A synthetic small-molecule inhibitor of checkpoint kinases 1 and 2 (Chk1 and Chk2) with potential antineoplastic activity. XL844 binds to and inhibits Chks 1 and 2, resulting in inhibition of cell cycle arrest, progressive DNA damage, inhibition of DNA repair, and, ultimately, tumor cell apoptosis. This agent also inhibits vascular endothelial growth factor receptor 1 (VEGFR1) and vascular endothelial growth factor receptor 3 (VEGFR3), important mediators of tumor angiogenesis and lymphogenesis, respectively. In the presence of DNA damage or incomplete DNA replication, eukaryotic cells activate cell cycle checkpoints that temporarily halt the cell cycle to permit DNA repair or completion of DNA replication to take place. In the presence of extensive damage or absence of timely repair, these checkpoint-signaling pathways may also trigger a pathway that effects apoptosis. Normal functions of Chks involve the initiation of cell-cycle arrest and the up-regulation of transcription genes involved with DNA excision repair and dNTP synthesis.