Phase I: evaluate the safety and tolerability two different dosing regimens of Thymosin alpha 1 in patients with advanced EGFR mutation positive NSCLC on Standard of Care (SoC) therapy. Phase II: evaluate the efficacy in terms of PFS of Thymosin alpha 1 in patients with advanced EGFR mutant NSCLC taking SoC as compared to SoC alone.

Phase I/Phase II, multi-center, open label, randomized, parallel group study to determine the safety/tolerability/efficacy of Thymosin alpha 1 in patients with sensitizing EGFR mutation positive NSCLC taking SoC versus SoC alone. The study will be conducted in subjects with sensitizing EGFR mutation positive Non Small Cell Lung Cancer. Subjects with sensitizing EGFR mutation positive NSCLC will be screened for eligibility by the clinical center involved. The study will be conducted in two parts. In Phase I patients will be randomized to one of two different dosing regimens of Thymosin alpha 1 for a treatment duration of 4 months. At the completion of Phase I, data will be reviewed and a single dosing regimen will be carried forward into Phase II. In Phase II patients will be randomized to SoC or Thymosin alpha 1 plus SoC for treatment duration of 12 months. All patients will be followed for approximately 18 months.