Rociletinib hydrobromide is a third-generation, selective inhibitor of the epidermal growth factor receptor (EGFR) with activity against the T790M mutation, which confers resistance to first- and second-generation EGFR tyrosine kinase inhibitors. It was developed for the treatment of non-small cell lung cancer (NSCLC) in patients with EGFR T790M mutations who progressed on prior EGFR-targeted therapies, such as gefitinib or erlotinib. By irreversibly binding to the mutated EGFR, rociletinib inhibits downstream signaling pathways, thereby suppressing cancer cell proliferation and survival. Although clinical development was discontinued in 2016 due to suboptimal efficacy and safety concerns (including QT interval prolongation), rociletinib hydrobromide remains available as a high-purity research reagent (e.g., 98% purity) for studies in oncology, drug resistance mechanisms, and EGFR signaling pathways. Its use requires careful handling and is typically under controlled laboratory conditions.