Application of combined use of antibody-drug conjugate ADC and radionuclide-drug conjugate RDC in preparation of medicine for treating gastric cancer, and medicine composition for treating gastric cancer

Abstract

The invention provides application of combined use of an antibody-drug conjugate ADC and a radionuclide-drug conjugate RDC in preparation of drugs for treating gastric cancer. The invention also provides a pharmaceutical composition for treating gastric cancer. The pharmaceutical composition is composed of the antibody-drug conjugate ADC and the radionuclide-drug conjugate RDC. According to the invention, the antibody-drug conjugate ADC and the radionuclide-drug conjugate RDC are combined for use, especially the ADC sequential RDC combined treatment group shows the optimal anti-tumor curative effect, and has controllable toxic and side effects.

Description

Technical Field

[0001] This application relates to the use of the combined use of antibody-drug conjugate (ADC) and radionuclide-drug conjugate (RDC) in the preparation of a drug for treating gastric cancer, and a pharmaceutical composition for treating gastric cancer. Background Art

[0002] Statistical data in 2022 showed that gastric cancer (GC) is the fifth most common cancer globally, with approximately 968,000 newly diagnosed cases worldwide. Despite various treatment methods, including surgery, chemotherapy, radiotherapy, and biologic targeted therapies, the annual death toll remains as high as 660,000. Therefore, there is an urgent need to develop more effective treatment strategies.

[0003] Claudin 18.2 (CLDN18.2) is a member of the Claudin protein family and plays a key role in maintaining epithelial cell polarity by interacting with other membrane proteins to form a complex intercellular junction network. This network also regulates paracellular transport and signal transduction pathways. It has been reported that more than 50% of GC patients express CLDN18.2, and the expression rate is as high as 80% in some populations. In addition, CLDN18.2 is expressed in both primary and metastatic lesions. Due to its highly specific expression in tumors, CLDN18.2 has become a potential therapeutic target for the development of anti-gastric cancer drugs.

[0004] In recent years, the research on targeted therapy against CLDN18.2 has advanced rapidly, including monoclonal antibodies, bispecific antibodies (BsAb), antibody-drug conjugates (ADC), and radionuclide-drug conjugates (RDC). Among them, the monoclonal antibody Zolbetuximab of CLDN18.2 has limited efficacy in clinical trials. However, ADC and RDC developed based on the monoclonal antibody of CLDN18.2, such as SYSA1801 [Pelster, M., Perez, C. A., Chandana, S. R., Uboha, N. V., Swami, A., McDonald, H., Srivastava, J., & Barve, M. A. (2024). A phase I study of EO-3021 in adult patients with solid tumors likely to express CLDN18.2. Journal of Clinical Oncology, 42(3_suppl), TPS429. https: / / doi.org / 10.1200 / JCO.2024.42.3_suppl.TPS429] and 177Lu-TST001 [Zeng Z, Li L, Tao J, et al. 177 Lu]-labeled anti-claudin-18.2 antibody demonstrated radioimmunotherapy potential in gastric cancer mouse xenograft models. Eur J Nucl Med Mol Imaging. 2024;51(5):1221-1232. doi:10.1007 / s00259-023-06561-1], showing more significant antitumor effects and controllable safety.

[0005] Both ADC and RDC achieve precise treatment by specifically targeting tumor cells. ADC uses monoclonal antibodies to highly specifically recognize antigens on the surface of tumor cells and directly deliver cytotoxic drugs to tumor cells, thus minimizing the toxicity to normal tissues. In contrast, RDC uses tumor-targeting molecules labeled with radioisotopes to provide precise radiotherapy, showing a strong cytotoxic effect on local, refractory lesions or metastatic sites. However, both types of drugs face inherent challenges: ADC will reduce efficacy due to the development of drug resistance, while RDC will cause radiation-related side effects.

