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How do checkpoint inhibitors such as ipilimumab help T cells attack cancer cells?

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Precancerous growth in a human colon — cancer View through an endoscope of a polyp, a benign precancerous growth projecting from the inner lining of the colon.

Checkpoint inhibitors like ipilimumab help T cells attack cancer cells by blocking specific proteins that normally act as "brakes" on the immune system.12

Under normal conditions, these checkpoint proteins—such as CTLA-4—help maintain self-tolerance and prevent the immune system from becoming overactive and damaging healthy tissues. However, cancer cells can exploit these pathways to evade detection and suppress the immune response.13

Ipilimumab is a monoclonal antibody that binds to and blocks the activity of CTLA-4. By inhibiting this negative regulatory signal, the drug effectively "releases the brakes" on T cells. This allows the immune system to overcome the inhibitory signals that would otherwise block T cells from killing their targets, thereby augmenting the immune response and enabling the destruction of tumor cells. While this approach can lead to significant immune-related side effects, it is capable of generating durable, long-lasting antitumor responses.21