This multicenter, open-label, Phase 1b study expansion cohort enrolled patients (aged {greater than or equal to}18 years) with advanced MET-negative, EGFRm NSCLC who had progressed on EGFR-TKIs. Patients were assigned to one of two cohorts by prior first-/second-generation [1G/2G] or T790M-directed EGFR-TKI and received osimertinib 80 mg QD and intermittent selumetinib....ORR was 66.7% (95% confidence interval: 34.9-90.1) in the prior 1G/2G EGFR-TKI group, 22.9% (10.4-40.1) in the prior 3G EGFR-TKI group, and 34.0% (2.7-7.2) overall; median PFS was 15.0 (2.7-33.0), 2.8 (1.6-5.5), and 4.2 months (2.7-7.2), respectively....The combination demonstrated antitumor activity supportive of further investigation in patients with MET-negative, EGFRm advanced NSCLC, who had progressed on a previous EGFR-TKI.