This study will assess the efficacy and safety of LM-302 Versus Treatment of Physician's Choice (TPC) in Subjects With locally advanced or metastatic, Claudin (CLDN) 18.2-positive, Gastric or Gastroesophageal Junction Adenocarcinoma who have progressed on or after 2 lines of systemic therapy

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