Prexasertib (LY2606368) is a selective, ATP-competitive second-generation checkpoint kinase 1 (CHK1) inhibitor with a K i of 0.9 nM and an IC 50 of <1 nM. Prexasertib inhibits CHK2 (IC 50 =8 nM) and RSK1 (IC 50 =9 nM). Prexasertib causes double-stranded DNA breakage and replication catastrophe resulting in apoptosis . Prexasertib shows potent anti-tumor activity .