD26 degrader P4-3, were simultaneously applied to KYSE-140 cells for 6 hours to investigate their degradation effect on CD26. The concentrations of PLH, PLY, and P4-3 were all 10 μM.

[0100] The results of the Western blot are shown below. Figure 3The cell group served as a blank control group. PLH, PLY, and P4-3 could all degrade CD26 in cells, but PLH and PLY showed better degradation effects than P4-3.

[0101] 2. Effects on cell viability.

[0102] The PLH and PLY prepared in this invention, along with the first-generation CD26 degrader P4-3, were simultaneously applied to NK cells for 24 hours to investigate their effects on cell viability. The concentrations of PLH, PLY, and P4-3 were all 10 μM.

[0103] See results Figure 4 The cell group served as the blank control group. After adding PLH, PLY, and P4-3 to NK cells for 24 hours, if the cell viability of the cell group was taken as 100%, the cell viability of P4-3 increased by 37%, and that of PLH and PLY increased by 129.9% and 126.5%, respectively (P < 0.05).

[0104] 3. Evaluation of the effectiveness of NK kills.

[0105] Esophageal cancer cells KYSE-140 were seeded in 96-well plates and cultured until the cell density reached 80%. The cells were then divided into five groups, each with an effector-to-target ratio of 1:1: NK cells, NK cells + PLH, NK cells + PLY, and NK cells + P4-3. The concentrations of PLH, PLY, and P4-3 were all 10 μM. The CCK8 level of KYSE-140 cells was measured after 24 hours. The cell group served as a blank control group. The groups with only NK cells were denoted as cell+NK, NK cells + PLH, NK cells + PLY, and NK cells + P4-3.

[0106] See results Figure 5 The killing effect of NK cells alone was 33%, and the killing effect increased to 51.67% when P4-3 was added to NK cells; the killing effect increased to 81.09% when LWH was added, and to 77.59% when LWY was added (P < 0.05).

[0107] Esophageal cancer cells (KYSE-140) were seeded in 96-well plates and cultured until the cell density reached 80%. The cells were then divided into five groups, each with NK cells, NK cells + PLH, NK cells + PLY, and NK cells + P4-3 added at an effector-to-target ratio of 1:1. The concentrations of PLH, PLY, and P4-3 were all 10 μM. Cytokine levels in the culture medium were measured after 24 hours. The cell group consisted of NK cells not stimulated by KYSE cells. The groups with only NK cells were denoted as cell+NK, NK cells + PLH as cell+PLH, NK cells + PLY as cell+PLY, and NK cells + P4-3 as cell+P4-3.

[0108] Measuring the levels of the cytokine INF-γ in the killing environment, such as Figure 6 As shown, the INF-γ levels in the cell group, cell+NK group, cell+p4-3 group, cell+LWH group, and cell+LWY group were 21.83 ng / ml, 37.33 ng / ml, 68.83 ng / ml, 83.83 ng / ml, and 84.17 ng / ml, respectively (P < 0.05).

[0109] 4. Validation of selectivity and tissue penetration.

[0110] PLH, PLY, and the degrading agent P4-3 prepared in this invention were applied to KYSE-140 cells for 3 h, 6 h, and 9 h, respectively, with a concentration of 10 μM for all three. The results showed that their isoenzymes DPP7, DPP8, and DPP9 were not degraded. (See attached figures). Figures 7-9 This demonstrates its high selectivity.

[0111] Furthermore, the polypeptide degrading agent described in this invention has a small molecular weight and one end is a natural short peptide, which has good tissue compatibility and can rapidly degrade the target protein in 6 hours.

[0112] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A peptide degrader that targets and degrades CD26, characterized in that, The polypeptide degrading agent is obtained by coupling a tetrapeptide and lenalidomide. The amino acid sequence of the tetrapeptide is either SEQ ID NO.1 or SEQ ID NO.2; The structural formula of the polypeptide degrader is any one of the following: 、 。 2. The method for preparing the polypeptide degrading agent as described in claim 1, characterized in that, Includes the following steps: The tetrapeptide was synthesized in a solid phase according to the amino acid sequence shown in SEQ ID NO.1 or SEQ ID NO.2; The tetrapeptide is coupled with lenalidomide to obtain the polypeptide degrading agent; The coupling process is as follows: The tetrapeptide and lenalidomide were co-dissolved in N,N-dimethylformamide, and then a condensing agent was added. The mixture was reacted in an alkaline environment under nitrogen protection at 24°C~26°C in the dark for 11h~14h.

3. The preparation method according to claim 2, characterized in that, The condensing agent is O-benzotriazole-N,N,N',N'-tetramethylurea tetrafluoroborate.

4. The preparation method according to claim 2, characterized in that, The molar ratio of the tetrapeptide to lenalidomide is 5:6~8.

5. The preparation method according to claim 2, characterized in that, The reaction conditions under nitrogen protection were 25°C and 12 hours in the dark.

6. The application of the polypeptide degrading agent as described in claim 1, characterized in that, The polypeptide degrading agent is used to prepare drugs for treating tumors; The tumor is esophageal cancer.

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