Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer

Historically, lung cancer was long considered a poorly immunogenic malignancy. In recent years, however, immune checkpoint inhibitors have emerged as promising therapeutic agents in non-small cell lung cancer (NSCLC). To date, the best characterized and most therapeutically relevant immune checkpoints have been cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death protein-1 (PD-1) pathway. In early studies, PD-1/programmed cell death ligand-1 (PD-L1) inhibitors demonstrated promising antitumor activity and durable clinical responses in a subset of patients. Based on these encouraging results, multiple different PD-1/PD-L1 inhibitors have entered clinical development, and two agents (nivolumab and pembrolizumab) have gained regulatory approval in the United States for the treatment of NSCLC. In several large, randomized studies, PD-1/PD-L1 inhibitors have produced significant improvements in overall survival compared with single-agent docetaxel delivered in the second-line setting, effectively establishing a new standard of care in NSCLC. In the present report, we provide an overview of the rationale for checkpoint inhibitors in lung cancer, recent clinical trial data, and the need for predictive biomarkers.