The rationale for targeting HER2 and HER3 comes from recognition that NRG1 binds HER3 to induce heterodimerization with other HER/ERBB kinases ... Fewer than 1% of solid tumors harbor NRG1 ...

Receptors are shown as two lobes connected by a transmembrane stretch. Binding of a ligand, neuregulin (NRG, blue square) or something EGF-like to the extracellular lobe activates the receptors.

Table 1: Kinase Activity and Ligand Binding Capability of ERBB Receptors Ligand binding to the extracellular domain, which is the portion of the receptor on the outside of the cell, leads to ...