As previously described, CD40 stimulation by CD40L‐expressing fibroblasts resulted in significant venetoclax resistance of CLL cells, which we and others showed to be correlated with upregulation of the Bcl‐2 family members Bcl‐XL, Mcl‐1, and Bfl‐1 [11, 13] (Fig. 1A). Here, MCL1 is linked to B-cell chronic lymphocytic leukemia.