Biomarker analysis of the DAISY trial

The phase II DAISY trial was the first to show clinical activity of the antibody-drug-conjugate (ADC) trastuzumab deruxtecan (T-DXd) in metastatic breast cancer patients with low, ultralow or even absent levels of HER2 expression. In this video, Dr Elisa Agostinetto (Institut Jules Bordet, Brussels, Belgium) and Dr Maria Fernanda Mosele (Gustave Roussy, Villejuif, France) discuss new biomarker data of this trial.

The presented biomarker analyses of the DAISY trial specifically looked for associations with a treatment response to T-DXd in patients with HER2 IHC0 metastatic breast cancer. In this respect, no association was found between the spatial distribution of ERBB-2 gene expression and a response to the treatment. Similarly, responses to T-DXd were also not associated with changes in the presence of GrB+/CD8 lymphocytes.

Despite the negative outcome of these analyses, both Dr Agostinetto and Dr Mosele underscored the importance of translational research in studies like DAISY. In fact, these research efforts are essential to get a better understanding of the mechanism of action of T-DXd in patients with (ultra)low levels of HER2 expression.