[0006] Existing data indicate that compared with CLDN18.2 monoclonal antibodies, both ADC and RDC show better antitumor effects and controllable safety. There is currently a lack of relevant research on comparing the antitumor efficacy and safety of ADC and RDC, as well as the exploration of combination therapy. Summary of the Invention

[0007] The present invention aims to use an ADC drug (SYSA1801) and an RDC drug ( 177 Lu-DOTA-SYSA1801mAb) derived from the same CLDN18.2 monoclonal antibody to compare the efficacy and safety of RDC and RDC combined with ADC drugs in the treatment of CLDN18.2-positive gastric cancer, and to evaluate whether different sequential methods will affect the efficacy.

[0008] Among them, the ADC drug is SYSA1801, also known as EO-302, SYSA1801mAb is a CLDN18.2 monoclonal antibody, and SYSA1801 is prepared by conjugating SYSA1801mAb with MMAE.

[0009] The present invention provides the use of the combined use of an antibody-drug conjugate ADC and a radionuclide-drug conjugate RDC in the preparation of a drug for the treatment of gastric cancer.

[0010] Among them, the antibody-drug conjugate ADC is SYSA1801 mAb; the radionuclide-drug conjugate RDC is 177 Lu-DOTA-SYSA1801mAb.

[0011] Furthermore, the mass ratio of the SYSA1801mAb to 177 Lu-DOTA-SYSA1801mAb is 1:1 based on SYSA1801.

[0012] Among them, the administration methods of the combined use include simultaneous, parallel, sequential, continuous, alternating or separate administration.

[0013] Among them, the administration method of the combined use is sequential administration, and the sequential administration method is: administered via the tail vein in two doses with an interval of 2 weeks. The first dose is the ADC drug, and the second dose is the RDC drug 177 Lu-DOTA-SYSA1801mAb.

[0014] The present invention provides a pharmaceutical composition for treating gastric cancer, which is composed of an antibody-drug conjugate ADC and a radionuclide-drug conjugate RDC.

[0015] Among them, the antibody-drug conjugate ADC is SYSA1801; the radionuclide-drug conjugate RDC is 177 Lu-DOTA-SYSA1801mAb.

[0016] Preferably, the mass ratio of the SYSA1801 to 177 Lu-DOTA-SYSA1801mAb is 1:1 based on SYSA1801.

[0017] Among them, the 177 preparation method of Lu-DOTA-SYSA1801mAb includes the following steps:

[0018] a. Synthesis of SYSA1801mAb-DOTA

[0019] Replace the solution of SYSA1801mAb with buffer A, add p-NCS-Bz-DOTA and incubate. After the reaction, replace the solution with buffer C solution again to obtain SYSA1801mAb-DOTA;

[0020] Among them, buffer A is Na 2 CO 3 -NaHCO 3, pH 9.5, 0.15 M; the buffer solution C is NaOAc-Ac, pH 5.5, 0.5 M;

[0021] b, 177 Synthesis of Lu-DOTA-SYSA1801mAb

[0022] Combine SYSA1801mAb-DOTA and 177 LuCl3 in a ratio of 1:2, incubate at 42 °C for 1 h; after the reaction, spot and develop, and purify by high performance liquid chromatography analysis.

[0023] The present invention combines the use of antibody-drug conjugate ADC and radionuclide-drug conjugate RDC. In particular, the ADC sequential RDC combination treatment group exhibits the optimal anti-tumor efficacy and is accompanied by controllable toxic side effects. Brief Description of the Drawings

[0024] Figure 1 Flow cytometry results confirm the CLDN18.2 expression level of transfected cells;

[0025] Figure 2 RDC drug 177 HPLC chart of Lu-DOTA-SYSA1801mAb;

[0026] Figure 3 Results of radioactive binding experiment of RDC drug in NUGC-4-CLDN18.2 cells;

[0027] Figure 4 Results of in vitro stability experiment of RDC drug;

[0028] Figure 5 Bio-distribution of RDC drug in tumor-bearing mice;

