A Phase II Study of Poziotinib in Patients with Epidermal Growth Factor Receptor (<i>EGFR</i>)-Mutant Lung Adenocarcinoma Who Have Acquired Resistance to EGFR–Tyrosine Kinase Inhibitors

Purpose We examined the efficacy of poziotinib, a second-generation epidermal growth factor receptor (EGFR)–tyrosine kinase inhibitor (TKI) in patients with lung adenocarcinoma with activating EGFR mutations, who developed acquired resistance (AR) to EGFR-TKIs. Materials and Methods This single-arm phase II study included EGFR-mutant lung adenocarcinoma with AR to erlotinib or gefitinib based on the Jackman criteria. Patients received poziotinib 16 mg orally once daily in a 28-day cycle. The primary endpoint was progression-free survival (PFS). Prestudy tumor biopsies and blood samples were obtained to determine resistance mechanisms. Results Thirty-nine patients were treated. Tumor genotyping was determined in 37 patients; 19 EGFR T790M mutations and two PIK3CA mutations were detected in the prestudy tumors, and seven T790M mutations were detected in the plasma assay. Three (8%; 95% confidence interval [CI], 2 to 21) and 17 (44%; 95% CI, 28 to 60) patients had partial response and stable disease, respectively. The median PFS and overall survival were 2.7 months (95% CI, 1.8 to 3.7) and 15.0 months (95% CI, 9.5 to not estimable), respectively. A longer PFS was observed for patients without T790M or PIK3CA mutations in tumor or plasma compared to those with these mutations (5.5 months vs. 1.8 months, p=0.003). The most frequent grade 3 adverse events were rash (59%), mucosal inflammation (26%), and stomatitis (18%). Most patients required one (n=15) or two (n=15) dose reductions. Conclusion Low activity of poziotinib was detected in patients with EGFR-mutant non-small cell lung cancer who developed AR to gefitinib or erlotinib, potentially because of severe-toxicityimposed dose limitation. Key words: Epidermal growth factor receptor, Poziotinib, Non-small-cell lung carcinoma, T790M, PIK3CA