Selumetinib eradicates CNS leukemia in an orthotopic primagraft model. Photomicrographs of brain sections stained with hematoxylin and eosin from mice engrafted with Ras pathway mutant ALL cells (L779) after treatment with selumetinib or CV (×20 objective) (A). Photomicrograph of 1 section from CV-treated mouse after increased magnification (×40) (B). Dot plot of the depth of leukemic infiltrate into the leptomeninges in CV- vs selumetinib-treated mice (C).