ATR and small cell lung carcinoma: Although ATR inhibitors have not yet been approved by the US Food and Drug Administration for lung cancer treatment, a phase II trial of an ATR inhibitor (berzosertib) in combination with a highly selective topoisomerase I inhibitor (topotecan) in patients with relapsed small cell lung cancer (SCLC), all of whom had evidence of disease progression after conventional treatment including chemotherapy or immunotherapy before participation, showed prolonged survival [18].