Auranofin, an approved drug for the treatment of rheumatoid arthritis, could serve as a potential new therapy for the treatment of Entamoeba histolytica infection, a common parasite worldwide. The finding appears online in Nature Medicine this week and highlights the utility of screening existing drugs for new purposes.

E. histolytica is an intestinal parasite that causes the potentially fatal infection amebiasis, killing around 70,000 people each year. In a screen for new antibiotics to treat this disease, Anjan Debnath and colleagues found that auranofin, a US Food and Drug Administration (FDA)-approved drug for the treatment of rheumatoid arthritis, inhibited E. histolytica growth in vitro and in two animal models of this infection. The authors suggest that auranofin inhibits E. histolytica thioredoxin reductase - an enzyme involved in defense against damage caused by oxygen metabolism - making the parasite more susceptible to oxidative stress.

Based on the potential clinical utility of these findings, the FDA has awarded auranofin status to treat amebiasis in humans.