On November 13, 2015, the FDA granted accelerated approval to osimertinib (TAGRISSO; AstraZeneca), a breakthrough therapy-designated drug for the treatment of patients with metastatic EGFR T790M mutation-positive non-small cell lung cancer, as detected by an FDA-approved test, with progression on or after EGFR tyrosine kinase inhibitor therapy. Approval was based on durable tumor response rates in two single-arm, multicenter trials: the dose extension cohort of a first-in-human trial (FIH; AURA extension; = 201) and a fixed-dose, activity-estimating trial (AURA2; = 210). Osimertinib was administered at 80 mg orally once daily. The objective response rates (ORR) per blinded independent committee review were 57% 95% confidence interval (CI), 50-64) in AURA extension and 61% (95% CI, 54-68) in AURA2. Median duration of response (DOR) could not be estimated. Supportive efficacy data from 63 patients in the dose-finding part of the FIH trial demonstrated an ORR of 51% (95% CI, 38-64), with a median DOR of 12.4 months. Common adverse events (AE) evaluated in 411 patients included diarrhea (42%), rash (41%), dry skin (31%), and nail toxicity (25%). Grade 3 to 4 AEs occurred in 28% of patients, and 5.6% discontinued treatment due to AEs. .