Background: Combinations of folinic acid, fluorouracil (5-FU), irinotecan, and oxaliplatin (FOLFIRINOX) along with GN are standard first-line treatment options for mPC. Despite treatment advances, mPC has a poor prognosis with a 5-year survival rate of < 5%, emphasizing an urgent need for new targeted therapeutics. Claudin 18.2 (CLDN18.2) is a tight junction protein restricted to normal gastric mucosa cells; however, in the context of malignant transformation, CLDN18.2 is frequently expressed in carcinomas derived from organs that do not normally express it, such as pancreatic adenocarcinoma (50-70% express CLDN18.2). Zolbetuximab is a chimeric IgG1 monoclonal antibody that specifically binds to CLDN18.2, designed to mediate cancer cell death through antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. Methods: This phase 2 study (NCT03816163) with a safety lead-in phase will assess safety and antitumor activity of zolbetuximab plus GN in patients (pts) with histologically confirmed mPC with high CLDN18.2 expression (≥75% of tumor cells demonstrate moderate-to-strong IHC staining). The safety lead-in will assess safety/tolerability of zolbetuximab (n = 3 at 1,000 mg/m² on Cycle 1 Day 1 then 600 mg/m² Q2W then expand/de-escalate using a 3+3 design) plus GN and confirm the recommended phase 2 dose (RP2D). Dose-limiting toxicities (DLTs), defined as a specified toxicity that occurs during the DLT assessment period and is related to zolbetuximab, will be assessed after Cycle 1 (28 days). After determining the RP2D, approximately 129 pts will be randomly assigned 2:1 to receive either zolbetuximab RP2D Q2W on Days 1 and 15 plus GN on Days 1, 8, and 15 of each cycle (Arm 1), or GN alone on Days 1, 8, and 15 of each cycle (Arm 2). Randomization will be stratified by ECOG performance status (0 or 1) and liver metastasis (yes or no). Imaging (CT/MRI) will be performed at baseline and every 8 weeks until investigator-assessed disease progression (per RECIST v1.1 criteria) or the start of other systemic anticancer treatment, whichever comes earlier. Primary objectives are to confirm RP2D (safety lead-in), to assess antitumor activity measured by overall survival (randomization phase), and to establish the safety/tolerability profile of zolbetuximab plus GN across the study. Key secondary endpoints in the randomization phase are progression-free survival and objective response rate. As of January 2020, this study is recruiting pts at 74 centers. Clinical trial information: NCT03816163.