Inhibitors of indoleamine-2,3-dioxygenase for cancer therapy: can we see the wood for the trees?

Nat Rev Cancer. 2009 Jun;9(6):445-52. doi: 10.1038/nrc2639.


Indoleamine-2,3-dioxygenase (IDO) is an immunosuppressive enzyme capable of inhibiting a destructive maternal T cell response against allogeneic fetuses. Expression of IDO is evident in tumours and is thought to enable escape from immunologically mediated rejection. Consequently, clinical trials using an inhibitor of IDO, 1-methyltryptophan (1MT), have been initiated. However, a review of the current literature indicates that we are far from understanding the biological relevance of IDO expression during tumorigenesis. A better understanding of IDO biology is needed to comprehend the effect of IDO inhibitors and to provide a rationale for their therapeutic application in cancer.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / immunology
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / metabolism*
  • Neoplasms / drug therapy*
  • Neoplasms / immunology


  • Antineoplastic Agents
  • Enzyme Inhibitors
  • Indoleamine-Pyrrole 2,3,-Dioxygenase