ATR and cancer: Therefore, cancers with loss‐of function mutations in HR pathway components such as BRCA1, ATM, ATR, RAD51, and FANC genes are susceptible to treatment with PARP inhibitors (Farmer et al, 2005; Bryant et al, 2005; McCabe et al, 2006; Lord & Ashworth, 2016; Ashworth & Lord, 2018).