Trastuzumab deruxtecan is an antibody–drug conjugate that has been granted accelerated approval by the US Food and Drug Administration for HER2-expressing unresectable or metastatic solid tumours. In their study in The Lancet Oncology, Egbert F Smit and colleagues describe the activity of trastuzumab deruxtecan in a cohort of patients with metastatic non-small-cell lung cancer (NSCLC) from the DESTINY-Lung01 trial. The patients analysed in this study had tumours characterised by HER2 immunohistochemistry scores of 2 or 3 without known HER2 mutations.