HER2 inhibition refers to the targeted therapy that aims to block the overexpression or activation of the human epidermal growth factor receptor 2 (HER2). HER2 is a protein that plays a critical role in cell growth and proliferation, and its overexpression is associated with more aggressive forms of cancer, particularly breast cancer. HER2 inhibition can be achieved through the use of monoclonal antibodies, such as trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1), which specifically target HER2-positive cancer cells. These therapies have been shown to improve outcomes in HER2-positive breast cancer patients, including increased survival rates and reduced risk of disease recurrence. In addition to breast cancer, HER2 inhibition is also being studied in other types of cancer, such as gastric cancer and non-small cell lung cancer, where HER2 overexpression has been identified as a potential driver of tumor growth. Overall, HER2 inhibition represents a targeted and effective approach to treating HER2-positive cancers and has significantly improved outcomes for patients with these types of cancers.