ERBB3 and breast cancer: In the SOLTI-TOT HER3 window-of-opportunity trial, a single dose of U3-1402 was evaluated as neoadjuvant therapy in HR + /HER2-negative BC, wherein it demonstrated an ORR of 45%, increased tumor cell activity, and cancer-infiltrating lymphocyte scoring with no significant correlation between response and pretreatment HER3 mRNA levels [114].