A Study Comparing BL-M05D1 With the Investigator's Choice of Treatment Regimen in Patients With Claudin (CLDN)18.2-Positive Advanced Gastric Cancer or Gastroesophageal Junction Adenocarcinoma (GC/GEJC) Who Have Received Prior First-Line Treatment

This trial is a registrational Phase III, randomized, open-label, multicenter study to evaluate the efficacy and safety of BL-M05D1 in patients with Claudin (CLDN) 18.2-positive advanced gastric cancer or gastroesophageal junction adenocarcinoma (GC/GEJC) who have received prior first-line treatment.

Inclusion Criteria: 1. Voluntarily sign the informed consent form and comply with the protocol requirements; 2. No gender restrictions; 3. Age: ≥18 years and ≤75 years; 4. Expected survival time ≥3 months; 5. Pathologically confirmed locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma; 6. Patients who have failed prior first-line standard therapy must have evidence of radiographic clear progression; 7. Ability to provide archived or fresh tumor tissue; 8. Must have at least one measurable lesion as defined by RECIST v1.1; 9. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; 10. Toxicity from prior anti-tumor therapy must have recovered to ≤ Grade 1 as defined by NCI-CTCAE v5.0; 11. No severe cardiac dysfunction, with left ventricular ejection fraction (LVEF) ≥50%; 12. Organ function levels must meet the requirements; 13. Coagulation function: International Normalized Ratio (INR) ≤1.5, and activated partial thromboplastin time (APTT) ≤1.5 × upper limit of normal (ULN); 14. Urine protein ≤2+ or \