On September 22, 2017, the FDA granted accelerated approval to pembrolizumab (KEYTRUDA, Merck) for use in patients with locally advanced or metastatic, gastric or gastroesophageal junction (GEJ) adenocarcinoma positive for PD-L1 as determined by an FDA-approved companion diagnostic (CDx) and progressing after ≥2 prior systemic therapies, including a fluoropyrimidine– and platinum-containing regimen, and, when appropriate, HER2–targeted therapy.