The Search for Predictive Biomarkers in Response to Immune Checkpoint Inhibitors and Associated Adverse Events

The introduction of immune checkpoint inhibitors (ICIs) as a part of immunotherapy represented a therapeutic breakthrough in the landscape of cancer treatment. The action of these inhibitors consists of blocking certain inhibitory receptors in the immune system. Blocking these inhibitory pathways, ICIs induce an enhanced T cell-mediated response necessary to neutralize tumor cells. Over the last 10 years, programmed death cell protein1 (PD-1), PD ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) have been among the inhibitory receptors most targeted by ICIs. Currently, this innovative therapeutic approach faces two major challenges: early identification of cancer patients who are likely to get a significant therapeutic benefit through the use of these inhibitors, and the second challenge is the early prediction of likely immune-related adverse events (irAEs) associated with such therapy. The aim of the present text is to discuss the current research efforts to discover and develop much needed effective biomarkers, which may represent an important step towards more efficient and risk-free immunotherapy. We also highlight the increasing role in clinical analyses of liquid biopsy sampling combined with mass spectrometry-based proteomics and how such combination is contributing to current research efforts to enhance the role of immunotherapy.