Our unexpected finding that permeabilized CLL cells are as sensitive to the induction of MOMP by drugs inhibiting MCL1 or BCLxL as to venetoclax (Fig. 1A) led us to investigate why assaying the inhibitors of the pro-survival BCL2 proteins with BH3 profiling do not reliably reflect the activity of such drugs on intact cells. Here, BCL2 is linked to B-cell chronic lymphocytic leukemia.