Rechallenge of afatinib for EGFR-mutated non-small cell lung cancer previously treated with osimertinib: a multicenter phase II trial protocol (REAL study)

Background Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of advanced non-small cell lung cancer (NSCLC) and contributed to the development of precision medicine. Osimertinib is a standard first-line (1L) treatment for EGFR-mutated NSCLC and has demonstrated superior survival benefits over previous-generation TKIs. However, resistance to osimertinib is nearly inevitable, and subsequent treatment strategies remain unmet medical needs in this setting. Afatinib, a second-generation EGFR-TKI, exhibits activity against certain uncommon EGFR mutation types in the 1L setting. There are a few case reports on the efficacy of afatinib against EGFR-dependent resistance after osimertinib treatment, although these have not been prospectively investigated. Methods The present phase II, single-arm multicenter trial aims to verify the efficacy and safety of afatinib rechallenge after 1L osimertinib resistance. Patients (aged ≥20 years) with advanced or recurrent non-squamous NSCLC harboring drug-sensitive EGFR mutations (deletion of exon 19 or L858R) who were previously treated with 1L osimertinib and second-line chemotherapy other than TKIs are considered eligible. Undergoing next-generation sequence-based comprehensive genomic profiling is one of the key inclusion criteria. The primary endpoint is the objective response rate; the secondary endpoints are progression-free survival, overall survival, and tolerability. Thirty patients will be recruited in December 2023. Discussion The results of this study may promote incorporating afatinib rechallenge into the treatment sequence after 1L osimertinib resistance, a setting in which concrete evidence has not been yet established. Registration UMIN Clinical Trial Registry: UMIN000049225.