CDK9 and neoplasm: Consistent with effective in vivo CDK9 inhibition following oral delivery, MCL-1 protein expression was decreased in a dose-dependent manner, as observed upon comparing both tumor lysates and immunohistochemically stained sections from mice receiving either vehicle, 100 mpk or 200 mpk voruciclib daily for 5 days (Figs 2d,e and S1).