Another highly selective, orally bioavailable ATRi, ceralasertib (AZD6738, an AZ20 analogue), has been shown to have single-agent efficacy in ATM-deficient and p53-deficient cancer cell lines and tumor models, with synergistic anti-proliferative effects when combined with chemotherapeutic and DNA damaging agents [202,203,204]. The gene discussed is TP53; the disease is cancer.