[0029] Figure 6 Weight change of each group of tumor-bearing mice after drug administration (overall / individual);

[0030] Figure 7 Weight change of each group of tumor-bearing mice after drug administration;

[0031] Figure 8 Survival of each group of tumor-bearing mice after drug administration;

[0032] Figure 9 Blood routine results of tumor-bearing mice after drug administration;

[0033] Figure 10 Liver function of tumor-bearing mice after drug administration;

[0034] Figure 11 Renal function of tumor-bearing mice after drug administration;

[0035] Figure 12 HE staining images of internal organs of tumor-bearing mice after drug administration. Detailed implementation methods

[0036] Example 1 Experiment on the combined use of the antibody-drug conjugate ADC and the radionuclide-drug conjugate RDC of the present invention

[0037] I. Materials and methods

[0038] 1. Cell culture and animal models

[0039] Lentivirus transfection of Claudin18.2 was purchased and used to cultivate a stable overexpressing Claudin18.2 NUGC-4-Claudin18.2 gastric cancer cell line (Chengdu Xiongyi Technology Co., Ltd., China). NUGC-4-Claudin18.2 cells were cultured in RPMI1640 medium. The medium was supplemented with 10% fetal bovine serum (Gibco) and 1% penicillin / streptomycin (Gibco). The cell line was incubated at 37 °C in a humid atmosphere containing 5% CO2. When the cell density reached about 75-90%, in vitro and in vivo experiments were respectively carried out. All animal experiments were approved by the Animal Ethics Committee of Mianyang Central Hospital. Female BALB / c-nu mice, 6-8 weeks old (Spebefu Biotechnology Co., Ltd., China), were purchased and used to establish a NUGC-4-Claudin18.2 xenograft tumor model. Each mouse was subcutaneously injected with 1×10 7 NUGC-4-Claudin18.2 cells for the subcutaneous tumor model (Ethical approval number: S20240210).

[0040] 2. Verification of Claudin18.2 highly expressing cell line by flow cytometry

[0041] First, 5×10 4 cells per well were pre-seeded in a 96-well U-bottom cell culture plate and centrifuged at 1300 rpm for 5 minutes. The cells were resuspended and washed twice with frozen FACS buffer (95% PBS, 5% FBS). The cells were placed in 50 μL of anti-human CLDN18.2 monoclonal antibody (SYSA1801mAb, provided by Shijiazhuang Pharmaceutical Group Jushi Biotechnology Co., Ltd.) and incubated on ice for 60 min. The antibody concentration in the first well was 15 μg / ml, and the dilution gradient was 2-fold, with a total of 12 gradients. The secondary antibody expressing the goat anti-human epitope was incubated in the dark for 30 minutes. After incubation, the cells were washed twice with FACS buffer as described above. The cells were resuspended in 200 μL of FACS buffer and analyzed in a Beckman Coulter FACSCalibur. Data of 3000 cells were collected and analyzed using BD FlowJo software.

[0042] 3. Drug Synthesis

[0043] 3.1 Synthesis of SYSA1801 mAb - DOTA

[0044] Add SYSA1801 mAb into an ultrafiltration tube (MWCO = 30 kDa, 100 sodium form SIGMA), and centrifuge to remove the solvent in the stock solution (13000 r / min, 10 min, 4 °C). Add an appropriate amount of buffer A (Na 2 CO 3 -NaHCO 3 , pH 9.5, 0.15 M), and after centrifugation, add buffer A again; this process is repeated three times. Transfer the purified antibody to a 1.5 ml centrifuge tube, and add p - NCS - Bz - DOTA with a 10 - fold molar ratio (20 nmol / μl, dissolved in DMSO). Incubate at a constant temperature of 37 °C on a shaker at a speed of 70 r / min for 1 h. After incubation, transfer the antibody to an ultrafiltration tube, add buffer C solution (NaOAc - Ac, PH 5.5, 0.5 M) and centrifuge again, repeating 3 times.

