EGFR/HER1, HER2, HER4

Class

Irreversible pan-HER (EGFR family) tyrosine kinase inhibitor

Pathway

EGFR/HER receptor signaling

Notes

original target text: EGFR/HER1, HER2, HER4 (pan-HER family, including exon19del/L858R EGFR mutations)

The HER (human epidermal growth factor receptor) family comprises four related receptor tyrosine kinases—EGFR (HER1), HER2, HER3, and HER4—embedded in the cell membrane. When their extracellular domains bind growth factors (or, in HER2's case, form partnerships with other HER members), they dimerize and activate intracellular kinase domains, triggering downstream signaling cascades such as RAS/MAPK and PI3K/AKT that drive cell proliferation and survival. In many cancers, mutations, amplifications, or overexpression of these receptors cause constant, growth-factor-independent activation, fueling tumor growth. Pan-HER inhibitors are small molecules designed to irreversibly bind the kinase domains of EGFR, HER2, and HER4 simultaneously, blocking their catalytic activity regardless of which combination of receptors a tumor relies upon. This broad coverage is particularly relevant for tumors bearing specific EGFR mutations (such as exon 19 deletions or the L858R substitution) that render the receptor constitutively active, as well as for cancers driven by HER2 overexpression. By covalently modifying the kinase active site, irreversible inhibitors achieve durable suppression of signaling even as drug levels fluctuate. This mechanism is central to treatment strategies in non-small cell lung cancer and HER2-driven breast cancer, among other malignancies where HER family signaling is a dominant growth driver.