Pevonedistat exposure results in variable degrees of cell cycle arrest that correlates with changes in key regulatory proteins of the cell cycle progression (p21 and CDC2). (A) MCL cell lines were exposed to pevonedistat (250 or 500 nM) for 48 hours. Subsequently, cells were fixed, stained with PI, and analyzed by flow cytometry. (B) MCL cell lines were exposed to pevonedistat (250 or 500 nM) or vehicle control. After 48 hours of drug exposure, changes in cell cycle regulatory proteins were studied by western blot analysis.