A Phase 3, Multicenter, Randomized, Open-label Study of SHR-A1811 (HER2-ADC) Compared With the Chemotherapy Treatment Chosen by the Investigators for Subjects With HER2-positive Metastatic and/or Unresectable Gastric Cancer or Gastroesophageal Junction Adenocarcinoma Who Have Progressed on or After First-line Anti-HER2 Therapy-containing Regimen
This study will assess the efficacy and safety of SHR-A1811 compared with treatment chosen by the investigator in participants with HER2-positive (defined as immunohistochemistry \[IHC\] 3+ or IHC 2+/in situ hybridization \[ISH\]+) gastric or GEJ adenocarcinoma (based on \[American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines who have progressed on or after a first-line anti-HER2 therapy-containing regimen.
• Age 18-75 years old, male and female;
• Histologically or cytologically confirmed gastric or gastroesophageal junction adenocarcinoma, and unresectable locally advanced or metastatic disease
• Prior anti-HER-2 containing treatment
• Progression on or after first-line standard treatment (Prior neoadjuvant or adjuvant therapy can be counted as a line of therapy if the subject progressed on or within 6 months of completing neoadjuvant or adjuvant therapy);
• Centrally confirmed HER2-positive (IHC 3+ or IHC 2+ and evidence of HER2 amplification by ISH) as classified by ASCO-CAP on a tumor biopsy
• At least one measurable lesion according to the solid tumor response Evaluation Criteria (RECIST 1.1);
• ECOG: 0-1;
• Expected survival ≥12 weeks;
• Good blood reserve and liver, kidney and coagulation function;
⁃ Willing to provide informed consent for study participation.