SpringWorks Therapeutics’ mirdametinib shows efficacy in neurofibromatosis study

SpringWorks Therapeutics (SWTX) announced that data from the pivotal, Phase 2b ReNeu trial of mirdametinib, an investigational MEK inhibitor, in adult and pediatric patients with neurofibromatosis type 1-associated plexiform neurofibromas, or NF1-PN, were published online in the Journal of Clinical Oncology. As of September 20, 2023, the ReNeu trial met its primary endpoint of confirmed objective response rate. During the 24-cycle treatment phase, the ORR was 41% in adults and 52% in children receiving mirdametinib treatment. An efficacy analysis that also included patients who achieved a confirmed objective response after 24 cycles of mirdametinib treatment resulted in an ORR of 45% in adults and 54% in pediatric patients. Of the patients who achieved a confirmed objective response during the treatment phase, 96% of adults and 100% of children had durable responses at the time of data cut-off, with 75% of adults and 76% of children having met or exceeded 12 months in response. Tumor volume reductions were deep and durable during the course of the study. Both cohorts reported significant and clinically meaningful improvement in patient- or parent proxy-reported secondary endpoint outcome measures of worst tumor pain severity, pain interference, and health-related quality of life. Mirdametinib was generally well tolerated in the ReNeu trial, with the majority of adverse events being Grade 1 or 2.