Keytruda (pembrolizumab) is a type of immunotherapy that works by blocking a protein called PD-1 on immune cells, which allows the immune system to attack cancer cells. While Keytruda has been shown to be effective in treating certain types of cancer, it can also cause side effects.

According to the Keytruda website [2], some of the most common side effects of Keytruda include fatigue, decreased appetite, nausea, diarrhea, constipation, rash, itching, and joint pain. These side effects can range from mild to severe and may require medical attention.

In addition to these common side effects, Keytruda can also cause more serious side effects, known as immune-mediated side effects. These occur when the immune system attacks healthy cells and tissues in the body. Immune-mediated side effects can affect any organ in the body and can be life-threatening if not treated promptly. Some of the immune-mediated side effects of Keytruda include pneumonitis (inflammation of the lungs), colitis (inflammation of the colon), hepatitis (inflammation of the liver), and endocrinopathies (disorders of the endocrine system).

It is important to note that not all patients will experience side effects from Keytruda, and the severity and duration of side effects can vary from person to person. Patients should talk to their doctor about the potential side effects of Keytruda and what to do if they experience any symptoms.

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