Pembrolizumab 100 mg is a medication used to treat various types of cancer, including melanoma, non-small cell lung cancer, and head and neck cancer. It is a type of immunotherapy that works by blocking the activity of a protein called the PD-1 receptor on the surface of T cells, preventing it from interacting with a protein called PD-L1 on cancer cells.

By blocking the PD-1 receptor, pembrolizumab allows T cells to recognize and attack cancer cells, improving the body's ability to fight cancer. Pembrolizumab is usually given as an intravenous infusion at a healthcare provider's office, hospital or clinic.

The recommended dose of pembrolizumab may vary depending on the type of cancer being treated, the patient's age and weight, and other factors, and is usually given every three to four weeks.