Another CXCR4 antagonist, POL5551, was shown to increase cytarabine sensitivity in a xenograft model of a high-risk pediatric ALL subtype, infant MLL-rearranged (MLL-R) ALL [207], indicating that disruption of the CXCR4/CXCL12 interaction may benefit children with high-risk ALL. This evidence concerns the gene CXCR4 and acute lymphoblastic leukemia.