The development of companion diagnostic assays enabling the detection and quantification of HER2 expression and ERBB2 amplifications has provided an important early example that has informed the development of many companion diagnostics for the identification of other drug targets. However, the introduction of trastuzumab deruxtecan and, potentially, other novel antibody–drug conjugates has created the need for assays that are much more sensitive. In this Review, the authors describe the historical development of HER2 companion diagnostic assays in breast and other HER2-positive cancers and highlight the possible, future, more sensitive methods of HER2 detection and quantification that might provide the next generation of companion diagnostics.
- Charles J. Robbins
- Katherine M. Bates
- David L. Rimm
