Novel SEQUEnced Immunotherapy With Anti-angiogenesis and Chemotherapy in Advanced gastroesophageaL Adenocarcinoma

Cohort 1 \[CLOSED\] Study treatment involves two segments: (1) Induction Immunotherapy segment with pembrolizumab monotherapy every 3 weeks until irRECIST PD and (2) Combination Therapy segment. Nab-paclitaxel may be utilized in place of paclitaxel at investigator's discretion for subjects with paclitaxel reactions. Cohort 2 Patients are randomized to Arm A or B. Treatment in both arms includes pembrolizumab + RAM + paclitaxel.