BCL2 and B-cell chronic lymphocytic leukemia: Furthermore, the small molecules that mimic the function of the BH3-only proteins have been tested in clinical trials, and even the inhibitor of Bcl-2 activity, Venotoclax/ABT-199, was recently approved by the U.S. Food and Drug Administration (FDA) for the treatment of chronic lymphocytic leukemia (CLL) (26, 27).