Selumetinib is primarily used in the treatment of certain types of cancer, particularly neurofibromatosis type 1 (NF1)-associated plexiform neurofibromas in pediatric patients. It works by inhibiting the MEK enzyme, which is part of the MAPK/ERK pathway that promotes cell growth and survival. By blocking this pathway, selumetinib helps to reduce the size of tumors and manage symptoms. It is often prescribed when surgical removal of the tumor is not feasible. Additionally, selumetinib is being investigated for its potential use in other cancers, such as melanoma, non-small cell lung cancer, and thyroid cancer, where the MAPK/ERK pathway is dysregulated. Its application offers a targeted therapy approach, minimizing damage to healthy cells compared to traditional chemotherapy.