Selumetinib for the Prevention of Plexiform Neurofibroma Growth in NF Type 1

Plexiform neurofibromas (PN) are known to cause significant morbidity in children with NF1. The recent FDA approval for selumetinib in children 2 years and older with inoperable symptomatic PN was based on the finding that selumetinib shrinks the majority of PN in children with NF1 and results in clinically meaningful benefit such as improvement in pain or range of motion. However, many morbidities, such as blindness or nerve damage, cannot be fully reversed with PN shrinkage. Therefore, there remains a critical need in this patient population to determine if young participants with PN in high-risk locations may benefit from early medical intervention prior to the development of clinical problems. This study will determine whether participants with asymptomatic PN in high-risk locations can potentially benefit from early treatment with selumetinib. Other: This trial will be operated through the Neurofibromatosis Clinical Trials Consortium, funded by the Congressionally Directed Medical Research Program under the Department of Defense which consists of 24 sites throughout the United States. Intervention: Selumetinib (KoselugoTM) at the FDA approved dose of 25 mg/m2/dose PO BID. Study Duration: 7 years Partcipant Durations: 5 years