By highlighting that it may be difficult to generate resistance phenotypes in this setting, our findings therefore support the targeted use of ATRi against tumours with impaired ATM function, and propose the attraction of inhibiting ATR rather than other DDR factors such as PARP in ATM-deficient tumours, where resistance can be imparted by single inactivation of various genes due to one primary mode of cell death (38). Here, ATR is linked to neoplasm.