Selumetinib Label Expands to Age 1 via Granule Bridging Strategy

AstraZeneca's selumetinib (KOSELUGO) now carries an FDA-approved indication extending to pediatric patients as young as 1 year of age for symptomatic, inoperable plexiform neurofibromas associated with neurofibromatosis type 1 -- a label expansion built not on a new efficacy trial, but on a formulation bridging strategy that CMC and regulatory teams across the industry will be studying closely. The September 10, 2025 approval covers both the existing capsule and a new oral granule formulation, with the age threshold dropping from 2 years to 1 year.

The regulatory pathway hinged on two data sets: a relative bioavailability study in healthy adults (Study 89) establishing adequate bridging between the oral granule and the approved capsule, and exposure matching between pediatric populations in the SPRINT Phase II Stratum I study (capsule, patients aged 2 and older) and the SPRINKLE study (oral granule, patients aged 1 and older). Demonstrated exposure equivalence allowed FDA to extrapolate efficacy from the older cohort to the younger one, bypassing the need for a full independent efficacy trial in the 1-to-2-year age band. For CMC teams managing pediatric formulation development, this approval illustrates how a well-constructed bioavailability bridging package -- anchored in ICH-aligned exposure matching -- can support meaningful label expansions with a leaner clinical data set.

Safety profile and dosing: The prescribing information carries warnings and precautions for cardiomyopathy, ocular toxicity, gastrointestinal toxicity, skin toxicity, elevated creatine phosphokinase, increased vitamin E levels, increased bleeding risk (capsule formulation), and embryo-fetal toxicity. Incidence data were updated to reflect a larger pediatric patient population; no new safety signals were identified. The recommended dose remains 25 mg/m2 orally twice daily, dosed by body surface area, continued until disease progression or unacceptable toxicity.

Selumetinib holds both breakthrough therapy and orphan drug designations. Healthcare professionals should report serious adverse events via FDA's MedWatch system or by calling 1-800-FDA-1088. Full prescribing information will be posted on Drugs@FDA. Source: FDA Drugs Resources and Information on Approved Drugs, published May 4, 2026.