Metal compounds for the treatment of parasitic diseases

J Inorg Biochem. 2008 Oct;102(10):1839-45. doi: 10.1016/j.jinorgbio.2008.05.010. Epub 2008 Jun 4.


The cysteine proteases of the trypanosomatid parasitic protozoa have been validated as targets for chemotherapy of Chagas' disease and leishmaniasis. Metal complexes of gold, platinum, iridium, palladium, rhodium and osmium have been reported to have activity against a variety of trypanosomatids, but the molecular target of these compounds has not been defined. The activity of gold(III) and palladium(II) cyclometallated complexes, and oxorhenium(V) complexes against mammalian and parasitic cysteine proteases was investigated. All gold(III) complexes (1-6) inhibited cathepsin B with IC(50) values in the range of 0.2-1.4 microM. Of the six palladium compounds, aceto[2,6-bis[(butylthio-kappa S)methyl]phenyl-kappa C]-, (SP-4-3)-palladium(II) (11) was the most potent inhibitor of cathepsin B with an IC(50) of 0.4 microM. A clear structure-activity relationship was observed with the oxorhenium(V) complexes with chloro[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium(V) (16) being the most potent inhibitor of cathepsin B with an IC(50) of 0.009 microM. Six complexes were further tested against the parasite cysteine proteases, cruzain from T. cruzi, and cpB from L. major; the most potent inhibitors were the two rhenium complexes (2(1H)-pyridinethionato-kappa S(2))[2,6-bis[(mercapto-kappa S)methyl]pyridine-kappa N(1)] oxorhenium(V) (15) and chloro[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium(V) (16). The compounds were also evaluated in assays for parasite growth. Two oxorhenium(V) compounds ((p-methoxyphenylthiolato-S)[2,6-bis[(mercapto-kappa S)methyl]pyridine-kappa N(1)] oxorhenium(V) (14) and (methanethiolato)[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium (V) (18)) and the palladium compound 11 inhibited T. cruzi intracellular growth, and compound 11 inhibited promastigote growth in three Leishmania species. In conclusion this preliminary data indicates that metal complexes targeted at parasite cysteine proteases show promise for the treatment of both Chagas' disease and leishmaniasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cathepsin B / antagonists & inhibitors
  • Cathepsin B / metabolism*
  • Chagas Disease / drug therapy*
  • Cysteine Endopeptidases / metabolism
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Cysteine Proteinase Inhibitors / therapeutic use
  • Humans
  • Inorganic Chemicals / chemistry
  • Inorganic Chemicals / pharmacology
  • Leishmania / drug effects*
  • Leishmaniasis / drug therapy*
  • Metals / pharmacology*
  • Metals / therapeutic use
  • Trypanocidal Agents / pharmacology*
  • Trypanocidal Agents / therapeutic use
  • Trypanosoma / drug effects*


  • Cysteine Proteinase Inhibitors
  • Inorganic Chemicals
  • Metals
  • Trypanocidal Agents
  • Cysteine Endopeptidases
  • Cathepsin B