LBA5 Background: Osimertinib is a 3rd-generation, CNS-active, EGFR-TKI with superior efficacy to comparator EGFR-TKI (gefitinib/erlotinib) in treatment-naïve EGFRm advanced NSCLC. Approx. 30% of pts with NSCLC present with early stage (I–IIIA) disease; surgery is the primary treatment. Adjuvant chemotherapy is standard of care in pts with resected stage II–III NSCLC and select stage IB pts; however, recurrence rates are high and other therapies are needed. ADAURA (NCT02511106) is a Ph III, double-blind, randomized study assessing the efficacy and safety of osimertinib vs placebo (PBO) in pts with stage IB–IIIA EGFRm NSCLC after complete tumor resection and adjuvant chemotherapy, when indicated. Following Independent Data Monitoring Committee recommendation, the trial was unblinded early due to efficacy; we report an unplanned interim analysis. Methods: Eligible pts: ≥18 years (Japan/Taiwan: ≥20), WHO PS 0/1, primary non-squamous stage IB/II/IIIA NSCLC, confirmed EGFRm (ex19del/L858R), complete resection of primary NSCLC with full recovery from surgery; postoperative chemotherapy was allowed. Pts were randomized 1:1 to osimertinib 80 mg once daily orally or PBO to receive treatment for up to 3 years and stratified by stage (IB/II/IIIA), mutation type (ex19del/L858R), and race (Asian/non-Asian). Primary endpoint: disease-free survival (DFS) by investigator in stage II–IIIA pts. Secondary endpoints: overall survival (OS) and safety. Data cutoff (DCO): 17 Jan 2020. Results: Globally, 682 pts were randomized to treatment: osimertinib n=339, PBO n=343. Baseline characteristics were balanced across arms (osimertinib/PBO): stage IB 31/31%, stage II/IIIA 69/69%, female 68/72%, ex19del 55/56%, L858R 45/44%. In stage II–IIIA pts, DFS hazard ratio (HR) was 0.17 (95% CI 0.12, 0.23); p<0.0001 (156/470 events); 2-year DFS rate was 90% with osimertinib vs 44% with PBO. In the overall population, DFS HR was 0.21 (0.16, 0.28); p<0.0001 (196/682 events); 2-year DFS rate was 89% with osimertinib vs 53% with PBO. OS was immature (4% maturity) with 29/682 deaths (osimertinib n=9, PBO n=20) at DCO. The safety profile was consistent with the known safety profile of osimertinib. Conclusions: Adjuvant osimertinib is the 1st targeted agent in a global trial to show a statistically significant and clinically meaningful improvement in DFS in pts with stage IB/II/IIIA EGFRm NSCLC after complete tumor resection and adjuvant chemotherapy, when indicated. Adjuvant osimertinib provides an effective new treatment strategy for these pts. Clinical trial information: NCT02511106.