Several RNR inhibitors are also used in anti-leukaemia therapies, such as hydroxyurea (HU) that targets RRM2 to treat chronic myeloid leukaemia (CML) and AML and the ribonucleoside analogues cytarabine and clofarabine that target RRM1 to treat acute leukaemia [23,24,25]. Here, RRM2 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.