BML-277 (Chk2 Inhibitor II) is an ATP-competitive inhibitor of Chk2 with IC50 of 15 nM. It is 1000-fold more selective toward Chk2 serine/threonine kinase than for Chk1 and Cdk1/B kinases. Chk2 Inhibitor II (BML-277) dose dependently protects human CD4(+) and CD8(+) T-cells from apoptosis due to ionizing radiation.