Overcoming EGFR(T790M) and EGFR(C797S) resistance with mutant-selective allosteric inhibitors

Abstract

EGFR tyrosine kinase inhibitors (TKIs) gefitinib, erlotinib and afatinib are approved treatments for non-small cell lung cancers harboring activating mutations in the EGFR kinase1,2, but resistance arises rapidly, most frequently due to the secondary T790M mutation within the ATP-site of the receptor.3,4 Recently developed mutant-selective irreversible inhibitors are highly active against the T790M mutant5,6, but their efficacy can be compromised by acquired mutation of C797, the cysteine residue with which they form a key covalent bond7. All current EGFR TKIs target the ATP-site of the kinase, highlighting the need for therapeutic agents with alternate mechanisms of action. Here we describe rational discovery of EAI045, an allosteric inhibitor that targets selected drug-resistant EGFR mutants but spares the wild type receptor. A crystal structure shows that the compound binds an allosteric site created by the displacement of the regulatory C-helix in an inactive conformation of the kinase. The compound inhibits L858R/T790M-mutant EGFR with low-nanomolar potency in biochemical assays, but as a single agent is not effective in blocking EGFR-driven proliferation in cells due to differential potency on the two subunits of the dimeric receptor, which interact in an asymmetric manner in the active state8. We observe dramatic synergy of EAI045 with cetuximab, an antibody therapeutic that blocks EGFR dimerization9,10, rendering the kinase uniformly susceptible to the allosteric agent. EAI045 in combination with cetuximab is effective in mouse models of lung cancer driven by L858R/T790M EGFR and by L858R/T790M/C797S EGFR, a mutant that is resistant to all currently available EGFR TKIs. More generally, our findings illustrate the utility of purposefully targeting allosteric sites to obtain mutant-selective inhibitors.

Third-generation epidermal growth factor receptor-tyrosine kinase inhibitors in T790M-positive non-small cell lung cancer: review on emerged mechanisms of resistance

“…For this reason, new EGFR inhibitors and combined therapies with other target agents are under evaluation ( (45). Whilst EAI045 seems to be inactive towards del19 variants, it demonstrated, when combined to cetuximab, to potently inhibit both double mutant L858R/ T790M and triple mutant L858R/T790M/C797S cells.…”

Patient with Three EGFR Mutations – Gradual Development of Resistance to Previous Targeted Treatment

“…Všechny výše zmíněné preparáty však narážejí na riziko vzniku další mutace v ATP vazebném místě a ztrátě jejich účinku. Tuto překážku lze překonat nově vyvíjenými inhibitory bez nutnosti vazby na tuto část EGFR genu [19,20]. Nejslibněji se jeví alosterický inhibitor EIA045 [19,20], který před-stavuje zcela nový typ EGFR inhibice.…”

Emerging uses of biomarkers in lung cancer management: molecular mechanisms of resistance

“…In mouse models, EAI045 in combination with cetuximab, an antibody that stops EGFR dimerization, has been shown to be effective against the L8585R/T790M and L858R/T790M/C797S EGFR mutants (38). Another drug regimen that is a powerful candidate to overcome triple-mutant EGFR is the combination of cetuximab with brigatinib, a potent and selective ALK/EGFR T790M inhibitor.…”