Keytruda, also known as pembrolizumab, is an immunotherapy medication used to treat various types of cancer. It works by interacting with the body's immune system to help detect and fight cancer cells [3][2].

Keytruda is a type of drug called a monoclonal antibody. It specifically targets a protein called PD-1 (programmed cell death protein 1), which is found on the surface of T-cells (a type of white blood cell) [1][3]. PD-1 plays a role in regulating the immune system, and cancer cells can use PD-1 to avoid being detected and attacked by the immune system [3].

By binding to PD-1, Keytruda blocks the interaction between PD-1 and PD-L1 (programmed death-ligand 1), a protein found on the surface of some cancer cells [1][3]. This blocking action prevents the cancer cells from avoiding detection by the immune system, allowing the T-cells to recognize and attack the cancer cells [3].

In summary, Keytruda works by inhibiting the PD-1/PD-L1 pathway, which helps the body's immune system to detect and destroy cancer cells [1][2][3].

Sources:
[1] <https://www.drugpatentwatch.com/p/biologics/tradename/KEYTRUDA>
[2] <https://www.keytruda.com/how-does-keytruda-work/>
[3] <https://www.cancerresearchuk.org/about-cancer/treatment/drugs/pembrolizumab>