Selumetinib sulfate is primarily used in the treatment of certain types of cancer, particularly in patients with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas. It works by inhibiting the MEK enzyme, which is part of the MAPK/ERK pathway, a signaling pathway that can promote cancer cell growth and survival. By blocking this pathway, selumetinib sulfate helps to reduce tumor size and alleviate symptoms associated with these tumors. It is often prescribed for pediatric patients when surgical removal of the tumors is not feasible. Additionally, ongoing research is exploring its potential efficacy in other cancers, such as melanoma (especially with BRAF mutations), non-small cell lung cancer, and thyroid cancer (including those with RET or NTRK mutations), where the MAPK/ERK pathway is dysregulated.