A Study to Compare QLS31905 and Chemotherapy With Placebo and Chemotherapy in Participants With Pancreatic Cancer

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.