Inclusion Criteria:  Age ≥18, male or female; Has histologically or cytologically confirmed pancreatic ductal adenocarcinoma (PDAC); Has not received prior systemic treatment for their locally advanced or metastatic PDAC; Has presence of measurable disease as defined by Response Evaluation Criteria in Solid Tumours (RECIST 1.1); Has a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Status; Has a life expectancy of at least 3 months; Has adequate organ function; If female of childbearing potential, have a negative serum pregnancy test within 7 days prior to first trial treatment; If female of childbearing potential or a male subject with a partner with childbearing potential, be willing to use a highly effective method of contraception (with a failure rate of less than 1.0% per year) from first study treatment to 24 weeks after completion of the trial treatment.  Exclusion Criteria:  Untreated active CNS metastasis or leptomeningeal metastasis. Is currently participating and receiving an investigational drug or has participated in a study of an investigational drug within 4 weeks or within 5 times of half-life (no less than 2 weeks), whichever is shorter prior to the first dose of trial treatment; Has received other anti-tumor treatment within 4 weeks or within 5 times of half-life (no less than 2 weeks), whichever is shorter prior to the first trial treatment; Major surgery for any reason, except diagnostic biopsy, within 4 weeks of the first administration of trial treatment and/or if the subject has not fully recovered from the surgery within 4 weeks of the first administration of trial treatment; Curative radiation within 3 months of the first dose of trial treatment. Radiation to more than 30% of the bone marrow or with a wide field of radiation should not be used within 4 weeks prior to the first administration of trial treatment; Subjects receiving immunosuppressive agents (such as steroids) for any reason should be tapered off these drugs before initiation of trial treatment (with the exception of subjects with adrenal insufficiency, who may continue corticosteroids at physiologic replacement doses, equivalent to < 10 mg prednisone daily, inhaled steroids and topical use of steroids); Vaccination within 28 days of the first administration of trial treatment, except for administration of inactivated vaccines (e.g., inactivated influenza vaccines); Has interstitial lung disease, or a history of pneumonitis that required oral or intravenous glucocorticoids to assist with management; History or current active autoimmune disease that might deteriorate when receiving an immunostimulatory agent； Previous malignant disease History of uncontrolled intercurrent illness Prior therapy with any antibody/drug targeting T cell coregulatory proteins Known severe hypersensitivity reactions to antibody drug； Is pregnant or breastfeeding; Other medical conditions that at the discretion of investigator interfere with the requirements of the trial in terms of safety or efficacy evaluation, or treatment compliance.