Cadonilimab Combined With S-1 or Capecitabine as Second-line Treatment for Advanced Pancreatic Cancer

Main Inclusion Criteria: * Signed written informed consent * Age 18-80, female or male * Histopathologically confirmed pancreatic ductal adenocarcinoma * Patients with locally advanced pancreatic cancer who have previously received standard first-line anti-tumor treatment (radiotherapy, chemotherapy, targeted or immunotherapy, etc.) * Locally advanced pancreatic cancer is defined as follows: a. The tumor has no distant metastasis; b. Pancreatic head/uncinate process: The tumor contacts the superior mesenteric artery \>180˚; c. Pancreatic body and tail: The tumor contacts the superior mesenteric artery or celiac artery \>180˚; The tumor contacts the celiac artery and infiltrates the abdominal aorta; d. The tumor invades the jejunal branch of the superior mesenteric artery. Portal vein-superior mesenteric vein cannot be safely reconstructed due to tumor invasion, vein occlusion, or involvement of a large range of jejunal branches of the superior mesenteric vein. * At least one measurable lesion (RECIST1.1) * ECOG PS 0-1 * Expected survival time\>3 months * Adequate organ function Main Exclusion Criteria: * Malignant diseases other than pancreatic cancer diagnosed within 5 years before the first dose (excluding radically resected basal cell carcinoma of the skin, squamous cell carcinoma of the skin, and/or radically resected carcinoma in situ) * Currently participating in interventional clinical research treatment, or having received other research drugs or used research devices within 4 weeks before the first dose * Active autoimmune disease * Allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation * Allergic to the active ingredients or excipients of this study drug, cadonilimab, S-1 or capecitabine * Have not fully recovered from any toxicity and/or complications caused by the intervention before starting treatment * History of HIV * Active HBV or HCV * Pregnant or breastfeeding women * Any severe or uncontrolled systemic disease * Active pulmonary tuberculosis * People with mental disorders who are unable to cooperate with treatment * Uncontrolled infection * The investigators assess that the subjects are unable to complete the entire trial process or are otherwise unsuitable for participating in this trial