This was an open-label, phase 1/2 study to evaluate safety, tolerability, pharmacokinetics, and antitumor activity of ASKB589 in combination with CAPOX and PD-1 inhibitors in first-line treatment of patients with locally advanced, recurrent, or metastatic gastric and esophagogastric junction adenocarcinoma.

A two-part, dose-escalation and expansion study of ASKB589 was initiated to determine the MTD, PK, PD, and efficacy in combination with chemotherapy and PD-1 inhibitors.

Inclusion Criteria:

1. Histopathologically confirmed unresectable locally advanced, recurrent, or metastatic adenocarcinoma of the gastric and gastroesophageal junction currently ineligible for surgery and radical radiotherapy.
2. Investigators determined that the present situation of the patient justifies chemotherapy plus immunotherapy as first-line treatment.
3. Tumor tissue samples are CLDN18.2 positive detected by central laboratory
4. ECOG performance status 0-1.
5. The results of the laboratory tests must meet all criteria
6. Life expectancy of at least 3 months.

Exclusion Criteria:

1. Known active central nervous system metastasis or suspected cancerous meningitis;
2. There are moderate to large amounts of abdominal and pleural fluid.
3. The presence of clinically uncontrollable third interspace fluid；
4. Patients with any other malignant tumors within the past 5 years.
5. Applicable to anti-HER-2 drug therapy；
6. Anti-CLDN18.2 antibody, anti-PD-1 antibody, or drug therapy at any time in the past；
7. Patients have received antitumor therapy during the first 4 weeks before study drug use;
8. Pregnant or lactating women; or women of childbearing age who have a positive blood pregnancy test during screening period; or women of childbearing age and their spouses who are unwilling to take effective contraceptive measures during the period of this clinical trial and within 6 months after the end of the clinical trial;