Prexasertib-d4 (LY2606368-d4) is the deuterium labeled Prexasertib (HY-18174). Prexasertib (LY2606368) is a selective, ATP-competitive second-generation checkpoint kinase 1 (CHK1) inhibitor with a Ki of 0.9 nM and an IC50 of 50=8 nM) and RSK1 (IC50=9 nM). Prexasertib causes double-stranded DNA breakage and replication catastrophe resulting in apoptosis. Prexasertib shows potent anti-tumor activity[1][2].