KOSELUGO (selumetinib) is an orally administered, selective inhibitor of mitogen-activated protein kinase kinases 1 and 2 (MEK1/2), which are key components of the RAS-RAF-MEK-ERK signaling pathway. This pathway is frequently dysregulated in various cancers and genetic disorders, including NF1. By inhibiting MEK1/2, selumetinib disrupts downstream signaling involved in cell proliferation and survival, thereby reducing tumor growth and associated morbidity in affected patients.

Clinically, KOSELUGO has demonstrated efficacy in reducing the volume of inoperable plexiform neurofibromas in pediatric patients with NF1, as evidenced by response rates in pivotal clinical trials. The drug is available in capsule form (10 mg and 25 mg strengths) and is administered based on body surface area, with dosing adjustments required for hepatic impairment and certain drug interactions. KOSELUGO represents a targeted therapeutic option for a population with limited alternative treatments.