Koselugo (selumetinib)

Higher selumetinib exposure appears to be associated with treatment-related adverse effects in pediatric NF1 patients. These findings support the potential role of TDM in optimizing selumetinib dosing and provide a preliminary therapeutic AUC range for individualized treatment strategies. Larger multicenter studies are needed to validate these results and refine exposure-guided dosing approaches.

Selumetinib treatment was associated with a significant, consistent, and durable decline in prescription pain medication utilization over 3 years. Patients who continued taking pain medications experienced nominal dose reductions, and patients who received selumetinib continuously experienced a decrease in prescription pain medication utilization.

P1, N=19, Active, not recruiting, National Cancer Institute (NCI) | Trial completion date: Mar 2026 --> Mar 2027

This Perspective synthesizes recent developments, including gene-based reclassification, emergence of MEK inhibitor therapy in NF1, renewed evaluation of bevacizumab and kinase-pathway inhibitor brigatinib, the discovery of a novel TβR1-RKIP pathogenic axis, and a brain-penetrant HDAC inhibitor in NF2-SWN. These insights highlight a shift toward precision-medicine strategies and mechanistically driven therapies poised to redefine future clinical care.

P1/2, N=217, Active, not recruiting, National Cancer Institute (NCI) | Trial completion date: Jul 2026 --> Mar 2027 | Trial primary completion date: Jul 2026 --> Jan 2026

The safety profile of selumetinib was generally consistent with the findings of the phase 2 SPRINT trial and Japanese phase 1 trial. No new safety concerns were identified.

FDA-approved mitogen-activated protein kinase kinase (MEK) inhibitors, selumetinib and mirdametinib, have shown ~30% tumor shrinkage in 70% and 42% pNF1 patients, respectively. This response was also observed in MPNST cell lines treated with MEK inhibitors. These findings suggest that adaptive activation of upstream and parallel survival pathways may counteract the intended effects of MEK inhibition and support the rationale for combination strategies to improve therapeutic outcomes in NF1-associated tumors.

These studies demonstrate in vitro efficacy for two candidate MPNST therapeutics which could reduce tumor burden and metastasis in NF1 patients.

P=N/A, N=124, Active, not recruiting, AstraZeneca | Recruiting --> Active, not recruiting

P1, N=30, Not yet recruiting, Girish Dhall, MD | Trial completion date: Mar 2034 --> Aug 2034 | Trial primary completion date: Mar 2033 --> Aug 2033

Mirdametinib represents a meaningful advance in the management of NF1-PNs, offering durable tumor volume reduction, improvements in pain and quality of life, and a manageable safety profile across age groups. While head-to-head comparisons with other MEK inhibitors are lacking, available evidence suggests a favorable balance of efficacy and tolerability that may support its use as a first-line systemic option in appropriately selected patients.

This case underscores the role of PAX5 in lineage plasticity and highlights the potential of targeted MEK inhibition in MAPK-driven HS arising from B-ALL. The authors have confirmed clinical trial registration is not needed for this submission.