The study is being conducted to evaluate the efficacy, safety and tolerability of SHR6390 in combination with nab-paclitaxel and gemcitabine in first-line treatment of subjects with advanced/metastatic pancreatic cancer.

This is an open-label, prospective, single-center, single-arm, Simon's two-stage design phase II study for unresectable advanced or metastatic pancreatic ductal adenocarcinoma (PDAC) subjects treated with SHR6390 plus nab-paclitaxel and gemcitabine.

In this research study, the main objectives include:

1. Evaluate objective response rate in patients with pancreatic cancer receiving SHR6390 plus nab-paclitaxel and gemcitabine.
2. Assess adverse side effects associated with the combination of SHR6390 with nab-paclitaxel and gemcitabine.

Inclusion Criteria:

1. Male or female of 18 to 75 years old;
2. Subjects are diagnosed with histologically confirmed unresectable advanced or metastatic pancreatic ductal adenocarcinoma with at least one measurable lesion according to the RECIST 1.1 standard (the CT scan length of the tumor lesion > 10 mm);
3. Subjects are naïve to systemic treatment;
4. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1;
5. Life expectancy ≥12 weeks;
6. Adequate organ performance based on laboratory blood tests;
7. The toxicity of the previous treatment has been restored to ≤1 level (if there is surgery, the wound has completely healed);
8. Women of childbearing potential and men must agree to use adequate contraception prior to study entry and for the duration of study participation;
9. Normal swallowing function;
10. Willing to consent and signed the informed consent, and able comply with the planned visit, research treatment, laboratory examination and other test procedures.

Exclusion Criteria:

1. Had other active malignant tumors within 5 years before entering the study;
2. Confirmed or suspicious new metastatic lesion in brain;
3. Subjects are allergy to experimental drugs or any excipients;
4. Coagulation disorders (INR>1.5, APTT>ULN);
5. Severe pleural effusion or ascites;
6. Severe and uncontrolled medical diseases, acute infections; recent history of major surgery for myocardial infarction (within 3 months);
7. Subjects combined with other anti-tumor drugs;
8. Chronic diarrhea or intestinal obstruction;
9. Pregnant or lactating women; Fertile subjects who are unwilling or unable to take effective contraceptive measures;
10. Subjects in any trial drug treatment;
11. Severe mental disorder;
12. Other situations that investigators considered should be excluded.