Targeting immune checkpoints: releasing the restraints on anti-tumor immunity for patients with melanoma.

Insight into the mechanisms of anti-tumor immunity has generated great enthusiasm for the treatment of patients with advanced melanoma. Particularly, negative regulators of the immune system, called immunologic checkpoints, have been found to play important roles in restraining otherwise effective anti-tumor immunologic responses. Therapies that target these negative regulator checkpoints, such as those directed against cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death 1 receptor (PD-1), have demonstrated promising clinical results. Treatment is generally well tolerated, but a novel spectrum of side effects, termed immune-related adverse events, has been experienced. Unfortunately, not all patients respond to these therapies, and evaluation of biomarkers predictive of response is ongoing. Based on their unique mechanisms of action, radiographic assessment of response differs from methods traditionally applied to cytotoxic chemotherapy. We expect ongoing and future efforts combining agents that target immunologic checkpoints with other immunotherapeutic approaches, targeted therapy, chemotherapy, and radiotherapy may additionally be beneficial.