LM-302 for the Treatment of Subjects With Claudin18.2-Positive Gastric and Gastroesophageal Junction Adenocarcinoma.

Inclusion Criteria: * Age 18-80 years old, male and female * Has histopathologically confirmed unresectable locally advanced or metastatic adenocarcinoma of the gastric/gastroesophageal junction (G/GEJ AC). * Has received and progressed on at least 2 lines of systemic therapy. A prior (neo)adjuvant systemic therapy that ended within 6 months prior to disease relapse is defined as the first line therapy. * Centrally confirmed CLDN18.2-positive * HER2 negative * 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. Exclusion Criteria: * Within the first 5 years of randomization, there is a history of malignant tumors other than GC/GEJ adenocarcinoma, except for skin basal cell carcinoma, cervical carcinoma in situ, breast carcinoma in situ, and skin squamous cell carcinoma that have been cured and cured after treatment * Individuals with a history of previous immunodeficiency, including those with other acquired or congenital immunodeficiency diseases, or those with a history of organ transplantation, allogeneic bone marrow transplantation, or autologous hematopoietic stem cell transplantation * Urine protein qualitative result ≥ 3+, or urine protein qualitative result is 2+and 24-hour urine protein quantification\>1g * Individuals with a history of severe cardiovascular and cerebrovascular diseases * Individuals who are unable to control or have serious illnesses, including but not limited to active infections requiring systemic antibiotic treatment within 2 weeks prior to initial medication, interstitial pneumonia/lung disease requiring intervention during screening, and tumor related pain requiring local treatment during screening * Current peripheral sensory or motor neuropathy ≥ grade 2 * Uncontrollable third space effusion in clinical practice * Received or planned to undergo major surgery or intervention during the study period within the first 28 days of randomization * The researcher determined that there are other situations that are not suitable for participation in this study