e20575 Background: A Phase III study (AURA3) demonstrated that osimertinib prolonged PFS compared to platinum doublet in patients with T790M-positive non-small-cell lung cancer (NSCLC) exhibiting acquired resistance to epidermal growth factor receptor- tyrosine kinase inhibitor (EGFR-TKI). Although the patients in the study had good PS and only one prior EGFR-TKI treatment, most practical patients had multiple prior EGFR-TKI and poor PS. Moreover, several patients exhibited symptomatic central nervous system (CNS) metastasis in clinical practice. In this study, we evaluated the efficacy and toxicity of osimertinib in clinical practice. Methods: We retrospectively analyzed 30 patients who were treated with osimertinib at our hospital from April 11th 2016 to September 30th 2016. The efficacy and toxicity was compared between the patients with matched and unmatched AURA3 eligibility criteria. Efficacy was evaluated according to RECIST ver.1.1 and toxicity was evaluated using CTCAE ver.4.0. Results: A total of 9 out of 30 patients matched the AURA3 eligibility criteria (PS ≤ 1 and one prior EGFT-TKI) and 21 patients were unmatched (PS ≥ 2 or two or more EGFR-TKI or symptomatic CNS metastasis). The overall response rate(ORR) of osimertinib was 78% and 67% for the matched and unmatched patients, respectively. The disease control rate (DCR) was 100% and 90% for the matched and unmatched patients, respectively. In addition, the response rate of symptomatic CNS metastasis was 67%. Regarding toxicity, grade 3/4 toxicities were observed in 22% of the matched patients and 33% of the unmatched patients. In the matched patients, the most frequent AE was a rash (89%) and the frequent grade 3/4 toxicities were a rash (22%) and pneumonitis (11%). In unmatched patients, the most frequent AE was also a rash (57%), but the frequent grade 3/4 toxicities were pneumonitis (14%), rash (10%), and neutropenia (10%). Conclusions: Both the ORR and DCR in the unmatched patients were slightly lower than the matched patients; however, osimertinib was still found to be beneficial in clinical practice.