A Study of Ramucirumab Plus Pembrolizumab in Participants With Gastric or GEJ Adenocarcinoma, NSCLC, Transitional Cell Carcinoma of the Urothelium, or Biliary Tract Cancer

Inclusion Criteria: * Metastatic disease or locally advanced, unresectable disease. * Has histopathologically confirmed gastric or GEJ adenocarcinoma with documented disease progression after 0-2 prior lines of systemic therapy * Has histopathologically confirmed nonsquamous or squamous NSCLC with documented disease progression after 0-3 prior lines of systemic therapy * Has histopathologically confirmed transitional cell carcinoma of the urothelium (bladder, urethra, or renal pelvis) with documented disease progression after 1-3 prior lines of systemic therapy * Has histologically confirmed biliary tract adenocarcinoma with documented progression after 1-2 prior lines of systemic therapy * Availability of tumor tissue for biomarker analysis from a newly obtained core or excisional biopsy or willing to undergo a tumor biopsy. For first line NSCLC participants only, PD-L1 expression should be 1% or higher. * Have an Eastern Cooperative Oncology Group Performance Status of 0 or 1. * Has adequate organ function. * Have an anticipated life expectancy of ≥3 months. Exclusion Criteria: * Have known brain metastases. * Has received ≥3 lines of prior systemic therapy for gastric or GEJ adenocarcinoma and BTC or ≥4 lines for NSCLC or urothelial cancer. * Has active autoimmune disease. * Known human immunodeficiency virus (HIV) infection. * Known active hepatitis B or hepatitis C infection. * Has received any previous systemic therapy targeting vascular endothelial growth factor (VEGF) or VEGF receptor, or programmed death (PD) 1 or PD-ligand 1/2 signaling pathways. * Have received a live vaccine within 30 days prior to enrollment. Seasonal flu vaccines that do not contain live virus are permitted. * Have had a serious or non-healing wound, ulcer, or bone fracture within 28 days prior to enrollment. * Have an elective or a planned major surgery during the course of the trial or has undergone major surgery within 28 days prior to enrollment.