Penpulimab Combined With Anlotinib and Nab-paclitaxel Plus Gemcitabine as First-line Treatment for Advanced Metastatic Pancreatic Cancer (RCT-PAAG)

Inclusion Criteria: Ages ≥18 years，ECOG ≤ 2，Estimated survival time > 3 months Histologically or Cytologically confirmed metastatic pancreatic adenocarcinoma Based on Response Evaluation Criteria In Solid Tumors (RECIST1.1), there should be at least one measurable lesion Patients have never received systematical anti-cancer therapy Laboratory examination meets the following requirements: White blood cell (WBC) ≥3.0×109/L; absolute neutrophil count (ANC) ≥1.5×109/L; Hemoglobin (HB) ≥90g/L; platelet count(PLT) ≥75×109/L; Total bilirubin (TBIL) ≤1.5× normal upper limit (ULN); Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST)≤2.5×ULN, if accompanied by liver metastasis, ALT and AST≤5×ULN; Serum creatinine (Cr) ≤1×ULN or creatinine clearance (CCr)≥50ml/min; Doppler ultrasound evaluation: left ventricular ejection fraction (LVEF) > 50% Patients of childbearing age should take appropriate protective measures before enrollment and during the trial Volunteer to join the study, sign the informed consent, have good compliance, and cooperate with follow-up Ability to follow the study protocol and follow-up procedures. Exclusion Criteria: Patients have ever received any systematical anti-cancer therapy in the past Patients who participated in other clinical trials in the past 4 weeks According to the investigator, patients who surgically available or potentially treatable(Patients who voluntarily give up surgical treatment can be enrolled after evaluation by the investigator) Patients with moderate ascites requiring drainage Patients with CNS metastases and/or carcinomatous meningitis Patients with history of other primary malignancies except: 1) complete remission before enrollment for at least 2 years and requiring no additional treatment during the study period; 2) Adequately treated non-melanoma skin cancer or lentiform malignancy with no evidence of disease recurrence; 3) Adequately treated carcinoma in situ with no evidence of disease recurrence; Patients with autoimmune disease or immune deficiency who are treated with immunosuppressive drugs Patients with bleeding tendency. Pregnant or lactating women. Drug abuse, clinical or psychological or social factors that impact informed consent or the conduct of the study Patients who may be allergic to PD-1 monoclonal antibody, anlotinib, albumin-bound paclitaxel and gemcitabine