Approval based on KOMET Phase III trial results which showed 20% overall response rate in tumor size reduction
Alexion, AstraZeneca Rare Disease’s KOSELUGO® (selumetinib), an oral, selective MEK inhibitor, has been approved in the US for the treatment of adult patients with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas (PN).1
The approval by the US Food and Drug Administration (FDA) was based on positive results from KOMET, the largest and only placebo-controlled global Phase III trial in this patient population. Data were presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting and published in The Lancet.2
NF1 is a rare, progressive, genetic condition usually diagnosed in early childhood, but often progressing into adulthood, that can impact every organ system.3,4 Up to 50% of people living with NF1 may develop a type of non-malignant tumor called PN that may affect the brain, spinal cord and nerves.4,5 PN may appear later in a person’s life and can grow and become large, leading to pain, disfigurement and muscle weakness, among other debilitating symptoms.4,5
Prof. Pierre Wolkenstein, MD, PhD, Head of the Department of Dermatology at Henri Mondor Hospital, APHP, Paris East University (UPEC), and Investigator of the KOMET trial, said: “The KOMET Phase III trial, which builds on the established clinical profile of KOSELUGO and its real-world use in pediatric patients, underscores its potential to address the substantial and oftentimes progressive clinical burdens associated with PN in adulthood. This approval reaffirms the role of KOSELUGO as a strong option for the treatment of adult and pediatric patients with NF1 PN.”
Marc Dunoyer, Chief Executive Officer, Alexion, said: “This expanded approval of KOSELUGO in adults with NF1 PN, together with the recently approved granule formulation for young children aged one year and older, enables much-needed continuity of care and supports patients across the disease journey in the US. As the first approved therapy in NF1 PN, backed by more than a decade of clinical evidence, KOSELUGO has transformed the treatment standard for this rare disease.”
Annette Bakker, PhD, Chief Executive Officer, Children’s Tumor Foundation, said: “We celebrate this FDA approval of KOSELUGO for adults with NF1 plexiform neurofibromas—a major step forward for NF patients everywhere. KOSELUGO has already changed what is possible for children with NF1, and now adults will benefit from that same progress. It is proof that NF research is delivering real results and opening the door to even more treatment options. This milestone shows what can be achieved when scientists, clinicians, industry and the NF community work together with one focus: getting effective treatments to patients faster.”
In the primary analysis of the KOMET Phase III trial, KOSELUGO showed a statistically significant and clinically meaningful overall response rate (ORR) of 20% (n=14/71, 95% confidence interval [CI]: 11, 31) compared to 5% with placebo (n=4/74, 95% CI: 2, 13; p=0.011) by cycle 16, with 86% of patients on KOSELUGO having an observed duration of response (DOR) of at least 6 months. After 12 cycles, patients on placebo were switched to KOSELUGO and patients on KOSELUGO remained on treatment for an additional 12 cycles.1
The safety of KOSELUGO in the KOMET Phase III trial was consistent with its known profile and established use in pediatric patients.2
KOSELUGO has been recently approved in the EU, Japan and other countries for the treatment of adult patients with NF1 who have symptomatic, inoperable PN based on data from the KOMET Phase III trial, and additional regulatory reviews are ongoing. In the US, KOSELUGO granules have recently been approved for pediatric patients one year of age and older with NF1 PN.
INDICATION
KOSELUGO is indicated for the treatment of adult and pediatric patients 1 year of age and older with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas (PN).
IMPORTANT SAFETY INFORMATION
WARNINGS AND PRECAUTIONS
Left Ventricular Dysfunction. KOSELUGO can cause cardiomyopathy, defined as a decrease in left ventricular ejection fraction (LVEF) ≥10% below baseline. In the pediatric safety pool, Grade 2 LVEF decrease occurred, as well as decreased LVEF of ≥20% resulting in dose interruption and dose reduction. The median time to first occurrence of LVEF decrease was approximately 12 months. In the adult population, Grade 2 LVEF decrease occurred, with decreased LVEF resulting in dose interruption. The median time to first occurrence of LVEF decrease was approximately 4 months. Assess ejection fraction by echocardiogram prior to initiating treatment, every 3 months during the first year of treatment, every 6 months thereafter, and as clinically indicated. Withhold, reduce dose, or permanently discontinue KOSELUGO based on severity of adverse reaction. In patients who interrupt KOSELUGO for decreased LVEF, obtain an echocardiogram or a cardiac MRI every 3 to 6 weeks until resolution. Upon resolution of decreased LVEF, obtain an echocardiogram or a cardiac MRI every 2 to 3 months.
Ocular Toxicity. KOSELUGO can cause ocular toxicity, including retinal vein occlusion (RVO), retinal pigment epithelial detachment (RPED), and blurred vision. In the pediatric safety pool, blurred vision, photophobia, cataracts, ocular hypertension, and retinal tear occurred. Blurred vision resulted in dose interruption. RPED occurred in the pediatric population during treatment with KOSELUGO and resulted in permanent discontinuation. In the adult population, blurred vision and vitreous floaters occurred in patients receiving KOSELUGO. Conduct ophthalmic assessments prior to initiating KOSELUGO, at regular intervals during treatment, and for new or worsening visual changes. Permanently discontinue KOSELUGO in patients with RVO. Withhold KOSELUGO in patients with RPED, conduct ophthalmic assessments every 3 weeks until resolution, and resume KOSELUGO at a reduced dose.
