1. Diagnosed with malignant diseases other than gastroesophageal junction tumors within 5 years before the first administration (excluding radically treated basal cell carcinoma of the skin, cutaneous squamous cell carcinoma, and/or carcinoma in situ after radical resection);
2. Known endoscopic evidence of active bleeding in the lesion;
3. Known evidence of distant metastasis;
4. Currently participating in therapeutic interventions of an interventional clinical study, or having received other drug therapies for malignant gastroesophageal junction tumors within 4 weeks before the first administration;
5. Having previously received the following therapies: anti-PD-1, anti-PD-L1 or anti-PD-L2 drugs, or drugs targeting another stimulatory or co-inhibitory T-cell receptor (including but not limited to CTLA-4, OX-40, CD137, etc.), or chemotherapy (including but not limited to S-1);
6. Having received systemic treatment with Chinese patent medicines with anti-tumor indications or drugs with immunomodulatory effects (including thymosin, interferon, interleukin, excluding those used locally to control pleural effusion) within 2 weeks before the first administration;
7. Having had active autoimmune diseases requiring systemic treatment (such as disease-modifying drugs, glucocorticoids or immunosuppressants) within 2 years before the first administration. Alternative therapies (such as thyroxine, insulin, or physiological glucocorticoids for adrenal or pituitary insufficiency, etc.) are not considered systemic treatment;
8. Receiving systemic glucocorticoid therapy (excluding nasal spray, inhaled or other forms of topical glucocorticoids) or any other form of immunosuppressive therapy within 7 days before the first administration of the study; Note: The use of physiological doses of glucocorticoids (≤ 10 mg/day of prednisone or equivalent drugs) is allowed;
9. Known allogeneic organ transplantation (except corneal transplantation) or allogeneic hematopoietic stem cell transplantation;
10. Known history of allergy to putlizumab, chemotherapeutic drugs used in this study or their components;
11. Before starting treatment, not having fully recovered from toxicities and/or complications caused by any interventions (i.e., ≤ Grade 1 or returning to baseline, excluding fatigue or alopecia);
12. Known history of human immunodeficiency virus (HIV) infection (i.e., positive for HIV 1/2 antibodies);
13. Untreated active hepatitis B (defined as positive HBsAg with HBV-DNA copy number greater than the upper limit of normal of the laboratory in the research center);
Note: Hepatitis B subjects meeting the following criteria can also be enrolled:
1) HBV viral load < 1000 copies/ml (200 IU/ml) before the first administration, and subjects should receive anti-HBV treatment during the entire study period of chemotherapeutic drug treatment to avoid viral reactivation; 14. Subjects with active HCV infection (HCV antibody positive and HCV-RNA level above the lower limit of detection); 15. Having received a live vaccine within 30 days before the first administration (Cycle 1, Day 1); Note: Administration of inactivated viral vaccines for seasonal influenza within 30 days before the first administration is allowed; however, intranasal attenuated live influenza vaccines are not allowed; 16. Pregnant or lactating women; 17. Having any severe or uncontrollable systemic diseases, such as:
1. Significant and severely symptomatic abnormalities in resting electrocardiogram in terms of rhythm, conduction or morphology, such as complete left bundle branch block, second-degree or higher atrioventricular block, ventricular arrhythmias or atrial fibrillation;
2. Unstable angina pectoris, congestive heart failure, chronic heart failure with New York Heart Association (NYHA) class ≥ 2;
3. Any arterial thrombosis, embolism or ischemia occurring within 6 months before enrollment, such as myocardial infarction, unstable angina pectoris, cerebrovascular accident or transient ischemic attack;
4. Poorly controlled hypertension with medication;
5. A history of non-infectious pneumonia requiring glucocorticoid treatment within 1 year before the first administration, or currently having clinically active interstitial lung disease;
6. Active pulmonary tuberculosis;
7. Having active or uncontrolled infections requiring systemic treatment;
8. Having clinically active diverticulitis, abdominal abscess, intestinal obstruction;
9. Liver diseases such as decompensated liver disease, acute or chronic active hepatitis;
10. Poorly controlled diabetes;
11. Patients with mental disorders who cannot cooperate with treatment; 18. Known dihydropyrimidine dehydrogenase deficiency; 19. Patients with gastrointestinal obstruction, or physiological dysfunction or malabsorption syndrome; Evidence of medical history, diseases, treatments or abnormal laboratory test values that may interfere with the study results, prevent the subjects from participating in the study throughout the process, or other situations that the researcher deems unsuitable for enrollment, or the researcher deems that there are other potential risks that make the subject unsuitable for participating in this study.