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Ibrutinib, which irreversibly inhibits Bruton tyrosine kinase, was evaluated for antitumor activity in a panel of non-small cell lung cancer (NSCLC) cell lines and found to selectively inhibit growth of NSCLC cells carrying mutations in the epidermal growth factor receptor (EGFR) gene, including T790M mutant and erlotinib-resistant H1975 cells. Ibrutinib induced dose-dependent inhibition of phosphor-EGFR at both Y1068 and Y1173 sites, suggesting ibrutinib functions as an EGFR inhibitor. Survival was analyzed by Kaplan-Meier estimation and log-rank test. All statistical tests were two-sided. In vivo study showed that ibrutinib statistically significantly suppressed H1975 tumor growth and prolonged survival of the tumor bearing mice (n = 5 per group). The mean survival times for solvent- and erlotinib-treated mice were both 17.8 days (95% confidence interval [CI] = 14.3 to 21.3 days), while the mean survival time for ibrutinib-treated mice was 29.8 days (95% CI = 26.0 to 33.6 days, P = .008). Our results indicate that ibrutinib could be a candidate drug for treatment of EGFR-mutant NSCLC, including erlotinib-resistant tumors. [ABSTRACT FROM AUTHOR]