<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>The sodium salt of camptothecin, an alkaloid isolated from the Chinese tree Camptotheca acuminata, with antineoplastic activity. During the S phase of the cell cycle, camptothecin selectively stabilizes topoisomerase I-DNA covalent complexes, thereby inhibiting religation of topoisomerase I-mediated single-strand DNA breaks and producing potentially lethal double-strand DNA breaks when encountered by the DNA replication machinery. The sodium salt of camptothecin is more water-soluble than the parent molecule. (NCI04)</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>