ERBB2 and breast cancer: T-DXd is also undergoing a phase III study on patients with HER2+ breast cancer and central nervous system (CNS) metastasis (DESTINY-Breast12 [23]) following favorable intracranial activity (ORRintracranial 46.2%) observed in the DEBBRAH trial, a single arm phase II study on patients with HER2-positive breast cancer and active CNS metastasis receiving T-DXd [24].