Background: The prognosis for advanced metastatic pancreatic adenocarcinoma remains dismal with median survival of 12-15 months in most recent trials, highlighting the urgent need for novel therapeutic agents. mFOLFIRINOX remains the standard of care for the first line treatment of advanced disease, with historical objective response rate (ORR) of ̃31%. Eryaspase, L-asparaginase (ASPNase) encapsulated in red blood cells (RBCs), is an investigational product under development. Following infusion, asparagine is actively transported in RBCs where it is hydrolyzed by encapsulated ASPNase. The reduction in plasma concentration of this essential amino acid leads to cancer cell death. A second line pivotal randomized phase III trial (Trybeca-1), which compares chemotherapy (Gemcitabine + Nab-Paclitaxel or 5-Fluorouracil + Irinotecan) with or without Eryaspase, has completed enrollment with results pending (NCT03665441). Methods: Patients with locally advanced or metastatic biopsy-proven pancreatic adenocarcinoma were treated with the combination of mFOLFIRINOX plus Eryaspase. The design was a standard 3 +3 dose escalation. mFOLFIRINOX was given as 5-Fluorouracil 2400 mg/m2 over 46 hours, Oxaliplatin 85 mg/m2, Irinotecan 150 mg/m2 plus Eryaspase 75 units/kg at dose level 0 or 100 units/kg at dose level 1. Key eligibility criteria include performance status of 0 or 1, locally advanced or metastatic disease, and adequate organ function. The primary objectives were to determine the maximum tolerated dose (MTD) and to determine the safety of this combination. Results: To date, nine patients have been enrolled with a mean age of 70. Four patients had locally advanced disease and five had metastatic disease. Three patients were enrolled at dose level 0 and six at dose level 1, with no dose limiting toxicities (DLT). Eight patients have had imaging to evaluate response: the ORR was 50% with four partial responses (PRs); 50% (N = 4) had stable disease (SD); disease control rate (PR + SD) was 100%. There were no grade 4 adverse events (AEs). The most common grade 3 AEs were hypokalemia (33%), fatigue (11%), and hypotension (11%); but they were beyond the DLT period of 28 days. The most common grade 1/2 AEs were neuropathy (78%), elevated liver enzymes (78%), nausea (78%), anemia (66%), fatigue (66%), diarrhea (66%), and mucositis (44%). Conclusions: The novel combination of mFOLFIRINOX plus Eryaspase was well tolerated with no DLT and has encouraging signs of clinical activity. The MTD has been declared with 5-FU 2400 mg/2, Oxaliplatin 85 mg/2, Irinotecan 150 mg/m2, and Eryaspase 100 units/kg. We plan to expand enrollment to further look at efficacy and are in the process of designing a larger randomized study in the first line setting pending results from the Trybeca-1 trial. Clinical trial information: NCT04292743.