Long-Term Hematologic Effects of Selumetinib Treatment in Children With Neurofibromatosis Type 1-Associated Plexiform Neurofibromas.

Selumetinib, a mitogen-activated protein kinase kinase inhibitor, was the first Food and Drug Administration-approved treatment for children with neurofibromatosis type 1-associated inoperable plexiform neurofibromas. We evaluated hematologic effects in 98 pediatric participants from the SPRINT Phase 1/2 trial (NCT01362803) with a median follow-up of 5.1 years (range: 0.2-11 years). Over 90% of values for white blood cell count, platelet count, absolute neutrophil count, and absolute lymphocyte count remained within normal limits across timepoints. There was a statistically significant, but unlikely clinically significant, decrease in absolute lymphocyte count and an increase in mean corpuscular volume. Selumetinib was not associated with apparent clinically significant hematologic changes.