A Trial of Adebrelimab Plus (SHR-A1811/SHR-A1904 With Chemotherapy) or SHR-8068 as Treatment for Gastric/GEJ Cancer

Inclusion Criteria:

1. Patients with histologically confirmed gastric or gastroesophageal junctionadenocarcinoma who have not received prior anti-tumor therapy forgastric/gastroesophageal junction cancer.

2. Age: ≥18 and ≤70 years, both male and female.

3. Ability to provide fresh tumor tissue (preferred) or archival formalin-fixedparaffin-embedded (FFPE) tumor blocks/unstained slides obtained within 6 monthsbefore enrollment.

4. Availability of biomarker testing results before enrollment.

5. ECOG performance status of 0-1.

6. Life expectancy ≥ 6 months.

7. Adequate organ and bone marrow function.

8. Female participants must be either non-childbearing potential or of childbearingpotential with a negative serum pregnancy test within 3 days prior to treatmentinitiation and not lactating. Childbearing-potential participants and their partnersmust agree to avoid sperm/ovum donation and comply with contraception requirementsfrom informed consent signing until 8 months after the last dose.

9. Voluntarily signed informed consent form, with willingness and ability to complywith scheduled visits, treatments, laboratory tests, and study procedures.

Exclusion Criteria:

1. Known squamous cell carcinoma, undifferentiated carcinoma, mixed adenocarcinoma withother histologic types, or other non-adenocarcinoma gastric cancers.

2. 20% body weight loss within 2 months before enrollment.

3. Prior treatments: Anti-tumor therapy for gastric/gastroesophageal junction cancer;Participation in other drug trials with last dose ≤4 weeks or ≤5 half-lives (whichever longer) before enrollment; Major surgery within 28 days beforeenrollment; Live attenuated vaccination within 28 days before enrollment or plannedduring/within 60 days after treatment.

4. Known hypersensitivity to any study drug component (Adebrelimab, SHR-A1811,SHR-A1904, SHR-8068, fluorouracil, capecitabine, tegafur/gimeracil/oteracil) orhumanized monoclonal antibodies.

5. Other malignancies within 5 years, except curatively treated basal/squamous cellskin cancer, superficial bladder cancer, cervical carcinoma in situ, ductal breastcarcinoma in situ, or papillary thyroid cancer.

6. History of immunodeficiency, organ transplantation, or active autoimmune disease.

7. Clinically significant bleeding within 3 months or bleeding predisposition atscreening; Arterial/venous thromboembolism within 6 months or at screening.

8. Non-healing wounds, active ulcers, or untreated fractures.

9. Active severe gastrointestinal disorders.

10. Interstitial pneumonia or lung disease.

11. Severe cardiovascular/cerebrovascular diseases or metabolic disorders.

12. Active HBV/HCV infection or HBV-HCV co-infection.

13. Active tuberculosis (TB) within 1 year by history/CT, or prior untreated active TB >1 year ago.

14. Severe infection within 4 weeks before first dose; CTCAE ≥Grade 2 active infectionrequiring systemic antibiotics within 2 weeks; Chronic infections potentiallyaffecting treatment/surgery.

15. History of drug abuse or illicit substance use.

16. Other conditions that may increase study risk, confound results, or render thepatient unsuitable per investigator judgment.