BCR and chronic myelogenous leukemia, BCR-ABL1 positive: As it is generally accepted that TK activity is required for the transforming ability of BCR–ABL fusion-proteins (Lugo et al, 1990; Oda et al, 1995), a specific inhibitor of TK function may represent a possible therapy for CML and other bcr–abl positive leukaemias (Levitzki and Gazit, 1995).