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Profiling Sensitivity to Targeted Therapies in EGFR-Mutant NSCLC Patient-Derived Organoids
Published on: November 22, 2021
Overcoming EGFR(T790M) and EGFR(C797S) resistance with mutant-selective allosteric inhibitors
Yong Jia1, Cai-Hong Yun2,3, Eunyoung Park2,3
1Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA.
Abstract:
The epidermal growth factor receptor (EGFR)-directed tyrosine kinase inhibitors (TKIs) gefitinib, erlotinib and afatinib are approved treatments for non-small cell lung cancers harbouring activating mutations in the EGFR kinase, but resistance arises rapidly, most frequently owing to the secondary T790M mutation within the ATP site of the receptor. Recently developed mutant-selective irreversible inhibitors are highly active against the T790M mutant, but their efficacy can be compromised by acquired mutation of C797, the cysteine residue with which they form a key covalent bond. All current EGFR TKIs target the ATP-site of the kinase, highlighting the need for therapeutic agents with alternative mechanisms of action. Here we describe the rational discovery of EAI045, an allosteric inhibitor that targets selected drug-resistant EGFR mutants but spares the wild-type receptor. The 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. However, as a single agent it is not effective in blocking EGFR-driven proliferation in cells owing to differential potency on the two subunits of the dimeric receptor, which interact in an asymmetric manner in the active state. We observe marked synergy of EAI045 with cetuximab, an antibody therapeutic that blocks EGFR dimerization, rendering the kinase uniformly susceptible to the allosteric agent. EAI045 in combination with cetuximab is effective in mouse models of lung cancer driven by EGFR(L858R/T790M) and by EGFR(L858R/T790M/C797S), 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.
Insights
A novel allosteric inhibitor, EAI045, shows promise for treating non-small cell lung cancer by targeting drug-resistant epidermal growth factor receptor (EGFR) mutations. Combined with cetuximab, it effectively combats resistant EGFR mutations in preclinical models.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) are standard treatments for non-small cell lung cancer (NSCLC) with activating EGFR mutations.
- Acquired resistance, often due to the T790M mutation, limits the long-term efficacy of current EGFR TKIs.
- Emergence of the C797 mutation further compromises treatments, necessitating novel therapeutic strategies targeting alternative mechanisms.
Purpose of the Study:
- To discover and characterize a novel therapeutic agent targeting drug-resistant EGFR mutants.
- To investigate the mechanism of action and efficacy of an allosteric inhibitor against various EGFR mutations.
- To evaluate the synergistic potential of the allosteric inhibitor in combination with existing therapies.
Main Methods:
- Rational drug design and structure-based crystallography to identify EAI045.
- Biochemical assays to determine the inhibitory potency of EAI045 against EGFR mutants.
- Cell-based proliferation assays to assess the efficacy of EAI045 as a single agent and in combination.
- In vivo studies using mouse models of NSCLC driven by resistant EGFR mutations.
Main Results:
- EAI045, an allosteric inhibitor, demonstrates low-nanomolar potency against EGFR L858R/T790M mutants.
- EAI045 exhibits limited efficacy as a single agent due to asymmetric interactions in dimeric EGFR.
- Combination therapy with cetuximab, an EGFR dimerization inhibitor, synergistically enhances EAI045's efficacy.
- EAI045 plus cetuximab shows significant effectiveness in preclinical models of NSCLC with EGFR(L858R/T790M) and EGFR(L858R/T790M/C797S) mutations.
Conclusions:
- EAI045 represents a new class of allosteric inhibitors targeting drug-resistant EGFR mutants.
- Combination therapy with cetuximab overcomes resistance mechanisms and demonstrates potent anti-cancer activity.
- Targeting allosteric sites offers a viable strategy for developing mutant-selective inhibitors against challenging cancer targets.
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