The KEYNOTE-811 trial demonstrated that pembrolizumab combined with first-line trastuzumab and chemotherapy significantly improved PFS in patients with PD-L1 CPS ≥ 1 metastatic HER2-positive GC, with the most common treatment-related adverse events (TRAEs) being diarrhea, nausea, and anemia [32]. The gene discussed is ERBB2; the disease is gastric cancer.