Emerging Tissue and Blood-Based Biomarkers that may Predict Response to Immune Checkpoint Inhibition

The immune system plays an essential role in the surveillance and eradication of neoplastic cells. This interaction is modulated via immunologic regulators (checkpoints). Antibodies that block the checkpoints cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and the programmed cell death protein 1 pathway (PD1/PD-L1) have demonstrated efficacy in a number of malignancies. However, response rates are variable, and administration of these antibodies can be associated with immune-related adverse events. Therefore, researchers are engaged in an effort to discover biomarkers that may predict response to these agents. This review focuses on potential blood and tumor-based biomarkers that have been assessed in patients treated with these checkpoint-blocking antibodies.