EGFR exon 20 insertion mutations display sensitivity to Hsp90 inhibition in preclinical models and lung adenocarcinomas

Purpose: EGFR exon 20 insertions account for up to 10% of all EGFR 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. Experimental Design: 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. Results: 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 heat shock protein 90 (Hsp90) chaperone system. We exploit this vulnerability to show that the non-geldanamycin 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 EGFR exon 20 insertion mutation had a confirmed radiographic response to luminespib. Conclusions: 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.

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