Selumetinib Receives FDA Approval for Neurofibromatosis Type 1 with Plexiform Neurofibromas
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🔔 Update: Selumetinib Is Now Approved for Children Aged 1 and Older
On September 10, 2025, the FDA approved treatment for neurofibromatosis type 1 (NF1) and symptomatic, inoperable plexiform neurofibromas (PN) in patients aged 1 and older in the pediatric population, with selumetinib (Koselugo) capsule + oral granule formulations.
- The age threshold fell from 2 to 1 → an opportunity for treatment at an earlier stage.
- Granule formulation → easier swallowing and greater dosing flexibility in young children.
- Evidence base: Posology/PK matching between SPRINT (≥2y, capsules) & SPRINKLE (≥1y, granules); a BA bridging study in adults (Study 89).
- Safety: Incidence figures were updated with broader pediatric data, with no new signal.
💊 New Medicines for an Inherited Disease
On February 11, 2025, the FDA also approved mirdametinib (a MEK inhibitor) for NF1 + symptomatic, inoperable PN in pediatric patients. This approval offers an alternative to selumetinib, so the range of treatments that target the MEK/ERK pathway has expanded.
- Why Is This Important? Different pharmaceutical properties and possible adverse-effect profile differences allow individualized selection.
- Practical message: In cases involving problems with selumetinib access/adherence or particular toxicity patterns, mirdametinib is a rational alternative.
Note: Both agents are MEK inhibitors; age, comorbidities, concomitant medicines, adverse-effect history and family/child adherence should be assessed together when choosing.
🧬 What Are Neurofibromatosis Type 1 (NF1) and Plexiform Neurofibromas?
NF1 results from a mutation in the tumor-suppressor NF1 gene and is a genetically inherited condition. Plexiform neurofibromas (PN) are benign tumors that can grow diffusely with many branches in peripheral nerve sheaths; however, they can cause disfigurement, pain, motor/respiratory/visual functional loss and surgical difficulties.
📜 The Initial Approval in 2020
On April 10, 2020, the FDA approved treatment for patients aged 2 and older in the pediatric population with NF1 and symptomatic, inoperable PN using selumetinib capsules. For NF1-associated PN, it was the first targeted therapy approved.
🔬 SPRINT Phase 2 Findings
n=50 children received, twice daily, 25 mg/m² selumetinib; those enrolled had significant morbidities such as disfigurement, pain, motor/respiratory/visual problems or bladder/bowel dysfunction.
- ORR 66% (partial response); response definition: tumor volume reduction on MRI of ≥20% (for at least 3–6 months).
- Duration of response: In 82% of responders, it lasted ≥12 months.
🛡️ Safety Profile (with Expanded Pediatric Data)
- Common (≥40%): vomiting, rash, abdominal pain, diarrhea, nausea, dry skin, fatigue, musculoskeletal pain, fever, acne, stomatitis, headache, paronychia and itching.
- Important warnings: cardiomyopathy; ocular toxicity (retinal vein occlusion, RPE detachment); gastrointestinal/skin toxicities; increased creatine kinase; capsule-associated vitamin E increase and related bleeding risk; embryo-fetal toxicity.
- Management: temporary interruption, dose reduction or permanent discontinuation according to severity.
💊 Dose and Formulation
| Form | Age | Recommended Dose | Administration |
|---|---|---|---|
| Capsule | ≥1 year (expanded in 2025; previously ≥2 years) | 25 mg/m² PO, 2 times daily | On an empty stomach; until progression or unacceptable toxicity |
| Oral granules | ≥1 year | 25 mg/m² PO, 2 times daily | Easier swallowing for young children; posology matched to capsules |
Note: between capsules and granules, comparative exposure (PK) similarity and, between SPRINT (capsules) and SPRINKLE (granules), exposure matching have been achieved.
🧭 Clinical Significance: Earlier and More Practical Treatment
- Opportunity for early intervention: The age threshold of 1 year allows treatment to begin before deformity and functional loss develop.
- Ease of administration: For young children, the granule formulation may improve treatment adherence.
- Personalization: The choice between selumetinib ↔ mirdametinib can be based on patient/family priorities and the toxicity profile.
Further information: FDA drug label and approval announcements (KOSELUGO).
Sources
2. FDA approves selumetinib for neurofibromatosis type 1 with symptomatic, inoperable plexiform neurofibromas.
fda.gov - 10 April 2020.
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