HB1801 + trastuzumab + pertuzumab

This is a three-drug combination regimen consisting of **HB1801**, **trastuzumab**, and **pertuzumab**. Both trastuzumab and pertuzumab are monoclonal antibodies targeting HER2 (ERBB2), commonly used together for HER2-positive breast cancer. Trastuzumab binds subdomain IV of HER2 and mediates antibody-dependent cellular cytotoxicity (ADCC) as well as direct inhibition of tumor cell proliferation. Pertuzumab binds subdomain II of HER2, blocking HER2 dimerization, and works synergistically with trastuzumab by preventing HER2/HER3 heterodimerization and further activating complement-mediated cytotoxicity and phagocytosis. The precise molecular mechanism for HB1801 in this context is not specified in available data, but based on its use alongside HER2-targeted antibodies in clinical trials, it is presumed to act as an additional therapeutic targeting HER2-positive tumors, possibly with an immunotherapeutic or cytotoxic mechanism. This three-drug regimen is being evaluated for first-line treatment of HER2-positive recurrent or metastatic breast cancer[3].