When assessed in non–gastric cancer–focused early phase clinical trials, ATRi such as ceralasertib (AZD6738), berzosertib (M6620, VX-970) or elimusertib (BAY1895344) can elicit significant antitumor effects (22–29), including profound responses in prostate, breast, endometrial, renal, or appendiceal tumors, some of which have ATM or ARID1A defects (30, 31). Here, ARID1A is linked to gastric cancer.