Keytruda (Pembrolizumab), an oncology product marketed by the global pharmaceutical giant Merck has received Orphan Drug Designation from the U.S. FDA for the treatment of gastric cancer, including gastroesophageal junction adenocarcinoma. Keytruda is a humanized antibody designed to block the programmed cell death 1 (PD-1) receptor. It is approved by the FDA in 2014 and is indicated for metastatic melanoma. Gastric cancer is a rare type of cancer commonly caused by H. pylori infection. It is asymptomatic at early stage and consequently, most gastric cancer is diagnosed at an advanced stage making effective treatment very challenging. Currently, Merck is sponsoring one Phase II and one Phase III clinical trials evaluating Keytruda’s efficacy and safety profile in patients with advanced gastric or gastroesophageal junction adenocarcinoma.