Activity of osimetrinib/AZD9291 in pretreated patients (pts) with epidermal growth factor receptor mutant (EGFRmt) non-small cell lung cancer (NSCLC), according to EGFR …

e20608Background: Osimertinib is an irreversible EGFR tyrosine kinase inhibitor (TKI), selective for EGFR TKI-sensitizing mutations and the T790M resistance mutation. We sought to determine the activity of osimertinib after progression on EGFR TKIs in pts with T790-negative ctDNA. Methods: A multicenter phase II study (clinicaltrials.gov NCT02771314) of osimertinib (80 mg daily) was conducted in pts with metastatic EGFRmt NSCLC, who had progressed after previous treatment with EGFR TKIs. Serial serum and/or plasma samples were drawn for ctDNA analysis at enrollment, 1 month and every 3 months of treatment, until disease progression. Efficacy outcomes in pts without the T790M mutation in ctDNA at baseline are reported. Results: Thirty-seven NSCLC patients with undetectable baseline T790M in the plasma have been enrolled. Median age was 67 years, 21.6% were male, and histology was …