Inclusion Criteria:
* Aged 18 to 75 years old.
* Histopathologically confirmed pancreatic adenocarcinoma meeting any one of the following conditions: (1) Unresectable locally advanced or metastatic pancreatic cancer, with no prior systemic anti-tumor therapy for advanced disease. Prior neoadjuvant/adjuvant chemotherapy is permitted, provided the interval from completion of prior chemotherapy to study drug administration is more than 6 months. (2) High-risk resectable or borderline resectable pancreatic cancer assessed by a multidisciplinary team.(3) Curative resection (R0 or R1 resection) performed without prior neoadjuvant therapy, and adjuvant treatment can be initiated within 12 weeks postoperatively.
* Presence of at least one measurable lesion per RECIST v1.1 (exclusive to participants in Cohort 3).
* Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1.
* Estimated survival time ≥ 3 months.
* Adequate bone marrow function: absolute neutrophil count (ANC) ≥ 1.5×10⁹/L, platelet count (PLT) ≥ 100×10⁹/L, hemoglobin (Hb) ≥ 90 g/L.
* Adequate liver function: alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 2.5×ULN (≤5×ULN allowed in patients with liver metastases); total bilirubin ≤ 1.5×ULN.
* Adequate renal function: serum creatinine (Cr) ≤ 1.5×ULN, or creatinine clearance ≥ 60 mL/min (calculated by Cockroft-Gault formula).
* Adequate coagulation function: prothrombin time (PT) and activated partial thromboplastin time (APTT) ≤ 1.5×ULN.
* Women of childbearing potential must have a negative serum/urine pregnancy test within 14 days prior to enrollment, be non-lactating, and agree to use effective contraception throughout the study and for 6 months after the last study treatment. Male participants must agree to effective contraception during the study and for 6 months after study completion.
* Able to understand the study information; participant or legal representative voluntarily provides written informed consent.
Exclusion Criteria:
* History of other malignant tumors within the past 5 years
* Known hypersensitivity or intolerance to any study drug or excipients.
* Confirmed homozygous or compound heterozygous DPYD variants leading to complete dihydropyrimidine dehydrogenase (DPD) deficiency.
* Presence of any of the following comorbidities: ① Severe or uncontrolled cardiovascular disease: New York Heart Association (NYHA) Class II or higher chronic heart failure, uncontrolled hypertension (systolic BP \>150 mmHg and/or diastolic BP \>90 mmHg despite stable medication), etc. ② Severe respiratory disorders: asthma requiring inhaled/systemic glucocorticoids, active chronic obstructive pulmonary disease, etc. ③ Confirmed neurological diseases (epilepsy, dementia, etc.) or Grade ≥2 peripheral sensory/motor neuropathy. ④ Uncontrolled diabetes mellitus (fasting blood glucose ≥10 mmol/L under stable treatment). ⑤ Severe chronic or active infections requiring ≥1 consecutive week of systemic antibacterial, antifungal or antiviral therapy (including tuberculosis). ⑥ Active HIV infection (HIV antibody positive); untreated active HBV (HBsAg/HBcAg positive with HBV-DNA above institutional upper limit of normal) or active HCV infection (HCV antibody positive with HCV-RNA above institutional upper limit of normal).
* Untreated active brain metastases (including symptomatic brain or leptomeningeal metastases). Participants with brain metastases are eligible only if brain lesions are stable on imaging performed ≥4 weeks prior to first study dose, no new neurological symptoms or baseline symptom relapse, and no systemic steroid administration for ≥14 days before study treatment initiation, with no evidence of new or enlarged metastatic lesions.
* Medical history as follows: ① Major abdominal/thoracic surgery within 28 days prior to first study dose, or planned major surgery during the study period (diagnostic puncture and infusion port implantation excluded). ② Severe cardiovascular/cerebrovascular events (myocardial infarction, unstable angina, cerebrovascular accident) within 6 months prior to enrollment; clinically silent lacunar infarcts are permitted.
* History of deep vein thrombosis or pulmonary embolism within 3 months prior to enrollment.
* Inability to swallow or untreated malabsorption syndrome.
* Receipt of any investigational product within 1 month prior to enrollment.
* Any other condition judged by the investigator to render the participant unsuitable for study participation.
