Data from TAS-121, A Selective Mutant EGFR Inhibitor, Shows Activity Against Tumors Expressing Various <i>EGFR</i> Mutations Including T790M and Uncommon Mutations G719X

Abstract

<div>Abstract<p>TAS-121 is a novel orally active selective covalent inhibitor of the mutant EGFR. We performed preclinical characterization of TAS-121 and compared its efficacy and selectivity for common <i>EGFR</i> mutations (Ex19del and L858R), first- and second- generation EGFR-tyrosine kinase inhibitor (EGFR-TKI) resistance mutation (T790M), and uncommon mutations (G719X and L861Q) with those of other EGFR-TKIs. We also commenced investigation of the clinical benefits of TAS-121. The IC<sub>50</sub> for intracellular EGFR phosphorylation was determined by using Jump-In GripTite HEK293 cells transiently transfected with <i>EGFR</i> expression vectors. Mouse xenograft models were used to evaluate the antitumor activity of TAS-121. TAS-121 potently inhibited common activating and resistance EGFR mutations to the same extent as another third-generation EGFR-TKI (osimertinib). In addition, TAS-121 showed equivalent inhibitory activity against some uncommon mutations such as G719X and L861Q. Furthermore, TAS-121 demonstrated greater selectivity for mutant EGFRs versus the wild-type EGFR compared with other EGFR-TKIs. Moreover, TAS-121 displayed antitumor activity in SW48 (<i>EGFR</i> G719S) and NCI-H1975 (<i>EGFR</i> L858R/T790M) xenograft models, and achieved an objective response in patients with NSCLC with <i>EGFR</i> mutations including G719A mutation. In conclusion, TAS-121 is a novel third-generation EGFR-TKI and demonstrates antitumor activities in patients with NSCLC expressing either common or uncommon EGFR mutations.</p></div>