PARP1 and breast cancer: By combination with olaparib, ceralasertib also showed preliminary response in HGSOC,173 SCLC174 and breast cancer.175 Impressively, 6 out of 13 PARP inhibitor resistant HGSOC patients demonstrated partial response upon co-treatment of olaparib and ceralasertib, indicating that ATR inhibition could circumvent PARP inhibitor resistance.173 Recently, ceralasertib in combination with durvalumab initiates a phase 3 study for the treatment of later line NSCLC patients (Table 2).