NSC 109555 is an inhibitor of checkpoint kinase 2 (Chk2), a serine/threonine kinase involved in the ATM-Chk2 checkpoint pathway. Drugs that target Chk2 in combination with DNA-damaging agents can be beneficial in cancer therapy. Studies in mice, rats, rabbits, dogs, and monkeys have shown that NSC 109555 displays toxic effects. A singe injection of the drug at a concentration of 12.5-25 mg/kg caused acute paralysis leading to apnea and death.
NSC109555 is a selective inhibitor of Chk2 (IC50 = 310 nM). The compound is reversible and competitive for ATP, and displays little or no activity against other related kinases, including Chk1, at concentrations up to 10 μM.
