Novel peptidomimetic compounds are disclosed, compounds that inhibit protein-protein interactions (PPI) of epidermal growth factor receptors (EGFR), also called human epidermal growth factor receptors (HERs), and that block signaling for cell growth in HER2-overexpressed cancers. The novel peptidomimetics specifically bind the HER2 protein, and thereby inhibit dimerization. The peptidomimetics disrupt both HER2-HER3 and EGFR-HER2 heterodimer formation. The peptidomimetics can be used in the treatment of various types of HER2-overexpressed cancers, including lung, breast, and ovarian cancers.
