Study of Pembrolizumab (MK-3475) in Previously-Treated Participants With Advanced Carcinoma of the Esophagus or Esophagogastric Junction (MK-3475-180/KEYNOTE-180)

Inclusion Criteria:

- Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- Life expectancy greater than 3 months

- Histologically-proven advanced/metastatic adenocarcinoma or squamous cell carcinoma of
the esophagus or advanced/metastatic Siewert type 1 adenocarcinoma of the EGJ

- Documented objective radiographic or clinical disease progression on two previous
lines of standard therapy

- Measurable disease based on Response Evaluation Criteria In Solid Tumors (RECIST) 1.1

- Can provide either a newly obtained or archival tumor tissue sample for intratumoral
immune-related testing and for anti-programmed cell death (PD-1)

- Female participants of childbearing potential must be willing to use adequate
contraception for the course of the study through 120 days after the last dose of
study medication

- Male participants must agree to use adequate contraception starting with the first
dose through 120 days after the last dose of study medication

- Adequate organ function

Exclusion Criteria:

- Currently participating and receiving study therapy or has participated in a study of
an investigational agent and received study therapy or used an investigational device
within 4 weeks of the first dose of study medication

- Has active autoimmune disease that has required systemic treatment within the 2 years
prior to the first dose of study medication

- Diagnosis of immunodeficiency or receiving systemic steroid therapy or any other form
of immunosuppressive therapy within 7 days prior to the first dose of study medication

- Known central nervous system (CNS) metastases and/or carcinomatous meningitis

- Prior anti-cancer mAb, chemotherapy, targeted small molecule therapy, or radiation
therapy within 2 weeks prior to first dose of study medication or not recovered from
adverse events due to a previously administered agent

- Prior therapy with a PD-1, anti-PD-Ligand 1 (PD-L1), or anti-PD-L2 agent, or
previously participated in a Merck pembrolizumab (MK-3475) study

- Has a known additional malignancy that has progressed or required active treatment
within the last 5 years with the exception of curatively treated basal cell carcinoma
of the skin, squamous cell carcinoma of the skin that has undergone potentially
curative therapy, in-situ cervical cancer, and in-situ or intra-mucosal pharyngeal
cancer

- Received a live vaccine within 30 days of the first dose of study medication

- Known history of Human Immunodeficiency Virus (HIV) infection

- Known active Hepatitis B or C

- History of non-infectious pneumonitis that required steroids or current pneumonitis

- Active infection requiring systemic therapy

- Known psychiatric or substance abuse disorders that would interfere with cooperation
with the requirements of the study

- Pregnant, breastfeeding, or expecting to conceive or father children within the
projected duration of the study, starting with the screening visit through 120 days
after the last dose of study medication