INNV-22. A case report of the first adult neurofibromatosis type 1 patient treated with mirdametinib

Abstract Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder characterized by café au lait macules, intertriginous freckling, Lisch nodules, central nervous system, and peripheral nerve tumors such as plexiform neurofibromas (PNs). Additionally, some patients experience learning disabilities and cognitive deficits. Although there was an FDA-approved drug for pediatric populations with inoperable PNs (selumetinib), there were no FDA-approved drugs for adults until February 2025, when Mirdametinib, a highly selective, allosteric, central nervous system-penetrant, MEK 1/2 inhibitor, was approved. It was evaluated in the ReNeu study, a phase 2b single-arm study, with 114 participants, including 58 adult and 56 pediatric patients. 41% of adults and 52% of children achieved a confirmed objective response. The most commonly reported adverse events were acneiform rash, diarrhea, and vomiting, all of which affected more than 50% of the participants. More severe side effects included left ventricular dysfunction and ocular toxicity, such as retinal vein occlusion and retinal pigment epithelium detachment. The median time to response in adults was 7.8 months. We report the case of a 39-year-old female patient with NF1, right optic glioma, and multiple cutaneous and plexiform neurofibromas. In 2021, she underwent a partial resection of a plexiform neurofibroma located on her right frontal scalp and eyelid. Despite the surgery, she continued to experience significant discomfort and disfigurement. She is the first adult patient to start treatment with Mirdametinib following its FDA approval. After three months of treatment, she has tolerated the medication well. She developed an acneiform rash on her face and trunk shortly after beginning treatment, which resolved with doxycycline and topical corticosteroids. To ensure her safety, she is closely monitored with echocardiograms and ophthalmological evaluations every three months.