Another ongoing phase 3b/4 study is Destiny-Breast12 (NCT04739761) [50], assessing effectiveness of T-DXd among patients without brain metastases (cohort 1) and with BMs (cohort 2), with pretreated (1-2 lines, excluded previous tucatinib) advanced/metastatic HER2-positive BC. The gene discussed is ERBB2; the disease is breast cancer.