Immune checkpoint inhibitors are cancer drugs that support the body’s immune system. They help the immune system to better recognize and attack cancer cells. Some cancer cells use natural “brakes” (known as immune checkpoints) in the immune system to hide from the body’s defences. Immune checkpoint inhibitors release these brakes. This allows the immune system to fight the cancer cells more effectively again. Because the immune system becomes more active in the process, side effects can occur, such as inflammation or skin rashes.