The CDKN2A gene locus is altered in up to approximately 57% of glioblastoma, most commonly as a homozygous deletion, and frequently with concurrent deletion of the CDKN2B locus. CDKN2A/CDKN2B loss may be associated with increased sensitivity to CDK4/6 inhibitors. W110* results in early truncation and confers a loss of function as demonstrated by loss of CDK binding and cell cycle control in culture. The clinicopathologic effects of the heterozygous rather than homozygous loss of CDKN2A in glial neoplasms remains to be further elucidated. The efficacy and toxicity profiles of these inhibitors in the context of a variety of cancer types are currently under evaluation in clinical trials.