Another BH3 mimetic, a dual BCL2/BCL2L1 (BCL-XL) inhibitor navitoclax (ABT-737) demonstrated clinical activity in patients with R/R CLL, but the overall response rate was rather low and administration of navitoclax was associated with severe “on-target” thrombocytopenia attributable to high-affinity inhibition of BCL-XL in megakaryocytes [60,61,62]. This evidence concerns the gene BCL2 and B-cell chronic lymphocytic leukemia.