Background: Liposomal irinotecan administered with 5-fluorouracil/leucovorin (5-FU/LV) is approved in the USA for metastatic pancreatic ductal adenocarcinoma (mPDAC) following progression with gemcitabine-based therapy. A phase 1/2 study in previously untreated locally advanced/metastatic PDAC showed promising anti-tumor activity with liposomal irinotecan 50 mg/m² free base + 5-FU 2400 mg/m² + LV 400 mg/m² + oxaliplatin (OX) 60 mg/m² on days 1 and 15 of a 28-day cycle (Wainberg et al. Ann Oncol 2019;30 Suppl 4: SO-005). Herein, we present the design of the phase 3 NAPOLI-3 study investigating the efficacy and safety of this regimen as first-line therapy in patients with mPDAC. Methods: NAPOLI-3 (NCT04083235) is a phase 3, open-label, randomized, global study in adults with histologically/cytologically confirmed pancreatic adenocarcinoma not previously treated in the metastatic setting. Patients are required to have one or more metastatic tumors measurable with computed tomography/magnetic resonance imaging and an Eastern Cooperative Oncology Group performance status score of 0–1. Site activation began in Dec 2019 and enrollment is ongoing. Random allocation (1:1) of 750 patients is planned to liposomal irinotecan + 5-FU/LV + OX (regimen as per phase 1/2 study) or nab-paclitaxel 125 mg/m² + gemcitabine 1000 mg/m² on days 1, 8 and 15 in a 28-day cycle. The primary endpoint is overall survival (OS). Secondary endpoints (progression-free survival [PFS] and overall response rate assessed with Response Evaluation Criteria in Solid Tumors v1.1 criteria) will be compared only if the primary endpoint shows superiority for liposomal irinotecan + 5-FU/ LV + OX over nab-paclitaxel + gemcitabine. Safety assessments include adverse-event monitoring. Patients will continue treatment until disease progression, unacceptable toxicity or study withdrawal, and will then be followed for survival every 2 months until death or study end (when all patients have died, withdrawn consent or are lost to follow-up). Clinical trial information: NCT04083235.