Immune checkpoint inhibition as a new treatment approach is undergoing extensive 
investigation in non-small cell lung cancer (NSCLC) and other malignancies. 
Unlike standard chemotherapy or targeted agents, which act directly on the tumor 
cells, immune checkpoint inhibitors work by restoring the immune system's 
capacity to eradicate tumors. Agents currently in active clinical development 
for lung cancer include ipilimumab, which modulates the cytotoxic 
T-lymphocyte-associated antigen 4 pathway, and multiple agents targeting the 
programmed death protein 1 (PD-1) pathway, both anti-PD-1 compounds (nivolumab, 
pembrolizumab [MK-3475]) and those that target programmed death ligand 1 
(PD-L1), a key ligand for PD-1 (BMS-936559, MPDL3280A). Preliminary evidence 
shows activity for these agents in NSCLC as monotherapy or in combination with 
chemotherapy. This article reviews the immune checkpoint inhibitors and the 
available data to date on their use in lung cancer. Clinical implications for 
the use of these therapies in NSCLC are discussed as they relate to their novel 
mechanisms of action, response patterns, and safety profiles.