Ahn MJ, Han JY, Lee KH, et al. - Including dose escalation, dose expansion, and dose extension parts, this first-in-human, open-label, multicentre, phase 1–2 study was undertaken to determine whether lazertinib [an irreversible, third-generation, mutant-selective, EGFR tyrosine kinase inhibitor (TKI)] has activity in patients with advanced non-small-cell lung cancer progressing after EGFR TKI therapy and whether it is safe and tolerable in these patients. Researchers also focused on its pharmacokinetics. Only dose escalation and dose expansion results are described in this study performed in 14 hospitals in Korea. Oral lazertinib 20 mg, 40 mg, 80 mg, 120 mg, 160 mg, 240 mg, or 320 mg once daily continuously in 21-day cycles was administered to the eligible patients. Findings revealed a tolerable safety profile of lazertinib, as well as its promising clinical activity in this patient population. There were no dose-limiting toxicities and no dose-dependent increment in adverse events. Grade 1–2 rash or acne and pruritus were the most commonly experienced adverse events.