[0045] 3.2 177 Synthesis of

[0046] To synthesize 177 Lu - DOTA - SYSA1801 mAb, we combined SYSA1801 mAb - DOTA and 177 LuCl3 (Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics) in a ratio of 1:2 and incubated in a metal bath at 42 °C for 1 h. After the reaction, the labeling rate of the sample was determined by thin - layer chromatography. Ultra - fine fiberglass paper (Agilent Technologies, cat.) No.: SG10001, itlc - sg - glass microfiber chromatography paper, impregnated with silica gel) was cut into strips 10 cm long and 1.5 cm wide. A marking line was drawn 1.5 cm from the bottom as a scale for spotting. Then, 2 μl of the radioactive sample was pipetted onto the marking line of the fiberglass strip. After spotting, the fiberglass strip was placed into a sodium citrate developing system (sodium citrate - citric acid, 0.5 M, PH = 5.5). The reaction mixture was purified by high - performance liquid chromatography. The preparative column was eluted with 13 - 33% acetonitrile in water containing 0.1% TFA at a flow rate of 20 mL / min for 20 min.

[0047] 3.3 In vitro Stability of the Synthesized Drug

[0048] To determine its in vitro stability, 10 μl 177Lu-DOTA-SYSA1801 mAb was added to 15 μl of normal saline and a culture medium containing 10% fetal bovine serum and normal saline in RPMI 1640. It was left standing at room temperature. The labeling rates of the two groups were measured by thin-layer chromatography at 4 h, 24 h, 48 h, 96 h, and 168 h respectively.

[0049] 4. In vitro targeting verification of the synthesized drug - binding experiment

[0050] 177 The preparation method of Lu-DOTA-SYSA1801 mAb was as described above. NUGC-4-Claudin18.2 cells (1×105 cells / well) were placed in a 100 μl centrifuge tube. 177 Lu-DOTA-SYSA1801 mAb was added to the cell suspension with a concentration of 0.025 - 10.000 nM, and its total binding amount was measured. By adding 50×EC50 cold SYSA1801 mAb to the NUGC-4-Claudin18.2 cell mixture, the non-specific binding was determined at one concentration. The cells were incubated with 5 μCi 177 Lu-DOTA-SYSA1801 mAb at room temperature for 1 hour and washed 3 times repeatedly with FACS. The bound and unbound radioactive components were collected and measured using a gamma counter (Turku, Japan). EC50 and Bmax were calculated using PRISM v9.0.

[0051] 5. In vivo targeting verification of the synthesized drug - biodistribution experiment

[0052] 0.8 MBq of 177 Lu-DOTA-SYSA1801 mAb was injected into the tail vein of tumor-bearing mice and sacrificed at selected time points (4 hours, 24 hours, 48 hours, 96 hours, and 144 hours). Samples were collected, weighed wet, and the radioactivity was measured using an automatic gamma counter (USTC Zonkia, GC-1500). The uptake values of major organs or tissues were calculated as the percentage of the injected dose per gram of tissue (%ID / g).

[0053] 6. Antitumor therapy experiment

[0054] When the volume of NUGC-4-Claudin18.2 xenografts grew to 732.75 ± 197.96 mm 3 in volume, the mice were randomly divided into 5 groups with n = 5 in each group. The drug doses of each group were calibrated with the same antibody dose. The specific grouping was as follows:

[0055] (1) RDC monotherapy (RDC) group: Administered twice via the tail vein with an interval of 2 weeks (d0, 14), single dose 177The administration dose of Lu-DOTA-SYSA1801 mAb was: 11.1 MBq (the dose of SYSA1801 mAb was: 150 μg).

