Pembrolizumab is a medication used in cancer treatment, specifically designed to help the immune system recognize and attack cancer cells. It belongs to a class of drugs known as immune checkpoint inhibitors, which work by blocking a protein called PD-1 that cancer cells use to evade immune detection. This drug is commonly prescribed for various types of cancer, including melanoma, lung cancer, and head and neck cancer. By enhancing the body's immune response, Pembrolizumab can improve survival rates and quality of life for patients undergoing cancer therapy.