Nazartinib mesylate is primarily used in the field of oncology, specifically targeting non-small cell lung cancer (NSCLC) with EGFR mutations. It functions as an epidermal growth factor receptor (EGFR) inhibitor, designed to block the activity of EGFR proteins that promote cancer cell growth. This makes it a potential therapeutic option for patients with advanced or metastatic NSCLC who have developed resistance to other EGFR inhibitors. Clinical trials have explored its efficacy in shrinking tumors and improving progression-free survival in patients with specific genetic profiles. Additionally, it is being investigated for its potential in treating other cancers where EGFR mutations play a significant role. Its application is closely monitored due to its targeted mechanism, which aims to minimize harm to healthy cells while effectively combating cancer progression.