For ongoing clinical trials, we searched in the clinicaltrials.gov database for recruiting and active, not recruiting trials, using the following keywords: “gastric cancer” OR “gastric adenocarcinoma” OR “gastroesophageal cancer” AND “HER2” OR “human epidermal growth factor receptor” OR “trastuzumab” OR “trastuzumab deruxtecan” OR “margetuximab” OR “ZW25” OR “trastuzumab emtansine”. This evidence concerns the gene ERBB2 and gastric cancer.