The addition of programmed cell death protein-1 (PD-1) inhibitors to chemotherapy (CT) or anti-CTLA4 (ipilimumab) has recently emerged as an effective first-line (1L) treatment for esophageal squamous cell carcinoma (ESCC), the most common form of esophageal cancer globally. The gene discussed is PDCD1; the disease is esophageal squamous cell carcinoma.