BCL2 and leukemia: Thereby, selective BH3-mimetics may have the advantage of displaying less toxicity on healthy cells.22 With the clinical approval of ABT-199/Venetoclax, a highly potent selective inhibitor of BCL-2 for the treatment of leukaemia, these BH3-mimetics are emerging as powerful new assets in the fight against cancer.22,23 Besides ABT-199, highly potent inhibitors have been discovered, which in the case of A1331852 selectively inhibit BCL-XL or in the case of S63845 selectively target MCL-1,24,25 thus allowing efficient inhibition of all main antiapoptotic BCL-2 proteins.