[0056] (2) ADC sequential RDC combination therapy (ADC+RDC) group: Administered by tail vein in two doses with an interval of 2 weeks (d0, 14). The first dose was the ADC drug (SYSA1801, provided by CSPC Jushi Biologics Co., Ltd.), the dose of SYSA1801 mAb was 150 μg, and the second dose was the RDC drug 177 Lu-DOTA-SYSA1801 mAb, the dose was: 11.1 MBq (the dose of SYSA1801 mAb was: 150 μg)

[0057] (3) RDC sequential ADC combination therapy (RDC+ADC) group: Administered by tail vein in two doses with an interval of 2 weeks (d0, 14). The first dose was the RDC drug 177 Lu-DOTA-SYSA1801 mAb, the dose was: 11.1 MBq (the dose of SYSA1801 mAb was: 150 μg), and the second dose was the ADC drug (SYSA1801, provided by CSPC Jushi Biologics Co., Ltd.), the dose of SYSA1801 mAb was 150 μg.

[0058] (4) Monoclonal antibody group: Administered by tail vein in two doses with an interval of 2 weeks (d0, 14), and the single-dose of SYSA1801 mAb was: 150 μg.

[0059] (5) Control (NS) group: Administered normal saline on day 0 and day 14.

[0060] The tumor size and mouse body weight were evaluated every Tuesday and Friday after injection. The study endpoint was set as the tumor volume reached 2000 mm 3 or the mouse body weight decreased by 20%. When the mice reached the observation endpoint, blood was collected for routine hematological evaluation and liver and kidney function tests. Tumors and major organs were taken for H&E staining analysis.

[0061] 7. Statistical analysis

[0062] IBM SPSS Statistics for Windows software (version 22.0; IBM, NY, Armonk, USA) was used. One-way ANOVA was used to compare the differences between multiple treatment groups. Differences at the 95% confidence level (P<0.05) were considered statistically significant.

[0063] II. Experimental results

[0064] 1. Cell transfection and animal model

[0065] The NUGC-4 cell line was transfected with lentivirus carrying CLDN18.2 to construct a stable gastric cancer cell line, namely NUGC-4-CLDN18.2 with high expression of CLDN18.2. Flow cytometry confirmed that CLDN18.2 was stably and highly expressed in NUGC-4-CLDN18.2 cells. Finally, a subcutaneous positive gastric cancer xenograft model was established using NUGC-4-CLDN18.2 cells for subsequent animal experiments (as Figure 1 shown).

[0066] 2. Drug synthesis, stability and in vitro targeting binding ability

[0067] Detected by high performance liquid chromatography, 177 the integrity and radiochemical purity of Lu-DOTA-SYSA1801mAb were greater than 99% ( Figure 2 ). Subsequently, it was incubated in NS and 1640 medium (containing 10% fetal bovine serum) for 7 days. Confirmed by radio-labeled thin layer chromatography, 177 Lu-DOTA-SYSA1801mAb did not degrade and had good stability. Figure 3 、 Figure 4 Radioligand binding assay was performed using NUGC-4-CLDN18.2 cells. 177 The saturation binding capacity (Bmax) of Lu-DOTA-SYSA1801mAb to NUGC-4-CLDN18.2 cells (1×10 5 ) was 1149±48.16 nmol, and the equilibrium dissociation constant (Kd) was 24.36±3.5 nmol / L.

[0068] 3. 177 Biodistribution of Lu-DOTA-SYSA1801mAb

[0069] The biodistribution results showed ( Figure 5 ), 177 Lu-DOTA-SYSA1801mAb effectively targeted tumors in the NUGC-4-CLDN18.2 model. With the passage of time, tumor uptake increased and reached a peak at 96 hours. Liver uptake reached a peak at 48 h, and kidney uptake reached a peak at 2 h. With the passage of time, the uptake values in the liver and kidney gradually decreased. With blood circulation, 177 Lu-DOTA-SYSA1801mAb was rapidly cleared from the blood, and the blood content decreased by about 90% from 2 hours to 24 hours.

