Inclusion Criteria:

          1. Males or females ≥ 19 years of age

          2. Non Small Cell Lung Cancer(Non-Squamous Cell Carcinoma) patients who had shown
             clinical benefits (Complete response(CR) or Partial response(PR) or Stable disease(SD)
             ≥6 months) from EGFR-TKIs as first line treatment and developed progressive disease,
             and then received cytotoxic chemotherapy more than 4 cycles and developed progressive
             disease, and then confirmed T790 negative and sensitizing EGFR mutation(E19Del, L858R,
             L861Q, G719X, E19insertion) positive in Histologic, cytologic specimen or blood.

          3. Patient with at least one measurable lesions according to RECIST v 1.1

          4. Expected life expectancy ≥ 12 weeks

          5. Eastern Cooperative Oncology Group(ECOG) performance status ≤ 2

          6. Patients who have proper hematologic, renal and hepatic functions as follows:

               -  Absolute neutrophil count(ANC) ≥ 1,500/mm³

               -  platelets ≥ 100,000/mm³

               -  Hemoglobin ≥ 9g/dL

               -  Total bilirubin ≤ 1.25 X UNL

               -  Aspartate aminotransferase(AST or SGOT) and alanine aminotransferase(ALT or SGPT)
                  ≤ 3.0 X UNL (if liver metastasis ≤5.0 X UNL)

               -  Alkaline phosphatase ≤ 2.5 X UNL (if liver metastasis ≤5.0 X UNL)

               -  Serum creatinine ≤ 1.5mg/dL

          7. patients who are willing to comply with study procedure and voluntarily provide
             informed consent with signature

        Exclusion Criteria:

          1. Patients who have preexisting or coexisting malignancies in other parts except for
             effectively treated non-melanoma skin cancer, cervical carcinoma in situ(CIS) cervical
             cancer within the last 5 years

          2. Patients with brain metastasis except for the followings:

             - Asymptomatic and stable brain metastases for which local treatment has been given:
             corticosteroids treatment isn't requiured for at least 2 weeks before starting the
             study treatment.

          3. Patients currently receiving palliative radiation therapy or have toxicities from
             radiation therapy at screening.

          4. Patients with clinically active history of interstitial lung disease(ILD), Drug
             induced ILD, Radiation pneumonitis

          5. Patients with clinically significant cardiovascular disease or myocardial infarction
             within the past 12 months.

          6. Patients with active infection or severe systemic disease that are difficult to
             include in this study

          7. Patients who received radiation therapy to target lesion of this study.

          8. Patients who had major operation within 4 weeks before starting the study treatment
             and were not fully recovered.

          9. Patients who were administered other study drugs within 4 weeks before starting the
             study treatment

         10. Males and females of reproductive potential who are not using an effective method of
             birth control and females who are pregnant or breastfeeding or have a positive
             pregnancy test prior to study entry

         11. Patients who are difficult to include in this study in accordance with the
             investigator's judgment

         12. Patients with histories of hypersensitivity to investigational product(IP) or any
             components of the agent

         13. Patients with any of the following genetic predispositions including galactose
             intolerance, Lapp lactase deficiency, lactose intolerance or glucose-galactose
             malabsorption

         14. Patient previously received cytotoxic chemotherapy within 2 weeks of IP administration

         15. Patient received Immunotherapy prior to the study participation

         16. Patients who are difficult to include in this study in accordance with the
             investigator's judgment due to severe adverse effects during previous EGFR TKI
             treatment