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