The main purpose of this study is to evaluate the safety and efficacy of Apatinib in combination with Gefitinib as compared to placebo in combination with Gefitinib in participants with stage ⅢB-IV Non-squamous non-small-cell lung cancer (NSCLC) harboring an activating epidermal growth factor receptor (EGFR) mutation (Del19 and L858R). Safety and tolerability of Apatinib in combination with Gefitinib will be assessed in the first portion (Part A) before proceeding to the second portion of this study (Part B).