A potent Chk1 inhibitor (IC50 = 8 nM); selective for Chk1 over FLT3, Chk2, and CDK1 (IC50s = 600, >10,000, and >10,000 nM, respectively) as well as a panel of 121 additional kinases at 10 μM; reverses cell cycle arrest at the G2/M phase induced by etoposide and SN-38 in HT-29 cells and gemcitabine in SW620 cells; potentiates the genotoxicity of SN-38, gemcitabine, and etoposide in HT-29, SW620, MiaPaCa-2, and Calu-6 cells; in combination with irinotecan or gemcitabine, increases the delay of tumor growth in SW620 and Calu-6 mouse xenograft models, respectively, at 75 mg/kg