How Immunotherapy Is Used To Treat Cancer

Immune Checkpoint Inhibitors

The immune system must be able to identify the difference between normal and foreign cells, as this allows it to target the foreign cells while leaving normal cells untouched. Every immune system does this by creating checkpoints, which act as stop signals to keep the body in check and trigger (or prevent) an immune system response. Unfortunately, cancer can often find ways to prevent being attacked by modifying the checkpoints, such as creating premature stops. This is where immune checkpoint inhibitors — which target PD-1, PD-L1, or CTLA-4 — come into play.

PD-1 is a T cell checkpoint protein preventing the T cell from attacking other non-cancerous cells in the body by acting as an off-switch when it attaches itself to PD-L1, another protein on some cells. However, some cancer cells contain PD-L1, which allows them to avoid immune attack. PD-1 or PD-L1 inhibitors stop the binding to cancer cells and boost the immune system’s attack response. CTLA-4 is another protein that acts as an off switch in the body. CTLA-4 inhibitors are designed to bind to CTLA-A and prevent its function, which boosts the immune system’s response.