Topotecan

**Semantic type:** Organic Chemical|Pharmacologic Substance

**Definition:** A semisynthetic derivative of camptothecin, a cytotoxic, quinoline-based alkaloid extracted from the Asian tree Camptotheca acuminata. Topotecan inhibits topoisomerase I activity by stabilizing the topoisomerase I-DNA covalent complexes during S phase of cell cycle, 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.

**Synonyms:** - (s)-10-[(dimethylamino)methyl]-4-ethyl-4,9-dihydroxy-1H-pyrano[3',4':6,7]indolizino[1,2-b]-quinoline-3,14(4H,12H)-dione - 9-[(dimethylamino)methyl]-10-hydroxy-(20S)-camptothecin - Hycamptamine - TOPOTECAN - Topotecan Lactone - topotecan