BCL2 and B-cell chronic lymphocytic leukemia: Subsequent rational drug discovery research efforts led to the development of VenclextaTM (ABT-199), the first orally active BCL-2 selective (BCL-XL-sparing) inhibitor [16] that has been recently approved in high risk patients with relapsed or refractory Chronic Lymphocytic Leukemia (CLL) [17].