Keytruda is a brand name for the drug pembrolizumab, which is a type of immunotherapy used to treat various types of cancer. Keytruda works by blocking a protein called PD-1 on the surface of immune cells, which allows the immune system to attack cancer cells more effectively [1].

Like all medications, Keytruda can cause side effects. Some common side effects of Keytruda include fatigue, nausea, diarrhea, loss of appetite, rash, itching, and joint pain [2]. These side effects are usually mild to moderate in severity and can be managed with medications or other supportive care.

However, Keytruda can also cause more serious side effects, known as immune-related adverse events (irAEs). These can occur when the immune system attacks healthy tissues in the body, leading to inflammation and damage. IrAEs can affect any organ system in the body, but the most common sites are the skin, lungs, liver, and colon [3].

Some of the most serious irAEs associated with Keytruda include pneumonitis (inflammation of the lungs), colitis (inflammation of the colon), hepatitis (inflammation of the liver), and endocrinopathies (disorders of the hormone-producing glands). These side effects can be life-threatening and require prompt medical attention [2][3].

In conclusion, Keytruda works by boosting the immune system's ability to fight cancer cells, but it can also cause side effects, including mild to moderate symptoms like fatigue and nausea, as well as more serious immune-related adverse events affecting various organs in the body. Patients receiving Keytruda should be monitored closely for side effects and report any symptoms to their healthcare provider immediately [2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/biologics/tradename/KEYTRUDA
[2] https://www.keytruda.com/side-effects/
[3] https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/side-effects-immunotherapy