Seliciclib (roscovitine or CYC202), a first-generation pan-CDK inhibitor with preferentially inhibitory activities toward CDK2, CDK7, and CDK9, is not approved nor widely used in clinical practice because of the toxic effect in GBM patients, while it exhibited antitumor activity on GBM patient-derived xenografts and glioblastoma cell lines [12,13]. Here, CDK2 is linked to glioblastoma.