Background: Pancreatic ductal adenocarcinoma（PDAC）is one of the most lethal malignancies worldwide and is characterized by extremely poor prognosis. Nab-paclitaxel plus gemcitabine has been recommended by international guidelines for first-line treatment of advanced PDAC but chemoresistance is difficult to avoid. Combination of immune checkpoint inhibitors (ICIs) and chemotherapy has demonstrated substantial promise for the treatment of several advanced malignancies. A few recent studies have begun to explore the effect of ICIs monotherapy or co in advanced PDAC with few meaningful results. KN046, a novel recombinant humanized bispecific antibody, can simultaneously block PD-1/PD-L1 and CTLA-4 pathways and restore T-cell immune response to tumor. The purpose of this study is to evaluate the efficacy and safety of KN046 plus nab-paclitaxel/gemcitabine as first-line treatment for unresectable locally advanced or metastatic PDAC. Methods: This ongoing phase II trial in China enrolled pts with histologically or cytologically confirmed unresectable locally advanced or metastatic PDAC who have ECOG PS of 0-1 and never received systemic anti-tumor therapy for advanced or metastatic diseases. KN046 (5mpk, Q2W) plus nab-paclitaxel (125mg/m², D1, 8, 15, Q4W) and gemcitabine (1000mg/m², D1, 8, 15, Q4W) were administered 4-6 cycles followed by KN046 (5mpk) maintenance therapy every 2 weeks. Tumour response was assessed according to RECIST 1.1 every 8 weeks. The primary endpoint is investigator-assessed ORR. Secondary endpoints are DCR, DOR, TTP, PFS, OS and safety. Results: As of December 15, 2020, 17 pts were enrolled, median (range) age was 56 (36-75) years, 9 pts ECOG 1, and 7 pts had liver metastases. Median KN046 exposure time was 9.5 wks. 9 pts were included in the efficacy analysis and 17 pts in the safety analysis. In best overall response assessment, there were 55.6% PR (5/9) and 33.3% SD (3/9). ORR was 55.6% (95% CI: 21.2̃86.3), and DCR was 88.9% (95% CI: 51.8̃99.7). The overall incidence of KN046 related treatment-emergent adverse events was 64.7%, with 29.4% were grade 3 TRAE. The most common KN046 related treatment-emergent adverse events (≥10%) were alanine aminotransferase increased (n = 5, 29.4%), nausea (n = 3, 17.6%), rash (n = 3, 17.6%), aspartate aminotransferase increased (n = 2, 11.8%), diarrhoea (n = 2, 11.8%), hyperphosphataemia (n = 2, 11.8%), pyrexia (n = 2, 11.8%), vomiting (n = 2, 11.8%). Conclusions: Combining KN046 with nab-paclitaxel and gemcitabine as first-line treatment for unresectable locally advanced or metastatic PDAC patients is safe and feasible, and lays the foundation for subsequent clinical trials. Clinical trial information: NCT04324307