CXCR4 and acute leukemia: Phase I studies have shown feasibility of adding the CXCR4 antagonist Plerixafor to sorafenib and GCSF in FLT3-mutated R/R AML (14), or to high-dose cytarabine and etoposide in pediatric patients with acute leukemias or myelodysplastic syndrome (MDS) (15).