[0070] 4. Antitumor efficacy

[0071] In the NUGC-4-CLDN18.2 model, on the 14th day after treatment, the NS group and the monoclonal antibody group gradually reached the ethical survival endpoint. There was no statistical difference in tumor volume between the two groups, P>0.05. The average tumor volume of the RDC monotherapy group was 686.86±153.12 mm 3 (TGI% was 105.32%). The average tumor volume of the RDC+ADC group was 713.65±271.28 mm 3 (TGI% was 100.60%). The average tumor volume of the ADC+RDC group was 278.79±381.72 mm 3 (TGI% was 137.93%). The average tumor volume of the monoclonal antibody group was 1906.58±71.11 mm 3 (TGI% was 4.57%). The average tumor volume of the NS group was 1997.88±71.11 mm 3 . On the 46th day after administration, the average tumor volume of the RDC monotherapy group was 871.63±503.97 mm3); the RDC+ADC group (941.74±803.32 mm 3 ), and the average tumor volume of the ADC+RDC group was 248.31±474.01 mm 3 ; (p<0.05). On the 153rd day after treatment, the CR rate of the ADC+RDC group was 40%, and the survival rate was 40%. The survival rates of the other groups were 0% (p<0.001). On the 14th day after administration, the body weights of the mice in the NS group and the monoclonal antibody group showed a slow upward trend. After the administration of the other treatment groups, the body weights of the mice decreased first and then gradually increased slowly. There was a statistically significant difference in body weight between the groups (p<0.05). On the 46th day after the first administration, the body weights of the mice in the RDC monotherapy group, the ADC+RDC group, and the RDC+ADC group showed a fluctuating upward trend. There was no significant difference in the body weights of the mice in each treatment group, P>0.05( Figures 6 - 8 ).

[0072] Table 1. Average tumor volume of each experimental group

[0073]

[0074] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0075] Table 2. Tumor inhibition rate of each treatment group

[0076]

[0077] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0078] Table 3. Survival rate and complete remission rate of each treatment group at 145 days

[0079]

[0080] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0081] Table 4. Average body weight of each treatment group

[0082]

[0083] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0084] 5. Toxic effects

[0085] Compared with the NS group, the monoclonal antibody group had the least changes in blood routine indexes and liver and kidney functions, while the RDC monotherapy group and the combination therapy group had larger change ranges. There were significant differences in renal function among the treatment groups, P < 0.01. There were significant differences in white blood cells and red blood cells among the treatment groups, P < 0.05. HE staining images at the treatment endpoint showed that the organizational structure levels of the heart, lungs, and liver in each group were complete, without obvious pathological structure changes, and there were no obvious differences among the groups. Compared with the NS group, the spleen and kidneys in the RDC and combination drug groups showed disordered splenic nodules, and partial structural damage and deformation of glomeruli and renal tubules (see Figures 9 - 12 ).

[0086] Table 5 Liver function of each treatment group.

[0087]

[0088] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0089] Table 6 Renal function of each treatment group.

[0090]

[0091] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0092] Table 7 Blood routine values of each experimental group.

[0093]

[0094] Note: P1: RDC vs. mAB; p2: RDC vs. NS; P3: RDC vs. RDC+ADC; P4: RDC vs. ADC+RDC; P5: mAB vs. NS; P6: mAB vs. RDC+ADC; P7; mAB vs. ADC+RDC; P8: NS vs. RDC+ADC; P9: NS vs. ADC+RDC; P10: RDC+ADC vs. ADC+RDC.

