While T-ALL patient-derived xenografts are unable to be maintained in cell culture for more than a few days, short-term treatment of a panel of T-ALL PDX cells revealed that the ATR inhibitor AZD6738 was toxic only to those from a case harboring a monoallelic BRCA2 truncating mutation (Fig 5D). The gene discussed is BRCA2; the disease is acute lymphoblastic leukemia.