The goal of this study is to evaluate the efficacy of QLS31905 in combination with chemotherapy (nab-paclitaxel plus gemcitabine [AG]) versus placebo in combination with chemotherapy (AG) in the treatment of CLDN18.2-positive advanced pancreatic cancer in adult participants.

Inclusion Criteria:

• Subjects voluntarily participate in the study and sign the informed consent form;
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1;
• Expected survival time ≥ 3 months;
• Histologically or cytologically confirmed diagnosis of pancreatic cancer;
• No prior systemic anti-tumor treatment for unresectable locally advanced or metastatic disease;
• At least one measurable lesion per RECIST v1.1;
• Patients with adequate cardiac, liver, renal function, etc.

Exclusion Criteria:

• History of malignancies other than the target cancer within 5 years prior to the first dose of the investigational product ;
• Underwent major organ surgery (excluding needle biopsy) or had significant trauma within 28 days prior to enrollment, or requires elective surgery during the study;
• Known central nervous system metastases;
• Patients with hepatitis B; patients with hepatitis C; patients who test positive for syphilis, or patients with a known history of HIV or positive HIV screening test;
• Patients with added risks associated with the study or may interfere with the interpretation of study results as determined by the investigator, or deemed unsuitable by the investigator.