Immunologic checkpoint blockade in lung cancer.

Despite the availability of radiotherapy, cytotoxic agents, and targeted agents, a high unmet medical need remains for novel therapies that improve treatment outcomes in patients with lung cancer who are ineligible for surgical resection. Building upon the early promise shown with general immunostimulatory agents, immuno-oncology is at the forefront of research in this field, with several novel agents currently under investigation. In particular, agents targeting immune checkpoints, such as the cytotoxic T-lymphocyte antigen-4 (CTLA-4) receptor and programmed death-1 (PD-1) receptor, have shown in early clinical trials potential for improving tumor responses and survival in patients with non-small cell lung cancer (NSCLC). Here, we examine the rationale for targeting immune checkpoints in lung cancer and review the clinical data from studies with immune checkpoint inhibitors currently in development. The challenges associated with optimizing treatment with these agents in lung cancer also are discussed.