Immunotherapy of cancer based on PD-1/PD-L1 blockade has prompted a revolution in cancer clinical management, albeit as yet immunotherapy-based treatment approaches in pancreatic cancer and biliary tract cancer (BTC) remain to have proven value, highlights the urgency for designing novel therapeutic strategies to combat these deadly diseases. The immunomodulatory effect of lenvatinib (Lenvatinib is an oral multi-kinase inhibitor) on tumor microenvironments may contribute to antitumor activity of immune checkpoint blockade. This one-arm, phase I/II study is designed to assess the safety and efficacy of the combined regimen of Durvalumab (anti-PD-L1 antibody), Lenvatinib and Paclitaxel albumin (nab-paclitaxel).

Inclusion Criteria:

1.Subjects must have histologically proven unresectable pancreatic cancer or biliary tract cancer 2.18 to 75 years old. 3.Life expectancy of at least 6 months. 4.Eastern Cooperative Oncology Group performance status 0-2. 5.Subjects must have at least one measurable lesion ≥ 1 cm as defined by response criteria.

6.Subjects with Anti-PD-1/L1 antibody treatment history are eligible which must be disease progression.

7.Adequate organ function. 8.Participants of childbearing potential must be willing to use an adequate method of contraception for the course of the study through 120 days after the last dose of study drug.

Exclusion Criteria:

1. Subjects with any autoimmune disease or history of syndrome that requires corticosteroids or immunosuppressive medications.
2. Serious uncontrolled medical disorders or active infections, pulmonary infection especially.
3. Prior organ allograft.
4. Women who are pregnant or breastfeeding.
5. Women with a positive pregnancy test on enrollment or prior to investigational product administration.
6. Subjects who are compulsorily detained for treatment of either a psychiatric or physical (eg, infectious disease) illness.