Gastrointestinal Toxicity. KOSELUGO can cause gastrointestinal toxicities, including diarrhea and colitis. In the pediatric safety pool (N=134), diarrhea occurred in 59% of patients, in addition to diarrhea resulting in permanent discontinuation and dose interruption. In the adult population (N=71), diarrhea occurred in 42% of patients who received KOSELUGO, in addition to diarrhea resulting in dose interruption. The median time to first onset of diarrhea was approximately 2 months in the pediatric safety pool and 1 month in the adult population. Advise patients to start an anti-diarrheal agent (eg, loperamide) and to increase fluid intake immediately after the first episode of diarrhea. Withhold, reduce dose, or permanently discontinue KOSELUGO based on severity of adverse reaction.
Skin Toxicity. KOSELUGO can cause severe rashes, including dermatitis acneiform. In the pediatric safety pool (N=134), rash occurred in 68% of patients. The most frequent rashes included dermatitis acneiform (47%) and maculopapular rash (31%). Pruritus, alopecia, and eczema occurred. In the adult population (N=71), rash occurred in 85% of patients who received KOSELUGO. The most frequent rash included dermatitis acneiform (66%). Alopecia and pruritus occurred in patients who received KOSELUGO. Grade 3 rash and rash resulting in dose interruption and dose reduction occurred in both the pediatric safety pool and the adult population. Permanent discontinuation also occurred in the adult population. Monitor for severe skin rashes. Withhold, reduce dose, or permanently discontinue KOSELUGO based on severity of adverse reaction.
Increased Creatine Phosphokinase (CPK). KOSELUGO can cause increased CPK, myalgia, and rhabdomyolysis. In the pediatric safety pool (N=134), increased CPK, based on laboratory data, occurred in 73% of patients, including Grade 3 or 4. In the adult population (N=71), increased CPK, based on laboratory data, occurred in 70% of patients who received KOSELUGO, including Grade 3 or 4. Increased CPK resulted in dose interruption and dose reduction in both the pediatric safety pool and adult population. Increased CPK concurrent with myalgia occurred in both populations, including one patient who permanently discontinued KOSELUGO for myalgia in the pediatric safety pool. Obtain serum CPK prior to initiating KOSELUGO, periodically during treatment, and as clinically indicated. If increased CPK occurs, evaluate for rhabdomyolysis or other causes. Withhold, reduce dose, or permanently discontinue KOSELUGO based on severity of adverse reaction.
Increased Levels of Vitamin E and Risk of Bleeding (KOSELUGO Capsules). KOSELUGO capsules contain vitamin E, which can inhibit platelet aggregation and antagonize vitamin K-dependent clotting factors. Supplemental vitamin E is not recommended if daily vitamin E intake (including the amount of vitamin E in KOSELUGO and supplement) will exceed the recommended or safe limits due to increased risk of bleeding. An increased risk of bleeding may occur in patients who are co-administered vitamin-K antagonists or anti-platelet antagonists with KOSELUGO capsules. Monitor for bleeding in these patients and increase international normalized ratio (INR) monitoring in patients taking a vitamin-K antagonist. Perform anticoagulant assessments more frequently and adjust the dose of vitamin-K antagonists or anti-platelet agents as appropriate. KOSELUGO oral granules do not contain vitamin E.
Embryo-Fetal Toxicity. KOSELUGO can cause fetal harm when administered during pregnancy. In animal studies, administration of selumetinib to mice during organogenesis caused reduced fetal weight, adverse structural defects, and effects on embryo-fetal survival at approximate exposures >5 times the human exposure at the clinical dose of 25 mg/m2 twice daily. Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential and males with female partners of reproductive potential to use effective contraception during treatment with KOSELUGO and for 1 week after the last dose.
ADVERSE REACTIONS
Common adverse reactions ≥40% in pediatric patients include vomiting, diarrhea, increased CPK, dry skin, paronychia, nausea, dermatitis acneiform, and pyrexia.
Common adverse reactions ≥40% in adult patients include rash (all), dermatitis acneiform, and diarrhea.
DRUG INTERACTIONS
Effect of Other Drugs on KOSELUGO
Concomitant use of KOSELUGO with a strong or moderate CYP3A4 inhibitor or fluconazole increased selumetinib plasma concentrations, which may increase the risk of adverse reactions. Avoid coadministration with KOSELUGO. If coadministration cannot be avoided, reduce KOSELUGO dosage.
Concomitant use of KOSELUGO with a strong or moderate CYP3A4 inducer decreased selumetinib plasma concentrations, which may reduce KOSELUGO efficacy. Avoid concomitant use with KOSELUGO.
SPECIAL POPULATIONS
Pregnancy & Lactation. Verify the pregnancy status of patients of reproductive potential prior to initiating KOSELUGO. Due to the potential for adverse reactions in a breastfed child, advise patients not to breastfeed during treatment with KOSELUGO and for 1 week after the last dose.
