Topotecan (Molecule of the Month for May 2012)
Topotecan is a chemotherapeutic agent that is a topoisomerase inhibitor. It is a water-soluble derivative of camptothecin. It is used in form of the hydrochloride to treat ovarian cancer and lung cancer, as well as other cancer types.
Hycamtin or topotecan is a semi-synthetic derivative of camptothecin. Camptothecin is a natural product extracted from the bark of the tree Camptotheca acuminata.
Topoisomerase-I is a nuclear enzyme that relieves torsional strain in DNA by opening single strand breaks. Once topoisomerase-I creates a single strand break, the DNA can rotate in front of the advancing replication fork. Topotecan intercalates between DNA bases. This intercalation disrupts the DNA duplication machinery when it reaches a site where topotecan is intercalated. This disruption prevents DNA replication, and ultimately leads to cell death. Mammalian cells cannot efficiently repair these double strand breaks. This process leads to breaks in the DNA strand resulting in apoptosis.
Formal Chemical Name (IUPAC)
(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
Update by Karl Harrison
(Molecule of the Month for May 2012 )