Biomedical applications of trastuzumab: as a therapeutic agent and a targeting ligand

Trastuzumab (TZ) is a humanized monoclonal antibody targeted to the extracellular domain of human epidermal growth factor receptor 2 (HER2), a tyrosine kinase receptor. TZ is approved by the Food and Drug Administration (FDA) for the treatment of HER2-overexpressing early stage and metastatic breast cancer and HER2-overexpressing metastatic gastric cancer. For breast cancer, it is recommended as both a single agent and in combination with standard chemotherapy. In the last few years, TZ has also been used as a targeting ligand. Overexpression of HER2 in breast cancer and the presence of free surface functional groups on TZ provide an opportunity to use it as a targeting ligand. TZ can be conjugated to various nanoparticulate systems such as dendrimers, polymeric, and protein nanoparticles to target drug delivery. TZ-conjugated inorganic nanoparticles have been reported for imaging and diagnostic purposes. This review summarizes the applications of TZ both as a therapeutic agent and as a targeting ligand.