Phase I Study MK-3475 With Chemotherapy in Patients With Advanced GI Cancers

This is a Phase I dose escalation trial to assess MTD of MK-3475 in combination with mFOLFOX6 followed by a safety expansion open label, nonrandomized trial with MK-3475 at MTD in combination with mFOLFOX6 and supplemental celecoxib in 4 cohorts of advanced/metastatic GI malignancies (pancreatic, gastro esophageal, colorectal/appendiceal adenocarcinoma and biliary carcinoma) to assess response rate, clinical benefit rate, progression free survival and overall survival. The safety expansion cohort will assess the effect of the addition of celecoxib to patients that do not respond to combination MK-3475/mFOLFOX treatment.