Keytruda (pembrolizumab) is a type of immunotherapy that works by blocking the PD-1 receptor on T cells, which allows them to recognize and attack cancer cells. While Keytruda has been shown to be effective in treating certain types of cancer, it can also cause side effects, some of which may be long-term.

According to Drug Patent Watch [1], the most common side effects of Keytruda include fatigue, rash, diarrhea, nausea, and decreased appetite. However, more serious side effects can occur, such as pneumonitis (inflammation of the lungs), colitis (inflammation of the colon), and hepatitis (inflammation of the liver).

In a study published in Cancer Currents Blog [2], researchers found that patients who received immune checkpoint inhibitors (ICIs) such as Keytruda for melanoma had a higher risk of developing autoimmune diseases such as thyroiditis, colitis, and pneumonitis. These side effects can occur months or even years after treatment and can be difficult to manage.

GoodRx [3] also notes that Keytruda can cause long-term effects on the immune system, such as increased susceptibility to infections and the development of other types of cancer.

It is important to note that not all patients who receive Keytruda will experience long-term side effects, and the benefits of the treatment may outweigh the risks for some individuals. However, it is essential to discuss any concerns about potential side effects with a healthcare provider before starting treatment.

Sources:
[1] https://www.drugpatentwatch.com/p/biologics/tradename/KEYTRUDA
[2] https://www.cancer.gov/news-events/cancer-currents-blog/2021/immune-checkpoint-inhibitors-melanoma-long-term-side-effects
[3] https://www.goodrx.com/pembrolizumab/long-term-effects-of-keytruda