Two other FTY720 derivatives, (S)-FTY720-OMe, (S)-FTY720-regioisomer, were found to reduce survival of chronic myeloid leukemia (CML) haematopoietic stem cells (HSC) but not normal HSCs 58 and caused PP2A activation without stimulating S1PR1 internalization and B cell lymphopenia 58. Here, PTPA is linked to chronic myelogenous leukemia, BCR-ABL1 positive.