trastuzumab + paclitaxel + pyrotinib

THPy is a combination drug regimen consisting of trastuzumab, paclitaxel, and pyrotinib. Trastuzumab is a monoclonal antibody that targets human epidermal growth factor receptor 2 (HER2). Paclitaxel is a taxane chemotherapy agent that interferes with microtubule function, thereby inhibiting cell division. Pyrotinib is a tyrosine kinase inhibitor (TKI) that targets HER2, epidermal growth factor receptor (EGFR), and HER4. This regimen is widely used as a first-line treatment for HER2-positive metastatic breast cancer, particularly in China. It has also been investigated in neoadjuvant settings for stage II-III HER2-positive breast cancer and is being explored for HER2-positive advanced breast cancer with brain metastases. While effective, THPy is associated with a higher incidence of adverse events, including grade 3/4 diarrhea, neutropenia, anemia, and fatigue, compared to other regimens.