Following two large phase 3 studies (DESTINY-Breast03, NCT03529110, DESTINY-Gastric01, NCT03329690), trastuzumab deruxtecan has been clinically approved by the FDA in 2019 for the treatment of unresectable or metastatic HER2 + breast cancer (BC) and in 2021 for the treatment of advanced or metastatic HER2 + gastric or gastroesophageal carcinoma and later in 2022 for the treatment of unresectable or metastatic HER2 + non-small cell lung cancer (DESTINY-Lung02) [68–70]. The gene discussed is ERBB2; the disease is non-small cell lung carcinoma.