Keytruda (pembrolizumab) is an immunotherapy drug used to treat various types of cancer. While it has shown promising results in fighting cancer, it can also have some severe side effects. It is important to note that not all patients will experience these side effects, and the severity can vary from person to person.

One of the most severe side effects of Keytruda is immune-mediated pneumonitis, which is inflammation of the lungs. This can cause symptoms such as shortness of breath, coughing, and chest pain. It is important to seek immediate medical attention if these symptoms occur [2].

Another severe side effect is immune-mediated colitis, which is inflammation of the colon. This can cause symptoms such as diarrhea, abdominal pain, and blood in the stool. Patients experiencing these symptoms should consult their healthcare provider [2].

Keytruda can also lead to immune-mediated hepatitis, which is inflammation of the liver. Symptoms may include yellowing of the skin or eyes, dark urine, and abdominal pain. It is important to contact a healthcare professional if these symptoms occur [2].

In some cases, Keytruda can cause immune-mediated endocrinopathies, which are disorders affecting hormone-producing glands. This can result in conditions such as hypothyroidism, hyperthyroidism, or adrenal insufficiency. Patients may experience symptoms such as fatigue, weight gain or loss, and changes in blood pressure. It is important to notify a healthcare provider if these symptoms arise [2].

Additionally, Keytruda can lead to immune-mediated nephritis, which is inflammation of the kidneys. Symptoms may include changes in urination patterns, swelling, and fatigue. Patients should seek medical attention if these symptoms occur [2].

Furthermore, Keytruda can cause immune-mediated skin reactions, such as rash, itching, and blistering. These reactions may be accompanied by fever and flu-like symptoms. It is crucial to inform a healthcare provider if these skin reactions appear [2].

While Keytruda has shown potential in treating cancer, it is essential to be aware of the potential severe side effects. Patients receiving Keytruda should closely monitor their health and promptly report any concerning symptoms to their healthcare provider.

Sources:
[2] Keytruda Official Website - Side Effects. Available at: https://www.keytruda.com/side-effects/
[3] National Cancer Institute - Immune Checkpoint Inhibitors and Melanoma: Long-Term Side Effects. Available at: https://www.cancer.gov/news-events/cancer-currents-blog/2021/immune-checkpoint-inhibitors-melanoma-long-term-side-effects