ATR and cancer: In conclusion, these results, derived using clinically available and actionable assays, advance our understanding of the association between DDR GAs in cancer, and support the investigation of immune checkpoint inhibitors, not only in tumour type-specific and biomarker-defined subgroups (e.g., mutated ARID1A, SMARCA4, ATR) but also in combination with ATR inhibitors, in the clinical setting.