HER2

Class

HER2-directed therapeutic (biologic, subcutaneous injection; precise antibody/ADC format not specified in available records)

Pathway

HER2 signaling blockade / HER2-directed targeting in HER2-expressing tumors

HER2 (human epidermal growth factor receptor 2) is a receptor tyrosine kinase belonging to the ErbB/HER family of cell-surface growth factor receptors. In normal tissue it helps regulate cell growth and division, but in a subset of cancers—most notably certain breast and gastric tumors—the HER2 gene is amplified, causing the receptor to be overexpressed. This excess HER2 dimerizes readily with itself or other HER family members, continuously activating downstream growth pathways (including RAS-MAPK and PI3K-AKT) independent of normal growth signals, driving uncontrolled proliferation and survival of tumor cells. Because HER2 overexpression is confined largely to tumor cells relative to normal tissue, it serves as a rational target for selective anticancer therapy. Several distinct strategies exploit this: monoclonal and bispecific antibodies bind the extracellular domain to block receptor dimerization and flag cells for immune destruction; small-molecule tyrosine kinase inhibitors block the intracellular kinase directly, which can also reach the brain, relevant for metastatic disease; antibody-drug conjugates use HER2 binding to deliver cytotoxic payloads directly into tumor cells; and radiopharmaceuticals use HER2 binding to localize radiation. This mechanism broadly matters across HER2-driven breast, gastric, and other epithelial cancers.