A drug used to treat a rare genetic condition called neurofibromatosis type 1. It is used in children aged 2 years and older who have plexiform neurofibromas that are causing symptoms and cannot be removed by surgery. It is also being studied in the treatment of some types of cancer. Selumetinib sulfate blocks proteins called MEK1 and MEK2, which may help keep abnormal cells or cancer cells from growing and may kill them. It is a type of kinase inhibitor and a type of targeted therapy. Also called AZD6244, Koselugo, and MEK inhibitor AZD6244.