Current status of immune checkpoint inhibitors in treatment of non-small cell lung cancer

Lung cancer remains a leading cause of cancer mortality worldwide, including in Korea. Systemic therapy including platinum-based chemotherapy and targeted therapy should be provided to patients with stage IV non-small cell lung cancer (NSCLC). Applications of targeted therapy, such as an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) and anaplastic lymphoma kinase (ALK) inhibitors, in patients with NSCLC and an EGFR mutation or ALK gene rearrangement has enabled dramatic improvements in efficacy and tolerability. Despite advances in research and a better understanding of the molecular pathways of NSCLC, few effective therapeutic options are available for most patients with NSCLC without druggable targets, especially for patients with squamous cell NSCLC. Immune checkpoint inhibitors such as anti-cytotoxic T lymphocyte antigen-4 or anti-programmed death-1 (PD-1) or programmed death-ligand 1 (PD-L1) have demonstrated durable response rates across a broad range of solid tumors, including NSCLC, which has revolutionized the treatment of solid tumors. Here, we review the current status and future approaches of immune checkpoint inhibitors that are being investigated for NSCLC with a focus on pembrolizumab, nivolumab, atezolizumab, durvalumab, and ipilimumab.