Topotecan
Encyclopedia
Topotecan hydrochloride (trade name Hycamtin) is a chemotherapy agent that is a topoisomerase I
inhibitor
. It is the water-soluble derivative of camptothecin
. It is used to treat ovarian cancer
and lung cancer
, as well as other cancer types.
After GlaxoSmithKline received final FDA approval for Hycamtin Capsules on October 15, 2007, Topotecan is the first topoisomerase inhibitor
for oral use.
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
.
Topoisomerase
Topoisomerases are enzymes that regulate the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double helical structure. For example, during DNA replication, DNA becomes overwound ahead of a replication fork...
inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
. It is the water-soluble derivative of camptothecin
Camptothecin
Camptothecin is a cytotoxic quinoline alkaloid which inhibits the DNA enzyme topoisomerase I . It was discovered in 1966 by M. E. Wall and M. C. Wani in systematic screening of natural products for anticancer drugs. It was isolated from the bark and stem of Camptotheca acuminata , a tree native to...
. It is used to treat ovarian cancer
Ovarian cancer
Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....
and lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
, as well as other cancer types.
After GlaxoSmithKline received final FDA approval for Hycamtin Capsules on October 15, 2007, Topotecan is the first topoisomerase inhibitor
Topoisomerase inhibitor
Topoisomerase inhibitors are agents designed to interfere with the action of topoisomerase enzymes , which are enzymes that control the changes in DNA structure by catalyzing the breaking and rejoining of the phosphodiester backbone of DNA strands during the normal cell cycle.In recent years,...
for oral use.
Indications (Approved uses)
- Ovarian cancerOvarian cancerOvarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....
(FDA May 1996). - Cervical cancerCervical cancerCervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages...
(FDA June 2006). - Small cell lung cancer (SCLC) (FDA Oct 2007).
Mode of action
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 DNADNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
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
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
.