This study will be conducted in 3 parts (i.e. dose escalation, dose expansion, and a phase 2 portion). The dose escalation part will investigate the safety and determine the recommended phase 2 dose and the recommended dosing regimen of TAS3351 administered orally. The dose expansion part will explore the efficacy of TAS3351 in NSCLC participants with C797S EGFR mutations. The phase 2 part will assess the efficacy of TAS3351 in NSCLC participants with C797S EGFR mutations.
