Inclusion Criteria:

          -  Patients must have histologically or cytologically confirmed locally advanced (stage
             IIIB) or metastatic (stage IV) EGFR mutant (ex19del, L858R) NSCLC.

          -  Requirements of EGFR mutation status and prior lines of treatment:

          -  Treatment naive patients, who have locally advanced or metastatic NSCLC with EGFR
             sensitizing mutation (e.g., L858R and/or ex19del), have not received any systemic
             antineoplastic therapy for advanced NSCLC and are eligible to receive EGFR TKI
             treatment. Patients with EGFR exon 20 insertion/duplication are not eligible. Note:
             patients who have received only one cycle of chemotherapy in the advanced setting are
             allowed.

          -  Patients who have locally advanced or metastatic NSCLC with EGFR sensitizing mutation
             AND an acquired T790M mutation (e.g., L858R and/or ex19del, T790M+) following
             progression on prior treatment with a 1st-generation EGFR TKI or 2nd-generation EGFR
             TKI. These patients may not have received more than 4 prior lines of antineoplastic
             therapy in the advanced setting, including EGFR TKI, and may not have received any
             agent targeting EGFR T790M mutation (i.e., 3rd-generation EGFR TKI).

          -  Patients who have locally advanced or metastatic NSCLC with EGFR sensitizing mutation
             and a "de novo" T790M mutation (i.e., no prior treatment with any agent known to
             inhibit EGFR including EGFR TKI). These patients may not have received more than 3
             prior lines of antineoplastic therapy in the advanced setting, and may not have
             received any prior 3rd generation EGFR TKI.

          -  Patients must have a site of disease amenable to biopsy, and be a candidate for tumor
             biopsy according to the treating institution's guidelines. Patients must be willing to
             undergo a new tumor biopsy during therapy on this study, and at screening if an
             archival tumor sample obtained since the diagnosis of advanced disease (1L patients)
             or since last treatment failure (2L+ patients) is not available.

        Exclusion Criteria:

          -  Patients with a history or presence of interstitial lung disease or interstitial
             pneumonitis, including clinically significant radiation pneumonitis.

          -  Patients with unstable brain metastases.

          -  Patients with a history of another malignancy.

          -  Patients with a known history of human immunodeficiency virus (HIV) seropositivity.

          -  Patients with clinically significant, uncontrolled heart disease.

          -  Patients participating in additional parallel investigational drug or medical device
             studies.

          -  Prior therapies:

          -  Patients who have been treated with EGFR TKI in the adjuvant setting within 6 months,
             unless acquired EGFR T790M is present in a tumor or blood sample obtained since the
             discontinuation of the EGFR TKI.

          -  Patients who have been treated with prior EGFR TKI targeting T790M (3rd generation).

          -  Patients who have been treated with systemic anti-neoplastic therapy within:

               -  2 weeks for fluoropyrimidine monotherapy

               -  6 weeks for nitrosoureas and mitomycin

               -  4 weeks or ≤ 5 half-lives (whichever is shorter) for biological therapy
                  (including monoclonal antibodies) and continuous or intermittent small molecule
                  therapeutics or any other investigational agent