ATR and cancer: In prospective trials of patients with metastatic urothelial carcinoma treated with anti-PD-1/PD-L1 blockade, the presence of a DDR mutation was associated with a higher response rate, longer progression-free survival and overall survival.34 There is in vitro evidence that ATR inhibition decreases PD-L1 expression, sensitizing cancer cells to T cell killing.35 This has led to multiple clinical trials currently evaluating ATR inhibitors in combination with ICIs.