The FDA expanded the label for AstraZeneca and Daiichi Sankyo’s Enhertu (trastuzumab deruxtecan) to include use with pertuzumab as a first‑line treatment for unresectable or metastatic HER2‑positive breast cancer. Concurrently, the agency approved Roche’s Pathway and Ventana HER2 assays to identify patients across the full spectrum of HER2 expression who may be eligible for Enhertu. The combined regulatory moves link therapeutic expansion with diagnostic access: wider companion diagnostic approvals enable clinicians to stratify patients across HER2 expression levels and guide treatment selection. Roche noted the approvals will support more personalized therapy decisions.