Background: HM61713 is an orally available EGFR mutation-specific inhibitor with sparing EGFR WT tumors that previously showed promising efficacy in T790M positive tumors at the dose of 300 mg (overall response rate; 29.2%). We report here on updated data from the ongoing phase I/II study of HM61713 in pts with advanced NSCLC who had failed previous EGFR-TKIs (NCT01588145). Methods: Advanced NSCLC pts with EGFR mutation positive tumor were enrolled in dose escalation cohort and received doses ranging from 75-1200 mg/day. After safety evaluation, separate expansion cohorts opened for pts who failed prior EGFR TKI pts at 800 mg QD dose, respectively to investigate efficacy and tolerability of HM61713 in pts with centrally confirmed T790M positive NSCLC. Results: As of 15 Dec 2014, 173 patients were enrolled, 55 and 118 in dose escalation and expansion parts, respectively. Maximum tolerated dose (MTD) was established as 800 mg once daily (QD). Dose limiting toxicities (DLTs) included abdominal pain, diarrhoea, idiosyncratic drug reaction, and elevation of aspartate aminotransferase, alanine aminotransferase, amylase and lipase. Treatment-related adverse events occurred in 87.3% of 165 pts; mainly diarrhea, rash, skin exfoliation, nausea, pruritus, decreased appetite and dry skin. In the 34 pts with centrally confirmed T790M who received HM61713 with a dose more than 650 mg, the overall response rate was 58.8%, (10 confirmed/10 unconfirmed partial responses) and 13 pts achieved disease stabilization (disease control rate; 97.1%). Updated data will be presented at the meeting. Conclusions: HM61713 showed an encouraging clinical anti-tumor activity with good tolerability in pts with T790M positive NSCLC. Clinical trial information: NCT01588145