Old Drugs Learn New Tricks

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NIGMS Communications Office

Diseases caused by tropical parasites are a major worldwide health problem. According to the World Health Organization, malaria alone kills more than 1 million people per year across the globe, and a child dies of malaria every 30 seconds. (1) Other scourges caused by parasites include Chagas' disease, leishmaniasis, sleeping sickness, and the AIDS-related infections toxoplasmosis and cryptosporidiosis. Scientists have not yet succeeded in developing vaccines against these parasitic infections, which collectively affect 3 billion people worldwide. (2) As a result, there is an urgent need for new, inexpensive treatments for these diseases.

Dr. Eric Oldfield, a chemist at the University of Illinois, discovered that a class of drugs called "bisphosphonates" currently approved by the Food and Drug Administration to treat osteoporosis and other bone ailments may also be useful for treating malaria, Chagas' disease, leishmaniasis, and the AIDS-related infections. 3 Previous research by Dr. Oldfield and his colleagues had hinted that the active ingredient in medicines such as Fosamax ® , Actonel ® , and Aredia ® blocks a key step in parasite metabolism. To test whether this was true, the researchers gave the medicines to five different parasites, each cultured in a plastic lab dish. The scientists found that low concentrations of the osteoporosis drugs killed the parasites, while sparing human cells. The researchers are now testing the drugs in animal models of the parasitic diseases and so far have obtained cures--in mice--of certain types of leishmaniasis.

Patients and doctors alike benefit when existing drugs find new uses. Since research efforts to develop vaccines against parasites have been largely unsuccessful to date, there is an urgent need for scientists to find new medicines to attack tropical parasites, which have also begun to develop resistance to currently effective medicines. If the ongoing studies demonstrate that bisphosphonate drugs work in larger animal models, the next step will be to determine if the medicines can thwart parasitic infections in humans. This could occur relatively quickly, since the medicines have already been approved for other uses, and therefore have already been tested for safety in people.


1 Fact Sheet No. 94--Malaria. World Health Organization, 1998.

2 Hirst SI, Stapley LA. Parasitology: the dawn of a new millennium. Parasitol. Today 2000; 16: 1-3.

3 Martin MB, Grimley JS, Lewis JC, Heath III HT, Bailey BN, Kendrick H, Yardley V, Caldera A, Lira R, Urbina JA, Moreno SNJ, Docampo R, Croft SL, and Oldfield E. Bisphosphonates inhibit the growth of Trypanosoma brucei, Trypanosoma cruzi, Leishmania donovani, Toxoplasma gondii, and Plasmodium falciparum: A potential route to chemotherapy. J. Med.Chem. 2001;44:909-16.

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Writer: Alison Davis, Science Writing Contractor