Abemaciclib mesylate showed significant inhibition of tumor growth in different murine xenograft models of human cancer, such as Colo-205 (colorectal cancer), NCI-H460 (NSCLC), U87 MG (glioblastoma), and JeKo-1 (MCL), all characterized by functional Rb tumor suppressor protein. This evidence concerns the gene RB1 and cancer.