Firstline Sequential AG and mFOLFOX Combined With Serplulimab and Bevacizumab Versus AG Chemotherapy Alone in Advanced Pancreatic Cancer

Inclusion Criteria: 1. Voluntarily agree to participate in the study and sign the informed consent; 2. ≥18 years of age and ≤75 years of age on the day of signing the informed consent form, regardless of gender; 3. Pancreatic ductal adenocarcinoma confirmed by pathologic histology or cytology; 4. No prior systemic therapy for unresectable locally advanced or metastatic pancreatic cancer; 5. Measurable lesions at baseline according to RECIST 1.1 criteria; if the subject has only 1 measurable lesion at baseline, the area of the lesion must not have received radiotherapy in the past or there must be evidence of significant progression of the lesion after completion of radiotherapy treatment; 6. the ECOG physical status score was 0 or 1 and the Expected survival ≥12 weeks; 7. No serious organic diseases of the heart, lungs, brain and other organs; 8. Adequate organ function 1. Bone Marrow Function: (no transfusion within 14 days prior to screening, no use of granulocyte colony stimulating factor \[G-CSF\], no use of drug correction) : i. Hemoglobin ≥90g/L; ii. Leukocytes ≥ 4.0 x 109/L, Neutrophils ≥1.5×109/L; iii. Platelet ≥80×109/L; 2. Coagulation function: PT or APTT ≤ 1.5 x ULN in subjects not receiving anticoagulation; if subjects are receiving anticoagulation, as long as the PT is within the range of the anticoagulant drug formulation; 3. liver function: (no albumin infusion within 14 days prior to screening): Serum total bilirubin ≤ 1.5 x ULN (with biliary obstruction, allowing enrollment of subjects undergoing biliary drainage or in the midst of stenting therapy who have a total bilirubin ≤ 2.5 x ULN). In subjects without liver metastasis, Aspartate aminotransferase (AST), alanine aminotransferase (ALT)≤2.5×ULN; In subjects with liver metastasis, ALT and AST≤5×ULN, but without elevated bilirubin; 4. Renal function: serum creatinine ≤1.5 x ULN, creatinine clearance (CCr) ≥50 mL/min, urinary protein \<2+ (if urinary protein ≥2+, 24-hour (h) urinary protein quantification can be carried out, and 24h urinary protein quantification \<1.0 g can be enrolled) 5. Heart function: New York College of Cardiology (NYHA) rating \< 3; Left ventricular ejection fraction ≥50%; 9. Male or female patients of childbearing potential will voluntarily use an effective method of contraception, such as a double-barrier contraceptive method, condoms, oral or injectable contraceptives, and an intrauterine device (IUD), for the duration of the study and up to 6 months after the last study dose. All female patients will be considered of childbearing potential unless the female patient is naturally menopausal, artificially menopausal or sterilized; 10. Subject's ability and willingness to comply with visits, treatment plans, laboratory tests, and other study-related processes as specified in the study protocol. Exclusion Criteria: 1. subjects with clear brain metastases on imaging or with meningeal metastases; 2. untreated spinal compression fractures not treated by surgery and/or radiotherapy; treated spinal compression fractures require disease stabilization for at least 2 weeks prior to enrollment; 3. high risk of gastrointestinal or abdominal bleeding as evaluated by the Investigator; 4. uncontrolled cancer pain; narcotic analgesics not at a stable dose at enrollment; 5. previous treatment with vascular endothelial growth factor (VEGFR) inhibitors or previous treatment with immune checkpoint inhibitors; 6. antitumor treatment with chemotherapy, small molecule inhibitors, immunotherapy (e.g., interleukin, interferon, or thymosin) within 28 days prior to enrollment in this study, and herbal medicine with antitumor indications within 14 days prior to dosing; 7. major surgical procedures \[such as transabdominal, transthoracic and other major surgeries; excluding diagnostic puncture such as ultrasonic endoscopy-guided pancreatic fine-needle aspiration biopsy (EUS-FNB), percutaneous hepatic perforation biopsy, peripheral venous catheterization, and biliary stent implantation\] or invasive treatments or operations with incomplete healing of the surgical incision, local anti-tumor treatment such as hepatic artery interventional embolization, hepatic metastasis cryo-ablation, radiofrequency ablation and other local anti-tumor treatments. radiofrequency ablation and other local antitumor therapy; 8. have received radical radiotherapy within 3 months prior to study entry; palliative radiotherapy 2 weeks prior to dosing is permitted, and the dose of radiotherapy meets local standards of care for palliative care; 9. required systemic corticosteroid (\>10 mg/day prednisone or equivalent of other corticosteroid for ≥7 consecutive days) or immunosuppressive therapy within 14 days prior to enrollment in this study; with the exception of inhaled or locally applied hormones, or physiologic replacement doses of hormone therapy due to adrenal insufficiency; short-term (≤7 days) corticosteroids are allowed for prophylaxis (e.g., contrast allergy) or treatment of Non-autoimmune conditions (eg, delayed hypersensitivity reactions caused by exposure to allergens) ; 10. subjects with uncorrectable albumin decline (serum albumin \<3.0 g/dL) 14 days prior to enrollment in this study; and 11. a 10% or greater weight loss in comparison to the weight loss at the time of ICF signing within 72 hours prior to enrollment in this study; and 12. within 72 hours prior to study entry, the subject's ECOG physical status score increases by ≥1 point compared to the ICF score; 13. within 28 hours prior to study entry, the subject's ECOG physical status score increases by ≥1 point compared to the ICF score; and 13. has received a live vaccine (including live attenuated vaccine) within 28 days prior to enrollment in this study; 14. previous or current interstitial pneumonia/pneumatosis, unless determined by the investigator to be inactive and not requiring hormonal therapy; and 15. pre-existing or current autoimmune disease, including