Inclusion Criteria:

          -  Confirmed EGFR mutation for non-small cell lung cancer associated with EGFR TKI
             sensitivity

          -  For Part 2, EGFR T790M mutation-positive tumor status

          -  Left ventricular ejection fraction (LVEF) ≥ institution's lower limit of the reference
             range

          -  For Part 1, evaluable or measurable disease as defined by RECIST, Version 1.1

          -  For Part 2, measurable disease as defined by RECIST, Version 1.1

          -  ECOG performance status 0 to 1

          -  Adequate organ function

        Exclusion Criteria:

          -  Prior treatment with EGFR TKI within 9 days of first study dose

          -  For Part 1, prior treatment with more than 2 prior lines of chemotherapy for advanced
             NSCLC

          -  For Part 2, prior treatment with osimertinib or other T790M active EGFR TKI

          -  For Part 2, prior chemotherapy for advanced NSCLC

          -  Active uncontrolled/symptomatic CNS metastases, carcinomatous meningitis, or
             leptomeningeal disease

          -  Investigational drug within 3 months or 5 half-lives, whichever is longer, of first
             study dose

          -  Concurrent radiotherapy, radiotherapy within 28 days of first study dose, previous
             radiotherapy to the target lesion sites, or prior radiotherapy to > 25% of bone marrow

          -  Prior hematopoietic stem cell or bone marrow transplantation