New frontiers in oncology: Immune checkpoint inhibitors in combination therapy

Substantial progress has been achieved in recent years in the field of cancer immunotherapy, with various strategies employed to elicit a host immune response against the tumor. Monoclonal antibodies have been successfully utilized in clinical trials to block key mediators of immune checkpoint pathways, including cytotoxic T-lymphocyte antigen 4, programmed cell death protein 1 and programmed cell death 1 ligand 1. Patients with a range of malignancies have been treated in these clinical trials, and significant benefits were reported among the majority of participants. In order to optimize the efficacy of anticancer immunotherapies, immune checkpoint inhibitors are being tested in combination with other therapeutics, such as immunomodulators, armed oncolytic viruses, chemotherapeutics and radiation therapy. This review discusses the important achievements reported in the field of immuno-oncology, along with a glimpse at future directions.