Blocking antibodies have been used in clinical trials of cancer treatments. The blocking antibody ipilimumab has been effectively used in the clinical treatment of melanoma, RCC, and NSCLC with some degree of success. This is accomplished through the blocking of the coinhibitory molecule CTLA-4. The blocking antibody does not directly target tumor cells, but rather blocks the regulatory functions of CTLA-4, resulting in enhanced T-cell function.
Some new treatments hypothesize the blocking of PD-1, a programmed cell-death protein, which will result in longer-lived T-cells. The blocking antibody BMS-936559 has been shown to bind to PD-L1 and prevent its binding to PD-1.
These new treatments are not without side-effects and immune-related adverse events have been observed in a variety of patients. The tolerance that immune cells normally have to host tissues can be lost, resulting in permanent damage to host cells.