Other study parameters
tumor
TUMOR
To measure abemaciclib phosphorylated RB (pRB) and topoisomerase II alpha (TopoIIα, specific for S phase) pharmacodynamic assays to assess CDK4/6 inhibition and cell cycle progression in biopsied tumor tissueTo measure dexamethasone concentrations in brain interstitial fluid to evaluate passive diffusion of known BBB permeable compoundTo measure urea concentrations in blood and brain interstitial fluid to evaluate in microdialysis catheter performanceTo conduct genomic sequencing of biopsied tumor tissue identifying driver mutations linked to targeted therapiesTo establish participant derived xenograft modeling in rodents using biopsied tumor tissueTo evaluate median progression free survival with continued abemaciclib with temozolomide therapyTo evaluate standard pharmacokinetic parameters comparing combined abemaciclib and temozolomide vs. abemaciclib alone vs. historical controls of temozolomide only