Study protocol for an open-label, single-arm, phase Ib/II study of combination of toripalimab, nab-paclitaxel, and gemcitabine as the first-line treatment for patients with unresectable pancreatic ductal adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease with a dismal response to single-use of immune checkpoint inhibitors (ICIs). ICIs combined with systemic therapy has shown efficacy and safety in various solid tumors. Nab-paclitaxel and gemcitabine (AG), as the standard first-line treatment for advanced PDAC, has been widely used in recent years. The combination of ICIs and AG chemotherapy appears to be a promising option in the treatment of PDAC. Methods: This is an open-label, single-arm, and single-center phase Ib/II trial. The enrolled subjects are the unresectable (locally advanced or metastatic) PDAC patients without previous systemic treatments. All subjects receive an intravenous injection of gemcitabine 1000 mg/m(2)and nab-paclitaxel 125 mg/m(2)on day 1 and day 8, along with toripalimab 240 mg at day 1 every 3 weeks. The subjects may discontinue the treatment because of progression disease (PD), intolerable toxicities, requirements of patients or researchers. For local advanced patients who are evaluated as partial response (PR), surgeons need to assess the surgical possibility. The primary objective of this trial is to evaluate the safety and overall survival (OS) of this combination therapy; and the secondary objective is related to the assessment of objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and the rate of resection or R0 resection after receiving toripalimab plus AG treatment. Besides, we expect to identify the predictive biomarkers (such as MMR protein and PD-L1 expression, the number of TILs, the small RNA of EBV and so on) and explore the correlation between these biomarkers and tumor response to this combined regimen. Discussion: This trial is the first attempt to evaluate the efficacy and safety of the combination of toripalimab plus AG chemotherapy as a first-line treatment for unresectable PDAC patients. The results of this phase Ib/II study will provide preliminary evidence for further assessment of this combined therapeutic regimen for unresectable PDAC patients.