MK2 Inhibitor in Combination With mFOLFIRINOX for Untreated Metastatic Pancreatic Ductal Adenocarcinoma

Inclusion Criteria: * Histologically or cytologically confirmed pancreatic ductal adenocarcinoma with no prior systemic treatment for advanced or metastatic disease. Patients with mixed cytology in their tumors such as adeno-squamous, mixed neuroendocrine-carcinoma are permitted if the portion of adenocarcinoma is predominant. Prior adjuvant/neoadjuvant therapy (including FOLFIRINOX or mFOLFIRINOX regimens) is allowed if progression occurred ≥ 12 months from the last dose of that therapy. A biopsy is not required to confirm advanced or metastatic disease. * Dose escalation: Diagnosis of advanced inoperable or metastatic disease, where mFOLFIRINOX (or classical FOLFIRINOX) is deemed a suitable option per the treating physician. * Dose expansion: Diagnosis of metastatic disease, where mFOLFIRINOX (or classical FOLFIRINOX) is deemed a suitable option per the treating physician. * Measurable disease by RECIST 1.1. * At least 18 years of age * ECOG performance status ≤ 1. * Adequate bone marrow and organ function as defined below: * Absolute neutrophil count ≥ 1.5 K/cumm * Platelets ≥ 100 K/cumm without transfusion within 2 weeks prior to C1D1 * Hemoglobin ≥ 9.0 g/dL without transfusion within 2 weeks prior to C1D1 * Total bilirubin ≤ 1.5 x IULN * AST(SGOT)/ALT(SGPT) ≤ 3.0 x IULN, unless there are liver metastases in which case AST and ALT ≤ 5.0 x IULN * Creatinine clearance \> 50 mL/min by Cockcroft-Gault * Baseline EKG with QTcF ≤ 460 ms. * Women of childbearing potential and men who are heterosexually active must agree to use adequate contraception as specified in the protocol. Contraception should continue for 1 month following last dose of zunsemetinib, 6 months following last dose of irinotecan, 9 months following last dose of oxaliplatin, and/or 3 months following last dose of fluorouracil. Should a woman (or the female partner of a male participant) become pregnant or suspect she is pregnant while participating in this study, she must inform her treating physician immediately. * Ability to understand and willingness to sign an IRB approved written informed consent document (or that of legally authorized representative, if applicable). Exclusion Criteria: * A history of other malignancy with the exception of 1) malignancies for which all treatment was completed at least 2 years before registration and the patient has no evidence of disease; 2) or known indolent malignancies that do not require treatment and will likely not alter the course of treatment of metastatic pancreatic cancer. * History of allogeneic organ or stem cell transplant. * Currently receiving any other investigational agents, or receipt of an investigational agent within 2 weeks or 5 half-lives of the agent, whichever is shorter. * Receipt of strong and moderate CYP3A4 and CYP2C8 inhibitors (including grapefruit), strong and moderate CYP3A and CYP2C8 inducers (see Appendices H and I), and drugs with QT prolonging potential within 5 half-lives of cycle 1 day 1. * Known brain metastases or CNS involvement, because brain metastases are often associated with poor functional status, shortened life expectancy and risk of toxicity. * A history of allergic reactions attributed to compounds of similar chemical or biologic composition to zunsemetinib, or other agents used in the study. * Clinically significant neuropathy ≥ grade 2. * Presence of interstitial lung disease that is symptomatic or may interfere with the detection or management of suspected treatment-related pulmonary toxicity. * Gastrointestinal conditions which could prevent absorption of zunsemetinib, in the opinion of the treating physician. * Inability to swallow pills. * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, or cardiac arrhythmia . * Pregnant and/or breastfeeding. Women of childbearing potential must have a negative serum pregnancy test within 7 days of C1D1. * Patients with HIV are eligible unless their CD4+ T-cell counts are \< 350 cells/mcL or they have a history of AIDS-defining opportunistic infection within the 12 months prior to registration. Concurrent treatment with effective ART according to DHHS treatment guidelines is recommended. * Major surgery within 28 days prior to C1D1. Major surgery refers to any surgical procedure that involves general or regional anesthesia, involves extensive resecting or altering of body parts, carries a higher risk of complications, or requires long recovery times. Central line placement is allowed. * Use of any live vaccines against infectious diseases (eg, influenza, varicella) within 4 weeks (28 days) of C1D1.