EGFR Exon 20 Insertion Mutations Display Sensitivity to Hsp90 Inhibition in Preclinical Models and Lung Adenocarcinomas

Abstract

exon 20 insertions account for up to 10% of all mutations in lung adenocarcinomas, representing the third most common cluster of mutations. The management of advanced cancers with these mutations remains elusive, without an approved inhibitor. Preclinical models of a representative set of EGFR exon 20 insertion mutations to evaluate the efficacy of different inhibitors and description of the clinical outcome of an advanced lung cancer. We show that select first-, second-, and third-generation EGFR inhibitors are unable to deter common EGFR exon 20 insertion mutants in concentrations that spare the wild-type kinase. Nonetheless, EGFR exon 20 insertion mutants associate with the Hsp90 chaperone system. We exploit this vulnerability to show that the nongeldanamycin Hsp90 inhibitor luminespib (formerly AUY922) degrades EGFR exon 20 mutations, downstream targets, and induces apoptosis. In addition, a patient whose EGFR inhibitor-insensitive lung adenocarcinoma harbored an exon 20 insertion mutation had a confirmed radiographic response to luminespib. The report confirms that EGFR exon 20 mutations are dependent on Hsp90 and are readily inhibited by the Hsp90 inhibitor luminespib; a treatment strategy that has been pursued in a confirmatory clinical trial (NCT01854034) for this group of lung adenocarcinomas that currently represent an unmet clinical need in precision oncology.

EGFR-A763_Y764insFQEA Is a Unique Exon 20 Insertion Mutation That Displays Sensitivity to Approved and In-Development Lung Cancer EGFR Tyrosine Kinase Inhibitors

“…2 Our group and others initially characterized EGFR-A763_Y764insFQEA as sensitive to EGFR TKIs in preclinical models. 2,[4][5][6] Clinical reports of benefit with the use of EGFR TKIs have been sparingly reported to date but seem to corroborate the preclinical data. We sought to: (1) determine the frequency of EGFR-A763_Y764insFQEA among other EGFR exon 20 insertion mutations; (2) confirm the therapeutic window of EGFR-A763_Y764insFQEA to clinically available first-, second-, third-generation, and in-development EGFR exon 20-specific TKIs; and (3) confirm radiographic responses and clinical benefit from approved and indevelopment EGFR TKIs by compiling the largest cohort of previously published and unpublished cases.…”

“…2 This negates a therapeutic window for these targeted therapies, and preclinical, and clinical development of novel EGFR TKIs for these mutants have thus been hampered; however, repurposed or newly developed TKIs are exhibiting a modestly favorable therapeutic window-EGFR exon 20 insertion mutations more readily inhibited than WT EGFR-in preclinical models (poziotinib, CLN-081) and early clinical studies (mobocertinib [previously known as TAK-788]) in both EGFRand ERBB2-mutated lung cancers. [3][4][5][6] However, the EGFR-A763_Y764insFQEA mutation (and the identical amino acid sequence of EGFR-D761_E762insEAFQ) sets itself apart from other exon 20 insertions as it stands at the transition of exon 19 and 20 of EGFR (Fig. 1A).…”

Preclinical Characterization of Mobocertinib Highlights the Putative Therapeutic Window of This Novel EGFR Inhibitor to EGFR Exon 20 Insertion Mutations

“…Off label use of approved EGFR TKIs is further supported for EGFR exon 18 indels/E709X, exon 19 insertions, exon 20 A763_Y764insFQEA, exon 18 to 25 kinase domain duplications and rearrangements. 1,2,5,9,10 The identification of EGFR TKIs or other therapies with a favorable therapeutic window for patients with EGFR exon 20 insertion-mutated tumors continues to be a significant unmet necessity.…”

Preclinical characterization of mobocertinib highlights the putative therapeutic window of this novel EGFR inhibitor to EGFR exon 20 insertion mutations

“…Footnote: ORR, overall response rate; DCR, disease control rate; PFS, progression-free survival (median); CI, confidence interval. Data was based on references [9] (mobocertinib), [12] (poziotinib) and [13] (osimertinib).…”

“…del19, -L858R, -L861Q, G719X, -S768I and -T790M. Off label use of approved EGFR TKIs is further supported for EGFR-exon 18 indels/E709X, -exon 19 insertions, -exon 20A763_Y764insFQEA, exon 18-25 kinase domain duplications and -rearrangements[1,2,5,9,10].…”