SpringWorks Therapeutics Initiates Rolling Submission of New Drug Application to the FDA for Mirdametinib for the Treatment of Children and Adults with NF1-PN

Mirdametinib Neurofibromatosis Type 1 Treatment

SpringWorks Therapeutics, Inc. (Nasdaq: SWTX), a commercial-stage biopharmaceutical company focused on severe rare diseases and cancer, announced today that the Company has initiated a rolling submission of a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for mirdametinib, an investigational MEK inhibitor, in pediatric and adult patients with neurofibromatosis type 1-associated plexiform neurofibromas (NF1-PN).

“There is tremendous potential for mirdametinib to address the substantial needs that exist for children and adults with NF1-PN, and the initiation of our rolling NDA submission brings us one step closer toward our goal of providing these patients with a best-in-class therapy that could make a significant impact on their lives,” said Saqib Islam, Chief Executive Officer of SpringWorks. “We are excited to advance the regulatory filing for our second product and look forward to working closely with the FDA on their review of our application.”  

The NDA submission includes data from the Phase 2b ReNeu trial, a multi-center, open-label study that opened across 50 sites in the U.S. and enrolled 114 patients across two cohorts (pediatric and adult). The primary endpoint was confirmed objective response rate (ORR), defined as ≥ 20% reduction in target tumor volume as measured by MRI and assessed by Blinded Independent Central Review (BICR). As of the data cutoff date of September 20, 2023, the BICR-confirmed objective response rate was 52% in pediatric patients and 41% in adult patients. Mirdametinib treatment showed deep and durable responses and demonstrated significant improvements in key secondary patient-reported outcome measures. Pediatric and adult patients in the ReNeu trial experienced statistically significant improvements from baseline in pain, quality of life, and physical function, as assessed across multiple patient-reported outcome tools. Mirdametinib was generally well tolerated in the trial, with the majority of adverse events (AEs) being Grade 1 or Grade 2. The most frequently reported AEs were rash, diarrhea, and vomiting in the pediatric cohort and rash, diarrhea, and nausea in the adult cohort.

The FDA and the European Commission have granted Orphan Drug designation for mirdametinib for the treatment of NF1. The FDA has also granted Fast Track designation for the treatment of patients ≥ 2 years of age with NF1-PN that are progressing or causing significant morbidity. In July 2023, the FDA granted mirdametinib Rare Pediatric Disease designation for the treatment of NF1, which provides eligibility for a priority review voucher upon FDA approval. SpringWorks expects to complete the NDA submission in the second quarter of 2024.


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