How do checkpoint inhibitors work against cancer?

Checkpoint inhibitors work by taking the brakes off your immune system so it can attack cancer.

Immune checkpoints are a normal part of the immune system. They engage when proteins on immune cells called T cells bind to partner proteins on other cells, sending an off signal that keeps the immune response from harming healthy cells. Some tumors take advantage of this by sending the off signal so T cells will not attack them.

Immune checkpoint inhibitors block the checkpoint proteins from binding with their partner proteins. This stops the off signal, which allows the T cells to kill cancer cells.

Different drugs target different checkpoints, such as CTLA-4, PD-1, or PD-L1. Some tumors make a lot of PD-L1 to shut down the T cell response, so blocking it can free the immune system to fight the cancer.