SpringWorks Therapeutics, Inc. announced that the European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) has adopted a positive opinion recommending the granting of a conditional marketing authorization for mirdametinib, a MEK inhibitor, for the treatment of symptomatic, inoperable plexiform neurofibromas (PN) in pediatric and adult patients with neurofibromatosis type 1 (NF1) aged 2 years and above. The European Commission (EC) will review the CHMP opinion and is expected to make a final decision regarding the approval in the third quarter of 2025. If approved, mirdametinib will be available in 1 and 2 mg capsules and in a 1 mg dispersible tablet, which dissolves easily in water.
The CHMP opinion was based on the Marketing Authorization Application (MAA) for mirdametinib, which was validated by the EMA in August 2024. The MAA centered on the primary results from the Phase 2b ReNeu trial, which enrolled 114 patients with NF1-PN age 2 years or older (58 adults and 56 pediatric patients). The study met the primary endpoint of confirmed objective response rate (ORR), as assessed by blinded independent central review, demonstrating an ORR of 41% (N= 24/58) in adults and 52% in children (N=29/56). The median best percentage change in target PN volume was -41% (range: -90 to 13%) in adults and -42% (range: -91 to 48%) in children. Among those with a confirmed response, 88% percent of adults and 90% of children had a response of at least 12 months duration, and 50% and 48%, respectively, had a response of at least 24 months duration. Both adults and children also experienced early and sustained significant improvements from baseline in pain and quality of life as assessed across multiple patient-reported outcome tools. Mirdametinib demonstrated a manageable safety and tolerability profile.
The most common adverse events (>25%) reported in adults receiving mirdametinib were rash, diarrhea, nausea, musculoskeletal pain, vomiting and fatigue. The most common adverse events (>25%) occurring in children were rash, diarrhea, musculoskeletal pain, abdominal pain, vomiting, headache, paronychia, left ventricular dysfunction and nausea. Mirdametinib is approved in the U.S. for the treatment of adult and pediatric patients 2 years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic plexiform neurofibromas (PN) not amenable to complete resection.
