DATO-BASE: DATOpotamab-deruxtecan for Breast Cancer Brain metAstaSEs

This is a single-arm, multi-cohort, open-label, phase II trial designed to evaluate the safety and efficacy of datopotamab deruxtecan for the treatment of CNS metastases in patients with HER2-negative metastatic breast cancer. Participants will be enrolled in three different groups: Cohort A for estrogen receptor (ER)-positive HER2-negative breast cancer, Cohort B for metastatic triple negative breast cancer, and Cohort C for HER2-negative metastatic breast cancer which has spread to the leptomeninges (which surround the brain or spinal cord). Datopotamab deruxtecan is a new type of anti-cancer drug called an "antibody drug conjugate" (ADC) that targets cancer cells expressing a specific molecule on the tumor cell membrane. The U.S. Food and Drug Administration (FDA) has not approved datopotamab deruxtecan as a treatment for metastatic, Human epidermal growth factor receptor-2 (HER2) negative breast cancer. The research study procedures include screening for eligibility, blood tests, questionnaires, and study treatment visits, Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) scans, electrocardiograms, echocardiograms, and cerebral spinal fluid (CSF) collection. It is expected that about 58 people will take part in this research study. Daiichi Sankyo Inc. is funding this study and providing the study drug, datopotamab deruxtecan.