trastuzumab + pyrotinib + exemestane + dalpiciclib

This is a four-drug combination regimen consisting of trastuzumab, pyrotinib, exemestane, and dalpiciclib. It is being investigated as a chemotherapy-sparing neoadjuvant or first-line treatment for patients with triple-positive breast cancer (TPBC), defined as estrogen receptor (ER)-positive, progesterone receptor (PR)-positive, and HER2-positive breast cancer. - **Trastuzumab** is a monoclonal antibody targeting the human epidermal growth factor receptor 2 (HER2), inhibiting HER2-mediated signaling and inducing antibody-dependent cellular cytotoxicity. - **Pyrotinib** is an oral irreversible pan-HER tyrosine kinase inhibitor that blocks the activity of HER1/EGFR, HER2, and HER4 receptors. - **Exemestane** is an aromatase inhibitor that suppresses estrogen synthesis by irreversibly binding to the aromatase enzyme. - **Dalpiciclib** is a small molecule cyclin-dependent kinase 4/6 (CDK4/6) inhibitor that blocks cell cycle progression in hormone receptor–positive breast cancer cells. The combination aims to simultaneously inhibit ER signaling, block multiple members of the HER family pathway, and arrest cell cycle progression. Early-phase clinical trials have shown promising antitumor activity with acceptable safety profiles in patients with TPBC[1][5].