Pembrolizumab for Metastatic NSCLC Patients Expressing PD-L1 Who Have Their Own PDX

Part A: Clinical trial (single arm study) in patients with metastatic non-small cell lung cancer (NSCLC) expressing PD-L1 after failure of platinum-based combination chemotherapy. Part B: PDX experiment using Hu-CD34 PDX model in specific population selected from Part A (Clinical trial part) - responder and non-responder. In-vivo experiment using Hu-CD34 PDX will be done for about seven subjects, and thirty-two (32) Hu-CD34 PDX mice will be established from single patient to see in-vivo response. This research using PDX (Part B) will be conducted sequentially on clinical trial part in selected-population based on clinical response of Pembrolizumab.