Please see Full Prescribing Information for KOSELUGO.
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Notes
NF1
NF1 is a rare, progressive, genetic condition that is caused by a spontaneous or inherited mutation in the NF1 gene.3,4 NF1 is associated with a variety of symptoms, including soft lumps on and under the skin (cutaneous neurofibromas) and, in up to 50% of patients, tumors called plexiform neurofibromas (PN) may develop on the nerve sheaths.4,5 These PN can cause clinical issues such as disfigurement, motor dysfunction, pain, airway dysfunction, visual impairment and bladder or bowel dysfunction.4,5
KOMET
KOMET is a global Phase III randomized, double-blind, placebo-controlled, multicentre trial designed to evaluate the efficacy and safety of KOSELUGO in adults with NF1 who have symptomatic, inoperable PN. The trial enrolled 145 adults from 13 countries across North America, South America, Europe, Asia and Australia, with participants’ baseline characteristics, including gender and distribution of PN, reflective of the global adult NF1 patient population. Patients were enrolled and randomized to receive KOSELUGO or placebo (1:1) for 12 28-day cycles. Participants were required to have diagnosis of NF1, at least one symptomatic, inoperable PN measurable by volumetric MRI analysis, chronic PN pain score documented during screening, adequate organ and marrow function and stable chronic PN pain medication use at enrollment.2,6
The primary endpoint is confirmed overall response rate (ORR) by cycle 16 as assessed by ICR. ORR is defined as the percentage of patients with confirmed complete response (disappearance of PNs) or partial response (at least 20% reduction in tumor volume). Secondary endpoints include improved PN-related pain and health-related quality of life (HRQoL) at cycle 12.2,6
After 12 cycles, patients on placebo were switched to KOSELUGO and patients on KOSELUGO remained on treatment for an additional 12 cycles. Patients who had the opportunity to complete 24 cycles of treatment have the option to participate in a long-term extension period and continue to receive KOSELUGO.2,6
KOSELUGO®
KOSELUGO® (selumetinib) is a kinase inhibitor that blocks specific enzymes (MEK1 and MEK2), which are involved in stimulating cells to grow. In NF1, these enzymes are overactive, causing tumor cells to grow in an unregulated way creating so-called plexiform neurofibromas (PN). By blocking these enzymes, KOSELUGO slows down the growth of tumor cells and, therefore, the PN growth.
KOSELUGO is approved in the US, EU, Japan, China and other countries for the treatment of certain pediatric patients with NF1 who have symptomatic, inoperable PN.
KOSELUGO is approved in the US, EU, Japan and other countries for the treatment of adult patients with NF1 who have symptomatic, inoperable PN, and additional regulatory reviews are ongoing.
KOSELUGO has been granted Orphan Drug Designation in the US, EU, Japan and other countries for the treatment of NF1.
Alexion
Alexion, AstraZeneca Rare Disease, is focused on serving patients and families affected by rare diseases and devastating conditions through the discovery, development and delivery of life-changing medicines. A pioneering leader in rare disease for more than three decades, Alexion was the first to translate the complex biology of the complement system into transformative medicines, and today it continues to build a diversified pipeline across disease areas with significant unmet need, using an array of innovative modalities. As part of AstraZeneca, Alexion is continually expanding its global geographic footprint to serve more rare disease patients around the world. It is headquartered in Boston, US. For more information, please visit www.alexion.us.
AstraZeneca
AstraZeneca is a global, science-led biopharmaceutical company that focuses on the discovery, development and commercialization of prescription medicines in Oncology, Rare Diseases and BioPharmaceuticals, including Cardiovascular, Renal & Metabolism, and Respiratory & Immunology. Based in Cambridge, UK, AstraZeneca's innovative medicines are sold in more than 125 countries and used by millions of patients worldwide. Please visit www.astrazeneca-us.com and follow the Company on social media @AstraZeneca.
Media Inquiries
US Media Mailbox: usmediateam@astrazeneca.com
References
1. KOSELUGO (selumetinib) US prescribing information; November 2025.
2. Chen, AP, et al. KOMET: a phase 3, multicentre, international, randomised, placebo-controlled study to assess the efficacy and safety of selumetinib in adults with neurofibromatosis type 1 and symptomatic, inoperable plexiform neurofibromas. The Lancet. 2025;405(10496):2217-2230.
3. Tamura R. Current understanding of neurofibromatosis type 1, 2, and schwannomatosis. Int J Mol Sci. 2021;22(11):5850.
4. Hirbe AC, et al. Neurofibromatosis type 1: a multidisciplinary approach to care. Lancet Neurol. 2014;13:834-843.
5. Bergqvist C, et al. Neurofibromatosis 1 French national guidelines based on an extensive literature review since 1966. Orphanet J Rare Dis. 2020;15(1):37.
6. ClinicalTrials.gov. Efficacy and safety of selumetinib in adults with NF1 who have symptomatic, inoperable plexiform neurofibromas (KOMET). NCT Identifier: NCT04924608. Available here. Accessed November 2025.