Keytruda, scientifically known as pembrolizumab, is an immunotherapy drug developed by Merck & Co. It revolutionizes cancer treatment by empowering the immune system to combat cancer cells, rather than directly attacking them like traditional chemotherapy. Approved by the Drug Controller General of India (DCGI) for 14 indications across eight tumor types, Keytruda is effective against cancers such as non-small cell lung cancer, melanoma, and triple-negative breast cancer. Studies indicate that Keytruda significantly improves survival rates and quality of life for patients by promoting tumor shrinkage and potentially leading to long-term remission. However, it can cause immune-related adverse events (irAEs) in 15-25% of patients, necessitating close monitoring. The cost of Keytruda in India is between ₹1.5 lakh and ₹2.16 lakh per vial, highlighting the need for patients to purchase it from reputable sources to ensure authenticity.