The Food and Drug Administration (FDA) has approved Koselugo (selumetinib; AstraZeneca) for the treatment of patients 2 years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas.

Koselugo is an inhibitor of mitogen-activated protein kinase kinases 1 and 2 (MEK1/2). The approval was based on data from the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP)-sponsored phase 2 SPRINT Stratum 1 trial, which evaluated the efficacy of Koselugo in 50 patients with NF1 and inoperable plexiform neurofibromas. 

Patients received Koselugo 25mg/m2 orally twice daily until disease progression or unacceptable toxicity. The primary end point was the overall response rate (ORR), defined as the percentage of patients with a complete response or partial response of ≥20% reduction in plexiform neurofibroma volume confirmed at a subsequent tumor assessment within 3-6 months. 

Results demonstrated an ORR of 66% (n=33; 95% CI, 51-79); confirmed partial response was observed in all patients. Additionally, duration of response lasting 12 months or longer was noted in 82% of patients (n=27). 

With regard to safety, the most common adverse reactions (≥40%) included vomiting, rash (all), abdominal pain, diarrhea, nausea, dry skin, fatigue, musculoskeletal pain, pyrexia, acneiform rash, stomatitis, headache, paronychia, and pruritus. Treatment with Koselugo has been associated with potentially serious adverse effects including cardiomyopathy, ocular toxicity, skin toxicity, and increased creatinine phosphokinase.

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Koselugo is supplied as 10mg and 25mg capsules in 60-count bottles. The capsules contain vitamin E (10mg capsules contain 32mg vitamin E; 25mg capsules contain 36mg vitamin E) and daily vitamin E intake that exceeds the recommended or safe limits may increase the risk of bleeding. Moreover, patients who are co-administered vitamin-K antagonists or antiplatelets with Koselugo may be at increased risk of bleeding.

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