*2.5.3.1 Immune check point inhibitors*

The creation of antibodies capable of blocking coinhibitory immune cell receptors, or "immune checkpoints" — T-cell surface receptors that, when activated by specific ligands, limit the T-cytotoxic cell's immunological response — is a hopeful improvement in cancer treatment. Tumour cells tend to overexpress the ligands that activate these inhibitory receptors, allowing them to evade the immunological response of T cells and proliferate freely. Despite the fact that over two dozen individual costimulatory receptors have been identified, two of them — CTLA-4 and programmed cell death 1 (PD-1), have been the focus of antibody-based immune checkpoint blockade (ICB) treatments [76].
