Abstract A157: Antitumor activity of tarloxotinib, a hypoxia-activated EGFR TKI, in patient-derived lung cancer cell lines harboring EGFR exon 20 insertions

Targeting exon 20 insertion mutations in lung cancer

PURPOSE OF REVIEW

The application of tyrosine kinase inhibitor (TKI) has successfully changed the standard of care in epidermal growth factor receptor ( EGFR ) positive non-small cell lung cancer. However, clinical survivals for patients with EGFR exon 20 insertions have failed to improve over the long period and the mutation appeared resistant to EGFR -TKIs. This overview focused on the current treatment strategies, summarized the emerging regimens for patients with EGFR exon 20 insertions, and demonstrated historical challenges and future development.

RECENT FINDING

Current clinical trials suggested that several regimens selectively-targeted EGFR exon 20 insertions presented potent antitumor activity, like mobocertinib and the bispecific anti- EGFR-MET monoclonal antibody amivantamab and were approved by Food and Drug Administration (FDA) in patients progressed beyond first-line treatment. Novel treatments, including DZD9008, CLN-081, revealed modest clinical efficacy as well and clinical trials are underway, which may lead to improvement of survival outcomes.

SUMMARY

Recent clinical evidence indicates that targeted therapies could improve survival benefits to some extent. More efforts on drug development are underway to bring higher response rates both extracranial and intracranial, sustained clinical remission, and better survival benefits.

Combination effects of ellagic acid with erlotinib in a Ba/F3 cell line expressing EGFR H773_V774 insH mutation

BACKGROUND

Epidermal growth factor receptor H773_V774 insH (EGFR-insH) is an EGFR exon 20 insertion mutation in non-small cell lung cancer (NSCLC), which is naturally resistant to available EGFR tyrosine kinase inhibitors (TKIs) and lacks a patient-derived cell line.

METHODS

A Ba/F3 cell line expressing EGFR-insH mutation (Ba/F3-insH cell line) was generated using an IL3-deprivation method. A cell proliferation assay was performed to screen natural compounds that exhibit a synergistic effect with erlotinib. Trypan blue staining was used to assess cell growth and crystal violate staining was recruited to evaluate clonogenic potential. Flow cytometry was used to detect EGFR expression and cell apoptosis. A xenograft model was created to evaluate the effect of ellagic acid (EA) with erlotinib on tumor growth.

RESULTS

EA was identified to synergistically inhibit the proliferation of Ba/F3-insH cells with erlotinib. The growth and clonogenic potential of Ba/F3-insH cells were definitely constrained by EA with erlotinib, whereas, the apoptosis of Ba/F3-insH cells was dramatically promoted by the combination. In a xenograft model of the Ba/F3-insH cell line, the combination treatment also exhibited a synergistic reduction in tumor growth.

CONCLUSIONS

In this study, we generated a Ba/F3 cell line expressing EGFR H773_V774 insH mutation and identified a synergistic treatment (EA with erlotinib) that markedly inhibited the viability of Ba/F3-insH cells in vitro and in vivo.

KEY POINTS

Our results indicated that the combination of ellagic acid with erlotinib has synergistic effects against EGFR H773_V774 insH mutation.

Targeting EGFR exon 20 insertion mutations in non-small cell lung cancer

Inframe insertions of three or more base pairs in exon 20 of the epidermal growth factor receptor (EGFR) gene were among the first EGFR mutations to be identified as oncogenic drivers in non-small cell lung cancer (NSCLC). However, unlike the classical EGFR L858R point mutation or exon 19 deletions, which represent the majority of EGFR mutations in NSCLC, low frequency EGFR exon 20 insertion mutations are associated with de novo resistance to targeted EGFR inhibitors and correlate with a poor patient prognosis. Here, we review the developments over the last 5 years in which pre-clinical studies, including elucidation of the crystal structure of an EGFR exon 20 insertion mutant kinase, have revealed a unique mechanism of kinase activation and steric conformation that define the lack of response of these EGFR mutations to clinically approved EGFR inhibitors. The recent development of several novel small molecule compounds that selectively inhibit EGFR exon 20 insertions holds promise for future therapeutic options that will be effective for patients with this molecular subtype of NSCLC.