Topoisomerase inhibitors

Topoisomerase inhibitors are chemical compounds that block the action of topoisomerases.

  • Intercalating drugs are used for cancer chemotherapy because they poison cells that are rapidly dividing, like the cells in a growing tumor
    • Action of topoisomerase begins by breaking one of DNA strands
    • then they induce a topological change in DNA such as relaxing supercoils or untangling strands
    • and finally they reconnect the DNA in its proper form.
  • Intercalating drugs block the reconnection step, freezing the topoisomerase after it has broken the DNA.
  • This is a problem for a dividing cell: when a replication fork reaches the site, a lethal double-strand break is formed as the replication machinery passes through the damaged DNA.


  1. Camptothecins
  2. Etoposide
  3. Doxorubicine

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