AZD6738 (Ceralasertib), a selective inhibitor of ataxia telangiectasia and Rad3-related protein (ATR), has demonstrated synergistic preclinical activity with a Bruton tyrosine kinase (BTK) inhibitor in TP53- and ATM-defective CLL cells (NCT03328273). Here, TP53 is linked to B-cell chronic lymphocytic leukemia.