BCL2 and B-cell chronic lymphocytic leukemia: Chronic lymphocytic leukaemia cells were exquisitely sensitive to ABT-199 (IC50=2.5 nM after 4-h exposure) but insensitive to A-1210477 and to a great extent to A-1331852 (IC50=1.1 μM) (Figure 2), thus confirming that CLL cells are addicted to BCL-2.