NSCLC harboring EGFR exon‐20 insertions after the regulatory C‐helix of kinase domain responds poorly to known EGFR inhibitors

Abstract

Anecdote clinical observations hint that non-small cell lung cancer (NSCLC) with exon-20 insertions might respond poorly to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), contrasting to those with classic mutations. Lack of patient-derived experimental models has been a major hurdle for the discovery of new treatment for the diseases. We established two NSCLC-PDXs harboring two different exon-20 insertions, LU0387-adenocarcinoma (ADC) with a nine-base insertion at 2319 (H773-V774insNPH) and LU3075-squamous cell carcinoma (SCC) with a nine-base insertion at 2316 (P772-H773insDNP). Both insertions immediately follow the regulatory C-helix of the kinase domain. Contrary to the generally good responses to EGFR inhibitors observed in PDXs with classic mutations, both exon-20 insertions are largely resistant to cetuximab and TKIs in vivo, suggesting fundamental difference from the classic EGFR mutations, consistent with the poor response rate to TKI seen in anecdotal clinic reports. It is worth noting that although responses are generally poor, they differ between the two exon-20 mutants depending on the type of TKI. In vitro drug sensitivity assays using established primary cell lines from our two PDXs largely confirmed the in vivo data. Our data from patient-derived experimental models confirmed that exon-20 insertions in domain immediately following the C-helix confer poor response to all known EGFR inhibitors, and suggested that these models can be utilized to facilitate the discovery of new therapies targeting NSCLC harboring exon-20 insertions.

Mechanisms and clinical activity of an EGFR and HER2 exon 20–selective kinase inhibitor in non–small cell lung cancer

“…However, modeling of EGFR A763insFQEA demonstrated that insertions before residue 764 do not exhibit this effect and do not induce drug resistance 16 . Moreover, in a patient-derived xenograft (PDX) model of NSCLC driven by an EGFR exon 20 mutation in which the insertions are in the loop after the α-C helix (EGFR H773insNPH), the third-generation EGFR TKIs osimertinib (AZD9291) and rociletinib (CO-1696) were found to have minimal activity 28 . In a recent study of rare EGFR and HER2 exon 20 mutations, the authors found a heterogeneous response to covalent quinazoline-based second-generation inhibitors, such as dacomitinib and afatinib; however, the concentrations that were required to target more common exon 20 insertion mutations were above what are clinically achievable 24 .…”

Molecular Pathology of Patient Tumors, Patient-Derived Xenografts, and Cancer Cell Lines

“…If such similarity is systematically verified and further quantified, the translational utility of PDXs can be immensely explored and expanded. We have built a large library of PDXs over the years (7,8,(10)(11)(12)(13) and also performed transcriptome sequencing and/ or microarray analysis. The pathologic relevance of PDXs to patient tumors, both histologically and molecularly, can now be examined by comparing TCGA and PDX data.…”

Trichomegaly and scalp hair changes following treatment with erlotinib in pulmonary adenocarcinoma patients: A case report and literature review

“…Notably, she has a rare mutation, which is an insertion mutation at exon 20 (p.V769_D770insASV). The majority of exon 20 insertion mutations reported to date are associated with resistance to TKIs (31,32). Her disease remained stable as of December 22, 2014, and the PFS is 36 months temporarily.…”