Venetoclax is a first-in-class, potent and highly selective, orally bioavailable, B-cell lymphoma-2 homology 3 (BH3)-mimetic antagonist of B-cell lymphoma 2 (BCL2), an anti-apoptotic protein constitutively overexpressed in chronic lymphocytic leukemia (CLL). This evidence concerns the gene BCL2 and B-cell chronic lymphocytic leukemia.