Notably, therapy with BCR axis inhibitors such as ibrutinib (Cervantes-Gomez et al., 2015), acalabrutinib (Patel et al., 2017a), and duvelisib (Patel et al., 2017b) results in a decline in MCL-1 protein levels in CLL cells, providing a mechanism-based rationale to combine them with venetoclax. This evidence concerns the gene MCL1 and B-cell chronic lymphocytic leukemia.