Epidermal growth factor receptor (EGFR) exon 20 insertion mutant (EGFR exon 20 ins)

The Epidermal Growth Factor Receptor (EGFR) exon 20 insertion mutant is a distinct oncogenic driver found in approximately 1% to 10% of non-small cell lung cancer (NSCLC) cases [1.2.1, 1.3.4]. These mutations are characterized by in-frame insertions or duplications of 3 to 21 base pairs within the kinase domain, primarily in the loop following the regulatory C-helix (amino acids 762–775) [1.2.1, 1.3.4]. Structurally, these alterations stabilize the receptor in an active conformation, leading to constitutive, ligand-independent signaling through pathways such as PI3K/AKT and MAPK/ERK [1.2.1, 1.2.3]. Unlike classical EGFR mutations, exon 20 insertions create a restricted ATP-binding pocket that confers intrinsic resistance to most first-, second-, and third-generation tyrosine kinase inhibitors (TKIs) [1.1.2, 1.4.2]. Therapeutic strategies have evolved to include specialized agents like the bispecific antibody amivantamab and novel TKIs such as mobocertinib and sunvozertinib [1.4.1, 1.4.3]. However, treatment is often limited by off-target inhibition of wild-type EGFR, resulting in common toxicities like rash and diarrhea, and the development of acquired resistance mechanisms such as the C797S mutation [1.1.2, 1.2.1]. Clinical detection typically requires high-sensitivity methods like next-generation sequencing (NGS) due to the heterogeneity of the insertion sequences [1.3.2]. Despite recent approvals, managing these patients remains a therapeutic challenge due to the narrow therapeutic window and the rapid emergence of resistance [1.4.2].

Other names

ErbB-1HER1EGFR ins20EGFR ex20insEGFR exon 20 insertions

Tyrosine kinase inhibition of the mutant EGFR kinase domain; bispecific antibody targeting of EGFR and MET extracellular domains; inhibition of constitutive, ligand-independent receptor signaling [1.2.1, 1.4.2].