[0095] In summary, the experimental results:

[0096] 177 Lu-DOTA-SYSA1801 mAb showed good tumor targeting in vivo and had higher tumor uptake compared with other tissues. On the 14th day, the mice in the monoclonal antibody group and the control group successively reached the tumor ethics endpoint. The average tumor volume of the control group was 1997.88 ± 71.11 mm 3 ; the average tumor volume of the monoclonal antibody group was 1906.58 ± 71.11 mm 3 , and the average tumor inhibition rate (TGI%) was 4.57%; the average volume of the RDC single-agent group was 686.86 ± 153.12 mm 3 , and the TGI% was 105.32%; the average value of the tumor volume in the RDC+ADC group was 713.65 ± 271.28 mm 3 , and the TGI% was 100.60%. The average value of the tumor volume in the ADC+RDC treatment group was 278.79 ± 381.72 mm 3 , and the TGI% was 137.93% (p<0.001). At 145 days after treatment, the complete tumor regression rate (CR%) of the ADC+RDC treatment group was 40%, the overall survival rate was 40%, and the survival rates of other groups were 0 (p<0.001). Compared with the NS group, the changes in the monoclonal antibody group were the smallest in terms of blood routine indicators and liver and kidney functions, while the changes in the RDC single-agent group and the combination treatment group were larger. There were significant differences in renal function among the treatment groups, P<0.01. There were significant differences in white blood cells and red blood cells among the treatment groups, P<0.05. HE staining images at the treatment endpoint showed that the organizational structures of the heart, lungs, and liver in each group were intact, without obvious pathological structural changes, and there were no obvious differences among the groups. Compared with the NS group, the spleen and kidneys in the RDC and combination treatment groups showed disordered splenic nodule structures, and partial structural damage and deformation of glomeruli and renal tubules.

[0097] III. Conclusion:

[0098] Compared with other treatment groups, the ADC sequential RDC combination treatment group showed the best anti-tumor efficacy with controllable toxic and side effects.

Claims

1. Use of antibody-drug conjugate ADC and radionuclide-drug conjugate RDC in combination for preparing drugs for treating gastric cancer.

2. The use according to claim 1, characterized in that: The antibody-drug conjugate ADC is SYSA1801mAb; the radionuclide-drug conjugate RDC is 177 Lu-DOTA-SYSA1801mAb。 3. The use according to claim 2, characterized in that: The SYSA1801 mAb described 177 The mass ratio of Lu-DOTA-SYSA1801 mAb was 1:1 based on SYSA1801.

4. The use according to any one of claims 1 to 3, characterized in that: The administration methods for combined use include simultaneous, concurrent, sequential, continuous, alternating or separate administration.

5. The use according to claim 4, characterized in that: The combined administration method is sequential administration, which is: two administrations via the tail vein, with an interval of 2 weeks, the first administration is ADC drug, and the second administration is RDC drug 177 Lu-DOTA-SYSA1801mAb.

6. A pharmaceutical composition for treating gastric cancer, characterized in that: It is composed of antibody-drug conjugate ADC and radionuclide-drug conjugate RDC.

7. The pharmaceutical composition for treating gastric cancer according to claim 6, characterized in that: The antibody-drug conjugate ADC is SYSA1801; the radionuclide-drug conjugate RDC is 177 Lu-DOTA-SYSA1801mAb.

8. The pharmaceutical composition for treating gastric cancer according to claim 7, characterized in that: The SYSA1801 and 177 The mass ratio of Lu-DOTA-SYSA1801 mAb was 1:1 based on SYSA1801.

9. The pharmaceutical composition for gastric cancer according to claim 7 or 8, characterized in that: The 177 The preparation method of Lu-DOTA-SYSA1801mAb comprises the following steps: a. Synthesis of SYSA1801mAb-DOTA The SYSA1801mAb solution was replaced with buffer A, p-NCS-Bz-DOTA was added for incubation, and then the solution was replaced with buffer C solution again to obtain SYSA1801mAb-DOTA; Wherein, buffer A is Na2CO3-NaHCO3, pH9.5, 0.15M; the buffer C solution is NaOAc-Ac, pH5.5, 0.5M; b. 177 Synthesis of Lu-DOTA-SYSA1801 mAb SYSA1801mAb-DOTA and 177 LuCl3 was mixed in a ratio of 1:2 and incubated at 42°C for 1 h. After the reaction, the samples were spotted and purified by high performance liquid chromatography.

Images