CHEK1 and small cell lung carcinoma: However, some more effective drug combinations to treat SCLC have recently been described, such as the combination of standard chemotherapy together with inhibitors affecting replication stress response genes such as CHK1 and ATR (Doerr et al., 2017, Sen et al., 2017), that showed enhanced synergy in SCLC overexpressing MYC (Nagel et al., 2019).