Anti-HER2 therapy has revolutionized the treatment of HER2-positive breast cancer. However, HER2 has emerged as a driver of various other cancers and the indications for HER2-targeted therapy have expanded to include diverse HER2-overexpressing as well as HER2-mutant tumour types beyond breast cancer, facilitated by the advent of novel agents with greater potency and distinct mechanisms of action. Some of these agents have demonstrated promising activity even against HER2-low cancers. Herein, Yoon and Oh describe the landscape of HER2 alterations and HER2-targeted drug development beyond breast cancer. They also discuss new insights into mechanisms of resistance and potential strategies by which they might be overcome.

BCMA-directed chimeric antigen receptor T cell therapies and bispecific T cell engagers are moving to earlier lines of therapy in multiple myeloma. In addition, combination therapy with the BCMA-targeting antibody–drug conjugate belantamab mafodotin at first or subsequent relapse has the potential to improve survival of patients with this disease. This increasing number of therapeutic options makes treatment selection and sequencing increasingly complex.

Chromosomal instability (CIN) is a dynamic phenotype characterized by changes in chromosome number and structure and is a hallmark of clinically aggressive malignancies. Nonetheless, the ability of cancer cells to tolerate CIN creates several potential therapeutic vulnerabilities. In this Review, the authors describe the development of CIN and how this phenotype promotes carcinogenesis and tumour progression as well as describing the various attempts to develop targeted therapies based on the specific vulnerabilities of these tumours.

The NETTER-2 trial provides the first phase III evidence that ¹⁷⁷Lu-dotatate is active as first-line therapy in patients with gastroenteropancreatic neuroendocrine tumours with a Ki-67 proliferative index of 10–55%. This approach is an important addition to the first-line therapeutic armamentarium, although treatment selection based on patient-specific and tumour-specific characteristics remains appropriate.