The study regimen will be administered on an outpatient basis and all medications are administered intravenously (IV). Subjects will receive treatment on Day 1 and Day 15 of each 28-day cycle consisting of the following: nanoliposomal irinotecan at 50 mg/m2, followed by oxaliplatin 60 mg/m2, followed by leucovorin at 400 mg/m2 30 minutes after completion of oxaliplatin, followed by 5-FU 2400 mg/m2 60 minutes after leucovorin completion. Subjects will receive up to 6 cycles of NALIRIFOX then based on response and per physician discretion, de-escalated maintenance treatment with NALIRIFOX minus oxaliplatin may continue. Subjects will continue de-escalated maintenance treatment until progression per RECIST 1.1, intolerable toxicity or physician/subject choice to discontinue.