202TiP SOLTI-1805 TOT-HER3 trial: A window-of-opportunity trial of patritumab deruxtecan (HER3-DXd) in patients with treatment-naïve, early breast cancer

HER3-DXd, a first-in-class HER3 directed antibody drug conjugate, has demonstrated clinically meaningful antitumor activity in heavily pre-treated HER2-negative (HER2-) metastatic breast cancer (BC) across a broad range of HER3 expression levels. TOT-HER3 aims to generate translational data and to explore potential predictive biomarkers of HER3-DXd activity. Recently, the results from Part A of the trial showed that one dose of HER3-DXd is associated with clinical response, increased immune infiltration and proliferation suppression in hormone receptor positive (HR+)/HER2- early BC (EBC) (Prat et al.