BMS-303141, with the chemical name 3,5-dichloro-2-hydroxy-N-(4-methoxy[1,1'-biphenyl]-3-yl)benzenesulfonamide, is a potent and selective small-molecule inhibitor of the checkpoint kinase 1 (Chk1). It functions by binding to the ATP-binding pocket of Chk1, thereby inhibiting its kinase activity. This compound is primarily utilized as a research tool in oncology and cell biology to study the DNA damage response pathway. Inhibition of Chk1 by BMS-303141 abrogates the S and G2/M cell cycle checkpoints, sensitizing cancer cells to DNA-damaging agents such as chemotherapy and radiation. It has been investigated for its potential to enhance the efficacy of genotoxic anticancer therapies. As a well-defined chemical probe, BMS-303141 is also relevant in the context of drug discovery as a reference compound or a starting point for the development of novel Chk1-targeted therapeutic agents.