An inhibitor of the cell cycle checkpoint kinase 2 (chk2) with potential chemopotentiating activity. Rabusertib binds to and inhibits the activity of chk2, which may prevent the repair of DNA caused by DNA-damaging agents, thus potentiating the antitumor efficacies of various chemotherapeutic agents. Chk2, an ATP-dependent serine-threonine kinase, is a key component in the DNA replication-monitoring checkpoint system and is activated by double-stranded breaks (DSBs); activated chk2 is overexpressed by a variety of cancer cell types.