1377P - Differential impact of EGFR exon 20 insertion location on tyrosine kinase inhibitor sensitivity

Background

EGFR exon 20 insertion mutations (EGFRex20ins) can be classified as near-loop and far-loop based on their location. The underlying structural difference between near- vs. far-loop EGFRex20ins and its impact on various other novel EGFR TKIs response are not well understood.

Methods

We assessed in vitro activity of multiple EGFR TKIs against a panel of BaF3 cells expressing EGFRex20ins mutations. Molecular Dynamics (MD) modeling of near- vs. far-loop EGFRex20ins, with and without binding of EGFR TKIs was performed. Clinical responses (tumor size reduction and progression free survival) were analyzed by near- vs. far-loop insertion location in ZENITH20 and EXCLAIM trials.

Results

In vitro testing with different EGFRex20ins indicated a favorable IC₅₀ for afatinib, CLN-081, and poziotinib in near-loop (A767-P772) versus far-loop (H773-R776) insertions, whereas mobocertinib had similar IC₅₀ values in near- and far-loop insertions. MD modeling using free-energy calculations indicated that wildtype EGFR displayed distinct inactive and active states with a relatively high transitional energy barrier. In comparison, the near-loop (S768insSVD) exhibited multiple states separated by shallow barriers whereas the far-loop (H773insNPH) was conformationally more rigid. The differential p-loop orientation change in near- vs. far-loop insertions played an active role in TKI binding, stabilization, and selectivity. Clinical data supported the in vitro differential impact of insertion location. In the ZENITH20 trial (n=82), in pre-treated EGFRex20ins lung cancer patients, poziotinib had superior activity in near-loop than far-loop tumors both on tumor size reduction (-25.9% vs. -9.8%, p=0.0014) and PFS (11.1 vs. 3.5 months, Log Rank p=0.016). In the EXCLAIM trial platinum-pretreated patients (n=76), mobocertinib demonstrated robust activity in both groups as assessed by tumor size reduction (near -38.5% vs. far -34.1%, p=0.59) and PFS (12.0 vs. 13.0, Log Rank p=0.99).

Conclusions

Preclinical and clinical data indicated that near- vs far-loop EGFRex20 insertions differentially impact sensitivity to individual TKIs. Thus, knowledge of insertion location may allow for more effectively tailored TKI therapy.

Clinical trial identification

ZENITH20: NCT03318939; EXCLAIM: NCT02716116.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Damon Runyon Foundation.

Disclosure

X. Le: Financial Interests, Personal, Advisory Board: AstraZeneca, Merck KGaA, Spectrum Pharmaceutics, Novartis, Boehringer Ingelheim, Eli Lilly, Hengrui, Janssen, Blueprint, Daiichi Sankyo, Regeneron, ArriVent, Abion, Pinetree Therapeutics, AbbVie; Financial Interests, Institutional, Coordinating PI: Eli Lilly, EMD Serono, Regeneron, Janssen; Financial Interests, Institutional, Research Grant: Arrivent; Financial Interests, Institutional, Funding: Teligene. J.P. Robichaux: Financial Interests, Personal, Affiliate: AstraZeneca. G. Bhat, F. Lebel: Financial Interests, Personal, Affiliate: Spectrum. S. Vincent, V. Bunn, Z. Su: Financial Interests, Personal, Affiliate: Takeda. J. Heymach: Financial Interests, Personal, Advisory Board: Genentech, Mirati Therapeutics, Eli Lilly & Co., Janssen Pharmaceuticals, Boehringer Ingelheim Pharmaceuticals, Regeneron, Takeda Pharmaceuticals, BerGenBio, Jazz Pharmaceuticals, Curio Science, Novartis, AstraZeneca, BioAlta, Sanofi, Spectrum Pharmaceuticals, GSK, Spectrum; Financial Interests, Personal, Full or part-time Employment: MD Anderson Cancer Center; Financial Interests, Institutional, Other, International PI for clinical trials: AstraZeneca; Financial Interests, Institutional, Other, International PI for two clinical trials: Boehringer Ingelheim; Financial Interests, Personal and Institutional, Other, Developed a drug: Spectrum; Financial Interests, Institutional, Coordinating PI: Takeda. All other authors have declared no conflicts of interest.