MCL1 and B-cell chronic lymphocytic leukemia: 32 These BH3 mimetics have shown promising efficacy in a variety of preclinical models (eg refs 31, 33) and ABT-263 and ABT-199 are now in advanced clinical trials for chronic lymphocytic leukemia and certain other malignancies.34, 35, 36, 37 High levels of Mcl-1 (or A1/BFL1) are likely to cause resistance26, 29, 38 and BH3 mimetics specific for Mcl-1 are under development.