ESR1 and B-cell chronic lymphocytic leukemia: ABT-199 has achieved promising anti-leukemia activity in patients with chronic lymphocytic leukemia (CLL) (Molica, 2015), and it has been reported to have preclinical activities in estrogen-receptor-positive breast cancer, acute myeloid leukemia (AML), early T cell progenitor leukemia, Myc-driven B cell lymphomas, and acute lymphoblastic leukemia (Alford et al., 2015, Chonghaile et al., 2014, Pan et al., 2014, Souers et al., 2013, Vaillant et al., 2013, Vandenberg and Cory, 2013).