Pembrolizumab and Lenvatinib for the Treatment of Advanced, Unresectable, or Metastatic Gastroesophageal Adenocarcinoma

Inclusion Criteria: * The subject (or legally acceptable representative if applicable) provides written informed consent for the trial * Male and female subjects who are at least 18 years of age on day of signing informed consent with histologically and cytologically documented diagnosis as gastric or gastroesophageal adenocarcinoma * Has a documented, previously treated, advanced (unresectable and/or metastatic) gastroesophageal adenocarcinoma that is incurable and for which prior first-line or later-line standard of care (SOC) treatments have failed. Prior neoadjuvant or adjuvant therapy included in initial treatment may not be considered first- or later-line SOC treatment unless such treatments were completed less than 12 months prior to the current tumor recurrence * Has submitted an evaluable tissue sample for biomarker analysis from a newly obtained irradiated. The tumor tissue submitted for analysis must be from a single tumor tissue specimen and of sufficient quantity and quality to allow biomarker study (see laboratory manual). A "newly obtained" tumor specimen, defined as a specimen obtained up to 6 weeks (42 days) prior to initiation of treatment on day 1, for biomarker characterization will be required for enrollment of all subjects. Tissue from tumor progressing at a site of prior radiation (at least 6 weeks interval after last radiation) may be allowed for biomarker characterization upon agreement from Merck. Subjects for whom newly-obtained samples cannot be p…