Topotecan

Topotecan
Systematic (IUPAC) name
(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 monohydrochloride
Clinical data
Trade names Hycamtin
AHFS/Drugs.com monograph
MedlinePlus a610007
Pregnancy
category
  • AU: D
  • US: D (Evidence of risk)
Routes of
administration		 Intravenous infusion, oral
Legal status
Legal status
Pharmacokinetic data
Bioavailability 31.4 % in humans[1][2]
Protein binding 35%
Metabolism Hepatic
Biological half-life 2-3 hours
Excretion Renal
Identifiers
CAS Number 123948-87-8 N 119413-54-6 (hydrochloride)
ATC code L01XX17 (WHO)
PubChem CID 60700
IUPHAR/BPS 7101
DrugBank DB01030 YesY
ChemSpider 54705 YesY
UNII 7M7YKX2N15 YesY
KEGG D08618 YesY
ChEMBL CHEMBL84 YesY
Chemical data
Formula C23H23N3O5 •HCl
Molar mass 457.9 g/mol
 NYesY (what is this?)  (verify)

Topotecan (trade name Hycamtin) is a chemotherapeutic agent that is a topoisomerase inhibitor. It is a synthetic, water-soluble analog of the natural chemical compound camptothecin. It is used in the form of its hydrochloride salt to treat ovarian cancer, lung cancer and other cancer types.

After GlaxoSmithKline received final FDA approval for Hycamtin Capsules on October 15, 2007, topotecan became the first topoisomerase I inhibitor for oral use.

Indications (approved uses)

Experimental use

As of 2016 experiments were under way for Neuroblastoma, Brainstem glioma, Ewing's sarcoma andAngelman's syndrome.

Angelman's syndrome

Angelman’s syndrome is a neuro-genetic disorder characterized by severe developmental delays, seizures, speech impairments and physical impairments. It is an epigenetic disease and other treatments focus on symptoms. It is caused by a deletion or mutation of the maternal allele for the ubiquitin protein ligase E3A.[8] UBE3A is expressed in most body tissues. However, in neurons only the maternal copy of the gene is expressed. UBE3A is located on chromosome 15 and the paternal copy for the gene is genetically imprinted and is silenced by an antisense RNA transcript. The maternal copy control center of the gene is methylated, suppressing transcription in the antisense direction while the paternal copy control center is unmethylated.[9]

Treatment involves unsilencing the paternal allele allowing the normal paternal UBE3A allele to be transcribed. UBE3A, in normal function, adds ubiquitin chains to proteins to target unnecessary or damaged proteins for degradation by the proteasome.[10]

16 topoisomerasesinhibitors unsilence paternal UBE3A. Topoisomerases are enzymes that regulate the unwinding of DNA.[11] Of these 16 inhibitors, topotecan was found to induce the strongest upregulation of UBE3A.[12] The enzymes bind to the DNA and cut the phosphate backbone, allowing the DNA to be unwound. Topotecan unsilences the paternal UBE2A allele by reducing the transcription of an antisense transcript. Topotecan inhibits topoisomerase I restoring UBE3A levels to wild-type range in cultured mince neurons.[13]

Transgenic mice with a fluorescently tagged UBE3A were used to test the effectiveness of unsilencing the paternal copy.[9] When tested on mice in vivo, topotecan affected the hippocampus, striatum and cerebral cortex but not the cerebellum unless a higher dose was administered (21.6 micrograms/hour for five days). The study suggested that the topoisomerase inhibitors have the potential to produce a normally functioning UBE3A protein. Most symptoms due to Angelman’s syndrome are traditionally treated by speech therapy, physical therapy and occupational therapy. Anti-seizure medication is often prescribed as seizures are a common symptom of Angelman’s syndrome.[14] These treatments target only symptoms.

This drug has been administered to cancer patients. It was well-tolerated when administered to pediatric and adult patients.

Mechanism 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 DNA by opening single strand breaks.[15] Once topoisomerase-I creates a single strand break, the DNA can rotate in front of the advancing replication fork. Topotecan intercalates between DNA bases in the topoisomerase-I clevage complex.[16] The binding of topotecan in the cleavage complex prevents topoisomerase-I from religating the nicked DNA strand after relieving the strain.[16] This intercalation therefore traps the topoisomerase-I in the cleavage complex bound to the DNA.[16] When the replication-fork collides with the trapped topoisomerase-I, DNA damage occurs.[16] The unbroken DNA strand breaks and mammalian cells cannot efficiently repair these double strand breaks.[17] The accumulation of trapped topoisomerase-I complexes is a known response to apoptotic stimuli.[18] This disruption prevents DNA replication and ultimately leads to cell death. This process leads to breaks in the DNA strand resulting in apoptosis.

Side effects

Generic versions

Two generic versions have been approved in the European Union. In Nov 2010 the US FDA approved a generic version.[19][20]

References

  1. ↑ "Clinical Pharmacology & Therapeutics - Wiley Online Library".
  2. ↑ "Abstracts".
  3. ↑
  4. ↑ "FDA Approval for Topotecan Hydrochloride". National Cancer Institute.
  5. ↑
  6. ↑
  7. ↑ "GSK Receives Approval for Hycamtin (topotecan) Capsules for theTreatment of Relapsed Small Cell Lung Cancer".
  8. ↑ (Huang et al)
  9. 1 2 Beaudet 2011.
  10. ↑ (Malzac)
  11. ↑ (Miller)
  12. ↑ (Malpass)
  13. ↑ (Huang)
  14. ↑ (Aditi and Williams)
  15. ↑ Pommier, Y., Leo, E., Zhang, H., Marchand, C. 2010. DNA topoisomerases and their poisoning by anticancer and antibacterial drugs. Chem. Biol. 17: 421-433.
  16. 1 2 3 4 Pommier, Yves. "Topoisomerase I inhibitors: camptothecins and beyond". Nature Reviews Cancer 6 (10): 789–802. doi:10.1038/nrc1977.
  17. ↑ Staker, B.L.; et al. (2002). "The mechanism of topoisomerase I poisoning by a camptothecin analog". PNAS 99 (24): 15387–15392. doi:10.1073/pnas.242259599.
  18. ↑ Bertrand, Richard; Solary, Eric; O'Connor, Patrick; Kohn, Kurt W.; Pommier, Yves (1994-04-01). "Induction of a Common Pathway of Apoptosis by Staurosporine". Experimental Cell Research 211 (2): 314–321. doi:10.1006/excr.1994.1093.
  19. ↑ "FDA Rubber-Stamps APP Pharma’s Generic Topotecan for Small Cell Lung and Cervical Cancers". 30 Nov 2010.
  20. ↑ DNA Topoisomerases and Cancer, Yves Pommier Editor, Humana Press 2012

Sources

External links

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