Clinical Study of Regorafenib and Nivolumab Plus Chemotherapy

Phase Ib part: To evaluate safety and tolerability in combination of Regorafenib, Nivolumab and chemotherapy in patient with unresectable advanced/recurrent gastric/ gastroesophageal junction/esophageal adenocarcinoma and to determine recommended dose in phase II part.

Phase II part: To evaluate safety and potential efficacy in combination of Regorafenib, Nivolumab and chemotherapy in patients in expanded arm.

The protocol treatment in this study is regorafenib and nivolumab plus CapeOX (Cohort A) / FOLFOX (Cohort B).

Regorafenib (the initial dose is 90 mg/dose) is orally administered daily for 21 days, followed by a 7-day washout period. Nivolumab is administered intravenously at a dose of 360 mg every 3 weeks (Cohort A) or 240 mg every 2 weeks (Cohort B).

Cohort A:CapeOX

* Capecitabine 1,000 mg/m\^2 administered orally, twice daily (Days 1 to 14 continuous dosing of CapeOX therapy) * Oxaliplatin 130 mg/m\^2 administered intravenously (Day 1 of CapeOX therapy) \*Repeat every 3 weeks as CapeOX therapy

Cohort B:FOLFOX

* Leucovorin 400 mg/m\^2 administered intravenously (Day 1 of FOLFOX therapy) * Fluorouracil 400 mg/m\^2 administered intravenously (Day 1 of FOLFOX therapy) and 1,200 mg/m2 administered intravenously (Days 1 to 2 of FOLFOX therapy) * Oxaliplatin 85 mg/m\^2 administered intravenously (Day 1 of FOLFOX therapy) \*Repeat every 2 weeks as FOLFOX therapy